Guidelines for Inspection and Strength Evaluation of Suspension Bridge Parallel Wire Cables (2004)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

2-1 CONTENTS SECTION 2 INSPECTION...............................................................................................................................2-1 2.1 INTRODUCTION .......................................................................................................................................2-6 2.2 INSPECTION INTERVALS AND LOCATIONS ...................................................................................2-6 2.2.1 Levels of Inspection ............................................................................................................................2-6 2.2.2 Inspections by Maintenance Personnel.............................................................................................2-6 2.2.3 Biennial Inspections............................................................................................................................2-7 2.2.3.1 CABLES IN SUSPENDED SPANS ................................................................................................2-7 2.2.3.2 CABLES INSIDE ANCHORAGES ................................................................................................2-8 2.2.4 Internal Inspections ............................................................................................................................2-9 2.2.5 Locations of Internal Inspections ....................................................................................................2-10 2.2.5.1 FIRST INTERNAL INSPECTION................................................................................................2-10 2.2.5.2 SECOND INTERNAL INSPECTION...........................................................................................2-11 2.2.5.3 ADDITIONAL INTERNAL INSPECTIONS................................................................................2-12 2.2.5.4 INSPECTIONS IF STAGE 4 OR BROKEN WIRES ARE FOUND ............................................2-12 2.2.5.5 ACOUSTIC MONITORING .........................................................................................................2-12 2.3 INTERNAL INSPECTIONS....................................................................................................................2-12 2.3.1 Planning and Mobilization...............................................................................................................2-12 2.3.1.1 GENERAL .....................................................................................................................................2-12 2.3.1.2 INSPECTION PLANNING ...........................................................................................................2-13 2.3.1.2.1 Review of Available Documents .............................................................................................2-13 2.3.1.2.2 Preliminary Field Observations and Cable Walk.....................................................................2-14 2.3.1.2.3 Interviews of Maintenance Personnel ......................................................................................2-14 2.3.1.2.4 Inspection Forms......................................................................................................................2-15 2.3.1.2.5 Tool Kit....................................................................................................................................2-15 2.3.1.2.6 Inspection QA Plan ..................................................................................................................2-17 2.3.1.2.7 Inspection Locations ................................................................................................................2-17 2.3.1.3 CONSTRUCTION PLANNING....................................................................................................2-17 2.3.1.3.1 Design of Work Platform.........................................................................................................2-17 2.3.1.3.2 Construction Equipment ..........................................................................................................2-17 2.3.1.3.2.a Cable Compactors............................................................................................................2-17 2.3.1.3.2.b Steel Straps.......................................................................................................................2-17 2.3.1.3.2.c Wire Wrapping Machines.................................................................................................2-18 2.3.1.3.2.d Wedging Implements ........................................................................................................2-18 2.3.1.3.3 Preparations for Suspender Removal.......................................................................................2-18 2.3.1.3.4 Replacing Wire Wrapping .......................................................................................................2-19 2.3.1.4 NON-DESTRUCTIVE EVALUATION (NDE) TECHNIQUES ..................................................2-19 2.3.1.4.1 Monitoring Devices .................................................................................................................2-19 2.4 INSPECTION AND SAMPLING ............................................................................................................2-20 2.4.1 Cable Unwrapping............................................................................................................................2-20 2.4.1.1 WRAPPING WIRE TENSION TESTS .........................................................................................2-20

2-2 2.4.1.2 REMOVAL OF WRAPPING WIRE .............................................................................................2-21 2.4.1.3 LEAD PASTE REMOVAL ...........................................................................................................2-21 2.4.1.4 CABLE DIAMETER .....................................................................................................................2-21 2.4.2 Cable Wedging ..................................................................................................................................2-21 2.4.2.1 RADIAL WEDGE LOCATIONS..................................................................................................2-21 2.4.2.2 WEDGE INITIATION AND ADVANCEMENT .........................................................................2-23 2.4.3 Wire Inspection and Sampling ........................................................................................................2-24 2.4.3.1 OBSERVATION AND RECORDING OF CORROSION STAGES............................................2-24 2.4.3.2 BROKEN WIRES ..........................................................................................................................2-25 2.4.3.2.1 Wedge Spacing ........................................................................................................................2-25 2.4.3.2.2 Wire Tracing ............................................................................................................................2-25 2.4.3.2.3 Failed Wire Ends......................................................................................................................2-26 2.4.3.2.4 Sample Size..............................................................................................................................2-26 2.4.3.2.5 Other Forms of Corrosion........................................................................................................2-26 2.4.3.3 PHOTOGRAPHIC RECORD ........................................................................................................2-27 2.4.3.4 MEASUREMENT OF GAPS AT WIRE BREAKS ......................................................................2-27 2.4.3.5 WIRE SAMPLING ........................................................................................................................2-27 2.4.3.5.1 Number of Samples..................................................................................................................2-28 2.4.3.5.2 Sample Location ......................................................................................................................2-29 2.4.3.5.2.a Stage 1 Wires....................................................................................................................2-29 2.4.3.5.2.b Stage 2 Wires....................................................................................................................2-29 2.4.3.5.2.c Stages 3 and Stage 4 Wires ..............................................................................................2-30 2.4.3.5.3 Number of Specimens in Each Sample and Length of Samples ..............................................2-30 2.4.4 Identification of Microenvironments ..............................................................................................2-31 2.4.4.1 PH OF INTERSTITIAL WATER..................................................................................................2-31 2.4.4.2 CORROSION PRODUCTS ...........................................................................................................2-31 2.4.4.3 PERMANENT PROBES................................................................................................................2-31 2.4.5 Cable Bands and Suspender Removals...........................................................................................2-31 2.4.5.1 CABLE BAND BOLT TENSION .................................................................................................2-31 2.4.5.2 SUSPENDER REMOVAL AND CABLE INSPECTION ............................................................2-32 2.4.5.3 SUSPENDER REINSTALLATION ..............................................................................................2-32 2.4.6 Inspection Plan Reevaluation ..........................................................................................................2-33 2.4.7 Reinstallation of the Cable Protection System ...............................................................................2-33 2.4.8 Inspection During Cable Rehabilitation .........................................................................................2-33 2.4.8.1 GENERAL .....................................................................................................................................2-33 2.4.8.2 INSPECTION NEEDS VS. OILING OPERATIONS ...................................................................2-34 2.4.9 Inspection and Testing in Anchorage Areas...................................................................................2-34 2.4.9.1 WIRES IN STRANDS ...................................................................................................................2-35 2.4.9.2 WIRES NEAR AND AROUND STRAND SHOES .....................................................................2-35 2.4.9.3 EYEBARS......................................................................................................................................2-35 2.4.9.4 WIRES INSIDE SPLAY CASTINGS ...........................................................................................2-36 2.4.9.5 ANCHORAGE ROOFS .................................................................................................................2-36 2.4.9.6 INSTRUMENTATION OF EYEBARS.........................................................................................2-36 2.4.9.7 DEHUMIDIFICATION .................................................................................................................2-37 2.4.10 Inspection of Cables at Saddles .......................................................................................................2-37 2.4.10.1 TOWER SADDLES.......................................................................................................................2-38 2.4.10.1.1 Tower Top Enclosures .............................................................................................................2-38 2.4.10.1.2 Exposed Saddles with Plate Covers .........................................................................................2-38 2.4.10.2 CABLE-BENT SADDLES ............................................................................................................2-38 2.4.10.2.1 Saddles Inside Anchorages ......................................................................................................2-38

2-3 2.4.10.2.2 Extended Anchorage Housing .................................................................................................2-38 2.4.10.2.3 Exposed Saddles and Plated Roofs ..........................................................................................2-39 2.5 FIGURES FOR SECTION 2....................................................................................................................2-40

2-4 FIGURES Figure 2.2.3.1-1. Typical cable biennial inspection form. ...........................................................................2-40 Figure 2.2.3.1-2. Typical summary form showing biennial inspection rating system. ................................2-41 Figure 2.2.3.1-3. Typical form for biennial inspection showing detailed ratings........................................2-42 Figure 2.2.3.2-1. Typical form for biennial inspection of cable inside anchorage......................................2-43 Figure 2.2.4-1. Graph of cable condition vs. age at last inspection. ...........................................................2-44 Figure 2.3.1.2.2-1. Damaged caulking and paint at cable band.. .................................................................2-45 Figure 2.3.1.2.2-2. Uneven wrapping. .........................................................................................................2-45 Figure 2.3.1.2.2-3. Ridge indicating crossing wires. ...................................................................................2-46 Figure 2.3.1.2.2-4. Hollow area indicating crossing wires. ........................................................................2-46 Figure 2.3.1.2.2-5. Damage to wrapping caused by vehicular impact. .......................................................2-47 Figure 2.3.1.2.4-1. Form for recording locations of internal cable inspections. ........................................2-48 Figure 2.3.1.2.4-2. Form for recording observed wire damage inside wedged opening.............................2-49 Figure 2.3.1.2.4-3. Form for recording locations of broken wires and samples for testing........................2-50 Figure 2.3.1.3.2.a-1. Cable compactor. .......................................................................................................2-51 Figure 2.3.1.3.2.c-1. Power-driven wrapping machine. ..............................................................................2-52 Figure 2.3.1.3.2.c-2. Manual wrapping machine.........................................................................................2-52 Figure 2.3.1.3.2d-1. Chisels and wedges. ....................................................................................................2-53 Figure 2.3.1.3.2d-2. Hydraulic wedges. .......................................................................................................2-54 Figure 2.4.1-1. Form for recording cable circumference. ...........................................................................2-55 Figure 2.4.1.2-1. Removal of wire wrapping. ..............................................................................................2-56 Figure 2.4.2.1-1. Additional wedges to inspect area with many broken wires. ...........................................2-57 Figure 2.4.2.2-1. Cable wedged for inspection. ...........................................................................................2-58 Figure 2.4.8.1-1. Inspection during cable rehabilitation.............................................................................2-59 Figure 2.4.9.2-1. Deterioration of wires found inside strand shoe..............................................................2-59

2-5 TABLES Table 2.2.4-1 Interval between internal inspections........................................................................................2-9 Table C2.4.3.5.1-1 Wire characteristics, Bridge X .......................................................................................2-28 Table C2.4.3.5.1-2 Wire characteristics, Bridge Z........................................................................................2-28 Table 2.4.3.5.1-1 Recommended number of wire samples for both cables ..................................................2-29 Table 2.4.3.5.3-1 Sample lengths and number of specimens from each sample..........................................2-30

GUIDELINES COMMENTARY 2-6 2.1 INTRODUCTION The evaluation of a suspension bridge cable requires considerable information about the condition and strength of the cable wires. Obtaining this information is the goal of an inspection. Several levels of inspection are performed on a single structure over time, but only internal inspections provide data for strength evaluation. In this section, instructions are given for conducting a thorough internal inspection, and specific recommendations are made regarding inspection frequency and choice of locations. Sample forms are included, as well as photographs of cables being inspected and cable defects. Inspections must be planned in advance. Preparing forms and hiring a contractor is part of getting ready. Sometimes the owner’s staff takes on the contractor’s tasks, such as constructing platforms and unwrapping and rewrapping the cable. The responsible parties, whoever they are, should be prepared for the removal of one or more suspenders and cable bands, if conditions require it. Some cable band bolt tensions should be checked by the team in either case. Wedges are driven into the cable to separate the wires for visual inspection and to take samples from inside the “grooves.” Measurements of wire retraction are used to estimate the capacity of the broken wires to redevelop their force. Portions of the cable inside the anchorages, and visible portions where the cable passes over the saddles, must be inspected. C2.1 Information obtained from surveys of U.S. bridge owners during development of these Guidelines led to the conclusion that a baseline inspection should be performed on a bridge when it has been in service for 30 years. 2.2 INSPECTION INTERVALS AND LOCATIONS 2.2.1 Levels of Inspection Three levels of inspection are recommended: periodic routine visual inspections by maintenance personnel of the cable exterior, biennial hands-on inspections, and more thorough internal inspections. C2.2.1 The inspector should walk the entire cable during a hands-on inspection. For an inspection to qualify as hands-on, the inspector must be sufficiently close to the cable to touch it, sound it or inspect it with a magnifying glass. 2.2.2 Inspections by Maintenance Personnel During normal maintenance operations such as ice removal, rinsing of splash zone residue, or touch-up painting, maintenance personnel should be observant of C2.2.2 Maintenance personnel, who are familiar with the cable, may observe changes in condition indicative of trouble more readily than an engineer or investigator

GUIDELINES COMMENTARY 2-7 changes in the appearance of the cable. This is especially true of changes that may indicate a potential problem, including: damage to the paint or wrapping caused by accidents, weathering of the paint system, corrosion or severe oxidation of the wrapping wires, loose caulking, and brown rust stains. Periodic inspection tours of the cable by maintenance personnel are recommended. Inspectors should begin by inspecting the underside of the cable with binoculars, and then walk the cable for its full length. The best times of the year for inspection tours are at the end of winter (March or April) to observe damage due to frost or deicing salts in the splash zone, and at the end of summer (September or October) to observe the effects of extreme heat on paint and caulking. Additional tours should be scheduled after severe snow, ice, rain or wind storms. During these inspections, the underside of the cable should be examined for evidence of water inside, such as dripping from the wrapping wire or weep holes in the lower cable band grooves. Unusually damp areas should also be noted. Observations of unusual conditions should be recorded and documented with color photographs. Both the date and location of the inspection are noted, along with the date of the storm that preceded the inspection, if applicable. This information may be extremely useful in determining sites for in-depth inspections. who visits the cable at intervals of two years or more. On-site observations can be instrumental in determining where internal inspections should take place. While inspection tours are classified as hands-on, in that they are made by walking along the length of the cable, they are not intended to replace biennial inspections. Only if problems are noted need a report be filed, and a rating system is not required. A database is highly recommended for summarizing actual maintenance operations (repair of damage, repainting, etc.) and inspection tour observations. The database should include: • report number, part of a consistent reference system • date of observation or maintenance operation • location of maintenance operation, damage or repair • description of maintenance operation, damage or repair (verbal description and numerical code for rapid searching of the database) • recommended action • reference to report of the action taken 2.2.3 Biennial Inspections Federally-regulated biennial inspections require that non-redundant members receive hands-on inspection. During these inspections, the condition of the items listed in Articles 2.2.3.1 and 2.2.3.2 should be reported on and rated. If a biennial inspection indicates the possible presence of internal corrosion, and the cable was never inspected internally in that particular area before, it should be in the near future. C2.2.3 Biennial inspections should not be thought of as an opportunity for internal inspection, because the cable may be compromised by unwrapping sections of it every two years. 2.2.3.1 CABLES IN SUSPENDED SPANS The conditions of the following bridge components should be reported on and rated as follows: • paint or surface protection, inspected for dried out, peeling, cracked and crazed paint, or puncture or tearing of the elastomeric barrier (rate 3 if localized and 1 if more than 12 inches long) C2.2.3.1 Forms used by inspectors in the field, as well as summary forms, should be prepared for the specific bridge being inspected. The ratings used in the Guidelines text and corresponding figures are specific to New York State. They progress from 1 (totally deteriorated, or in failed condition) to 7 (new condition, no deterioration). Unless the wrapping wire or other components are

GUIDELINES COMMENTARY 2-8 • caulking at cable bands, for gaps or cracks (rate with the cable bands as indicated in Figure 2) • handropes and stanchions, for broken wires, tightness and corrosion (rate 3 if broken wires are present or loose, rate 1 if handropes or stanchions are broken) • wire wrapping, inspected for anomalies, including: o unequal tension of wire plies, indicated by unevenness in wrapping surface (rate 4) o bunching below or separating above the cable bands (rate 4) o gaps in wrapping, corroded or broken wrapping wire (rate 3 for small gaps, rate 1 for broken wrapping) o surface ridges, indicative of crossing wires and hollow areas (rate 4) • cable saddles or anchorage penetrations, for damaged sleeves, bellows or flashing (rate 1 if cracks that can admit water are present) • bottom of cable or cable bands, for rust stains or dripping water, indicative of internal corrosion (rate 1 or 2 and recommend internal inspection) Figure 1 shows an example of an inspection form. Figures 2 and 3 show forms used to report the conditions found. Figure 2 summarizes the rating system for various types of defects in wrapping and cable bands, while Figure 3 is a more detailed listing for each cable panel or cable band. A bridge plan, tower elevation, and cable elevation (refer to Figure 2.3.1.2.4-1) should also be included in the inspection report. actually new, the highest rating used is 5 (minor deterioration, but functioning as originally designed). Other agencies use a scale of 1 to 9, and ratings should be adjusted proportionally. Ratings applied to paint are often specified by the bridge owner. If no such guide exists, the rating system recommended by the state in which the bridge is located should be used. 2.2.3.2 CABLES INSIDE ANCHORAGES The following anchorage features should be reported on and rated according to state specifications: • strands inside the anchorages, for corrosion or broken wires, and swelling or bulges at the strand shoes • anchorage walls and roof, for signs of water entry • eyebars and strand wires, for signs of C2.2.3.2 Ratings for these items should follow the system specified by the state in which the bridge is located. l ing at cable bands, for gaps or cra ks (rate with the cabl b nds as indicated in Figure 2.2.3.1-2) 2.2.3.1-1 shows an xample of an inspection form. Figures 2.2.3.1-2 and 2.2.3.1-3 show forms used t report the conditions found. Figure 2.2.3.1-2 ummarizes the rating system or various types of defects i wrapping and cable bands, while Figure 2.2.3.1-3 is a more detailed listi g for each cable panel or cable band. A bridge plan, tower elevation, and cable elevation (refer to Figure 2.3.1.2.4-1) should also be included in the inspection report.

GUIDELINES COMMENTARY 2-9 condensation • points of contact between eyebars and the concrete mass, for signs of corrosion • eyebars and anchorage strands, for paint anomalies Figure 2.2.3.2-1 shows a typical form for recording the condition of strands and eyebars inside the anchorages. 2.2.4 Internal Inspections Internal inspections are necessary at some point during the life of a cable. The inspection intervals given in Table 1 are suggested, regardless of the cable’s external condition. Access to internal wires requires removal of the external protective system. The details of conducting an internal inspection are described in Article 2.3. Table 2.2.4-1 Interval between internal inspections Inspection Number Maximum Corrosion Stage Found in Previous Inspection* Age of Bridge at Last Inspection (Years) Interval (Years) First 30 Additional 1-(2) any age 30 2-(3) 40 or more 20 2-(3) 30 10 3-(4) 60 or more 20 3- (4) less than 60 10 4 any age 10 broken wires any age 5 * Each corrosion stage may include up to 25% of the surface layer of wires in the next higher stage, indicated by the number in parentheses. Stage 4 may include 5 broken surface layer wires. At the discretion of the owner and the investigator, the suggested intervals could be adjusted based on the history of past internal inspections of the bridge, or special conditions encountered, e.g., the presence of dissimilar metals such as copper or bronze in contact with or in close proximity to the wires, local C2.2.4 The recommended intervals of inspection reflect the data taken from condition inspections of 31 bridges of various ages, described in NCHRP Report 10-57, the reported maximum corrosion stages may have been reached well before the cables were inspected. The data indicate that there is a grace period of about 10 years after a bridge is completed before deterioration begins. The bridges have been separated into two groups according to mean trends of their rates of deterioration (see NCHRP Report 10-57. Eleven bridges with slowly deteriorating cables were designated Group A, for which the interval of time required to advance from one corrosion stage to the next was about 20 years. The 20 bridges that fall into Group B took only half that time to advance from stage to stage. The rate of advancement from one stage to the next is nearly linear; it increases slightly (i.e., the interval from one stage to the next is slightly smaller) as the corrosion becomes worse. Figure 1 shows the linear rate of deterioration. The recommended intervals between inspections are based on these rates of advancement, shown in Figure 1. In all cases, an internal inspection is recommended when the bridge is 30 years old, based on the observation that 7 bridges had Stage 3 or worse corrosion before the age of 40 years. The first inspection can be used to establish whether the cable is deteriorating rapidly or slowly. Once Stage 4 corrosion is present, the interval between inspections should be shortened to 10 years for all bridges. Whenever broken wires are found, the interval to the next inspection should be 5 years. A large percentage of Stage 4 wires also merits another inspection in 5 years. Many of the bridge cables were opened only for a short distance, and the information is sketchy. In addition, . e bridges have been separated into two groups according to mean tre ds f th ir rat s of deterioration ( ee section 2.3.4 f th final report for NCHRP Project 10-57, on the accompanying CD. Eleven bridges with slowly deteriorating cables were des gna ed Group A, for which the nterval of time required to advance from one corrosion s age to the next was about 20 years. The 20 bridges that fall into Group B took only half that ime to advance from stage to stage. 2.2.4-1 shows the lin ar rate of deterioration. 2.2.4-1 are uggested, regardless of th cable’s external condition. Acc ss to int rnal w quires removal ofthe external protective system. The details of conducting a internal inspection ar described in

GUIDELINES COMMENTARY 2-10 deterioration from traffic collisions, or overheating the wires during a maintenance operation. The interval between inspections should be shortened to 5 years when Stage 4 corrosion is found in more than 10% of the wires in the cable. A description and photographs of the four corrosion stages can be found in Article 1.4.2.2 and Figure 1.4.2.2-1. 2.2.5 Locations of Internal Inspections Internal inspections should be made where there are external signs of internal deterioration. These signs include: • loose wrapping • dripping water from the cable interior • rust stains • damaged caulking at the cable bands • surface ridges that indicate crossing wires below the wrapping • hollow sound when the cable surface is tapped If no external indications of deterioration are found, then the inspection locations should be selected according to the method described below. C2.2.5 No definitive statement can be made about where the worst conditions in the cable are most likely to be found. In only one of five bridges, for which data is available from at least 16 locations along the cable, did the greatest loss of strength occur at a low point of the cable. In the other four bridges, the maximum strength loss occurred near the quarter point of the main span or near the center of the side span. Furthermore, on one of the bridges, maximum strength loss above the low point of the cable was 3.5 times greater than at the low point. 2.2.5.1 FIRST INTERNAL INSPECTION The first internal cable inspections should be made at a minimum of 3 locations along each cable, selected as follows. • one in each cable at a low point of the main span • one in each cable at or near a low point of the side span • one in the first cable in the main span, above the low point at a distance of from 30% to 70% of half the main span • one in the other cable in a side span, above the low point at a distance of from 30% to 70% of the side span The cables should be opened for a length of at least 16 feet at each location, and wedged as deeply as possible at 4 locations around the perimeter. If the corrosion of the wires exceeds Stage 2, wedging should take place at 8 locations around the perimeter, and the opening should be extended to a full panel length. This is to enable the driving of wedges far enough inside the cable to determine the depth of Stage 3 or worse C2.2.5.1 During inspections, Stage 3 corrosion has been found at one or more of the low points whenever there was significant strength loss at any location higher up. There are 4 low points on each cable: in the 2 panels adjacent to the lowest cable band in the main span, and in the lowest panel in each side span, usually that panel on the span side of the anchor or cable bent saddle where the least slope occurs. In cables that have 2 panel points at the same midspan elevation, there will be 5 low points, one of which is the entire center panel. It is recommended that 2 low points be inspected on each cable in the first inspection, and the other 2 (or 3) in the second inspection. The inspection of 1 location above the low point of each cable is recommended in the first inspection, and not less than 2 such locations in the second inspection. When there are more than 2 cables on the bridge, the same inspection pattern described in Article 2.2.5.1 should be applied to each pair of cables. It is not likely that wire corrosion on a 30-year-old bridge will exceed Stage 2, although some Stage 3 corrosion may be present in the exterior wires. Thus, the cable opening need only be long enough to remove

GUIDELINES COMMENTARY 2-11 corrosion and to remove 16-foot-long samples. a 10-foot-long sample from the outer two layers for testing. The inspection team should, however, be prepared to open up a greater length of cable if more serious corrosion be found. 2.2.5.2 SECOND INTERNAL INSPECTION When the first internal inspection reveals only Stage 1 or Stage 2 corrosion, the second internal inspection should be made at not less than 4 locations along each cable, following the logic of the previous choices. The low point location in the main span should be adjacent to the low point location previously inspected, but the side span location should be in the side span opposite the one previously inspected. One location in the main span and one in a side span above the low points should also be inspected. A 16-foot-long opening will suffice, but if either Stage 3 or Stage 4 corrosion is found, opening and wedging should be increased (follow the instructions in Article 2.2.5.1). When the first internal inspection reveals Stage 3 corrosion, or Stage 4 corrosion to a depth of 3 wires or less, each cable should be internally inspected at 6 locations, including any one of the 3 previously inspected panels that exhibited Stage 2 corrosion or greater, and 3 additional locations recommended for the first inspection. Locations that exhibited only Stage 1 corrosion in the first inspection need not be reopened at this time, but additional locations above the low points should be selected to bring the total locations to 6. All 6 locations should be inspected for the full length between cable bands, with wedges driven to the center of the cable, or as deeply as possible. Whenever Stage 4 corrosion is present to a depth greater than one wire, and the center of the cable cannot be reached with a full panel length unwrapped, one cable band per cable should be removed to assess the condition of wires at the center of the cable. When the first internal inspection reveals Stage 4 corrosion to a depth of more than 3 wires, at least 16% and preferably 20% of the panels in each cable should be inspected. Four low points and 2 locations near the towers should be inspected; the balance of locations should be selected at random in the remainder of the cable between the low points and the towers, one each from contiguous groups of panels that are approximately C2.2.5.2 If corrosion does not exceed Stage 1 during the first inspection, a bridge cable could be 60 years old when the second inspection takes place. The inspection team should be prepared to open additional locations higher up on the cable at that time, if Stage 4 corrosion is found at any of the 4 recommended locations. In three of the inspection reports mentioned in Article C2.2.5, little deterioration was found adjacent to the towers. Therefore, only 2 locations near the towers are recommended for inspection when Stage 4 corrosion is found. Whenever there is any sign of deterioration inside the cable adjacent to the saddles, or in the saddle housings, or if the housing or the sleeves at the saddles show signs of water entry, these locations should be added to the list of recommended inspection sites. A method of estimating the minimum strength of a cable from the findings of an inspection presented in NCHRP Report 10-57 depends on the adequacy of the sampling. The estimated error in the minimum strength is 11% when 16% of the panels in the cable are inspected, and 8% when 20% of the panels are inspected. The method and the estimated error are based on the results from the only bridge for which sufficient data are available. i i str t of a cable from the findings of an inspection presented in he final report for NCHRP Project 10-57, on the accompanying CD depends on the ad quacy of the sampling. The estimated error in the minimum strength is 11% when 16% of the panels in the cable are inspected, and 8% when 20% of the panels are inspected. Th method and the stimated rror are based the esults f om the only bridge for which sufficient data are available.

GUIDELINES COMMENTARY 2-12 equal in number. The full length of panels between cable bands should be inspected, with wedges driven to the center of the cable, or as deeply as possible. At least 2 cable bands should be removed to facilitate inspection to the center of the cable and under the bands. 2.2.5.3 ADDITIONAL INTERNAL INSPECTIONS The number of locations to be opened after the second inspection depends on the conditions revealed by previous inspections, and the sites should again be chosen following the instructions in Article 2.2.5.2. 2.2.5.4 INSPECTIONS IF STAGE 4 OR BROKEN WIRES ARE FOUND When more than 10% of the wires in a cable panel are found to be Stage 4 in any inspection, the cable should be scheduled for a full interior inspection, and remedial action, such as the introduction of corrosion inhibitors, should be taken. Installation of an acoustic monitoring system is strongly recommended to listen for and locate continuing wire breaks. C2.2.5.4 Stage 4 corrosion is usually accompanied by cracked and broken wires. Whenever more than 10% of the wires in a cable panel are found to be in this condition, a full-length inspection of the cable is warranted, along with some cable band removal to inspect the wires underneath. 2.2.5.5 ACOUSTIC MONITORING When Stage 3 wires or worse were found in a previous inspection, it is recommended that an acoustic monitoring system be installed and monitored for a period of 12 to 18 months prior to the next internal inspection (see Article 2.3.1.4.1). The inspection locations should be selected to coincide with wire breaks, if any occur. At the discretion of the investigator or owner, the same system could be installed even if the wires found in a previous inspection were only Stage 1 or Stage 2. C2.2.5.5 Broken wires in the cable are an indication of active corrosion, and the sites of breaks are prime locations for future inspection. 2.3 INTERNAL INSPECTIONS 2.3.1 Planning and Mobilization Internal inspections require planning, but they also require the flexibility to respond as the inspection progresses and to alter initial plans if necessary. Contractor-assisted inspection must be managed so as not to compromise accessibility, even to areas not originally specified. 2.3.1.1 GENERAL The review of drawings, specifications and documents from prior inspections is required to provide background for planning a successful cable

GUIDELINES COMMENTARY 2-13 investigation, defined in part as one that requires minimum alterations during execution. 2.3.1.2 INSPECTION PLANNING Before determining inspection locations, the investigator should perform the series of actions described in this section. 2.3.1.2.1 Review of Available Documents The investigator should review bridge design reports, and become familiar with the design details at cable bands and cable saddles. If available, the specifications of wire and eyebar materials should also be checked. Records of previous inspections, however localized, may shed light on the causes of previous damage and suggest locations of potential damage, which could be important in the eventual assessment of cable capacity. Review of maintenance records may be of use in pinpointing areas where caulking or wrapping have failed in the past, or where water has been observed to be leaking from the cable or through the anchorage roof. The answers to the following questions may be useful in determining inspection locations, requirements for laboratory testing, and data needed for reliability analysis: • Are the wires galvanized or bright? If they are galvanized, the zinc coating should be tested. • Were the wires originally greased or oiled? If so, the wires may be less deteriorated, but corrosion may appear as short black sections on the wire. • What is the specified wire cast diameter? Small cast diameters indicate that wire cracking is more likely. • Are the original wire strengths and other mechanical properties available from acceptance testing or from specification records? If not, the full number of samples of Stage 1 and Stage 2 wires recommended in Article 2.4.3.5.1 should be taken during the first inspection. When original wire strengths are available, then at least 10 wires from these stages, for 3 tensile tests per sample, should be taken during the first inspection, with the balance of samples required taken during the C2.3.1.2.1 A highly stressed cable (a safety factor below 2.5) has less margin for strength loss due to corrosion than a cable designed for lower stresses. A live to dead load ratio greater than 0.2 may indicate large deflections, especially if stiffening trusses or girders are slender. Such deflections may cause paint to crack or damage at the sleeves and caulking, and special attention to inspection of these details is indicated.

GUIDELINES COMMENTARY 2-14 second inspection. • Are test results of wire chemistry available? If not, chemical tests should be made. • Was the cable aerially spun, or does it have shop-fabricated parallel wire strands, which tend to have fewer crossing wires because the cable is highly compacted? • Is water penetration a possibility at the sleeves and flashings of the saddle housing, or at deck penetrations? If so, careful observations of these areas must be made. • What is the dead load stress? What is the design live load stress? These values are needed in preparing the final report. If they are not available, or if there have been modifications to the bridge, or if there have been changes in the traffic load or pattern, the cable forces will have to be recalculated. High stress in the cables indicates that wire cracking is possible. • Which paint systems were used according to painting records? The information may lead to a better analysis of the coating performance. 2.3.1.2.2 Preliminary Field Observations and Cable Walk Walking on bridge sidewalks or maintenance walkways allows for observation of the lower portions of the cable. A cable walk is essential to make close observations of the external appearance of the cable. The items listed in Article 2.2.3.1 should be observed, along with the following: • Paint cracks along wrapping wire valleys • Poor compaction, evidenced by noticeable angularity of the cable • Broken or torn elastomeric membranes or cracked Lucite cable shells on newer protection systems Figures 1 through 5 illustrate some of these conditions. C2.3.1.2.2 These observations serve as general background and may help to establish inspection sites. Rusted handropes may be a safety hazard and should be repaired prior to the inspection. 2.3.1.2.3 Interviews of Maintenance Personnel Interviews of on-site personnel are useful, especially when they have performed maintenance tasks such as cleaning and painting the bridge, removing ice, and rinsing the splash zone.

GUIDELINES COMMENTARY 2-15 The information known to the maintenance staff may not have been formally recorded, but it could be valuable in determining the origin of damage and its time of inception. 2.3.1.2.4 Inspection Forms A well-prepared inspection form facilitates the recording of data in the field. Sample forms are given in Figure 1, Figure 2 and Figure 3. Figure 1 shows the elevations of each cable, for indicating the locations of inspected panels. Figure 2 shows an inspection form for a 9,990-wire cable. One or more copies are needed for each wedge line in each inspected panel. The observed conditions of the wires inside the wedged opening are recorded on these forms. A typical filled-in form is shown in Appendix C. Figure 3 shows a cross-section of the cable that can be used to record the locations of broken wires near the surface of the cable, and also to map the internal conditions observed in the cable. C2.3.1.2.4 Inspection forms must be tailored to the details of the cable to be inspected. The number of rings in the cable shown in Figure 2 and Figure 3 are calculated using Equation 4.3.1.1-1. If more or less than 9.990 wires are in the cable, the number of rings shown in the figures will vary accordingly. 2.3.1.2.5 Tool Kit Investigators or inspectors should have a simple but practical set of tools that permit the observation and recording of all essential data. At minimum, it must include the following (other items to be added at the discretion of the investigator): • Clipboard and supply of pens and pencils, fastened around neck or shoulder, or kept in a knapsack, but never carried loose in one’s hand. • Adequate number of blank forms. An inspection of eight wedge lines per panel will require at least 24 sheets for each panel. • Sturdy pocketknife to test wrapping or scrape corrosion products from wrapping and exposed wires. Among other uses, it aids in the collection of grease samples. • Flashlight, the most powerful one that fits into a knapsack. Absolutely essential for observing wires, especially in the lower half of the cable, it also helps to focus a camera in a dark area before exposing the film with a flash. • Steel ruler(s) and tapes, for various purposes. • Steel tape, with sufficient rigidity to reach 18 C2.3.1.2.5 Cable environments are always breezy or windy places. Inspection forms need to be anchored to a clipboard at both ends (possibly with a rubber band at the bottom) for taking good notes and preventing the forms from flying away. Pens have a way of disappearing. The inspectors should have a supply of pens and pencils sufficient to ensure an uninterrupted inspection. Although pens are preferable for filling in inspection forms, they may be useless on a humid day. HB graphite pencils can be used instead. The break location in a wire is not always visible. Loose wires are evidence of a break nearby, and are revealed in response to prodding with a rigid implement. Long implements are required to test deep wires, in which case a rigid wooden stick can be used if the wire pick is too short. A 1/16-inch-thick aluminum or brass sheet can be used to count the depth of a wire. The sheet should be drilled down the center with holes the same diameter as the wires and then split into two, so that notches are formed by the remaining parts of the holes. Numbers should be inscribed on the sheet next to the notches to aid in counting. Since most wires are very nearly 5 mm in diameter, a metric ruler can be carried to determine the depth of the wire from the surface. Dividing the red inspection form facilitates the recording of data in the field. Sampl forms are given in Figure 2.3.1.2.4-1, Figure 2.3.1.2.4-2 and Figure 2.3.1.2.4-3. Figure 2.3.1.2.4-1 shows the elevatio s of ach cable, for dicating the locations of inspected panels. .3.1.2.4-2 shows an inspection form for a 9,990-wire cable. One or more copies a e needed for each w dge line in each inspected panel. The observed conditions of the wir s inside the wedged opening are recorded on these forms. A typical f lled-in form is show in Appendix C. 2.3.1.2.4-3 shows a cross-section of e cable that can be used to record the locatio s of broken wires near the surface of the cab e, and also to map the internal conditions observed in the cable. .3.1.2.4-2 and Figure 2.3.1.2.4-3 are calculated using Equation 4.3.1.1-1. If more or less than 9.990 wires are i the cable, the number of rings shown in the figures will vary accordingly.

GUIDELINES COMMENTARY 2-16 inches into the cable. Wires are identified by counting from the surface of the cable or by measuring their distance from the surface. • Wire pick, made from a screwdriver with a round shank and well-rounded edges at the tip, to prod for loose wires and pry at surface deteriorated wires to inspect the layer below. It should not be used on Stage 1 or Stage 2 wires, to avoid damaging the zinc coating. • Small ruler, for proportioning the damage recorded in photographs. • Flexible tape, to measure cable diameters for evaluating cable compaction. • Dial gage caliper, to measure loss of section, especially in anchorage areas. For loss of section that is gradual, a micrometer is sufficient. • A camera (traditional print or digital), required for a photographic record of conditions exposed by wedging. • Good lighting (directed flash, ring flash or externally directed floodlight) for obtaining adequate photographic records. Conventional flash units flood the area outside the wedged opening and cannot illuminate the wedged cavity. • Tags for identifying sampled wires, typically of Manila paper, and ballpoint pen or some kind of permanent marker that won’t be smudged by grease or water. Tags with wires or twine and reinforced holes for attachment to sampled wires are preferable. • pH paper with a minimum range of 0.5 pH units, to determine the acidity of liquid on cable wires. They are usually available in small spools, with a calibration chart, from industrial supply houses. • Several sterile, tightly sealable sample jars, in case water or corrosion products are found that require sampling. • Industrial mirror with telescoping arm, 8 inches square, to observe the underside of the cable as the inspector walks on it. • Attachment means immediately at hand, for measured depth by 5, gives the depth into the cable in terms of wire diameters. As a backup for identification tags, a strip of duct tape can be wrapped around the wire and marked with a ball point pen. Pharmacies sell small sealable plastic jars that are used for urine samples but can be used also for collecting water and corrosion product samples from the cable. ASA 400 color film is recommended for greater flexibility. A 50 mm or 28-80 mm zoom lens is recommended for recording objects at close range, especially those deep in the cable, which can be seen only by a camera positioned directly over the wedged opening. A minimum of 3 megapixels is recommended for digital cameras to provide sufficient resolution.

GUIDELINES COMMENTARY 2-17 securing all tools, including clipboard, pens and pencils, to the handrails or platform. 2.3.1.2.6 Inspection QA Plan Inspection and sampling must be done in a verifiable manner. For quality control, more than one inspector should make observations and both parties should agree on the identification and demarcation of corrosion stages. Inspectors should be trained by an experienced investigator. The QA plan should identify the lead inspector and the assistant inspector, and describe what steps they will take to minimize error in data collection. C2.3.1.2.6 It is crucial that sampled wires be representative of the damage, so that testing data result in sound statistics for wire properties. 2.3.1.2.7 Inspection Locations Preparations for inspection include the selection of cable panels to be inspected. As the inspection proceeds, the investigator may alter this plan and choose to open different panels. 2.3.1.3 CONSTRUCTION PLANNING Access to the cable is provided by a contractor in most cases, or maintenance personnel. Panel inspections follow a predetermined order to some extent. When construction contracts are used, they should be flexible enough to provide for unexpected inspection requirements. 2.3.1.3.1 Design of Work Platform Work platforms are designed for the safety of construction and inspection personnel, and for containment of hazardous material. The platform should be constructed in a manner that safeguards tools and wedges, and prevents them from dropping onto the roadway or the waterway. C2.3.1.3.1 Wedges have been known to be ejected from the cable and fall down onto the roadway. Tenting that encloses the platform should eliminate this potential hazard. Wedges can also be held in place with straps that wrap around the cable to protect personnel on the platform. 2.3.1.3.2 Construction Equipment 2.3.1.3.2.a Cable Compactors It is essential that the compactor have sufficient capacity to recompact the unwrapped cable, to its original diameter. This may require a three- or four- jack assembly, depending on jack and cable size. Typical compactor details are illustrated in Figure 1. To prevent cable band slippage, the compactor should be placed at least 1.5 cable diameters from the edge of a cable band. C2.3.1.3.2.a Placing the compactor immediately adjacent the cable band on its downward-sloping side could reduce the cable diameter within the band itself, possibly causing the band to slip. 2.3.1.3.2.b Steel Straps jack assembly, depending on jack and cable size. Typical comp ctor details are illu trated in Figure 2.3.1.3.2.a-1.

GUIDELINES COMMENTARY 2-18 In the last stages of compaction, the cable is held together with steel straps to help it keep its shape; the straps are removed as the wrapping proceeds. Reusable synthetic straps are also used for this purpose. 2.3.1.3.2.c Wire Wrapping Machines Wire wrapping machines may be manually-driven or power-driven. With some quality supervision, manual devices can provide as tight a wrapping as power equipment, but they are recommended only for short lengths of cable. Figure 1 and Figure 2 show two kinds of wrapping machines. Tension is controlled in the wrapping wires by opening the tensioner jaws of manual machines or by wire spool friction in power machines. Both tensioner jaws and spools are calibrated and must be monitored during the wrapping operation. C2.3.1.3.2.c It is usually more efficient to use manual wrapping devices for small investigations, because of the relatively high cost of power-driven machines and the lengthy lead times required to obtain them. 2.3.1.3.2.d Wedging Implements Several types of wedging implements are employed during inspection, including wide bronze non-sparking chisels, and wood, plastic and hydraulic wedges. Chisel and wedge details are shown in Figure 2.3.1.3.2.d-1. To prevent wire damage, flat non-sparking chisels, 3 to 4 inches wide and preferably bronze, should be used to initiate wedging. Long flat screwdrivers with square shanks are not recommended. The best wedges for penetrating the cable are made of oak, rock maple, or high-molecular-weight polyethylene. The wedges should taper 1 inch for each 5 inches of length. To minimize wedge damage, wedge tips should be rounded approximately to a 1/8-inch diameter. Hydraulic wedges can be used to provide wide openings with minimum effort. A hydraulic device is shown in Figure 2.3.1.3.2.d-2. C2.3.1.3.2.d A suitable bronze starting chisel can be fabricated easily from a 3/8-inch x 4-inch flat bronze bar. The tip should match the one shown in Figure 2.3.1.3.2.d-1. Wedge tips wear out or become bent out of shape in the course of wedging, and constant repair is necessary. 2.3.1.3.3 Preparations for Suspender Removal Suspender removal requires an analysis of the forces that are necessary to dislocate the suspender from its anchored position and the forces that are transferred to adjacent suspenders. Capacity checks of the anchoring brackets and of the stiffeners and ropes at the adjacent remaining suspenders are mandatory to ensure safety. The equipment required for removal of short suspenders includes framing, jacks, and tension rods to bring the truss and cable closer together. For long suspenders, special equipment must be designed to pull C2.3.1.3.3 The investigator and the contractor usually collaborate on the design of equipment. The engineer is responsible for capacity checks. Suspender brackets on the stiffening trusses are typically designed to allow for suspender replacement. Capacity checks are a formality in most cases. However, increases in dead load unforeseen by the original designer may require such a check along with design of modifications. 2.3.1.3.2.c-1 and Figure 2.3.1.3.2.c-2 show two kinds of wrapping machines.

GUIDELINES COMMENTARY 2-19 the suspender against the truss for disconnecting the two. Temporary suspenders may be required to carry the force of the removed suspenders, so as to avoid overstressing adjacent suspenders or the stiffening truss and girder. 2.3.1.3.4 Replacing Wire Wrapping The wire tension should be high enough for the wire to remain in tight contact with the cable under all conceivable temperatures and live load conditions. The wrapping wire loses tension by as much as two- thirds because of creep in the zinc coating. The following expression for wire tension during rewrapping can be used: P= where: ν = Poisson’s ratio σLL = live load stress in the cable α = coefficient of thermal expansion ∆T = maximum estimated difference in temperature between the wrapping wire and average cable temperature E = Modulus of Elasticity of the wrapping wire dw = diameter of the wire ∆T will be larger for large cables than for smaller ones. 2.3.1.4 NON-DESTRUCTIVE EVALUATION (NDE) TECHNIQUES Many private companies and institutions are marketing NDE equipment. Investigators should always be aware of what is available and what can be expected from NDE devices at the time they plan an investigation. Technologies are developing at a fast pace. Often, willingness to try a new technology will lead to its modification, making it suitable for application to bridge cables. Public authorities and investigators must evaluate any proposed or potential technology by testing it against objective criteria that derive from the specific characteristics of bridge cables and information required for strength assessment. C2.3.1.4 Despite the great need for NDE diagnostic evaluation, existing devices are of limited value. New and improved technologies may be developed for determining the most damaged cable areas, but hands- on visual inspections are still required for the foreseeable future. A discussion of NDE techniques is included in NCHRP Report 10-59. Acoustic Monitoring is a good example of an existing technique that has been successfully adapted to cable work. 2.3.1.4.1 Monitoring Devices Acoustic monitoring devices should be installed on a C2.3.1.4.1.a There are devices that detect changes in the behavior of 3(νσLL +αE ∆T)πdw2/4 t eed for E diagnostic evaluation, i re of li ited value. New and improved technologies may be developed for determining the most amaged cable area , but h nds-on visual inspectio s are still required for the foreseeabl f ture. A discussion of NDE t chniq es is included in the inal report for NCHRP Project 10-57, on the accompanying CD.

GUIDELINES COMMENTARY 2-20 cable that has many Stage 4 or broken wires to determine whether deterioration is continuing and at what pace. If wires continue to break, or if the frequency of breaks accelerates, the inspection schedule should be revised. If an additional 0.5% of the wires in a panel break after an inspection, then an immediate re-inspection and evaluation of the panel is recommended. cables or detect wire failures as they occur. Given known baseline behavior and damage information, a record of conditions may be constructed over time. Acoustic Transmission (AT) technology is used to detect wire failures on large cables, because the sound waves of a break that travel through the steel can be detected at receptors placed on the cable surface. Wire failures have distinctive sound signatures that are easily differentiated from normal bridge noise. The arrival times of the sound at several different receptors are compared to pinpoint the location of the break. Some U.S. bridges have been fitted with Acoustic Transmission equipment along both cables, or at least along parts of them. This service is provided under the generic technological name of “Acoustic Monitoring.” Monitoring devices cannot determine existing conditions directly, and are not diagnostic. However, the technology can be used to determine which panels have wires that are breaking, and hence which panels are most likely to have damage. This could eliminate much of the current guesswork involved in selection of panels to be opened. 2.4 INSPECTION AND SAMPLING 2.4.1 Cable Unwrapping Prior to unwrapping the cable, the investigator should record any notable surface defects, such as gaps in the wrapping wire, damaged paint, and white or brown rust emanating from the cable. C2.4.1 The conditions listed apply to cables wrapped with wire, whereas other protection systems may exhibit different defects, which should also be noted (e.g., cracks in polymeric coverings or tears in neoprene wrapping). 2.4.1.1 WRAPPING WIRE TENSION TESTS The wire should be strain-gaged before cutting if the tension in the existing wire is required. The loss in stress after cutting, while the wire is held to the cable circumference, provides the wire tension. The same procedure is used for single wrapping plies or for all the plies at once. C2.4.1.1 If the original tension is known, then the tension in the unwrapped wire is compared to find out how much tension has been lost, and whether the existing tension is adequate. Measurement of the shortening that occurs when the wrapping wire extends over several loops is difficult to accomplish and interpret because of the friction among the plies. Hence, strain gaging is recommended rather than measuring the shortening of a wire after cutting. The circumference of the cable should be measured prior to unwrapping. If the steel tape is sensitive totemperature changes, the temperature should be recorded at the same time. A form that can be used to record these measurements is shown in Figure 2.4.1-1.

GUIDELINES COMMENTARY 2-21 2.4.1.2 REMOVAL OF WRAPPING WIRE Removal of the wrapping wire is a health hazard as well as an environmental one. Workers should wear masks and handle the wire in such a way that the lead waste is contained. Workers should also take care not to generate airborne dust, unless the entire panel is covered and enclosed, and then a filtering system should be used to protect workers from the dust that accumulates inside. C2.4.1.2 Blood testing for lead toxicity of all personnel involved in cable unwrapping, inspection, and rewrapping is mandatory. See Article 1.3.2. 2.4.1.3 LEAD PASTE REMOVAL The lead paste under the wrapping is usually dry and friable. Some of it falls onto the platform floor as the wrapping is removed. Some of it adheres weakly to the cable wires and may be dispersed by the lightest breeze. It should be dislodged by striking the cable with a wooden implement and the remainder removed with a soft wire brush. Before wedging the cable, the unwrapped surface should be vacuumed. Wedging will cause additional lead dust and waste to be dislodged from the cable. Spraying or brushing on a light coating of oil will minimize the production of this additional dust. C2.4.1.3 Monitoring of airborne dust must comply with environmental protection guidelines. 2.4.1.4 CABLE DIAMETER The cable circumference should again be measured after the wrapping has been removed. Measurements should be taken immediately adjacent to the cable bands, 12 inches from the ends of the bands and at the center of the panel. The cable diameter without wrapping should be calculated, as well as the solids ratio of the cable, which is a comparison of the total metallic area of the steel wires to the area in the cable circumference without wrapping wire. C2.4.1.4 The cable diameter, which is calculated from the circumference measurement, is required so that the cable can be rewrapped to its original degree of compaction or more. The solids ratio of a well- compacted cable usually varies between 0.80 and 0.82. If the value is significantly smaller, it may indicate that the reported number of wires in the cable is incorrect. In this case, the number must be verified by counting the wires inside the anchorage. 2.4.2 Cable Wedging The cable is wedged radially at panel locations, as described in Article 2.4.2.1. In general, wedging should be done where damage is suspected. 2.4.2.1 RADIAL WEDGE LOCATIONS When 8 wedge lines are required, they should be located at every 45 degrees around the cable circumference. When less than 8 wedge lines are required, the spacing is adjusted accordingly. The C2.4.2.1 The upslope is sometimes used as a convenience for determining direction, because compass directions are not easily established inside an enclosure. Angular or other designations may be used instead of clock To avoid dispersal of lead and lead paint, wrapping wire should be handled carefully when it is transported to the temporary storage site. Figure 2.4.1.2-1 shows wrapping wire in the process of removal.

GUIDELINES COMMENTARY 2-22 wedge lines are usually given clock designations to describe their angular positions from the top of the cable: 12:00 at top of cable 1:30 at 45°, clockwise from top of cable 3:00 at 90°, clockwise from top of cable 4:30 at 135°, clockwise from top of cable 6:00 at 180°, clockwise from top of cable 7:30 at 225°, clockwise from top of cable 9:00 at 270°, clockwise from top of cable 10:30 at 315°, clockwise from top of cable Not all cable conditions require wedging on all 8 lines. On the other hand, some cables may need additional wedging to improve the statistical data, especially if the damage is severe. The following guidelines are recommended for determining the number and position of the wedge lines: • Always start wedging at one of the bottom lines (4:30, 6:00, or 7:30), especially if nothing is known about the condition of the cable, or unless the plan is to open a minimum of 8 wedge lines. • When only Stage 1 corrosion is found in all three of the lowest wedge lines, select 1 more wedge line in the splash zone, if there is one, at either 1:30, 3:00, 9:00 or 10:30. • When no more than Stage 2 corrosion is found, a minimum of 6 wedge lines are recommended, including the bottom 3, plus 9:00 and 3:00 and either 1:30 or 10:30, preferably in the splash zone. • When Stage 3 corrosion or worse is found, open all 8 wedge lines. • When a significant number of broken wires are found, additional lines should be opened in the regions where Stage 4 wires are found. Figure 2.4.2.1-1 shows a cable with broken wires wedged for inspection. • For cables with a diameter greater than 24 inches, 8 additional wedge lines between the 8 recommended above should be opened. They should extend deep enough to permit designations. The bottom of the cable is usually more deteriorated than the top or sides. By starting at the bottom, it is likely that the worst condition will be encountered. When the outer surface of the cable is in Stage 1 condition, wedging in the rest of the cross-section can be minimized, because the condition is usually worse at the surface than at the center. Near the cable low points, the side of the cable facing a roadway will receive the most splash from passing cars and will often be more deteriorated than the side facing away from the roadway. When many broken wires are found, Stage 4 corrosion is expected to extend deep inside the cable, and additional wedge lines are justified to determine its extent. On larger cables, additional wedge lines are recommended in the outer half of the cable radius where the wedges are at maximum spacing, to avoid reducing the fraction of wires that are observed. This helps to minimize the margin of error in the calculations.

GUIDELINES COMMENTARY 2-23 inspection of the wires at least halfway to the center of the cable. 2.4.2.2 WEDGE INITIATION AND ADVANCEMENT Wedging should be initiated with one of the non- sparking implements recommended in Article 2.3.1.3.2.d. The wedges are then driven further into the cable with a sledgehammer. Photographs of cables wedged for inspection are shown in Figure 2.4.2.1-1. Start wedging at the middle of the panel (or cable opening if less than a panel) and insert additional wedges about every 4 feet, working toward the cable bands. Drive all the wedges to a uniform depth of about 3 inches, then advance them in sequence for 3 inches at a time until the center of the cable or the recommended depth is reached. The following difficulties must be recognized and overcome to advance wedging. • Gap crossing (i.e., the wire crosses the wedged opening) occurs whenever the wedge is being driven along a path on one side of a wire (or wires) that is opposite to the side where an adjacent wedge was driven. The condition has to be recognized quickly, because it impedes driving and may damage wires. The wedge should be pulled out and relocated on the same side of the wire as the prior wedge. • Rejection occurs when a wire that lies in the middle of the path of the blunt edge of the wedge will not be pushed aside by the wedge. The worker experiences a loosening and regression of the wedge to a position that is further out than before the hammer blow. The wire is pushing the wedge back. Driving must cease to prevent wire damage, and the wire should be pushed aside on the same side as the other wedged wires with a non-sparking chisel. • Strewing occurs whenever broken wires are present. Wedges will often drive the part of a broken wire nearest to the broken end into deeper layers of the cable, causing the broken wire to cross the paths of several intact wires, and often preventing the wire’s broken ends from being seen. This condition cannot always be prevented, but it can be minimized. Start at the center of the panel and drive all wedges to a short and uniform depth. Identify broken C2.4.2.2 Sometimes lubrication of the wedge with petrolatum or linseed oil is helpful in driving the wedges. The investigator should be certain that the lubricant used is compatible with the corrosion-inhibitive coating, if there is one.

GUIDELINES COMMENTARY 2-24 wires, and advance wedges first at locations away from the broken wire ends. Advance wedges at the ends last, while holding the wires with additional wedges near the break. • Where broken wires are strewn, as evidenced by the wires turning inward at a wedge location, they should be returned to their original position after the inspection, using hooked wire picks. Failure to do so will cause voids inside the cable and crossing wires, both sources of additional damage. • Wedge tip bending occurs where the cable offers excessive resistance to penetration. The wedge tip will select the easiest path, which is not necessarily radial. The first 3 inches of the wedge will sometimes bend until driving becomes impossible, even when the wedge has penetrated only a small distance into the cable. The problem can be corrected by pulling out the wedge and advancing it from the point where the opening is radial with a non-sparking implement, and then driving it radially again. 2.4.3 Wire Inspection and Sampling The purpose of the inspection is to identify corrosion in the cable wires, and to quantify it according to defined stages by finding its limits in the cross-section of the cable. Sampling of wires determines the physical properties of the wires in each stage, which are required for estimating cable capacity. An example of a filled-in form for a cable cross-section in a panel is presented in Appendix C. 2.4.3.1 OBSERVATION AND RECORDING OF CORROSION STAGES The inspector should identify the corrosion stage of the wires on both exposed faces of the wedged opening. This is done visually, using the photographs in Figure 1.4.2.2-1 as a guide. The wire condition is recorded for at least 3 segments, each approximately 6 feet long, along the length of a panel. An observed wire should be first assigned the highest observed stage in the segment. Each wire is then reassigned the highest corrosion stage found on that wire in the opening length, after comparing the recorded data for the wire in each segment. Data are entered on inspection forms similar to the one C2.4.3.1 A corrosion stage may cover only a very short length of wire, in some cases less than one inch. This is especially true of wires with black or gray rings of zinc depletion, which, whenever present, should be counted separately. Laboratory testing is used to determine the stage they belong to. Only the highest stage found along the length of the wire is used in the analysis of cable capacity in Section 5; it is determined from the data on the forms after the inspection. The object of keeping these records is to be able to

GUIDELINES COMMENTARY 2-25 shown in Figure 2.3.1.2.4-2. A typical record of data, using the form, is presented in Appendix C. develop a cross-sectional map of the wire stages, as shown in Appendix C, which is a useful visual tool to show the extent of damage. The map should represent the worst condition of all cable segments within the panel. 2.4.3.2 BROKEN WIRES Wires found broken in the outer layers of the cable should be located on the cable cross-section shown in Figure 2.3.1.2.4-3. Both the tangential location and depth into the cable should be noted. The maximum cable depth at which broken wires are seen should also be noted. The number and location of broken wires that are observed inside wedged openings more than a few layers from the surface of the cable are noted on the form shown in Figure 2.3.1.2.4-2. C2.4.3.2 Broken wires can usually be detected in the layer of wires below the outermost layer. If several adjacent wires are broken, then it is possible to detect wires up to 4 layers down. Wires broken at greater depths can only be seen inside the wedged openings. 2.4.3.2.1 Wedge Spacing Wedges should be spaced at about 4-foot intervals. This allows for observing wire conditions deep inside the wedged cavity. After recording the wire conditions found, wedges should be removed so that the spacing is doubled. If there are loose wires, they tend to project out into the wedged opening or to respond to prodding. Investigators should experiment to determine the wedge spacing most suited to detecting loose wires. Pullout of the intermediate wedges should be partial to facilitate the observation of loose wires deep inside the cable; otherwise, loose wires closer to the surface will hide the deeper ones from view. C2.4.3.2.1 At a 4-foot spacing of wedges, loose wires are not visible. Prodding the wires will not give any indication that they are loose, because they are being tightly held by the wedges. Experience has shown that loose wires with a free coil radius of 4 to 6 feet will become evident at a minimum wedge spacing of 6 feet. 2.4.3.2.2 Wire Tracing Wires are identified by their distance from the surface of the cable. Many times the same wire will not show up at the same distance from the surface within the panel being inspected, because of poor parallelism or the formation of a surface lip during wedging. When there are several adjacent loose wires, to avoid double counting, it is necessary to prod the loose wire at one section and observe its longitudinal movement in other sections. Tracing should be done for all loose wires

GUIDELINES COMMENTARY 2-26 with unidentified ends. 2.4.3.2.3 Failed Wire Ends Whenever a wire breaks, two wire ends are formed, one corresponding to each side of the break. In the counting of broken wires, both ends of each wire should be accounted for. Avoid the double counting that occurs whenever the ends of the same wire are identified as belonging to two different wires. Whenever only one end is visible, probe to find the end of a loose wire nearby that is beneath the surface of the wedged opening. C2.4.3.2.3 Not all ends of broken wires are visible. Often, wire breaks occur near or under cable bands, where wedging is impossible. Several inspections have shown that there is roughly the same number of broken wires in a given length of cable under or near a cable band as in the observed portion of the panel before the cable band is removed. However, this may not be the case for each bridge and should be further investigated by the removal of one or more cable bands whenever numerous broken wires are found. In the process of recording, it is necessary to count all loose wires and all failed wire ends, and to eliminate all loose wires ends that have already been counted. 2.4.3.2.4 Sample Size Broken or loose wires sometimes project from underneath the surface exposed by the wedges. This complicates the estimate of the size of the sample, and may lead to even larger errors in the estimate of broken wires in the cable. To minimize this type of error, the investigator should count broken wire ends and loose wires that come from underneath the wedged surface as well as those from the wedged surface proper, and record them separately. C2.4.3.2.4 In one experience, the broken wire ends from underneath the wedged surface were approximately equal to those on the surface. The origin of the loose wires could not be properly traced, due to the large quantity of broken wires. The size of the observed wire sample, for purposes of counting broken wires, was conservatively taken to be 3/2 times the wires on the surface of the exposed cavity. The assumption was that only surface loose wires were visible. 2.4.3.2.5 Other Forms of Corrosion The inspector should look for and record all other significant types of corrosion on the same form that is used for reporting corrosion stages. Significant corrosion includes • Pitting • General corrosion, that causes a reduction in the diameter of the wire (report the diameter). • Crevice corrosion, in which the attack and corrosion product are primarily along the contact surface of adjacent wires When these conditions are prevalent (i.e., observed in more than one or two wires in a wedged opening), additional samples for testing should be removed to establish whether additional corrosion stages need to be created for strength evaluation. When these conditions are not prevalent, the recommended number of samples for each corrosion stage should include a number of

GUIDELINES COMMENTARY 2-27 these wires with the condition noted, proportional to their incidence. 2.4.3.3 PHOTOGRAPHIC RECORD Typical as well as singular or atypical conditions should be photographed in color. For each photograph taken, the number given to the roll of film and the number of the exposure should be recorded on the inspection form. The direction of the view and the target wire or area should be noted. C2.4.3.3 The condition of wires is better described with photographs than with words. Cameras that date the exposure facilitate identification. Often, taking a photograph of an object not associated with wire inspection (e.g., an adjacent cable, the tower, or the roadway), and noting it on the form, is an aid to establishing the date and general location of the photographic record. 2.4.3.4 MEASUREMENT OF GAPS AT WIRE BREAKS As many ends of broken wires as possible should be brought into alignment and the gap between the ends measured. The record of information should include the depth into the cable of the measured separation and the panel in which it took place. It should also be noted whether the measurement occurred with the cable band or wrapping in adjacent panels removed. Whenever a sample wire is removed from the cable for testing, the gap that forms after the first cut should be measured. A scratch is made on each side of the cut prior to making the cut. The distance between the two scratches is measured before and after cutting the wire. C2.4.3.4 Friction among the wires, especially under wide cable bands, can redevelop the force in a broken wire. From measured gaps in broken wires, the capacity of the cable band to develop wire tension can be estimated on a statistical basis, based on known dead load and postulated live load at the time of measurement. Live load error will not create a large error in the wire tension estimate, because the live load is usually a small percentage of the total load. 2.4.3.5 WIRE SAMPLING Sample locations should be recorded on the cable cross-section inspection form shown in Figure 2.3.1.2.4-3. Samples from broken wires should not be used for strength testing or for determining the fraction of wires that are cracked. A new wire should be spliced to the cut ends of a sampled wire to restore continuity. The new wire is tightened to the same tension as the other wires in the cable. The complete procedure for replacing a cut wire is given in Appendix D. Since sampling requires the removal of wires from the cable, it should be kept to a minimum because the splice between the replacement wire and the end of the existing wire is never as strong as the original wire. C2.4.3.5 The object of sampling is to characterize the physical properties of wires in each of the various corrosion stages using laboratory tests. The properties that are of interest to the investigator are the following: • The extent of and variation in zinc oxidation, to estimate the remaining usefulness of the protective coating and to evaluate the susceptibility of the wires to initiation of stress corrosion at the holidays in the zinc. • The strength of the corroded wires, because degraded wire may be embrittled, or have surface corrosion, corrosion pits or propagating cracks. All these conditions, implying loss of strength, only start at Stage 3, with embrittlement. Stage 3 wires may contain pits and a few cracks; Stage 4 wires usually contain many cracks. As the inspection proceeds, investigators have to become aware of all the possible anomalies that may reduce wire strength, for which wires will require

GUIDELINES COMMENTARY 2-28 testing. Sampling of broken wires to test for strength may overestimate the capacity of continuous cracked wires, because whenever a wire breaks in the cable, the force in the wire drops to zero, possibly halting crack growth in the remainder of the wire. Also, broken wires are known to contain cracks, so that samples from these wires cannot be used to determine the number of Stage 4 wires that are cracked. Therefore, only unbroken wires should be sampled for strength testing. Broken wires removed from the cable during repairs, however, should be saved for testing corrosion products. 2.4.3.5.1 Number of Samples A full set of Stage 1 samples and at least half the recommended number of Stage 2 samples (if Stage 2 is present) should be removed during the first inspection. These samples may be combined with additional samples removed during the second inspection to bring the total number of samples to the recommended number. No further samples of these stages are required in future inspections. C2.4.3.5.1 The zinc coating tests recommended for Stage 2 wires should be performed on Stage 1 wires from the first inspection for use as a baseline in future inspections. The proposed numbers of samples are calculated on the basis of test results that indicate a reduction in tensile strength and an increased variation of strength properties as corrosion advances. The wire characteristics given in Table C2.4.3.5.1-1 and Table C2.4.3.5.1-2 were used to estimate the errors in cable strength at a 97.5% confidence level. These characteristics are from laboratory tests on the wires of two bridges, identified as Bridge X and Bridge Z. Table C2.4.3.5.1-1 Wire characteristics, Bridge X % Loss of Strength Coefficient %Variation % of Wires Cracked Stage 2 0% 2% 0% Stage 3 1% 3% 5% Stage 4 3% 4% 64% Cracked 16% 13% N/A Table C2.4.3.5.1-2 Wire characteristics, Bridge Z % Loss of Strength Coefficient %Variation % of Wires Cracked Stage 2 1% 3% 0% Stage 3 5% 4% 5% Stage 4 6% 4% 64% Cracked 30% 26% N/A The recommended number of samples to be taken for each corrosion stage is given in Table 2.4.3.5.1-1. The number of proposed samples has been selected to minimize the error in estimated cable strength.

GUIDELINES COMMENTARY 2-29 Whenever adjacent panels are assumed to be perfect (no deterioration), application of these wire characteristics result in the estimated strength losses given in Table 2.4.3.5.1-1. Whenever deteriorated wires are present in the adjacent panels, strength losses will be greater. Table 2.4.3.5.1-1 Recommended number of wire samples for both cables Estimated Error (97.5% confidence) Estimated Cable Strength Loss Corrosion Stages Present in Worst Panel Observed Total Number of Samples Bridge Bridge Stage 1 Stage 2 Stage 3 Stage 4 Stage 1 Stage 2 Stage 3 Stage 4 X Z X Z 100% 0% 0% 0% 10 -- -- -- 3% 5% 0 0 >0% 0% 0% 10 15 -- -- 3% 5% 0% 0% >0% 10% 0% 10 15 35 -- 3% 5% 1% 2% >0% 20% 10% 10 15 35 60 4% 5% 9% 10% >0% 40% 20% 10 15 35 60 4% 6% 16% 18% 2.4.3.5.2 Sample Location 2.4.3.5.2.a Stage 1 Wires The first panels to be unwrapped should be at the low points: 2 samples of Stage 1 wires should be removed from each panel, one at 6:00 and one at 3:00 or 9:00, on the side facing the roadway, or splash zone. One sample should be removed at random locations from each of the two remaining panels opened during the first inspection. 2.4.3.5.2.b Stage 2 Wires From 1 to 3 samples of Stage 2 wires should be taken from each panel. At the low points, one should be removed at 6:00 and one at 3:00 or 9:00 on the side facing the roadway. A third sample location may be randomly selected. If no Stage 2 wires are found at the first location, then the samples should be taken from another location where Stage 2 is found, and the number of samples in each panel increased to provide

GUIDELINES COMMENTARY 2-30 the recommended number. 2.4.3.5.2.c Stages 3 and Stage 4 Wires The recommended number of samples given in Table 2.4.3.5.1-1 should be divided randomly among the planned number of inspection locations, with at least 0.5 and at most 1.5 times the average number of samples taken in any one panel. If no wires of the required stage are found in a panel, than the number assigned to that panel should be randomly added to the remaining uninspected panels. Not more than 10 samples of Stage 3 and 10 samples of Stage 4 should be taken in any one panel. For planning purposes, the following percentages of Stage 3 and Stage 4 wires may be assumed in applying table 2.4.3.5.1-1: • First inspection – 10% Stage 3, 0% Stage 4 • Second inspection – 20% Stage 3, 10% Stage 4 • Later inspections – percentages estimated by the investigator from previous inspections Samples should be selected at random in each inspected panel, using tables of random sample locations prepared in advance for several different groupings of Stage 3 or Stage 4 wires. C2.4.3.5.2c It is possible that in early inspections the total number of Stage 3 and/or Stage 4 wire samples will be smaller than recommended, especially if a large number of higher stage wires is found in the last panel opened. In this case, the error in estimated strength may be greater than is assumed in Table 2.4.3.5.1-1. The next inspection, however, should take place in 5 to 10 years, and the greater number of panels inspected at that time will provide enough samples. 2.4.3.5.3 Number of Specimens in Each Sample and Length of Samples Table 2.4.3.5.3-1 Sample lengths and number of specimens from each sample Minimum Number of Specimens from Each Sample Corrosion Stage of Sample Strength Tests Weight of Zinc Tests Preece Tests Sample Length (feet) 1 4 1 4 12 2 4 1 4 12 3 10 0 0 16 to 20 4 10 0 0 16 to 20 C2.4.3.5.3 When the corrosion stage varies along the length of a sample wire, the specimens to be tested for strength should be cut from the worst areas of the wire. When Stage 3 is found during the first inspection, or Stage 4 to a depth not greater than one wire, remove 12-foot-long samples of Stage 3 and Stage 4 and test 4 specimens. When Stage 4 is found to a depth greater than one wire during the first inspection, extend the length of cable that is unwrapped to remove 16-foot- long samples of Stage 4 wires. The recommended number of specimens to be cut from each sample for tensile and zinc loss testing, along with the recommended sample length, are found in Table 2.4.3.5.3-1.

GUIDELINES COMMENTARY 2-31 2.4.4 Identification of Microenvironments The field or laboratory tests described in this subsection may be useful in identifying the conditions inside the cables that are causing the observed deterioration. C2.4.4 Researchers and engineers are trying to identify the microenvironments that produce wire corrosion. It is possible that many different types of environments attack bridges, causing wire deterioration at different rates. Therefore, it is useful to characterize the nature of the environment that is affecting the cable under inspection. 2.4.4.1 pH OF INTERSTITIAL WATER During inspection, condensed droplets of moisture or even moving water may be seen on cable wires. The water should be tested with pH test paper strips. If possible, samples of the water should be collected and placed in new tightly-sealed inert containers and refrigerated to prevent gas loss. The samples should be sent to a laboratory to detect the presence of dissolved gasses and salts that are known pollutants, such as chlorides, sulfates and nitrates. 2.4.4.2 CORROSION PRODUCTS Corrosion products can be removed from the bridge. It is useful to select specimens from these samples for the study of corrosion products. This can also be done for zinc compounds scraped from the wrapping wire 2.4.4.3 PERMANENT PROBES Although not currently available, permanent probes could be inserted at critical locations inside the cable. They might be used to identify time-dependent wet-dry cycles and indicate the presence and pH of water, the availability of oxygen, and other factors. C2.4.4.3 The presence of water is evidence that corrosion of the wires may be taking place. The pH of the water indicates the aggressiveness of the environment inside the cable. A low pH indicates high acidity, which could be responsible for rapid depletion of the zinc coating. 2.4.5 Cable Bands and Suspender Removals Cable bands are an integral part of the suspension system. They also play a role in maintaining cable capacity once wires begin to fail. Cable band bolt tensions affect the capacity of the cable band to develop cable force in broken wires, as well as their ability to transfer the tangential component of cable force to the cable without slipping. Cable bands have to be removed to compare the level of deterioration in areas of the cable that are near the cable band with areas in the middle of the panel. C2.4.5 While wire damage in or near the cable bands has been found to approximately equal wire damage in the rest of the panel, this may not always be the case. It should be checked whenever Stage 4 or broken wires are present. 2.4.5.1 CABLE BAND BOLT TENSION During wire inspections, it is customary to inspect cable band bolt tensions. This is accomplished by measuring bolt length, while the bolt is both tight and loose. The measurements are made with an C2.4.5.1 During cable inspections, the cable band bolt tension may have to be determined for assessing reliability against band slippage. While this aspect of the work is not directly related to cable capacity, it is useful to

GUIDELINES COMMENTARY 2-32 extensometer, which has a sensitivity of 10-4 inches. Extensometers are provided with spherical tips that bear inside conical center holes provided at the bolt ends. One bolt is inspected at a time, and retightened immediately thereafter to the originally specified tension. All bolts of the cable band should be tested. The caulking between cable band halves is removed prior to measuring bolt tension, and the center holes in the bolt cleaned of paint and debris. A zero reading of the extensometer is made prior to loosening a bolt. Three to four readings are averaged to arrive at the zero reading. The bolt is then loosened, and three to four readings on the tension-free bolt are again averaged. The difference in these two sets of readings is the elongation of the bolt due to tensile stress. The bolt tension is computed from this elongation. The bolt length is taken from the underside of the head to the center of the nut. If the original bolt tension installation force is known, the measured bolt tensions should provide an estimate of the force reduction over time, due to creep in the zinc on the bridge wires or gradual compaction of the cable. know the cable band bolt clamping force and the friction among wires that it may generate. There may be as much as a 15% error from the real average tension of the bolts in a band if 16 cable bands are inspected, but the safety factors and reliability against slippage are large enough to encompass the error. A long-reach micrometer reading to 10-4 inch can be used instead of an extensometer reading, but spherical anvils are required, and they must be checked for compatibility with the holes at the bolt ends. 2.4.5.2 SUSPENDER REMOVAL AND CABLE INSPECTION Removal of a suspender and its cable band requires contractor assistance and must be carefully planned and executed. Before removal, a suspender should be match-marked against the cable and its length recorded in such a way that the suspender and its socket can be reinstalled easily in its original location and orientation. The exact location of the cable band on the cable should also be marked. Where inspection of two adjacent panels is performed for deeper access into the cable, the wedge line should be continuous through both panels and the cable band area. A cable wedged to achieve this task is illustrated in Figure 2.4.2.2-1. The removed suspenders can be seen where they loop over the cable. C2.4.5.2 Sections of the cable that can be inspected without band removal should be differentiated from sections that cannot. This is necessary to obtain estimates of unobservable defective wires in locations where the cable bands are not removed. Then, the worst damage for the entire panel can be mapped in the cable cross- section. 2.4.5.3 SUSPENDER REINSTALLATION The cable must be recompacted before the band is reinstalled, and the band placed at the exact location on the cable it was in prior to removal. Failure to do so may result in a change of suspender tension. Bolts

GUIDELINES COMMENTARY 2-33 should be retightened to the bolt tension originally specified. The band grooves should be aligned in a vertical plane. The reinstalled suspender should be aligned with match marks on the cable. The suspender should be jacked down so that the suspender sockets can be placed in the anchoring brackets while the original orientation of the entire suspender is maintained. This procedure should ensure that the tension in the suspender legs before removal is recovered. 2.4.6 Inspection Plan Reevaluation After initial inspection of what are assumed to be the worst panels, the investigator should compare the predicted and actual damage. This may lead to a reduction of wedging or an increase in the number of panels to be inspected, or other alterations of the inspection plan. 2.4.7 Reinstallation of the Cable Protection System Upon completion of inspection and sample removal, the cable must be recompacted and the cable protection replaced. Recompaction to the level of original compaction, based on previous measurements of the cable diameter, can be accomplished using a hydraulic compactor (see Article 2.3.1.3.2a). The cable diameter should be no more than that measured before removal of the wrapping less two times the wrapping wire diameter. Steel or stiff plastic (e.g., Kevlar) binding straps should be applied around the cable at intervals of 12 to 18 inches to hold the compaction until the wrapping is applied. A protective paste should be applied just ahead of the wrapping machine, and the cable rewrapped using a machine that can apply a tension of at least 300 pounds to each ply of the wrapping wire. The completed wrapping should then be painted using a paint system specified by the bridge owner, and the grooves at the cable bands caulked to exclude water. C2.4.7 Generally, the protection system is replaced to meet current standards. Water-based paint systems or membranes provide excellent protection and prevent water from entering the cable through the wire- wrapped area. However, for partial protection that replaces only limited inspection areas, this may not be an advantage. If water has had the opportunity to enter an aging protection system in areas that have not been inspected, a good paint system on the newly wrapped area may cause the water to be retained inside the cable. It is important that at low cable points, the replacement protection system be provided with sufficient weep holes to allow the water to escape. Many authorities are reexamining the use of red lead pastes and are experimenting with substitutes or even no paste at all, placing their confidence in the quality of the exterior protection system. Many cable bands are caulked today with polyurethane or polysulfide caulking rather than the caulked lead wool that may have been used when the cable was first constructed. For more information on protection systems, refer to Article 1.4.2. and Article 1.4.3. 2.4.8 Inspection During Cable Rehabilitation 2.4.8.1 GENERAL When cables are damaged to a level of Stage 3 C2.4.8.1 The larger part of inspection work requires access to

GUIDELINES COMMENTARY 2-34 corrosion or worse, or when the wrapping system is deteriorated and requires replacement, some authorities opt for oiling the cables to arrest corrosion, albeit for a limited time, and replacing the exterior protection system, because it has to be removed to perform the oiling operation. These conditions favor inspection of the wires in all cable panels, which can be done after removal of the wrapping. Figure 2.4.8.1-1 shows a cable wedged for a rehabilitation operation. While the wedge alignment is not radial as normally is the case, the openings provided can still be used successfully for internal inspection. cable wires and replacement of the protection system. It would be wasteful to replace the protection system, which is associated with cable damage, and miss the opportunity of inspecting the wires for very little additional cost. 2.4.8.2 INSPECTION NEEDS VS. OILING OPERATIONS Cable oiling starts at high cable locations and proceeds downward. To conduct inspections that are not affected by the oiling operation, wedging must be done several panels ahead of the oiling, so that the wedge locations are inspected before the oil arrives. Wedging for oiling does not always offer adequate openings for assessing the worst cable damage. Therefore, auxiliary wedging at the bottom of the cable is necessary for inspection purposes. Since the wedging must be done before the oil gets there, wrapping should be removed far ahead of the oiling work, and bottom- of-cable wedging conducted independent of wedging for oiling. 2.4.9 Inspection and Testing in Anchorage Areas The cables in the anchorages splay outward after passing over a splay saddle or through a splay casting. The wires are not wrapped in the splay, and thus are easier to inspect. Cable strands are connected to the anchorage with strand shoes and eyebars, or with sockets and rods. The inspection of these components is discussed below. Recently constructed suspension bridges often use shop-fabricated parallel wire strands (PWS) in place of aerially-spun strands. Anchorages on these bridges will look different from those described, and the inspection forms will also look different from the examples presented in these Guidelines, but the principles of inspection are the same. The inspector must prepare forms specific to each bridge, and the inspection should cover all items relevant to aerially-spun cables, substituting, for example, “strand sockets” for “strand C2.4.9 Many anchorages are susceptible to water condensation, because their concrete masses serve as heat sinks. Furthermore, many anchorage roofs function as roadway decks with construction joints at or near the curb line. This allows surface water to penetrate the anchorage and drip on the splayed strands and eyebars closest to the roadway. Makeshift diversions for roof water have met with little success. Field experience has demonstrated that corrosion mechanisms inside the anchorages are significantly different from the ones in the protected cable in the main span and side spans from bent saddle to bent saddle. This is evidenced by the differences in appearance of corroded wires. In wet anchorages, there is considerable surface corrosion and wire failure occurs after significant section loss. In contrast, wire failure in the protected cable occurs after embrittlement and

GUIDELINES COMMENTARY 2-35 shoes” and “anchorage system” for “eyebars.” The primary difference will be that PWS construction always uses a socket at the anchorage point of the strand instead of a strand shoe, and usually uses a steel framework instead of eyebars to anchor the sockets. pitting with “flat and invert” breaks and little or no section loss. 2.4.9.1 WIRES IN STRANDS The strands inside the anchorage should be wedged open on at least one transverse and one vertical line. The investigator may add more wedging at locations that show the worst damage. The minimum diameter of corroded wires should be measured and recorded. C2.4.9.1 In general, anchorage strands have more damage at the lower end of the strand (i.e., near their anchorage points), than at higher locations, although upper portions of the strands may also be damaged where water runs through the splay casting or drips into the cable just below the splay casting. 2.4.9.2 WIRES NEAR AND AROUND STRAND SHOES In wet anchorages, strand wires deteriorate the most where water collects over time. This generally occurs in the bottom half-strand, adjacent to or in contact with The area is difficult to access, and wire damage can only be guessed at from the surface. This incomplete information is insufficient to estimate the total wire damage. Experience on some bridges indicates that if there are several broken wires at the edge of the strand shoe accompanied by section loss in surface wires that have not yet failed, then a worse condition is likely to be present in an inaccessible area of the strand. The investigator must exercise engineering judgment about the potential capacity of the strand, and whether the strand should be rehabilitated, in the context of overall strand group conditions and of the need to restore cable strength in the anchorage area. C2.4.9.2 Strand cutting and re-anchoring allows for estimating the condition and capacity of strands of similar exterior appearance. NDE devices, in use or in development, do not permit a reasonable estimate of damage in the wires in the area around the strand shoe. 2.4.9.3 EYEBARS All eyebars should be carefully examined during biennial inspections, and the presence of corrosion products, exfoliating rust and loose paint reported. The corrosion product on some of the more accessible eyebars should be removed with hammer and chisel to a degree sufficient for determining section loss. Where section loss on the eyebars is suspected, all paint and corrosion products on the eyebars should be removed by shot blasting. The extent of section loss is measured using specially designed calipers on a minimum of five equally spaced locations along the width of the eyebar. The loss on the narrow faces of the C2.4.9.3 In wet anchorages, a heavy deposit of corrosion products is often found on the surface of the eyebars just above the point where they enter the concrete mass. The extent of the damage is visually deceiving, because the corrosion products may consist of a dense black oxide that adheres tightly to the metal, often not removed in preparation for painting. The corrosion normally does not extend below the surface of the concrete. In some anchorages, access for visual observation may be so limited that a video camera is required. the strand shoe, as illustrated in Figure 2.4.9.2-1 (the end of the steel tape indicates the location of the front edge of the strand shoe).

GUIDELINES COMMENTARY 2-36 eyebars should also be determined. The surface of the corroded eyebar is usually too rough to allow the use of ultrasonic thickness-measuring devices, but a test should be conducted to determine their suitability. The remaining area of the eyebars should be calculated from these measurements and used in turn to calculate the capacity of the eyebars to anchor the strands. Removal of corrosion products manually is not advisable, regardless of accessibility, because the products are strongly adherent to the base metal and cannot be dislodged with a hammer. Rust is best removed with shot blasting. Pack rust removal should be executed by a contractor. The capacity of both strands and eyebars is estimated with a technique that is equivalent to calculating the cable capacity with the Limited Ductility Model, described in Section 5. All strands may be considered clamped at the splay casting or splay saddle, and this point is mathematically moved to strain the assembly of eyebars and strands. The force in each strand is calculated from the elongation. As an assembly of an eyebar plus attached strand reaches its strength, the eyebar yields or the strand fails, and part or all of the force in the assembly is distributed to the other elements. The sum of strand forces is the force in the cable; and the maximum force reached is the strength, which may be less than the sum of the individual strengths. 2.4.9.4 WIRES INSIDE SPLAY CASTINGS Inspection is required if there is any indication of wire damage inside the splay castings. Engineering and construction planning are necessary for temporary upward relocation of the splay casting, which permits separation of the strands and provides access. Only competent contractors with experience in bridge wire and cable inspection should be engaged for this work. The primary purpose of such inspection is to determine the condition of the wires. Wires that have significant section loss or are broken should be replaced. New zinc-coated wires are spliced to a sound point on the damaged wires. All ferrules should be outside the final splay casting location. The access that is provided should permit inspection of all wires, facilitating estimation of cable capacity in the splay casting area. C2.4.9.4 The engineering work will most likely require installation of guide frames to maintain all the strands at the same length. Failure to adjust the strand alignment may result in undesirable movement of the cable and suspended structure. The procedure also seeks to maintain the same tension in all the wires at all times. 2.4.9.5 ANCHORAGE ROOFS When the strands display significant damage, anchorage roofs should be inspected to identify sources of moisture. 2.4.9.6 INSTRUMENTATION OF EYEBARS Whenever live load stress ranges coupled with temperature change effects on the cable are required by the investigator, it may be possible to instrument the eyebars to obtain the needed data. The effects on the C2.4.9.6 AASHTO design loads and load factors are often not applicable to long span suspension bridges. Their use may lead to low safety indices, unrepresentative of real conditions.

GUIDELINES COMMENTARY 2-37 eyebars can be translated to effects anywhere in the suspended span area, providing that the anchorage and tower saddles are free to move. If necessary, temperature effects on the cable can be determined separately by installing instrumentation for temperature on the cable and calculating changes of stress on the cable by analytic means. To eliminate the effect of temperature changes on the eyebars, one full bridge circuit per eyebar is recommended. Two gages should be placed on each eyebar at opposite ends of the horizontal centerline to determine the flexural stress component in the eyebar. A line of strands chosen diagonally across the strand group is a sufficiently large enough sample to guarantee good averages. The force in the outer strands should be corrected by multiplying by the cosine of the angle that the outer strand makes with the center strand. Instrumentation and data acquisition is an effective means of estimating bridge loads, especially fatigue loading stress ranges and histograms. More accurate live loads and stress ranges than those obtained from instrumenting eyebars can be obtained by instrumenting the cable wires directly while the cable is unwrapped. This should be done in the span beyond anchorages or cable-bent saddles. At least 8 strain gages should be attached to wires at 45-degree intervals around the cable. 2.4.9.7 DEHUMIDIFICATION Whenever a dehumidification system is installed in the anchorage, the system should be inspected in the presence of maintenance personnel or a mechanical engineer familiar with its operation, according to the following procedure: • Measure the relative humidity immediately upon opening the chamber. • Measure the relative humidity for a 2-hour period on a humid or rainy day. • Test the operation of the equipment to verify that it starts when the relative humidity is raised to the level the equipment is set for (an electric pot can be used to boil water in the chamber to accomplish this), and that it turns off when the humidity is reduced to normal levels by removing the source. • Inspect gaskets at doors and other openings for leakage. 2.4.10 Inspection of Cables at Saddles Cable wires inside saddles have not been inspected on any bridge to date. Observation of wires is possible only from the top of the saddle and at its ends, where the cable is visible all around its surface, but not inside. No currently available or soon to be available NDE devices can assist in estimating wire damage in saddle areas. C2.4.10 A saddle is a turning point of the cable; contact between the saddle and the cable is necessary to support the bridge. Based on past inspection experience, the surface wires in the saddle itself are usually in good condition, especially if they are covered with wax. There are exceptions: on one bridge, the top of the cable in the tower saddles was covered with bird excrement, despite the presence of a tower

GUIDELINES COMMENTARY 2-38 The wires at the top of the saddle and inside protective sleeves should be inspected, starting with the second time the cable is inspected, unless signs of water entry are observed earlier. Half the saddle wires should be observed during the second inspection and half during the third. enclosure. There was no protective wax or other coating on the wires, and the upper layer of wires experienced section loss. It is not necessary to observe inside the saddle cover or housing during the first inspection. The second inspection may occur as early as 35 or 40 years, or as late as 60 years, after completion of the bridge. In either event, these areas should be inspected starting with the second inspection. 2.4.10.1 TOWER SADDLES There are two types of enclosures for tower saddles, requiring different access routes for observing wires. 2.4.10.1.1 Tower Top Enclosures Tower top enclosures are extensions of the tower. They may consist of a penthouse covering the entire top surface of the tower, or of a series of separate enclosures, one for each saddle. The enclosures cover the entire saddle and permit observation of saddles and exposed wires by the mere opening of an access door. 2.4.10.1.2 Exposed Saddles with Plate Covers The saddles are exposed at the tops of towers, but have top plates cap-bolted onto the sides of the saddle retainers, thus protecting the cable. Flashings are similarly mounted. To access the wires, plates and flashings must be removed temporarily. Cables within saddles have often been protected with a layer of wax (beeswax and paraffin are used for this purpose). This protection should be replaced after inspection, either in kind or with another type of waterproof coating. 2.4.10.2 CABLE-BENT SADDLES Cable-bent saddles are placed on top of a rigid frame structure or on separate columns to accommodate a change in the direction of a cable as it deflects downward into the anchorage at the end of the side spans. The enclosures for these saddles are of several types. 2.4.10.2.1 Saddles Inside Anchorages Bent saddles reside inside the anchorage structure, where saddle and surface wires are exposed and observable. 2.4.10.2.2 Extended Anchorage Housing Steel or concrete housings extend from the anchorage structure above the roadway and contain the bent strut

GUIDELINES COMMENTARY 2-39 and saddle. Within these housings, saddle and surface wires are observable. 2.4.10.2.3 Exposed Saddles and Plated Roofs Exposed saddles with plated roofs create conditions similar to the ones described in Article 2.4.10.1.2. Cable bents with exposed saddles extend through the anchorage roof. Wires are protected by plated roofs bolted to the sides of the saddles. To access the wires, plates and flashings must be temporarily removed.

2.5 FIGURES FOR SECTION 2 Figure 2.2.3.1-1. Typical cable biennial inspection form. 2-40

2-41 Figure 2.2.3.1-2. Typical summary form showing biennial inspection rating system.

2-42 BD 188 (1/96) BIN NYS DEPT. OF TRANSPORTATION BRIDGE INSPECTION REPORT SHEET OF . TEAM ASST. TEAM LEADER: L EADER: DATE Feature Carried: Feature Crossed: NEW PREV PAINT 5 5 5 BMS/10 81 band 5 5 3 BMS/10 81-82 wrap 5 5 5 BMS/10 82 band 5 5 4 MMS/10 81-82 wrap 5 5 5 MMS/10 81 band 5 5 3 MMS/10 80-81 wrap 5 5 5 MMS/10 80 band 4 4 3 89S MMS/10 79-80 wrap 4 5 5 MMS/10 79 band 5 5 3 MMS/10 78-79 wrap 5 5 5 MMS/10 78 band 5 5 3 MMS/10 77-78 wrap 4 5 5 MMS/10 77 band 4 4 3 89S MMS/10 76-77 wrap 4 5 5 MMS/10 76 band 5 5 3 MMS/10 75-76 wrap 5 5 5 MMS/10 75 band 5 5 3 MMS/10 74-75 wrap 5 5 5 MMS/10 74 band 5 5 3 MMS/10 73-74 wrap 5 5 5 MMS/10 73 band 5 5 3 MMS/10 72-73 wrap 5 5 5 MMS/10 72 band 5 5 3 MMS/10 71-72 wrap 5 5 5 MMS/10 71 band 5 5 3 MMS/10 70-71 wrap 5 5 5 MMS/10 70 band 5 5 3 MMS/10 69-70 wrap 5 5 5 MMS/10 69 band 5 5 3 MMS/10 68-69 wrap 5 5 5 MMS/10 68 band 5 5 5 MMS/10 67-68 wrap 5 5 5 MMS/10 67 band The seal between the cable band and the bottom portion of the cable is missing. There are overlapping wires near PP 80. The seal between the cable band and the bottom portion of the cable is missing. The seal between the cable band and the bottom portion of the cable is missing. There are overlapping wires near PP 80. LOC. & SPAN TP 350 - [28] PRIMARY MEMBERS RATINGS CABLE A PHOTO NO. PP MEMBER REMARKS Figure 2.2.3.1-3. Typical form for biennial inspection showing detailed ratings.

2-43 Figure 2.2.3.2-1. Typical form for biennial inspection of cable inside anchorage.

2-44 Condition of Cables on 31 Bridges vs. Age at Last Inspection 0 1 2 3 4 5 6 0 40 80 120 160 Age at Last Inspection (years) Co nd iti o n GROUP A GROUP B Linear (ALL) Linear (GROUP A) Linear (GROUP B) Condition = presence of corrosion stage of same number (e.g., Condition 1 = presence of Stage 1, any amount). See Figures 2.2-3 to 2.2-6 for illustrations of Corrosion Stages 1 to 4 Stage 0 = new wire Stage 1 = start of zinc deterioration (very slight) Stage 2 = Wires covered with "white rust" Stage 3 = 0 to 30% of surface with ferrous corrosion Stage 4 = over 30% of surface with ferrous corrosion Stage 5 = broken wires present Group A = Bridges whose cables deteriorate slower than the average of all 31 bridges Group B = Bridges whose cables deteriorate faster than the average of all 31 bridges Note "A": Where two data points coincide, the second point is shown directly below the first. See note "A" Figure 2.2.4-1. Graph of cable condition vs. age at last inspection.

2-45 Figure 2.3.1.2.2-1 Damaged caulking and paint at cable band. Figure 2.3.1.2.2-2. Uneven wrapping.

2-46 Figure 2.3.1.2.2-3. Ridge indicating crossing wires. Figure 2.3.1.2.2-4. Hollow area indicating crossing wires.

2-47 Figure 2.3.1.2.2-5. Damage to wrapping caused by vehicular impact.

2-48 Figure 2.3.1.2.4-1. Form for recording locations of internal cable inspections.

2-49 Figure 2.3.1.2.4-2. Form for recording observed wire damage inside wedged opening.

2-50 Figure 2.3.1.2.4-3. Form for recording locations of broken wires and samples for testing. SAMPLE FOR TESTING

2-51 Figure 2.3.1.3.2.a-1. Cable compactor.

2-52 Figure 2.3.1.3.2.c-1. Power-driven wrapping machine. Figure 2.3.1.3.2.c-2. Manual wrapping machine.

2-53 1.5” R + 4 ” 4” R/10 or 3/4” whichever is less 3” TIP DETAIL 1/16” dia Round all edges 1/16” radius Round corners 1/16” dia STARTING TOOL Material: Bronze See tip detail(R = C ab le Ra diu s) 1/16” dia (See tip detail) R + 4” 4” 1/2” 3” Round all edges 1/16” radius Round corners 1/16” dia ALTERNATE STARTING TOOL Material: Bronze (R = C ab le Ra diu s) 4” R = C ab le Ra diu s 4” Round corners 1/8” dia WEDGE Material: Rock Maple or Oak See tip detail 1 10 TIP DETAIL 1/8” dia Figure 2.3.1.3.2.d-1. Chisels and wedges. Note: For cables with a radius greater than 12 inches, wedges can have smaller slope, resulting in a maximum thickness of about 2.5 inches.

2-54 Figure 2.3.1.3.2.d-2. Hydraulic wedges.

2-55 Figure 2.4.1-1. Form for recording cable circumference.

2-56 Figure 2.4.1.2-1. Removal of wire wrapping.

2-57 WEDGES Figure 2.4.2.1-1. Additional wedges to inspect area with many broken wires.

2-58 Figure 2.4.2.2-1. Cable wedged for inspection.

2-59 Figure 2.4.8.1-1. Inspection during cable rehabilitation. Figure 2.4.9.2-1. Deterioration of wires found inside strand shoe.