Development and Calibration of AASHTO LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals (2014)

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.

5 Agency Survey AASHTO member states were surveyed to obtain guid- ance regarding their practices related to design, fabrication, construction, and asset management. The questions and raw survey results are provided in Appendix D (available on the TRB website). The primary findings are provided in Table 2. Literature U.S. and International Specifications Domestic and selected international specifications were reviewed for application. Each is briefly discussed in Table 3. Research Papers and Reports Numerous research reports and papers were reviewed for an understanding of past, current, and new specification devel- opment. This project was not designed to create new work in the area of load or resistance but rather to incorporate existing work and to calibrate the specifications for load and resistance factor design. Readers are led to work by Roy et al. (2011), Stam et al. (2011), and Connor et al. (2012) on fatigue resistance and loading. Kaczinski et al. (1998) and Dexter and Ricker (2002) form the basis of many articles on fatigue loading and resistance. The works of Roy et al. and Stam et al. were compared, and this comparison is summarized in Appendix E (on the TRB website). These projects were ongoing at the time of the pres- ent project. NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features (Ross et al., 1993) has long been used for safety performance evaluation, and the Manual for Assessing Safety Hardware (MASH) (AASHTO, 2009) has replaced that document. The researchers sought information from numerous reports upon which the new ASCE/SEI (Structural Engineering Insti- tute) 7-10 was based (e.g., Vickery and Waldhera, 2008, Vickery et al., 2009a, 2009b, 2010). Textbooks Some textbooks on structural reliability were helpful (e.g., Nowak and Collins, 2000, and a general chapter on the topic in Barker and Puckett, 2013). Resistance Sections The steel and aluminum resistance sections were rewritten incorporating the latest standards and methods. Section 5: Steel Design employs methods from the American Institute of Steel Construction (AISC, 2010), and Section 6: Aluminum Design employs methods from the Aluminum Design Manual (Aluminum Association, 2010). Section 7: Prestressed Con- crete Design, Section 8: Fiber-Reinforced Composite Design, Section 9: Wood Design, and Section 13: Foundation Design remain largely unchanged in concept but were recast into LRFD format and calibrated. Section 10: Service ability Requirements was recast for LRFD; however, load and resistance factors were set to unity, resulting in no conceptual modifications from STD-LTS-5 (or 6). Section 11: Fatigue Design was substantially modified from STD-LTS-5. However, work by Roy et al. (2011), Stam et al. (2011), and Connor et al. (2012) on fatigue resistance was extensively used in both the STD-LTS-6 and the LRFD-LTS specifications. These modifications were closely coordinated between AASHTO SCOBS T-12, the researchers noted here, and the present research team. Fabrication, Materials, and Detailing (Section 14) The fabrication section is new for the LRFD-LTS specifi- cations and contains information that was moved from the STD-LTS resistance sections. The AASHTO LRFD Bridge C H A P T E R 2 Findings

6Table 2. Summary of survey findings. No. Finding Summary Relevance to the LRFD-LTS Specifications 1 Thirty-six agencies responded to the survey. Reasonable sample of interested agencies. 2 When failures occur, typically they are due to fatigue-related issues. Data are available for assessing fatigue-related failure. Changes in fatigue design could be justified. 3 The number of failures relative to the number of structures in the inventory is small. The overall performance of existing structures (STD-LTS designs) is good and likely acceptable. Calibrating to existing designs appears to be reasonable. 4 About 76% of the respondents have used vibration mitigation devices. Specification changes are needed for determining the performance of and/or designing using dampeners. This is beyond the research scope and could be a future research project to develop unified test methods. 5 Approximately 31% have special details for fatigue resistance designs. These details have been surveyed in other work. NCHRP Project 10-80 relied on work by Roy et al. (2011), Stam et al. (2011), and Connor et al. (2012) for Section 11: Fatigue Design. 6 About 25% have specifications or practices for base-plate design. LRFD-LTS specifications incorporate the latest research for sizing base plates (Roy et al., 2011). 7 Little interest was indicated for fiber- reinforced composite poles. Section 8: Fiber-Reinforced Composite Design was given a lower priority (time and effort). 8 Anchor bolt failures have been observed for strength, fatigue, and corrosion. Anchor bolts were addressed with respect to strength, fatigue, and construction. 9 Approximately 71% use ACI 318 Appendix D for design of anchorages. ACI 318-11 Appendix D is suggested within the LRFD- LTS specifications [American Concrete Institute (ACI), 2011]. 10 A325 bolts are most commonly used. A325 bolts were used in all examples. 11 Hooks and straight anchor bars are used in about one-third and two-thirds of cases, respectively. Both hook and straight anchor bars are considered. 12 About 38% of the respondents have observed foundation failures. No specification action was taken in this regard. Section 13: Foundation Design provides guidance. Most departments of transportation (DOTs) use standards for drilled shafts, etc. 13 Approximately 35% used AASHTO LRFD for design, and 52% used Brom’s method. AASHTO LRFD is commonly used; appropriate references or repeated provisions are appropriate. Brom’s method was kept in the LRFD-LTS specifications. 14 Nearly 90% of respondents are satisfied with the approach of the STD-LTS, with the following notable exceptions: 20% indicated a need for change in Section 3: Loads [ASCE/SEI (Structural Engineering Institute) 7- 10 update]. 28% indicated a need for change in The LRFD-LTS specifications use the new ASCE/SEI 7-10 wind loads. Section 11 was extensively modified to include the most recent fatigue research. This work was adopted in the LTS-6. Section 11: Fatigue Design. (Several suggestions were made; the most important is incorporation of the latest research.) There were not many comments about aluminum. Section 6: Aluminum Design was updated to be consistent with the Aluminum Design Manual (Aluminum Association, 2010).

7 Table 3. Specifications reviewed. Specification Comments AASHTO STD-LTS-5 (5th edition) This was the allowable stress (standard) specification when the project started. AASHTO STD-LTS-6 (6th edition) This is the current STD-LTS (2013). These specifications incorporate recent work on fatigue resistance and fatigue loading for high-mast towers. Section 11 in STD-LTS-6 is conceptually identical to the LRFD-LTS specifications. AASHTO Bridge Construction Specifications (AASHTO LRFD, 2013) The bridge construction document was reviewed for application to LTS. It is cited in the LRFD-LTS specifications with application to fabrication and construction. AASHTO LRFD Bridge Design Specifications (BDS) (2009-2013) The LRFD-BDS were used where possible to avoid duplication and parallel maintenance in the future. There was some consideration of merging the LRFD- LTS specifications with the LRFD-BDS; however, the LRFD-LTS specifications are distinct, and users of LRFD-LTS specifications are often different from LRFD-BDS users. ACI 318-2011 Appendix D from this document is cited for use for anchorages. Again, this information is not repeated and will likely be kept current by the ACI. Precast/Prestressed Concrete Institute (PCI), 2010 Reference was reviewed for information on poles. Aluminum Association, 2010 The LRFD-LTS specifications, Section 6, parallel the aluminum design specification. This incorporates the most recent design procedures into the LTS. ASCE, 2010 The LRFD-LTS specifications directly employed the new wind hazard maps and the research on which they are based. This keeps the wind loading unified with the most used U.S. standards. AASHTO, 2009 The Manual for Assessing Safety Hardware (MASH) was reviewed for roadside safety, breakaway components, etc. MASH is cited where appropriate as it is the standard that AASHTO and FHWA are using moving forward. National Design Specification (AWC, 2012) The National Design Specification was reviewed for the LRFD approach for wood design. The LRFD-LTS specifications parallel this specification. Canadian Standards Association (CSA), 2006 The Canadian specifications were reviewed for wind load provision for the strength and fatigue limit states. The CSA uses a rigorous and theoretically based approach to luminaire poles. This is based on a generalized stiffness and mass approach to model vortex–induced vibration. This was not employed since NCHRP was engaged in research for a high-mast tower to establish the fatigue loading that accounts for transverse- and along-wind effects. The research was implemented into the LRFD-LTS specifications, Section 11: Fatigue Design. Eurocode 1: Actions on Structures – Part 1-4: General Actions – Wind Actions There was nothing that was compelling enough to change the researchers approach of being consistent with ASCE/SEI 7-10. Eurocode 3: Design of Steel Structures – Part 3-1: Towers, Masts, and Chimneys – Towers and Masts The Eurocode employs methods that are similar to CSA for mast and towers. This might be an alternate approach for AASHTO in order to address smaller luminaire poles. ASTM Standards ASTM standards are cited throughout the LRFD-LTS specifications.

8Construction Specifications were employed where applicable, in addition to the American Welding Association guide- lines for steel and aluminum. Various ASTM standards were reviewed for their applicability to the fabrication process. Specific articles are: 14.1 Scope, 14.2 Working Drawings, 14.3 Steel Structures, 14.4 Aluminum Structures, 14.5 Prestressed Concrete Structures, 14.6 Composite (Fiber-Reinforced Polymer) Structures, 14.7 Wood Structures, and 14.8 References. These articles address: • Materials, • Bolted connections, • Welded connections, • Castings, and • Fabrication (tolerances). Since this is the first edition for this section, it is expected that the community will continue to offer T-12 ideas for improvement based on best practices and new research. Construction (Section 15) The construction section is new for the LRFD-LTS and contains information that was moved from the STD-LTS resistance sections. The AASHTO LRFD Bridge Construction Specifications were employed where applicable, in addition to the American Welding Association guidelines for steel and aluminum. Specific articles are: 15.1 General 15.2 Erection 15.3 Anchor Bolts 15.4 Bolted Connections 15.5 Steel Structures 15.6 Aluminum Structures 15.7 Prestressed Concrete Structures 15.8 Composite (Fiber-Reinforced Polymer) Structures 15.9 Wood Structures 15.10 Foundations 15.11 References In part, the following items are addressed: • Primarily reference-applicable portions of the AASHTO LRFD Bridge Construction Specifications, • Current state of practice and provisions, • Proper fastener tightening and connection fit-up of end plates, and • Information to achieve a structural grout pad, if desired. Inspection and Reporting (Section 16) Section 16 was written more toward an advisory perspec- tive because current regulation does not mandate inspections of ancillary structures. Currently, FHWA has a document on the inspection of ancillary structures with a more general treatment to ensure that a consistent and proper inspec- tion is performed. Section 16 is also new to the LRFD-LTS specifications. The articles are: 16.1 Scope 16.2 Types of Inspections 16.3 Inspection Frequency 16.4 Qualifications and Responsibilities of Inspection Personnel 16.5 Safety 16.6 Planning, Scheduling, and Equipment 16.7 Inspection Forms and Reports 16.8 Elements and Element System 16.9 Procedures 16.10 References An important part of this report is the new article 16.8: Elements and Element Systems. The element set presented within includes two element types, identified as national ancillary structure elements (NASE) and ancillary structure management elements (ASME). The com- bination of these two element types makes up the AASHTO element set. All elements, whether they are NASE or ASME, have the same general requirements: • Standard number of condition states, and • Standard number of comprised condition states, such as good, fair, poor, and severe general descriptions. A detailed description of each element is located in Appen- dix D of the LRFD-LTS specifications. Table 4 illustrates one element description (steel anchor rods). Element titles and brief descriptions for NASE, ASME, and protective coatings are provided in Table 5, Table 6, and Table 8, respectively. Table 7 provides smart flags (defects), and Table 9 describes environmental factors (states). Asset Management (Section 17) Section 17 was written in an advisory manner because current regulations do not mandate management of ancil- lary structures. However, the trend is toward more formal

Element #702 Steel Anchor Rods Count National Ancillary Structure Elements Description Element defines all steel anchor rods extending from the foundation, and includes all washers and nuts. Inclusive of weathering steel. Quantity Calculation The quantity is the sum of the number of exposed steel anchor rods. Condition State Definitions Defect Condition State 1 Condition State 2 Condition State 3 Condition State 4 Corrosion None Freckled rust Section loss The condition is beyond the limits established in condition state three (3), warrants a structural review to determine the strength or serviceability of the element or ancillary structure, or both. Connections Sound Sound Isolated failures Misalignment None Present, but less than 1:20 Greater than 1:20 Cracking/Fatigue None None Cracks exist Feasible Actions Condition State 1 Condition State 2 Condition State 3 Condition State 4 Do Nothing Protect Do Nothing Protect Do Nothing Protect Repair Rehab Do Nothing Replace Rehab Elemental Commentary None Table 4. Element description. (continued on next page) Table 5. National ancillary structure elements. Element No. Title Description 701 Concrete Foundation Element defines all reinforced concrete foundations. Grout pads are not included. 702 Steel Anchor Rods Element defines all steel anchor rods extending from the foundation, and includes all washers and nuts. Inclusive of weathering steel. 703 Aluminum Anchor Rods Element defines all aluminum anchor rods extending from the foundation, and includes all washers and nuts. 704 Steel Base Plate Element defines all steel base plates connecting the columns to the anchor rods, and includes all gusset plates, their welds, and the weld from the column to the base plate. Inclusive of weathering steel. 705 Aluminum Base Plate Element defines all aluminum base plates connecting the columns to the anchor rods, and includes all gusset plates, their welds, and the weld from the column to the base plate. 706 Steel End Support Column Element defines all steel end support columns. Inclusive of weathering steel. 707 Aluminum End Support Column Element defines all aluminum end support columns. 708 Concrete End Support Column Element defines all concrete end support columns. 709 Timber End Support Column Element defines all timber end support columns. 710 Steel End Support Frame Element defines all steel end support frames, including the uprights, horizontals, and diagonals. Inclusive of weathering steel.

Table 5. (Continued). 711 Aluminum End Support Frame Element defines all aluminum end support frames, including the uprights, horizontals, and diagonals. 712 Steel High-Mast Light or Luminaire Support Column Element defines all steel high-mast light or luminaire support columns. Inclusive of weathering steel. 713 Aluminum High-Mast Light or Luminaire Support Column Element defines all aluminum high-mast light or luminaire support columns. 714 Concrete High-Mast Light or Luminaire Support Column Element defines all concrete high-mast light or luminaire support columns. 715 Fiberglass High-Mast Light or Luminaire Support Element defines all fiberglass high-mast light or luminaire supports. 716 Bolted, Welded, or Slip Joint Splice Connection for Steel End Support or High-Mast Luminaire (HML) Element defines all steel base plates (and bolts), welds, or slip-fit connections for splices located in steel end supports (or frames) or high-mast light or luminaire supports. Inclusive of weathering steel. 717 Bolted, Welded, or Slip Joint Splice Connection for Aluminum End Support or HML Element defines all aluminum base plates (and bolts), welds, or slip-fit connections for splices located in aluminum end supports (or frames) or high- mast light or luminaire supports. 718 End Support-to-Chord Connection Element defines all plates, bolts, and welds connecting support columns to chords. Inclusive of weathering steel. 719 Steel Single Chord Span Element defines all steel spans composed of single chords (mast arm). Inclusive of weathering steel. 720 Aluminum Single Chord Span Element defines all aluminum spans composed of single chords (mast arm) or braced cantilever (trombone-type) luminaire or signal support arms. 721 Steel Truss Span Element defines all steel spans composed of multiple chords with or without trussing. Inclusive of weathering steel. 722 Aluminum Truss Span Element defines all aluminum spans composed of multiple chords with or without trussing. 723 Span-Wire Assembly Element defines all span wires and connections to other span wires and to supports. 724 Steel Bridge Mount Assembly Element defines all steel assemblies mounted to bridge fascias, including all connections. Inclusive of weathering steel. 725 Aluminum Bridge Mount Assembly Element defines all aluminum assemblies mounted to bridge fascias, including all connections. 726 Bolted, Welded, or Slip Joint Splice Connection for Steel Span Element defines all steel base plates (and bolts), welds, or slip-fit connections for splices located in steel spans or luminaire arms. Inclusive of weathering steel. 727 Bolted, Welded, or Slip Joint Splice Connection for Aluminum Span Element defines all aluminum base plates (and bolts), welds, or slip-fit connections for splices located in aluminum spans or luminaire arms. Element No. Title Description Element No. Title Description 801 Sign Panel This element defines all sign panels. 802 Sign Panel Face Material Element defines the face material of all sign panels. 803 Catwalk This element defines all catwalks. 804 Handrails This element defines all catwalk handrails. 805 Luminaires/Signal Heads This element defines all luminaires and/or signal heads. 806 Electrical/Mechanical System This element defines the mechanical/electrical system. 807 Dampeners This element defines all visible dampeners. 808 Miscellaneous Attachments This element defines all equipment or devices mounted to the structure that are not covered under other elements. Table 6. Ancillary structural management elements.

11 Element No. Title Description 950 Steel Protective Coating The element is for steel elements that have a protective coating such as paint, galvanization, or another top coat steel corrosion inhibitor. 951 Concrete Protective Coating This element is for concrete elements that have a protective coating applied to them. These coatings include silane/siloxane waterproofers, crack sealers such as high molecular weight methacrylate, or any top coat barrier that protects concrete from deterioration and reinforcing steel from corrosion. Table 8. Protective coatings. Steel Cracking/Fatigue Aluminum Cracking/Fatigue Anchor Rod Standoff Impact Damage Undersized Components/Elements Grout Pads Guardrail/Protection Distortion Non-Foundation Concrete Cracking Non-Foundation Concrete Efflorescence Settlement Misalignment Steel Section Loss Steel Out-of-Place Bending Erosion Element No Title 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 . Table 7. Smart flags (defect flags). management programs to all assets: bridges, pavements, tunnels, and now ancillary structures. Several departments of transportation (DOTs) have existing inventory systems to log their inspection data, and these are beginning to be used for asset management. Section 17 articles are: 17.1 Scope 17.2 Notation 17.3 Management Organization 17.4 Components of an Ancillary Structure File 17.5 Replacement Considerations 17.6 Maintenance Program 17.7 References A similar format to that of the AASHTO Manual for Bridge Evaluation (AASHTO, 2010) was used. Article 17.5 contains a host of considerations for replacement, such as: • Structural condition, • Functionality, • Roadway improvements, and • Aesthetics. It also contains new information on estimated remaining fatigue life, assessment of dents, and unreinforced holes. Section 17 should be a reasonable beginning to the subject of asset management and should provide a basis for expan- sion and enhancement as methods and best practices evolve. Environment Description 1—Benign Neither environmental factors nor operating practices are likely to significantly change the condition of the element over time, or their effects have been mitigated by the presence of highly effective protective systems. 2—Low Environmental factors, operating practices, or both either do not adversely influence the condition of the element or their effects are substantially lessened by the application of effective protective systems. 3—Moderate Any change in the condition of the element is likely to be quite normal as measured against those environmental factors, operating practices, or both that are considered typical by the agency. 4—Severe Environmental factors, operating practices, or both contribute to the rapid decline in the condition of the element. Protective systems are not in place or are ineffective. Table 9. Environmental factors (states).