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588 Recommended ABC Construction Specifications XX Special Requirements for Prefabricated Elements and Systems for Accelerated Bridge Construction Table of Contents XX.1 GENERAL XX.1.1 Description XX.1.2 Benefits XX.2 RESPONSIBILITIES XX.2.1 Design XX.2.2 Construction XX.2.3 Inspection XX.3 MATERIALS XX.3.1 Description XX.3.2 Concrete XX.3.3 Steel XX.3.4 Closure Pours XX.3.5 Grout XX.3.6 Couplers XX.4 FABRICATION XX.4.1 Qualifications of the Fabricator XX.4.2 Fabrication Plants XX.4.3 Fabrication Requirements XX.4.4 Fabrication Tolerances XX.4.5 Yard Assembly XX.5 SUBMITTALS XX.5.1 Shop Drawings XX.5.2 Assembly Plan XX.6 QUALITY ASSURANCE XX.7 HANDLING, STORING, AND TRANSPORTATION A p p e n d i x H
589 XX.8 GEOMETRY CONTROL XX.8.1 General XX.8.2 Camber and Deflection XX.8.3 Equalizing Differential Camber XX.8.4 Finishing of Bridge Deck XX.8.4.1 Diamond Grind Bridge Deck XX.8.4.2 Saw Cut Groove Texture Finish XX.9 CONNECTIONS XX.9.1 Requirements for UHPC Joints in Decks XX.9.2 Requirements for Mechanical Grouted Splices XX.9.3 Requirements for Posttensioned Connections XX 9.4 Requirements for Bolted Connections XX.10 ERECTION METHODS XX.11 ERECTION PROCEDURES XX.11.1 General Requirements for Installation of Precast Elements XX.11.2 General Procedure for Superstructure Modules XX.11.3 General Procedure for Pier Columns and Caps XX.11.4 General Procedure for Abutment Stem and Wingwalls (supported on piles)
590 xx.1 General XX.1.1 Description This specification for prefabricated elements and modular systems for Accelerated Bridge Construction (ABC) supplements the requirements of the LRFD Construction Specifica- tions. The work addressed in this section consists of manufacturing, storing, transporting, and assembling prefabricated substructure and superstructure elements and modular sys- tems, specifically intended for accelerated bridge construction applications, including decked precast prestressed girders, decked steel girder modules, abutments and wings, pier columns and caps, and precast concrete bridge barriers herein referred to as elements or modular systems in accordance with the contract plans. C XX.1.1 Commentary Accelerated Bridge Construction is a project classification in which prefabricated bridge elements and modular systems are used to accelerate bridge construction. Bridge elements that have tradi- tionally been cast-in-place or erected in pieces are either manufactured off-site and/or sub- assembled and erected as a unit to facilitate faster construction on-site and reduce related impacts to traffic. Prefabricated bridge elements for substructures typically consist of precast concrete ele- ments connected in the field to create a homogeneous unit, and superstructure modules typically consist of concrete or steel girder pairs prefabricated with composite concrete deck slabs. The fabrication of bridge elements and modular systems is performed off-site (or on-site away from traffic) under controlled conditions. Following fabrication, the bridge elements or modules are transported to the work site for rapid field installation. XX.1.2 Benefits Accelerated Bridge Construction structure types are intended to minimize field construc- tion time, simplify field construction operations and improve quality control (i.e., quality and durability of structure). Utilizing Accelerated Bridge Construction structure types can increase construction zone safety through reduced exposure time, minimize traffic impacts due to construction operations, minimize construction environmental impacts, and stream- line overall construction operations. By replacing typical cast-in-place concrete construction with factory-produced precast ele- ments (both stand-alone substructure elements and girder/deck superstructure modules), several benefits are realized. Controlled conditions associated with factory production of prefabricated bridge elements result in higher-quality precast elements with less variability. Mass production can yield significant time savings for bridges requiring similar elements. xx.2 Responsibilities XX.2.1 Design Similar to a traditional bridge project, the engineer-of-record is responsible for the final design of the bridge. As such, design of all the bridge elements and systems is the responsibil- ity of the engineer-of-record. Design of the prefabricated bridge elements should not only consider the final in-service condition (typical design condition) but should also consider construction loading, including a feasible means of construction. Special design consider- ation should therefore be given to loading, due to construction conditions such as transpor- tation, support on blocking, and unique (one-time) demands during erection. Projects designated as Accelerated Bridge Construction should include plan details cor- responding to the anticipated accelerated construction methods. Basic schematic graphics
591 illustrating the anticipated construction methods (suggested erection sequence) as well as details to facilitate the anticipated construction methods (such as lifting lugs or similar) should be provided in the details. C XX.2.1 Commentary Projects intended to utilize Accelerated Bridge Construction design concepts should be directly designated as such. Plans and special provisions shall impose construction time restrictions and mandate shortened construction schedules. To ensure consistency in receipt of construction bids, bridge type designation as Accelerated Bridge Construction should not be left solely to the con- tractor. Value engineering studies could also afford opportunities to redesign a âconventionalâ bridge type using ABC design concepts to achieve shortened construction schedules. Assurance should be provided to verify that the design assumptions and planned construction activities are consistent since the design details are highly dependent upon the assumed con- struction methods. One method to achieve this assurance would be to require (per plan or speci- fication) that the contractor submit the proposed construction methods (i.e. module picking locations, temporary support locations, etc.) to the engineer-of-record for approval prior to beginning construction. XX.2.2 Construction The contractor shall be responsible for the safe construction of the bridge. This responsibil- ity includes the design and construction of any temporary structures, falsework, or special- ized equipment required to construct the bridge. In addition, the contractor shall be responsible for producing the proposed bridge in an undamaged condition with correct geometry to industry standard with built-in dead load stresses and erection stresses which are consistent with the design assumptions. The contractor shall be responsible for performing all construction operations with appli- cable project guidelines. The contractor shall be responsible for hiring a competent engineer with the requisite qualifications to design the temporary works or complete the proposed construction engineering in accordance with his defined means and methods. The require- ment for a qualified construction engineer working on behalf of the contractor shall be clearly identified in the contract documents at the direction of the Contracting Authority and the Engineer of Record. C XX.2.2 Commentary The bid plans should be sufficiently developed with regard to construction loadings and allow- able erection stresses on elements and components as design assumptions are generally not made part of bid documents. The bid plans should also include one feasible method of erection. Such measures are needed to assure contractors will have a set of constructable plans that can built in the designated time frames specified in the contract documents at bid time. XX.2.3 Inspection The owner or the ownerâs representative is responsible for inspection of the bridge construc- tion as the owner deems appropriate. Two phases of inspection should be implemented for Accelerated Bridge Construction projects. Fabrication inspection should monitor the fabrication operations in the shop and/ or at the site casting facility to verify the quality of the physical pieces to be used in the bridge construction. Materials, quality of workmanship, shop operations, and geometry are issues that should be addressed for the fabrication inspection process. Field inspection should
592 verify that the proposed erection methods are executed in the field and that the final in-place bridge elements meet provisions per plans and special provisions. Specific contractor means- and-methods should be reviewed to ensure the contractorâs methodology conforms to the assumptions made during design and/or addresses concerns that may arise if deviating from the original design intent. xx.3 Materials XX.3.1 Description The materials used for prefabricated elements and systems, closure pours, and connections shall conform to the requirements of the LRFD Bridge Construction Specifications, the other articles in this section, and the project special provisions. XX.3.2 Concrete High Performance Concrete (HPC) for prefabricated elements shall conform to the require- ments of Section 8 of the LRFD Bridge Construction Specifications and the project special provisions. XX.3.3 Steel Structural steel, reinforcing steel, and prestressing steel for prefabricated elements shall con- form to the requirements of the LRFD Bridge Construction Specifications and the project special provisions. XX.3.4 Closure Pours High early strength Self-Consolidating Concrete (SCC) mix designs for substructure closure pours and pile pockets, as shown on the plans, shall comply with the requirements of the project special provisions. 1. A high early strength Ultra High Performance Concrete (UHPC) mix design for super- structure closure pours, as shown on the plans, shall comply with the requirements as specified below and the requirements of the project special provisions. MATERIAL Ultra High Performance Concrete (UHPC) The material shall be Ultra High Performance Concrete consisting of the following com- ponents all supplied by one manufacturer: ⢠Fine aggregate; ⢠Cementitious material; ⢠Superplasticizer; ⢠Accelerator; and ⢠Steel fibers, specifically made for steel reinforcement with a minimum tensile strength 360,000 psi (2,500 MPa). ⢠Water that is potable or free from foreign materials in amounts harmful to concrete and embedded steel. Qualification Testing. The contractor shall complete the qualification testing of the UHPC 2 months before placement of the joint. The minimum concrete compres- sive strength shall be 10,000 psi at 48 hours and 24,000 psi at 28 days. The minimum
593 flexural strength at 28 days shall be 5,000 psi. The compressive strength shall be measured by ASTM C39. Concrete flexural strength shall be according to ASTM C78. Only a concrete mix design that passes these tests may be used to form the joint. XX.3.5 Grout A structural nonshrink grout shall be applied at all pier column joints to ensure uniform bearing, as shown on the plans. Nonshrink grout shall be high-performance structural non- shrink grout that has low-permeability; quick-setting, rapid strength gain; and high-bond strength. Mix grout just prior to use according to the manufacturerâs instructions. Follow manufacturerâs recommendation for dosage of corrosion inhibitor admixture. Use struc- tural nonshrink grout that meets a minimum compressive strength of 4,000 psi within 24 hours when tested as specified in AASHTO T106. The grout shall be prepackaged, commer- cially available, and approved prior to use. XX.3.6 Couplers Where shown on the plans, use grouted splice couplers to join precast substructure elements. Provide couplers that use cementitious grout placed inside a steel casting. Use grouted splice couplers that can provide 100% of the specified minimum tensile strength of the connecting Grade 60 reinforcing bar. This equates to 90 ksi for reinforcement conforming to ASTM A615 and 80 ksi for reinforcing conforming to ASTM A706. xx.4 Fabrication XX.4.1 Qualifications of the Fabricator The elements shall be provided by a fabricator with experience in the manufacture of similar products, satisfactory to the Contracting Authority, and shall provide documen- tation demonstrating adequate staff, appropriate forms, experienced personnel, and a quality control plan. XX.4.2 Fabrication Plants All manufacturing plants/casting facilities shall satisfy the following minimum requirements: 1. Plant Casting The precast concrete manufacturing plant used for the prefabrication of prestressed con- crete elements shall be certified by the Prestressed Concrete Institute Plant Certification Program. All precast products used in the bridge system shall be fabricated by the same precast plant. The Fabricator shall submit proof of certification prior to the start of production. Certification shall be as follows: ⢠For deck panels, certification shall be category B2 or higher. For straight strand mem- bers, certification shall be category B3 or higher. For draped strand members, certifica- tion shall be in category B4. ⢠Site-casting shall conform to the Alternate Site Casting provisions listed herein and prequalified by the Engineer.
594 2. Site Casting If the contractor elects to fabricate the non-prestressed bridge elements at a temporary casting facility, the casting shall comply with the provisions listed below: A. Equipment Use equipment meeting the following requirements: 1. Casting Beds For precast concrete, use casting beds rigidly constructed and supported so that under the weight (mass) of the concrete and vertical reactions of hold-ups and hold-downs there will be no vertical deformation of the bed. 2. Forms Use forms for precast true to the dimensions as shown in the contract documents, true to line, mortar tight, and of sufficient rigidity to not sag or bulge out of shape under placement and vibration of concrete. Ensure inside surfaces are smooth and free of any projections, indentations, or offsets that might restrict differential move- ments of forms and concrete. 3. Curing a) Use a method of curing that prevents loss of moisture and maintains an internal con- crete temperature at least 40°F (4°C) during the curing period. Obtain Engineerâs approval for this method. b) When using accelerated heat curing, do so under a suitable enclosure. Use equipment and procedures that will ensure uniform control and distribution of heat and prevent local overheating. Ensure the curing process is under the direct supervision and con- trol of competent operators. c) When accelerated heat is used to obtain temperatures above 100°F, record the tem- perature of the interior of the concrete using a system capable of automatically pro- ducing a temperature record at intervals of no more than 15 minutes during the curing period. Space the systems at a minimum of one location per 100 feet of length per unit or fraction thereof, with a maximum of three locations along each line of units being cured. Ensure all units, when calibrated individually, are accurate within ±5°F (3°C). Do not artificially raise the temperature of the concrete above 100°F for a minimum of 2 hours after the units have been cast. After the 2-hour period, the temperature of the concrete may be raised to a maximum temperature of 160°F (71°C) at a rate not to exceed 25°F (15°C) per hour. Lower the temperature of the concrete at a rate not to exceed 40°F (22°C) per hour by reducing the amount of heat applied until the interior of the concrete has reached the temperature of the surrounding air. d) In all cases, cover the concrete and leave covered until curing is completed. Do not under any circumstances remove units from the casting bed until the strength require- ments are met. 4. Removal of Forms If forms are removed before the concrete has attained the strength which will permit the units to be moved, immediately replace the protection and resume curing after the forms are removed. Do not remove protection any time before the units attain the specified compressive strength when the surrounding air temperature is below 20°F (-7°C). 5. Tolerances Fabrication tolerances shall conform with Section 4.4 of these specifications.
595 6. Surface Finish Finish as surfaces which will be exposed in the finished structure as provided in Section 8.10 of the LRFD Bridge Construction Specifications. XX.4.3 Fabrication Requirements Do not place concrete in the forms until the engineer has inspected the form and has approved all materials in the precast elements and the placement of the materials in the form. Provide the Engineer a tentative casting schedule at least 2 weeks in advance to make inspection and testing arrangements. A similar notification is required for the shipment of precast elements to the job site. Obtain a minimum compressive strength of 500 psi prior to stripping the form. Mini- mum compressive strength prior to moving unit shall be 4,500 psi or as provided in the project plans or specifications. The precast elements will have a minimum cure of 14 days prior to placement. Supply test data such as slump, air voids, or unit weight for the fresh concrete and com- pressive strengths for the hardened concrete after 7, 14, and 28 days, if applicable. Finish the precast elements according to Section 8.10 of the LRFD Bridge Construction Specifications. Decked girder systems shall be supported at the bearing points during deck casting opera- tions and storage. Shored construction is not allowed. Contract Documents shall include a completed table of âanticipated deflections.â The deflection control shall be checked prior to pouring and monitored throughout the pouring process. The prefabricated superstructure span shall be preassembled to ensure a proper match between modules to the satisfaction of the Engineer before shipping to the job site. The procedure for leveling any differential camber shall be established during the preassembly and approved by the engineer. The modules shall be matched as closely as possible for cam- ber and match-marked. Dimensions shall be provided to the contractor for setting precast substructure elevations. The modules should be measured for sweep and the bearing anchor bolt locations recon- figured as needed. Anchor bolts may be cast into the precast pier cap or, at the Contractorâs option, drilled and grouted into the precast pier cap, at no additional cost to the Contracting Authority. XX.4.4 Fabrication Tolerances Fabrication tolerances shall be according to standard precast practice. PCI MNL-116 Manual for Quality Control for Plants and Production of Precast and Prestressed Con- crete Production or PCI MNL-135-00 Tolerance Manual for Precast and Prestressed Con- crete Construction shall be consulted for more detailed tolerances for precast elements. Tolerances for project-specific requirements shall be detailed in the project plans and specifications. Construct modules to the following minimum tolerances unless noted otherwise: ⢠Deck surfaces must meet a 1/8 inch in 10-foot straightedge requirement in longitudinal and transverse directions. ⢠Control of camber during fabrication is required to achieve ride quality. Differences in camber between adjacent modules shall not exceed ¼ inch at the time of erection. Estab- lish the differential camber by preassembling the modules as required herein. ⢠Ensure beam seat bearing areas are flat and perpendicular transversely to the vertical axis of the beam.
596 XX.4.5 Yard Assembly Contractor should ensure that the prefabricated elements will fit-up and align properly before shipping from the precast facility. Assembling each superstructure and substructure composed of prefabricated elements in the yard prior to shipping the elements to the proj- ect site would be a suitable way for performing such verification. If assembled in the yard, use blocking to simulate the support of the elements and the spacing between the elements. Verify the construction of all elements in compliance with all plan requirements. All con- nections shall be dry fit in the fabrication yard prior to installation of the elements at the bridge site. XX.5 Submittals The submittals requiring written approval from the Engineer are as follows: XX.5.1 Shop Drawings The Contractor shall prepare and submit shop details and all other necessary working draw- ings for approval in accordance with the requirements of project specifications. The Con- tractor shall submit six copies of the shop drawings for approval. Fabrication shall not begin until written approval of the submitted shop drawings has been received from the Engineer. Deviation from the approved shop drawings will not be permitted without written order or approval of the Engineer. Prepare shop drawings under the seal of a licensed Professional Engineer. Submit xx sets for approval 28 days before fabrication. The Shop Drawings shall include, but not necessarily be limited to, the following: ⢠Show all lifting inserts, hardware, or devices and locations on the shop drawings for engi- neerâs approval. ⢠Description of method of curing, handling, storing, transporting, and erecting the sections. ⢠Show locations and details of the lifting devices and lifting holes, including supporting calculations, type, and amount of any additional precast concrete reinforcing required for lifting. ⢠Show any leveling inserts in the deck and include the leveling procedure for modules. ⢠Show details of vertical elevation adjusting hardware. ⢠Show minimum compressive strength attained for precast concrete deck and concrete traffic rail prior to handling the modules. ⢠Show details of structural steel, shear connectors, and bearing assemblies as well as elas- tomeric bearing pads. ⢠Quantities for each section (concrete volume, reinforcing steel weight, and total section weight). Do not order materials or begin work until receiving final approval of the shop drawings. The Contracting Authority will reject any module fabricated before receiving written approval or outside of specified tolerances, subject to the review of the engineer. The Con- tractor shall be responsible for costs incurred due to faulty detailing or fabrication. XX.5.2 Assembly Plan Prepare the assembly plan under the seal of a licensed Professional Engineer. Submit xx sets for approval 28 days before fabrication.
597 The assembly plan shall include, but not necessarily be limited to, the following: ⢠A work area plan, depicting known utilities overhead and below the work area, drainage inlet structures, protective measures, etc. ⢠Details of all equipment that will be employed for the assembly of the superstructure, substructure, and approach slabs. ⢠Details of all equipment to be used to lift modules including cranes, excavators, lifting slings, sling hooks, jacks, etc. Include crane locations, operation radii, lifting calculations, etc. ⢠Computations to indicate the magnitude of stress in the prefabricated components dur- ing erection are within allowable limits and to demonstrate that all of the erection equip- ment has adequate capacity for the work to be performed. ⢠Detailed sequence of construction and a CPM schedule for all operations. Account for setting and cure time for any grouts and concrete closure pours, splice couplers, and fill of pile pockets. ⢠Methods of providing temporary support of the elements. Include methods of adjusting, bracing, and securing the element after placement. ⢠Procedures for controlling tolerance limits. ⢠Methods for leveling any differential camber between adjacent modules prior to placing closure pour. ⢠Methods of forming closure pours, fill concrete, and sealing lifting holes. ⢠Methods for curing grout, closure pour, and lifting hole concrete. ⢠Method for diamond grinding to achieve deck profile and transverse or longitudinal grooving. Method of verification of deck smoothness. ⢠A list of personnel that will be responsible for the grouting of the reinforcing splice cou- plers. Include proof of completion of two successful installations within the last 2 years. Training of new personnel within 3 months of installation by a manufacturerâs technical representative is an acceptable substitution for this experience. In this case, provide proof of training. xx.6 Quality Assurance 1. When precast members are manufactured in established casting yards, the manufacturer shall be responsible for the continuous monitoring of the quality of all materials and concrete strengths. Tests shall be performed in accordance with AASHTO or ASTM methods. The Engineer shall be allowed to observe all sampling and testing, and the results of all tests shall be made available to the engineer. 2. An owner representative will inspect the fabrication of the members for quality assur- ance. This inspection will include the examination of materials, work procedures, and the final fabricated product. At least fourteen (14) days prior to the scheduled start of casting on any member or test section, the Fabricator shall contact the owner to provide notice of the scheduled start date. The Inspector shall have the authority to reject any material or workmanship that does not meet the requirements of the contract documents. The inspector shall affix an acceptance stamp to members ready for shipment. The Inspectorâs acceptance implies that, in the opinion of the Inspector, the members were fabricated from accepted materials and processes and loaded for shipment in accordance with the contract requirements. The Inspectorâs stamp of acceptance for shipment does not imply that the members will not be rejected by the Engineer if subsequently found to be defec- tive. The Fabricator shall fully cooperate with the Inspector in the inspection of the work in progress. The Fabricator shall allow the Inspector unrestricted access to the necessary areas of the shop or site casting yard during work hours. 3. Permanently mark each module with date of fabrication, supplier identification, and module identification. Stamp markings in fresh concrete.
598 4. Prevent cracking or damage of precast components during handling and storage. 5. Replace defects and breakage of precast concrete deck and concrete traffic rail according to the following: 44 Modules that sustain concrete damage or surface defects during fabrication, handling, storage, hauling, or erection are subject to review or rejection. 44 Obtain approval before performing concrete repairs. 44 Concrete repair work must reestablish the moduleâs structural integrity, durability, and aesthetics to the satisfaction of the Engineer. 44 Determine the cause when damage occurs and take corrective action. 44 Failure to take corrective action, leading to similar repetitive damage, can be cause for rejection of the damaged module. 44 Cracks that extend to the nearest reinforcement plane and fine surface cracks that do not extend to the nearest reinforcement plane but are numerous or extensive are sub- ject to review and rejection. 6. Modules will be rejected for any of the following reasons: 44 Fabrication not in conformance with the contract documents. 44 Full-depth cracking of concrete and concrete breakage that is not repairable to 100% conformance to the actual product is cause for rejection. 44 Camber that does not meet the requirements required by the plans or shop drawings. 44 Honeycombed texture. 44 Dimensions not within the allowable tolerances specified in the contract documents. 44 Defects that indicate concrete proportioning, mixing, and molding not conforming to the contract documents. 44 Damaged ends, preventing satisfactory joints. 44 Damage during transportation, erection, or construction determined to be significant by the Engineer. 7. The plant (or fabricator) will document all test results for structural concrete. The quality control file will contain at least the following information: 44 Module identification 44 Date and time of fabrication of concrete pour 44 Concrete cylinder test results 44 Quantity of used concrete and the batch printout 44 Form-stripping date and repairs if applicable 44 Location/number of blockouts and lifting inserts 44 Temperature and moisture of curing period 44 Document lifting device details, requirements, and inserts xx.7 Handling, Storing, and Transportation 1. Damage/Cracking Prevent cracking or damage of prefabricated elements and modules during handling and storage and transportation is central to the success of an ABC project as each component is an integral part of the finished structure. Modules damaged during handling, storage, or transportation will be repaired or replaced at the Contract Authorityâs direction at no cost to the Contract Authority. The Prime Contractor will be liable for repairing or replacing the damaged modules to the satisfaction of the Engineer, irrespective of the source of the damage. The PCI New England Region Bridge Member Repair Guidelines, Report PCINER-01- BMRG, shall be used in conjunction with this specification to identify defects that may occur during the fabrication and handling of bridge elements determine the conse- quences of the defects, appropriate repair procedure if warranted and making decisions on acceptance/repair or rejection.
599 2. Precast Element Sizes The size of precast elements should be finalized by the precaster and the contractor with consideration for shipping restrictions, equipment availability, and site constraints. The final element sizes will be shown on the assembly plan. 3. Lifting Devices The design and detailing of the lifting devices is the responsibility of the fabricator. Lifting devices shall be used in a manner that does not cause damage, cracking, or torsional forces. The Contractor will provide the spacing and location of the lifting devices on the shop drawings and calculate handling stresses. Lifting devices should be placed to avoid being visible once the prefabricated ele- ment is placed or should be detailed with recessed pockets that can be patched after installation. 4. Safety The contractor shall be responsible for the safety and stability of prefabricated elements during all stages of handling, transportation, and construction. 5. Handling and Storing Beams shall be stored horizontal, in an upright position, supported at their designated bearing points. Follow Chapter 5 of the PCI Design Handbook for handling and erection bracing requirements. The angle between the top surface of the precast element and the lifting line shall not be less than sixty degrees, when measured from the top surface of the precast elements to the lifting line. If two cranes are used, the lifting lines should be vertical. Modules shall be lifted at the designated points by approved lifting devices properly attached to the module and proper hoisting procedures. The Contractor is responsible for handling stresses in the modules. The Contractor will provide the spacing and loca- tion of the lifting devices on the shop drawings and calculate handling stresses. The Con- tractor shall include all necessary precast element modifications to resist handling stresses on the shop drawings. The locations of the lifting points shall be chosen so that the antici- pated flexural tensile stress induced in the top of the structural concrete slab for the assumed support locations is no greater than the allowable stress. The Contracting Authority may institute an instrumentation program to monitor handling and erection stresses in the modules. The contractor shall provide the necessary cooperation for the instrumentation program. Storage areas shall be smooth and well compacted to prevent damage due to differen- tial settlement. Precast elements shall be stored in such a manner that adequate support is provided to prevent cracking or creep-induced deformation (sagging) during storage for long peri- ods of time. Precast elements shall be checked at least once per month to ensure that creep-induced deformation does not occur. Modules shall be protected from freezing temperatures (0°C, 32°F) for 5 days or until precast concrete attains design compressive strength detailed on the plans, whichever comes first. Do not remove protection any time before the units attain the specified com- pressive strength when the surrounding air temperature is below 20°F. Modules may be loaded on a trailer as described above. Shock-absorbing cushioning material shall be used at all bearing points during transportation. Tie-down straps shall be located at the lines of blocking only. The modules shall not be subject to damaging torsional, dynamic, or impact stresses. Care should be taken during handling, storage, and transportation to prevent cracking or damage. Units damaged by improper storage or handling shall be replaced or repaired to the satisfaction of the owner at the Contractorâs expense. Contractor will be responsible for any schedule delays due to rejected elements.
600 6. Transportation Minimum compressive strength prior to moving unit shall be 4,500 psi or as provided in the project plans or specifications. A 48-hour notice of the loading and shipping schedule shall be provided to the Con- tracting Authority. Transport modules horizontal with beams on the bottom side for support. Support the modules at approximately the same points they will be supported when installed. Material, quality, and condition after shipment will be inspected after delivery to the con- struction site, with this and any previous inspections constituting only partial acceptance. xx.8 Geometry Control XX.8.1 General Construction geometry control for differential camber, skewness, and cross slope are key to ensuring proper fit-up of prefabricated elements and systems. The contractor shall check the elevations and alignment of the structure at every stage of construction to ensure proper erection of the structure to the final grade shown on the design plans. Use vertical adjustment devices to provide grade adjustment to meet the eleva- tion tolerances shown on the substructure elevation plans. Pier columns and pier cap eleva- tions can be adjusted with shim stacks contained in the grouted joints. Girder seat elevations at the erected abutments and piers shall not deviate from the plan elevations by more than ± ¼ inch. Corrections and adjustments for grade shall be done only when approved by the engineer. Bridge cross slope up to 4 degrees can be accommodated by tilting the superstructure modules with respect to plumb. The slope of the bridge seat shall conform to the bridge cross slope. Corrections for grade by shimming or neoprene pads shall be done only when approved by the engineer. XX.8.2 Camber and Deflection Differential camber of prestressed girders can lead to dimensional problems with the con- nections. Control of camber during fabrication is required to achieve ride quality. Schedule fabrication so that camber differences between adjacent deck sections are minimized. Dif- ferences in camber between adjacent modules shall not exceed 1â8 inch at the time of erection. Establish the differential camber by preassembling the modules as required herein. XX.8.3 Equalizing Differential Camber Differential camber in prestressed girders is a common occurrence. Several steps can be taken during the fabrication and storage stages of the girder to minimize the potential for differential camber in girders that will be placed adjacent to each other in the bridge. In general, all aspects of the fabrication process should be as uniform as possible for each girder. Mix design and concrete batch quality should be carefully monitored. Cure time should not vary, which may inadvertently occur if only some of the girders are permitted an extended curing period. Location of temporary supports for girders in fabrication yard should be uniform. Exposure to sunlight should also be uniform. Estimates of girder camber should be made with the recognition that girder camber is inherently variable due to the many parameters that influence it. Allowances should therefore be made in tolerances in the project to permit a reasonable level of deviation not exceeding ¼ inch of actual camber from predicted values. Skews cause special problems with decked girders that are not present in cast-in-place systems. When the ends of the girders are skewed, the corners of the deck will have different
601 elevations because one corner is farther âupâ the camber curve than the other corner. Conse- quently, for a skewed girder, the top elevation of the deck at the obtuse corner is higher than at the acute corner. A method to eliminate the saw tooth effect is to increase the bearing elevation of each adjacent girder as you move from the acute corner of the deck to the obtuse corner. For steel composite modular systems, dead load deflections for the steel beam and dia- phragms alone and for the weight of the deck, back wall, and barriers shall be shown on the plans at every tenth point. Differences in camber between adjacent modules shall not exceed 1â8 inch at the time of erection. Establish the differential camber by preassembling the mod- ules as required herein. Equip all deck sections with leveling inserts for field adjustment or equalizing of differen- tial camber. The inserts with threaded ferrules are cast in the deck, centered over the beamâs web. A minimum tension capacity of 5,500 lb is required for the inserts. After all adjustments are complete and the deck sections are in their final position, fill all leveling insert holes with a nonshrink epoxy grout. Have available a leveling beam and suitable jacking assemblies for attachment to the level- ing inserts of adjacent beams. Adjust the deck sections to the tolerances required. More than one leveling beam may be necessary. If the prescribed adjustment tolerance between deck sections cannot be attained by use of the approved leveling system, shimming the bearings of the deck sections may be necessary. C XX.8.3 Commentary One important consideration in ABC is eliminating the differential camber between the precast girders. It is important to develop an adequate means of removing the differential camber between the girders on site. Differential camber in prefabricated elements could lead to fit-up problems and riding surface issues. If the differential camber is excessive, dead load can be applied to the high beam to bring it within the connection tolerance. LRFD Article 2.5.2.4, Rideability, requires the deck of the bridge shall be designed to permit the smooth movement of traffic. Construction tolerances, with regard to the profile of the finished deck, shall be indicated on the plans or in the specifications or special provisions. The number of deck joints shall be kept to a practical minimum. Where concrete decks without an initial overlay are used, consideration should be given to providing an additional thickness of 0.5 in. to permit correction of the deck profile by grinding and to compensate for thickness loss due to abrasion. While the application of an overlay helps overcome finite geometric tolerances, it also requires another significant critical path activity prior to opening a structure to traffic. Todayâs avail- ability of low-permeability concretes and corrosion-resistant reinforcing steels allows owners to forego the use of overlays on bridge decks. With prefabricated superstructure construction, the objective is to develop methods that achieve the final ride surface without the use of overlays. Control of cambers during fabrication and equalizing cambers or leveling in the field is intended to achieve the required ride quality. An attractive option is diamond grinding decks with sacrificial cover to obtain the desired surface profile. Such a method can be faster and more cost-effective. Accurate predictions of the deflections and camber are difficult to determine since modulus of elasticity of concrete, Ec, varies with stress and age of concrete. The effects of creep on deflections are difficult to estimate. An accuracy of 10% to 20% is often sufficient. Three methods typically employed to level girders are: Jacking â A cross beam and portable hydraulic jack are used to apply counteracting forces to the tops of girders to adjust the elevations of the girder surfaces to a level condition. Surcharging â Heavy weights are loaded onto the tops of girders to reduce differential camber. Surcharging will likely only work for minor differential camber, as the differential camber level- ing forces can be significant.
602 Crane-Assisted Leveling â A crane is used to lift one end of the girder to bring the connectors near the middle of the girder into vertical alignment with the adjacent girderâs connectors. Welds are made or clamps are installed and the crane incrementally lowers the lifted end to progres- sively bring further connectors along the longitudinal joint into vertical alignment. XX.8.4 Finishing of Bridge Deck XX.8.4.1 Diamond Grind Bridge Deck Diamond grind the bridge deck for profile improvement as required by the plans, to a maxi- mum depth of ½ inch, in conformance with the LRFD Construction Specifications. An additional thickness of ½ inch (minimum) should be incorporated in the deck to permit correction of the deck profile by grinding. Diamond grinding of the bridge deck shall not begin until the UHPC closure pour concrete has reached the specified minimum compres- sive strength of 10 ksi. XX.8.4.2 Saw Cut Groove Texture Finish Saw cut longitudinal grooves into top-of-bridge deck using a mechanical cutting device after diamond grinding. Saw cutting grooves shall conform to Section 8 of the LRFD Bridge Construction Specifications. xx.9 Connections XX.9.1 Requirements for UHPC Joints in the Deck Prior to the initial placement of the UHPC, the contractor shall arrange for an on-site meet- ing with the materials supplier representative and the Engineer. The contractorâs staff shall attend the site meeting. The objective of the meeting will be to clearly outline the procedures for mixing, transporting, finishing, and curing of the UHPC material. Mock-ups of each UHPC pour shall be performed prior to actual UHPC construction and conducted per the requirements of the special provisions and the recommendation of the materials supplier representative. The mock-up process shall be observed by the materi- als supplier representative. Forming, batching, placing, and curing shall be in accordance with the procedures recom- mended by the materials supplier and as submitted and accepted by the Materials Engineer. All the forms for UHPC shall be constructed from plywood. Use top and bottom forms for UHPC joints. Two portable batching units will be used for mixing of the UHPC. The contractor shall follow the batching sequence as specified by the materials supplier and approved by the District Materials Engineer. Each UHPC placement shall be cast using one continuous pour. No cold joints are permitted. An epoxy bonding coat shall be applied to the HPC deck interface with the UHPC joint. Surface preparation for the joint interface shall be as required in the project special provisions. The concrete in the form shall be cured according to materials supplier recommendations at minimum temperature of 60°F to attain the design strength. XX.9.2 Requirements for Mechanical Grouted Splices A template will be required for accurate mechanical splice placement during element fabri- cation and/or field cast conditions to ensure fit-up between joined elements. Placement
603 tolerances should be as recommended by the manufacturer. The grouting process should follow the manufacturerâs recommendations for materials and equipment. All connections between precast elements be dry fit in the fabrication yard prior to installation of the ele- ments at the bridge site. Grouted Splice couplerS Submit xx copies of an independent test report confirming the compliance of the coupler, for each supplied coupler size, with the following requirements: ⢠Develop 100% of the specified minimum tensile strength of the attached Grade 60 rein- forcing bar. This equates to 90 ksi bar stress for an ASTM A615 bar and 80 ksi bar stress for an ASTM A706 bar. ⢠Determine through testing the amount of time required to provide 100% of the specified minimum yield strength of the attached reinforcing bar. Use this value to develop the assembly plan timing. Submit the specification requirements for the grout, including required strength gain to develop the specified minimum yield strength of the connected reinforcing bar. XX.9.3 Requirements for Posttensioned (PT) Connections Requirements for posttensioning in the LRFD Specifications shall apply for PT connections. PT connections can be used between precast concrete elements. Common types of PT connections are between pieces in a segmental box girder bridge, in pier columns and pier caps, and in precast concrete bridge decks. PT has been combined with grouted shear keys to connect deck elements here the PT is run in the longitudinal direction on typical stringer bridges. The PT systems typically include multiple grouted strands in ducts and grouted high strength thread bars. XX.9.4 Requirements for Bolted Connections Requirements for bolted connections in LRFD Specifications shall apply for bolted connec- tions between prefabricated steel elements and modules. xx.10 erection Methods It shall be the contractorâs responsibility to employ methods and equipment which will produce satisfactory work under the site conditions encountered and project time constraints. C XX.10 Commentary Erection of bridge elements and modules may be done using land-based cranes or using special- ized equipment supported by the permanent bridge or by temporary beams. Some suggested erection methods suitable for rapid replacement applications are as follows: C XX.10.1 Conventional Erection Methods Conventional erection methods refer to the typical construction methods that are employed in most bridge construction applications. Bridge element erection is done using cranes (rubber-tire or crawler). Cranes may be land-based or barge-mounted.
604 Advantages of this type of erection method include the following: ⢠Conventional cranes are readily available for purchase or rental. ⢠Construction crews are familiar with working with conventional cranes. ⢠Conventional cranes can be used to erect bridge elements with a variety of geometric configurations. ⢠Operation is relatively simple using charts provided by the crane manufacturer which show allowable capacity for particular crane geometry and load radius. Disadvantages of this type of erection method include the following: ⢠Required crane sizes increase with increased load and pick radius. ⢠Cranes require substantial space and foundation base for operation. Positioning and oper- ation often require traffic disruptions. ⢠Access to erect structure may be challenging based on site conditions (adjacent rivers, steep grades, existing structures, or other geometric constraints, etc.) C XX.10.2 Specialized Erection Methods C XX.10.2.1 Straddle Carriers A straddle carrier is a self-propelled frame system in which the supported load is located within the central portion of the frame. Commonly used in the precast concrete industry to transport long and heavy precast beams, these commercially available rolling gantry cranes can be used in bridge construction in certain situations. For bridge superstructure erection/demolition applications, the straddle carrier would be sup- ported by either the permanent bridge or by temporary beams. Straddle carriers typically support the load and their own self-weight on two bases (either rubber-tire or crane rail) with fixed transverse dimensions between wheels. Due to heavy wheel loads, concrete bridge decks are typically insufficient to support straddle carriers at areas away from the supporting girders. As such, straddle carriers are generally limited to use in applications with parallel supporting elements (temporary beams or permanent girders). Potential advantages include eliminating the need for a crane (especially advantageous in high-elevation or over-waterway construction applications) and potentially avoiding traffic dis- ruptions on the intersected roadway. Potential disadvantages include limited availability and limited use based on fixed dimen- sions and existing bridge condition. C XX.10.2.2 Specialty Erection Trusses Specialty erection trusses can be utilized to facilitate rapid and repetitive construction opera- tions. Steel trusses are fabricated in modules which allow shipping in pieces and assembly at the work site. Following assembly, the erection trusses are positioned to support a rolling gantry crane used to erect the new prefabricated bridge elements. One type of specialty erection truss is referred to as Above Deck Driven Carrier (ADDC). Following assembly on site, these trusses are rolled into position on the existing bridge, tempo- rarily supported on blocking at the piers, and used to support the rolling gantry system. Another type of erection truss is referred to as Launched Temporary Truss Bridge (LTTB). Following assembly on site, these trusses are moved into position by launching them parallel to the bridge while support is provided on temporary falsework. These trusses are used to support the rolling gantry system. Potential advantages include eliminating the need for a crane (especially advantageous in high-elevation or over-waterway construction applications) and potentially avoiding traffic dis- ruptions on the intersected roadway.
605 Potential disadvantages include required custom design and fabrication as well as limited use based on field conditions. C XX.10.2.3 Self-Propelled Modular Transporters There are families of high-capacity, highly maneuverable transport trailers called Self-Propelled Modular Transporters (SPMTs) that are being used in ABC applications to transport and erect prefabricated elements, modular systems or complete spans. SPMTs have been particularly favored for removing the existing span moving the prefabricated superstructure from the stag- ing area to its final position. SPMTs can also be adapted to install prefabricated deck and superstructure elements and modules from above where the use of land-based cranes is not feasible. The term âmodularâ in the title describes the ability to connect the trailers in various configu- rations to form a larger transporter. The SPMTs are highly maneuverable and can be moved and rotated in all three dimensional axes. The FHWA document entitled Manual on Use of Self- Propelled Modular Transporters to Remove and Replace Bridges is recommended for more infor- mation on these machines. xx.11 erection procedures XX.11.1 General Requirements for Installation of Precast Elements and Systems 1. Dry fit adjacent precast elements in the yard prior to shipping to the site. 2. Establish working points, working lines, and benchmark elevations prior to placement of all precast elements. 3. Place precast elements in the sequence and according to the methods outlined in the assembly plan. Adjust the height of each precast element by means of leveling devices or shims. 4. Use personnel that are familiar with installation and grouting of splice couplers that have completed at least two successful projects in the last 2 years. Training of new per- sonnel within 3 months of installation by a manufacturerâs technical representative is an acceptable substitution for this experience. 5. Keep bonding surfaces free from laitance, dirt, dust, paint, grease oil, or any contami- nants other than water. 6. Follow the recommendations of the manufacturer for the installation and grouting of the couplers. XX.11.2 General Procedure for Superstructure Modules 1. Do not place modules on precast substructure until the compressive test result of the cylinders for the precast substructure connection concrete has reached the specified minimum values. 2. Survey the top elevation of the precast concrete substructures. Establish working points, working lines, and benchmark elevations prior to placement of all modules. 3. Clean bearing surface before modules are erected. 4. Lift and erect modules using lifting devices as shown on the shop drawings in confor- mance with the assembly plans. 5. Set module in the proper location. Survey the top elevation of the modules. Check for proper alignment and grade within specified tolerances. Approved shims may be used between the bearing and the girder to compensate for minor differences in elevation between modules and approach elevations. Follow match-marks.
606 6. Temporarily support, anchor, and brace all erected modules as necessary for stability and to resist wind or other loads until they are permanently secured to the structure. Support, anchor, and brace all modules as detailed in the assembly plan. 7. Differences in camber between adjacent modules shipped to the site shall not exceed the prescribed limits. If there is a differential camber, the contractor shall apply dead load to the high beam to bring it within the connection tolerance. A leveling beam can also be used to equalize camber. The leveling procedure shall be demonstrated during the preassembly process prior to shipping to the site. The assembly plan shall indicate the leveling process to be applied in the field. If a leveling beam is to be used, have available a leveling beam and suitable jacking assemblies for attachment to the leveling inserts of adjacent modules. Equip all modules with leveling inserts for field adjustment or equal- izing of differential camber. The inserts with threaded ferrules are cast in the deck, centered over the beamâs web. A minimum tension capacity of 5,500 lb is required for the inserts. 8. Saturate surface dry (SSD) all closure pour surfaces prior to connecting the modules. Apply an epoxy bonding coat as required by the project specifications. 9. Form closure pours and seal lifting holes as required by the approved assembly plan. The closure pour forms and the sealed lifting holes shall be free of any material such as oil, grease, or dirt that may prevent bonding of the joint. Apply epoxy bonding coat where required by plans or specifications. 10. Cast UHPC closure pours and fill lifting holes with UHPC as shown on the plans. Cure closure pours and lifting holes. 11. Remaining concrete defects and holes for inserts shall be repaired as required by the Engineer. 12. Do not apply superimposed dead loads or construction live loads to the prefabricated superstructure until the compressive test result of the cylinders for the UHPC closure pour concrete has reached the specified minimum compressive strength of 10 ksi. XX.11.3 General Procedure for Pier Columns and Caps 1. Lift the precast element as shown in the assembly plan using lifting devices as shown on the shop drawings. 2. Survey the elevation of the completed structure directly below the element. Provide shims to bring the bottom of the element to the required elevation. 3. Set the element in the proper horizontal location. Check for proper horizontal and ver- tical alignment within specified tolerances. Remove and adjust the shims and reset the element if it is not within tolerance. 4. Check the grouted splice couplers between adjacent elements that will support com- mon precast elements in future stages of construction. Set the element and install the couplers once the connection geometry is established and checked. 5. Install temporary bracing if specified in the assembly plan. 6. Allow the grout in the coupler to cure until the coupler can resist 100% of the specified minimum yield strength of the bar prior to removal of bracing and proceeding with installation of elements above the element. XX.11.4 General Procedure for Abutment Stem and Wingwalls (supported on piles) 1. Lift abutment stem precast element or wingwall precast element as shown in the assem- bly plan using lifting devices as shown on the shop drawings. 2. Set the precast element in the proper horizontal location. Check for proper alignment within specified tolerances.
607 3. Adjust the devices prior to full release from the crane if vertical leveling devices are used. This will reduce the amount of torque required to turn the bolts in the leveling devices. Check for proper grade within specified tolerances. 4. Place high early strength self-consolidating concrete around pile tops as shown on the plans. Allow concrete to flow partially under the precast element. The entire underside of the precast element need not be filled with concrete. 5. Do not remove the installation bolts (if used) or proceed with the installation of addi- tional precast elements above until the compressive test result of the cylinders for the pile connection concrete has reached the specified minimum values.
