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3Problem Statement Highway construction projects have considerable impact on the public. The most apparent consequences are increased travel times in congested work zones and a degradation in traffic safety. Field assembly of prefabricated bridge systems offers one means of significantly reducing construction time. Bridge elements that can be made of precast portland cement concrete include girders, deck panels, pier columns, pier caps, abutments, and railing systems. Previous research led to the use of posttensioning and overlays as means of providing connection durability and ride quality (1-6). Issues that have been addressed include panel fabrication and placement tolerances, shear connec- tions, vertical alignment, final grade adjustment, drainage, and parapet connections. A significant body of data is avail- able for development of a guide specification for the design, fabrication, and construction of posttensioned and overlaid full-depth, precast concrete bridge deck systems. Develop- ment of a full-depth precast concrete bridge deck panel sys- tem that did not require a cast-in-place (CIP) overlay and that had a ride quality suitable for high-speed traffic would be a significant step toward a totally prefabricated bridge construction system. Elimination of deck panel system post- tensioning would also mean fewer traffic delays and less reliance on specialty subcontractors. Objective and Scope of the Research The objectives of this project were to develop (a) recom- mended guidelines for the design, fabrication, and construction of full-depth precast concrete bridge deck panel systems with- out the use of posttensioning or overlays and (b) connection details for new deck panel systems. To accomplish those objec- tives, six tasks were performed. Task 1âRelevant literature on bridge projects built with full- depth precast concrete panel systems was collected, reviewed, and summarized. Information on issues related to these sys- tems, such as grouting materials, shear key details, and connec- tions between precast panels and superstructure, was collected and studied. In addition, relevant practice and other informa- tion related to the design, fabrication, and installation of full- depth precast concrete bridge deck panel systems was collected and studied. Task 2âA survey was prepared and sent to bridge engi- neers in departments of transportation (DOTs) in the United States and Canada, as well as consulting firms, precast con- crete producers, and members of the Precast/Prestressed Concrete Institute (PCI) Committee on Bridges and the TRB Concrete Bridges Committee. Task 3âConnection details for full-depth precast concrete deck systems, which can be used with steel and prestressed concrete girders, were developed and evaluated experimentally. These details satisfy the following conditions: high durability, fast construction time, good ride quality, and high structural performance. The focus centered on deck systems that needed no longitudinal posttensioning or overlay. The connection details (panel to panel and panel to superstructure) were used to develop two precast deck systems. The first system is trans- versely pretensioned, and the second system is conventionally reinforced. Both systems are conventionally reinforced in the longitudinal direction, and neither uses an overlay. Task 4âA detailed experimental research plan, which in- cluded pullout specimens, push-off specimens, a full-scale bridge specimen, and two full-scale beam specimens, was developed and conducted to evaluate the structural perfor- mance, capacity, and constructability of the connection details. Task 5âGuidelines for the design, detailing, fabrication, and construction of full-depth precast concrete bridge deck panel systems were developed. Task 6âSpecification language and commentary neces- sary to implement full-depth precast concrete bridge deck panel systems were developed for the AASHTO LRFD Bridge Design Specifications (7). C H A P T E R 1 Introduction
Research Approach Various types of full-depth precast concrete bridge panel systems have been developed and used during the past 50 years. The majority of these systems use longitudinal post- tensioning and overlays. Longitudinal posttensioning is typically used to put the panel to panel connection in compression to prevent water leakage and to provide the longitudinal reinforcement re- quired for distribution of live loads. Posttensioning may, however, increase the cost of the deck construction, especially if it means bringing in a qualified subcontractor. Also, a lack of practical quality control procedures related to splicing and grouting the posttensioning ducts may lead to corrosion of the longitudinal posttensioning reinforcement, which could jeopardize its functionality. Because of these concerns, many DOTs have stopped using full-depth precast concrete deck panel systems on bridges. Overlays on precast concrete deck systems provide added corrosion protection of the deck reinforcement and hide any differences in color between the precast panels and the grouted areas, such as the shear pockets and panel-to-panel joints. Overlays also provide a smooth riding surface. Adding an overlay, however, slows construction time and raises costs. To encourage bridge designers to use precast concrete deck systems, this project took the following approach: 1. The connection details and the proposed systems satisfy the following conditions: ⢠They do not use longitudinal posttensioning. ⢠They do not use any proprietary products. ⢠The precast panels can be fabricated off the construc- tion site or at a precast yard. ⢠The grouted areas are minimized and kept as hidden as possible. ⢠No overlay is required. 2. Guidelines for design, detailing, fabrication, and installa- tion were developed. 3. Specification language for the AASHTO LRFD Bridge Design Specifications was developed (7). Organization of the Report Chapter 1 provides the introduction and research approach and describes the problem statement and research objectives. Chapter 2 summarizes the findings of the literature review and the national survey related to full-depth precast concrete bridge deck systems, panel to panel and panel to superstruc- ture connection details, and the grouting materials used with these systems. Chapter 3 provides (a) details of two proposed full-depth precast concrete deck panel systems, where new details of panel to panel and panel to girder connections were developed and used; (b) details of the experimental program used to test for the structural performance and constructability of the developed connection details; (c) design, fabrication, and installation guidelines; and (d) language for the AASHTO LRFD Bridge Design Specifications related to design, fabrication, and installa- tion of full-depth precast concrete deck systems (7, 8). Chapter 4 summarizes the significant conclusions of this project and provides suggestions for future research. The appendices are not published herein but are available on the TRB website (http://www.trb.org/TRBNet/Project Display.asp?ProjectID=354). Appendix A provides a sum- mary of the information collected from the national survey and literature review. Appendix B provides the design calcu- lations of the proposed full-depth precast concrete bridge deck system CD-1. Appendix C provides proposed guidelines for design, detailing, fabrication, and installation of full-depth precast concrete bridge deck panels. Appendix D provides proposed revisions to Section 9 of the AASHTO LRFD Bridge Design Specifications. Appendix E provides information on the specifications of selected commercial grout material. Appen- dix F provides information on the finite element analysis con- ducted for the new panel to girder connection details. Applicability of the Results to Highway Practice The project was structured to provide design and details that can be directly implemented on highway bridges de- signed in accordance with the AASHTO LRFD specifications. The design, fabrication, and installation guidelines presented in Chapter 3 and in Appendix C of this report can be used by designers in various steps of project design, such as prelimi- nary and final design, production shop detailing, production and installation, and quality control. Several items presented in Chapter 3 of this report are intended for possible inclusion in the AASHTO LRFD Bridge Design Specifications. 4
