Eliminating Rebar Splicing in Transverse Joints of Precast Full Depth Bridge Deck Panels PDF Download
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Author: David M. Gee Publisher: ISBN: Category : Languages : en Pages : 108
Book Description
This study looks at the removal of longitudinal rebar splicing when sufficient longitudinal post-tensioning is provided for full-depth precast deck panels for simply supported bridges. Full-depth precast prestressed concrete deck panels are high quality plant produced pretensioned panels. They are often post-tensioned at the site to provide an average net compression in the joint of at least 250 psi due to effective prestress. This is to ensure adequate transfer of load as truck wheels pass over the joint. This net compression on the transverse joint is not explicitly clear by the AASHTO LRFD Bridge Design Specifications. Based on this section, it is unclear if the use of post-tensioning that provides a net compression of at least 250 psi at the joint, due to effective prestress, still requires the coupling of rebars over the transverse joint. However, in cast-in-place deck construction, no longitudinal post-tensioning is generally introduced and no transverse joint is required. It is a requirement of the ASSHTO LRFD Bridge Design Specifications that secondary reinforcement be placed continuously along the direction of traffic. Following the empirical deck design in AASHTO, two-thirds of the primary transverse reinforcement should be provided for secondary longitudinal reinforcement. The problem is observed when a number of designers insist on strictly following the code for full-depth precast deck panel designs without considering the impact of longitudinal post-tensioning and naively emulating cast-in-place practice without taking full advantage of precast concrete. Although providing secondary reinforcement for each precast panel is possible, the number of splices and the number of pockets for field splicing due to these extended bars become a significant challenge to this type of construction. By using sufficient net compression at the joint, rebar splicing can be removed. The objective of this research is to investigate the post-tensioning level required to eliminate rebar splices in transverse joints for full-depth precast deck panels. Two full scale full-depth precast deck panels were post-tensioned to multiple levels varying the net compression at the joint between 100 to 350 psi. Static tests with a point load simulating one-wheel load of the 32-kip axle multiplied by the dynamic allowance factor (1.75 for the deck joint) was applied to the panel-to-panel connection joint for various post-tensioning levels. The test results show that when a net compression of at least 300 psi is applied at the transverse joint, rebar splicing is not needed. This is supported by the lack of cracking that occurs when applying the 32-kip loading along the joint. Testing along the longitudinal joint was also conducted as a separate research topic, and some of the results are presented. The main objective of this testing was to determine the viability of using a staggered rebar joint with a minimal joint width. This was accomplished by using ultra-high-performance concrete (UHPC) and self-consolidating concrete (SCC) with steel fibers to enhance the ductility and strength of the joint. By using a joint that gives sufficient development length of the bars, which is shorter for fiber reinforced concretes, it is shown that the joint detailing is adequate for service loadings.
Author: David M. Gee Publisher: ISBN: Category : Languages : en Pages : 108
Book Description
This study looks at the removal of longitudinal rebar splicing when sufficient longitudinal post-tensioning is provided for full-depth precast deck panels for simply supported bridges. Full-depth precast prestressed concrete deck panels are high quality plant produced pretensioned panels. They are often post-tensioned at the site to provide an average net compression in the joint of at least 250 psi due to effective prestress. This is to ensure adequate transfer of load as truck wheels pass over the joint. This net compression on the transverse joint is not explicitly clear by the AASHTO LRFD Bridge Design Specifications. Based on this section, it is unclear if the use of post-tensioning that provides a net compression of at least 250 psi at the joint, due to effective prestress, still requires the coupling of rebars over the transverse joint. However, in cast-in-place deck construction, no longitudinal post-tensioning is generally introduced and no transverse joint is required. It is a requirement of the ASSHTO LRFD Bridge Design Specifications that secondary reinforcement be placed continuously along the direction of traffic. Following the empirical deck design in AASHTO, two-thirds of the primary transverse reinforcement should be provided for secondary longitudinal reinforcement. The problem is observed when a number of designers insist on strictly following the code for full-depth precast deck panel designs without considering the impact of longitudinal post-tensioning and naively emulating cast-in-place practice without taking full advantage of precast concrete. Although providing secondary reinforcement for each precast panel is possible, the number of splices and the number of pockets for field splicing due to these extended bars become a significant challenge to this type of construction. By using sufficient net compression at the joint, rebar splicing can be removed. The objective of this research is to investigate the post-tensioning level required to eliminate rebar splices in transverse joints for full-depth precast deck panels. Two full scale full-depth precast deck panels were post-tensioned to multiple levels varying the net compression at the joint between 100 to 350 psi. Static tests with a point load simulating one-wheel load of the 32-kip axle multiplied by the dynamic allowance factor (1.75 for the deck joint) was applied to the panel-to-panel connection joint for various post-tensioning levels. The test results show that when a net compression of at least 300 psi is applied at the transverse joint, rebar splicing is not needed. This is supported by the lack of cracking that occurs when applying the 32-kip loading along the joint. Testing along the longitudinal joint was also conducted as a separate research topic, and some of the results are presented. The main objective of this testing was to determine the viability of using a staggered rebar joint with a minimal joint width. This was accomplished by using ultra-high-performance concrete (UHPC) and self-consolidating concrete (SCC) with steel fibers to enhance the ductility and strength of the joint. By using a joint that gives sufficient development length of the bars, which is shorter for fiber reinforced concretes, it is shown that the joint detailing is adequate for service loadings.
Author: Mohsen A. Issa Publisher: ISBN: Category : Concrete bridges Languages : en Pages : 278
Book Description
A literature review concerning the objectives of the project was completed. A significant number of published papers, reports, etc., were examined to determine the effectiveness of full depth precast panels for bridge deck replacement. A detailed description of the experimental methodology was developed which includes design and fabrication of the panels and assembly of the bridge. The design and construction process was carried out in cooperation with the project Technical Review Panel. The major components of the bridge deck system were investigated. This includes the transverse joints and the different materials within the joint as well as composite action. The materials investigated within the joint were polymer concrete, non-shrink grout, and set-45 for the transverse joint. The transverse joints were subjected to direct shear tests, direct tension tests, and flexure tests. These tests exhibited the excellent behavior of the system in terms of strength and failure modes. Shear key tests were also conducted. The shear connection study focused on investigating the composite behavior of the system based on varying the number of shear studs within a respective pocket as well as varying the number of pockets within a respective panel. The results indicated that this shear connection is extremely efficient in rendering the system under full composite action. Finite element analysis was conducted to determine the behavior of the shear connection prior to initiation of the actual full scale tests. In addition, finite element analysis was also performed with respect to the transverse joint tests in an effort to determine the behavior of the joints prior to actual testing. The most significant phase of the project was testing a full-scale model. The bridge was assembled in accordance with the procedures developed as part of the study on full-depth precast panels and the results obtained through this research. The system proved its effectiveness in withstanding the applied loading that exceeded eight times the truck loading in addition to the maximum negative and positive moment application. Only hairline cracking was observed in the deck at the maximum applied load. Of most significance was the fact that full composite action was achieved between the precast panels and the steel supporting system, and the exceptional performance of the transverse joint between adjacent panels.
Author: Kayde Steven Roberts Publisher: ISBN: Category : Languages : en Pages : 192
Book Description
Accelerated bridge construction has quickly become the preferred method for the Utah Department of Transportation (UDOT) as well as many other DOT's across the United States. This type of construction requires the use of full depth precast panels for the construction of the bridge deck. The segmented deck panels produce transverse joints between panels and have come to be known as the weakest portion of the deck. Cracking often occurs at these joints and is reflected through the deck overlay where water accesses and begins corrosion of the reinforcement and superstructure below. For this reason post-tensioning of the deck panels is becoming a regular practice to ensure that the deck behaves more monolithically, limiting cracking. The current post-tensioning used by UDOT inhibits future replacement of single deck panels and requires that all panels be replaced once one panel is deemed defective. The new curved bolt connection provides the necessary compressive stresses across the transverse joints but makes future replacement of a single deck panel possible without replacing the entire bridge deck. To better understand the behavior of the new curved bolt connection under loadings, laboratory testing was undertaken on both the curved bolt and the current post-tensioning used by UDOT. The testing specimens included full-scale, full-depth, precast panels that were connected using both system. The testing induced typical stresses on the panels and connections, subjecting them to negative bending and shear. The overall performance of the curved bolt proved satisfactory. The moment capacity of both connections surpassed all theoretical calculations. The yield and plastic moments were 17% and 16% lower, respectively, than the UDOT post-tension system while at those moments deflection was relatively the same. Due to the anchorage location of the curved bolts, the reinforcement around the transverse joint received up to 5 times the strain of that of the post-tension connections. Although both systems performed well when subjected to shear forces and as compared to the theoretical capacities, the post-tension connection greatly surpassed the curved bolt in shear capacity.
Author: HNTB Corporation, Genesis Structures Inc, Structural Engineering Associates, and Iowa State University Publisher: Transportation Research Board ISBN: 0309274109 Category : Languages : en Pages : 976
Book Description
This report from the second Strategic Highway Research Program (SHRP 2), which is administered by the Transportation Research Board of the National Academies, documents the development of standardized approaches to designing and constructing complete bridge systems for rapid renewals.
Author: Publisher: ISBN: Category : Bridges Languages : en Pages : 75
Book Description
Precast bridge deck panels can be used in place of a cast-in-place concrete deck to reduce bridge closure times for deck replacements or new bridge construction. The panels are prefabricated at a precasting plant providing optimal casting and curing conditions, which should result in highly durable decks. Precast panels can be either full-depth or partial-depth. Partial-depth panels act as a stay-in-place form for a cast-in-place concrete topping. This study investigated only the behavior of full-depth precast panels. The research described in this report had two primary objectives. The first was to develop a performance specification for the grout that fills the haunch between the top of the beam and the bottom of the deck panel, as well as the horizontal shear connector pockets and the panel-to-panel joints. Tests were performed using standard or modified ASTM tests to determine basic material properties on eight types of grout. The grouts were also used in tests that approximated the conditions in a deck panel system. Based on these tests, requirements for shrinkage, compressive strength, and flow were established for the grouts. It was more difficult to establish a test method and an acceptable performance level for adhesion, an important property for the strength and durability of the deck panel system. The second objective was to quantify the horizontal shear strength of the connection between the deck panel and the beam prestressed concrete beams. This portion of the research also investigated innovative methods of creating the connection. Push-off tests were conducted using several types of grout and a variety of connections. These tests were used to develop equations for the horizontal shear strength of the details. Two promising alternate connections, the hidden pocket detail and the shear stud detail, were tested for constructibility and strength. The final outcome of this study a set of recommendations for the design, detailing, and construction of the connection between full-depth precast deck panels and prestressed concrete I-beams. If designed and constructed properly, the deck panel system is an excellent option when rapid bridge deck construction or replacement is required.
Author: Publisher: ISBN: Category : Bridges Languages : en Pages : 68
Book Description
Experimental tests were performed at Virginia Tech to investigate transverse panel-to-panel connections and horizontal shear connector block-outs for full-depth precast concrete bridge deck panels. The connections were designed for a deck replacement project for a rural three-span continuous steel beam bridge in Virginia. Two reinforced and four post-tensioned connections were designed and tested in cyclical loading. Each connection was tested on a full-scale, two-beam setup in negative bending with a simulated HS-20 vehicle. The block-outs for the horizontal shear connections were also scrutinized during construction and testing. Several surface treatments were investigated to determine the best strategy to limit cracking and leakage at the grout-concrete interface. The strain profile, cracking patterns, and ponding results are presented for all specimens. The reinforced connections and two post-tensioned connections with 167 psi initial stress experienced cracking and leaked water by the end of the cyclic loading regime. In two connections post-tensioned with an initial compressive stress of 340 psi, the tensile stress in the deck under full live load remained below approximately 3√(f'c). These transverse connections did not leak water, did not have full-depth cracking, and maintained a nearly linear strain distribution throughout the design life. Full-depth deck panels may be effectively used on continuous bridges if post-tensioning force is applied to the transverse connections to keep the total tensile stress (remaining prestress minus live load stress) below 3√(f'c) . The block-outs with a sand-blasted surface or an epoxy primer combined with a grout that met the requirements recommended by Scholz et al. (2007) had only slight water leakage, and had smaller cracks at the grout-concrete interface than the control samples. These surface treatments are recommended for best long-term performance.
Author: David M. Gee
Author: David M. Gee
Author: Sameh S. Badie
Author: Mohsen A. Issa
Author: Kayde Steven Roberts
Author: Scott M. Markowski
Author: Maher K. Tadros
Author: HNTB Corporation, Genesis Structures Inc, Structural Engineering Associates, and Iowa State University
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