Precast Girder Bridges Research Articles

Development of Nonproprietary Ultra-High-Performance Concrete Mixtures for Precast Bridge Girders

Development of Nonproprietary Ultra-High-Performance Concrete Mixtures for Precast Bridge Girders

Just‐in‐time scheduling problem with due windows and release dates for precast bridge girders

AbstractAs the prefabrication construction method plays an increasingly important role in the construction of cross‐sea bridges, coordinating the schedule between off‐site prefabrication and on‐site assembly becomes crucial and challenging. This paper studies a just‐in‐time single‐machine scheduling problem with due windows and release dates, which originates from the production and supply process of large segments of precast steel box girders in bridge construction. To solve this problem, we equivalently decompose it into the independent and same type of subproblems and formulate a mixed‐integer linear mathematical programming model. Furthermore, we propose a branch‐and‐bound algorithm with the initialization of a novel linear early and tardy dispatching rule with due windows to solve the problem exactly. The dispatching rule, based on the local dominance criteria with due windows, is designed and used to improve the upper bound. Moreover, a lower bound is obtained by further decomposing and relaxing the subproblems. Finally, the parameter of the dispatching rule is calibrated, and the best search strategy of the branch‐and‐bound algorithm is determined. The comprehensive computational experiments carried out show the efficiency and effectiveness of the proposed branch‐and‐bound algorithm.

Experimental and numerical study on shear behavior of shear pockets between ultra-high-performance and normal concrete for precast girder bridges

Ultra-high-performance concrete (UHPC) has been widely utilized in precast bridge girders as a new material to reduce structural self-weight and improve constructional efficiency. Typically, UHPC and normal concrete (NC) are implemented to construct precast girders and deck, respectively, and cast-in-place shear pockets are used to connect these two. However, these shear pockets are vulnerable components that affect the integrity of UHPC-NC bridge superstructure. Thus, to comprehensively and deeply investigate the shear performance of shear pockets, a push-off test on block specimens and a bending test on a scaled bridge superstructure are conducted in this study. In addition, A refined finite element model (FEM) is proposed for UHPC-NC interface, which incorporates the effects of cohesion, dowel action of reinforcement and frictional force. The accuracy of the proposed FEM is validated against experimental data. Besides, the code equations are evaluated by push-off test results. The push-off test results verify that reinforcement across the interface plays a critical role in enhancing the shear strength between UHPC and NC, and NC is a weak region for the UHPC-NC interface, which should be paid much attention when designing. The experimental and numerical results of the bending specimen indicate that NC deck and UHPC girder connected by shear pockets with shear reinforcement can satisfy the performance requirements of a bridge girder, showing satisfactory integrity for UHPC and NC members under flexure. Furthermore, design equations specified in ACI318R-19, AASHTO, MC-10 and Eurocode 4 can provide a satisfactory prediction of shear strength at UHPC-NC interface, as demonstrated by comparing with experimental results.

Anchorage length of patented wire cables in prestressed bridge girders

Abstract This paper briefly describes the methodology, performance and the obtained results of unique experiments performed on original I-73 precast bridge girders. The main objective of the experiments was to determine the actual anchorage length of corroded-through fully grouted prestressing reinforcement (prestressing wires), which is important for determination of the residual load-bearing capacity of prestressed structures. Observation probes leading all the way to the prestressing wires were drilled on selected sections of the girders along the length of the prestressing reinforcement. Optical image acquisition devices were then installed at these probes. Subsequently, controlled breakage of the patented wires (corrosion failure simulation) and observation of the changes that occurred in the prestressing wires after relief of stress were carried out. Evaluation of the experiments was then performed by analyzing the images obtained before and after the prestressing reinforcement failure.

Construction and Performance Monitoring of Innovative Ultra-High-Performance Concrete Bridge

The application of Ultra-High-Performance Concrete (UHPC) materials in rehabilitating bridges and constructing primary bridge components is increasing rapidly across the world because of their superior strength and durability characteristics when compared to regular concretes. However, there have been few new bridges constructed using UHPC materials with regular formworks, ready-mix trucks, and construction equipment. This paper presents a comprehensive report encompassing the design, construction, and performance monitoring of a new bridge constructed in Iowa using a unique UHPC technology that includes steel fibers of two different lengths embedded in the concrete. By using optimized lengths of steel fibers, both the tensile strength and the toughness were increased. The UHPC material was produced with local cement and aggregates in the US using typical ready-mix concrete equipment. This paper discusses the experience gained from the design and construction process including mix design, batching, delivery of steel fibers to the ready-mix concrete batch unit, and post-tensioning of precast slabs at the jobsite. For four years after construction, the joints of the bridge decks were monitored using strain sensors mounted on both sides of the deck joints. The strain values were quite similar between the two sides of each joint, indicating a good load transfer between precast bridge girders. A bridge was successfully constructed using a unique UHPC technology incorporating two different lengths of steel fibers and utilizing local cement and aggregates and a ready-mix truck, and has been performing satisfactorily with a good load transfer across post-tensioned precast girder joints.

Finite Element Modeling of Longitudinal Field-Cast Connections Between Precast Deck Bulb-T Bridge Girders

An alternative mix design using polypropylene fiber-reinforced high early strength concrete was proposed by the Idaho Transportation Department for the longitudinal connections between deck bulb-T precast bridge girders in accelerated bridge construction. In this paper, finite element models of the pullout behavior of headed reinforcing bars in the closure pour and bending tests of beams representing a 30 cm strip of the bridge deck were developed. The smeared crack model was used for concrete, while cohesive zone modeling showed good results in representing the interface between the closure pour and precast concrete. Steel–concrete bond-slip behavior was observed to be one of the most significant factors affecting the results. A scheme to simulate this behavior using zero-length nonlinear spring elements was designed. The finite element models were able to produce results similar to the experimental findings.

Applicability of GPR and a rebar detector to obtain rebar information of existing concrete structures

Much of Canada’s existing infrastructure was constructed during 1950s, 1960s and 1970s. These include all transportation infrastructures such as bridges, highways, tunnels, etc. It is important to know the condition of these aging infrastructures in terms of their load carrying capacity to ensure their safety and serviceability. There are several old reinforced concrete slab bridges within the network of Ministry of Forests in B.C. Canada that have unknown rebar spacing, cover and diameter. This research paper discusses the application of Ground Penetrating Radar (GPR) and a Rebar detector in obtaining valuable information about rebar diameter, spacing and cover depth required to determine the structural capacity (load rating) of bridge decks. For this, GPR and the rebar detector have been applied on an existing bridge deck, a precast bridge girder and a reinforced concrete test slab panel available in the materials lab at the Facility for Innovative Materials and Infrastructure Monitoring (FIMIM) at the University of Victoria (UVic). To assess the applicability of GPR and Profoscope (Rebar Detector) in obtaining rebar information, the results obtained using both the techniques were compared in terms of their errors in determining all three parameters of rebar; diameter, spacing and cover depth. The results were validated by measuring the actual diameter, spacing and cover depth of the rebar in the reinforced concrete test slab available in the lab at UVic.

Rollover stability of precast concrete beams supported by elastomeric bearing pads

Abstract During construction of precast girder bridges, there is the concern on rollover instability of the beams when exclusively supported by elastomeric bearing pads. This type of failure has been the focus of recent research due several accidents reported. However, these studies have not considered the nonlinear behavior of elastomeric bearing pads and the lift-off effect. Therefore, this paper presents a parametric study with a finite element model calibrated with experimental results, reported in the literature, through a nonlinear geometrical analysis and considering that concrete behaves linearly. Besides, the experimental results are compared to simplified approaches which account the pad nonlinear behavior and the lift-off effect by utilizing its secant rotational stiffness. From the results, the difference between the instability load from nonlinear geometrical analysis and experimental results was 8.7 %, and the simplified eigenvalue solution and experimental was 11.4 %, which was the best fit compared to the other existing analytical models. From the parametrical analysis, the instability load was considerably decreased by varying the initial lateral deflection, the skewed pad rotation, top flange width and the span of the beam.

Evaluation of precast bridge girder cracking: The role of volume change

Evaluation of precast bridge girder cracking: The role of volume change

Reinforced Concrete Beams and Slabs with Bonded CFRP Laminates: Strain Compatibility Paradox

Externally bonded Fibre Reinforced Polymers (FRP) Laminates have been extensively used to strengthen reinforced concrete beams and slabs in flexure. Most design codes of practice provisions assume full strain compatibility between the FRP laminates and the concrete section in order to estimate the moment re-sistance of this hybrid system. However, as shown here, strain compatibility is lost during the early stages of loading. The current design methodologies account for premature failure due to interfacial crack debonding mechanisms by limiting the strains in the FRP to low values, resulting in the use of only a small portion of the FRP laminate capacity. Experimental investigations previously performed on precast bridge girders, hollow core slabs, and beam specimens – all with CFRP laminates bonded to their soffits – highlight the loss of strain compatibility and interfacial debonding. In this paper, recommendations are presented in order to tackle both issues.

Washington State Evaluation of Performance-Based Concrete for Bridge Decks

The Washington State Department of Transportation (DOT) revamped its bridge deck concrete specifications in an effort to eliminate or reduce early-age restraint cracking in bridge decks. Restraint cracking is caused by length changes resulting from shrinkage or temperature effects that are restrained by girders and internal reinforcement and show up primarily as transverse through cracks. Bridge decks constructed with the revised concrete specification are commonly referred to as “performance-based bridge decks” because the revised specification removes prescribed requirements and adds performance criteria such as shrinkage and permeability limits. Contractors are required to submit test results to prove their concrete mix design meets the specified performance requirements. The performance-based specification was first implemented in mid 2011 and is now included in the 2014 Standard Specifications. To evaluate the effectiveness of the revised concrete specification, bridges recently constructed with the performance-based specification and the traditional specification were visually inspected for cracks. The cracking severity was used to compare the bridges and can be used to draw conclusions on the effectiveness of the revised specification to prevent or reduce early-age restraint cracking in the bridge decks. This study evaluated and documented the effectiveness of the changes made to the Washington State DOT concrete specification for bridge decks and sought to identify any improvements that could be made to the current performance-based specification. The study found that the current performance-based concrete specification resulted in fewer restraint cracks than the traditional concrete specification and worked better for precast girder bridges than for steel girder bridges.

Detailed Study of Bridges Out of Thin Walled Precast Concrete Elements

Due to the very competitive costs compared to in-situ concrete as well as to steel elements, the precise executions and the economic value, precast elements are able to not only reduce the construction period but also reduce construction costs. With these positive attributes in mind the Institute for Structural Engineering at the TU Wien decided to investigate the application of thin walled precast elements in bridge construction in order to compete with steel girders. The main goal of the research is the development of elements that are light enough to handle during transport and lift operations and at the same time stable enough to be filled with in-situ concrete resulting in a monolithic structure. To assess the durability of precast bridge girders fatigue tests were carried out. Furthermore a detailed study of the joints and the applied joint filling material was conducted resulting in a widespread comparison of various grouts.

Establishing optimal gap size for precast beam bridges with a buffer-gap-elastomeric bearings system

A partial (hybrid) seismic isolation scheme for precast girder bridges in the form of a “buffergap- elastomeric bearings” system has been endorsed in the literature as an efficient seismic design system. However, no guides exist to detail an optimal gap size for different configurations. A numerical study is established herein for different scenarios according to Euro code seismic requirements in order to develop guidelines for the selection of optimal buffer-gap arrangements for various design cases. Various schemes are hence designed for ductile and limited ductility behavior of the bridge piers for different seismic demand levels. Seven real ground records are selected to perform incremental dynamic analysis of the bridges up to failure. Bridges with typical short and high piers are studied; and different values of initial gaps at piers are also investigated varying from a zero gap (i.e., fully locked) condition up to an initial gap at piers that is three quarters the gap left at abutments. Among the main conclusions is that the as-built initial gaps at piers (and especially large gap sizes that are ≥1/2 as-built gaps at abutments) do not practically reduce the seismic design demand and do not affect the reserve capacity of the bridge against failure for bridges featuring long piers, especially when these bridges are designed a priori for ductile behavior. To the contrary, the “buffergap- elastomeric bearings” system is more effective for the bridge schemes with short piers having a large difference between the stiffness of the bearings and that of their supporting (much stiffer) squat piers, particularly for designs with limited ductility. Such effectiveness is even amplified for the case of larger initial as-built gap sizes at piers.

New Precast Bridge Girder with Combined Prestressing

Traditionally, the major part of highway bridges in Slovakia is realized using the precast concrete technology. The common Slovak precast girders are produced to the34 m length as one element. Nowadays, there is an increasing demand for more economical and resisting bridge structures with longer spans. The company Vahostav-Sk-PREFA, Ltd as the main supplier of precast elements for highwaybridge 207, in cooperation with theUniversity of Zilina and the designer company Dopravoprojekt Inc. Liptovsky Mikulas, developed a new precast girder MDP for the span 38 m with combined prestressing. Some experiences and results of verifying flexural test with numerical analysis of that girder are presented in this paper.

Connections Between Simply Supported Concrete Beams Made Continuous: Results of NCHRP Project 12-53

Precast bridge girders can be made continuous for live loads with the provision of a moment connection over the supports. NCHRP Project 12-53 examined methods for making this type of moment connection. This is usually done by placing negative moment reinforcement in a cast-in-place deck over the support and by placing a diaphragm between the girder ends. To counteract positive moments caused by creep and shrinkage, positive moment connections are often provided at the girder ends. An experimental study of the strength of six different positive moment details, involving either extended strand or extended bar, was conducted. The results showed that all details had sufficient strength. Details using additional stirrups in the diaphragm were found to have increased ductility, and the use of horizontal web bars increased capacity. Two full-size specimens were tested to determine the level of continuity after cracking occurs at the joints. One of these specimens was also monitored for several months to determine the effects of creep, shrinkage, and temperature on the connections. It was found that expansion and contraction of the deck caused by heat of hydration and changes in ambient temperature greatly affected the system. However, an anticipated formation of negative moment caused by differential shrinkage did not occur. Even when the positive moment connection was near failure, the system maintained 70% continuity even when cracked. The system was also found to have adequate negative moment capacity.

Connections between Simply Supported Concrete Beams Made Continuous

Precast bridge girders can be made continuous for live loads with the provision of a moment connection over the supports. NCHRP Project 12–53 examined methods for making this type of moment connection. This is usually done by placing negative moment reinforcement in a cast-in-place deck over the support and by placing a diaphragm between the girder ends. To counteract positive moments caused by creep and shrinkage, positive moment connections are often provided at the girder ends. An experimental study of the strength of six different positive moment details, involving either extended strand or extended bar, was conducted. The results showed that all details had sufficient strength. Details using additional stirrups in the diaphragm were found to have increased ductility, and the use of horizontal web bars increased capacity. Two full-size specimens were tested to determine the level of continuity after cracking occurs at the joints. One of these specimens was also monitored for several months to determine the effects of creep, shrinkage, and temperature on the connections. It was found that expansion and contraction of the deck caused by heat of hydration and changes in ambient temperature greatly affected the system. However, an anticipated formation of negative moment caused by differential shrinkage did not occur. Even when the positive moment connection was near failure, the system maintained 70% continuity even when cracked. The system was also found to have adequate negative moment capacity.

Contribution of Intermediate Diaphragms in Enhancing Precast Bridge Girder Performance

The objective of this study was to determine the effect of intermediate diaphragms on the stiffness of precast prestressed AASHTO type bridge girders, combined with the actual bearing stiffness and thermal changes. Some of the parameters studied include the presence of intermediate diaphragms, bridge skewness, temperature change, and an increase in bearing stiffness due to cold temperature or aging. A finite element model of a bridge superstructure containing Florida Bulb Tee 78 girders was created. This model was subjected to an HL93 truck load as suggested by the AASHTO LRFD. Results indicate that intermediate diaphragms have a modest positive effect of reducing the maximum deflections for the chosen girder, with the effect varying with skewness and thermal change.