Prestressed Concrete Box Beam Research Articles

Numerical investigation on early age performance of ultra-high-performance concrete shear keys between an adjacent prestressed concrete box beams

Adjacent precast prestressed concrete box beam bridges have been widely utilized for decades and have shown satisfactory performance. However, significant issues regarding to the longitudinal shear key cracking have been noted by bridge maintenance personnel. The cracks are typically initiated at beam-shear key interfaces due to shrinkage and temperature and propagate due to applied load. Recently, ultra-high-performance concrete (UHPC) was employed in the shear keys with the anticipation to prevent joint cracking. Although the field-collected data at early age from bridge utilizing UHPC shear keys indicated promising performance, the results only reflected the early age joint behavior at locations which were instrumented during the field test. In the current study, a 3D finite element (FE) model was developed to calculate the early age stresses due to shrinkage and temperature. The results indicated that the UHPC material associated with a specific shear key configuration created a “self-locked” phenomenon that generated compression on the upper level shear key. The early age tensile stress during the first couple of days near the end of the joint was relatively small compared to the tensile strength of UHPC material. Although the interface had sufficient capacity to resist the early age stresses, it is still a critical component and needs to be designed with sufficient capacity.

Estimation of bond strengths and design parameters for precast concrete-UHPC shear key interface in box beam bridge

Adjacent precast prestressed concrete box beam bridge is often the choice for short-to-medium span bridges. However, it has been reported that box beam bridges experienced reoccurring longitudinal cracks at beam-shear key interfaces. The interface experiences a complex stress state represented by tensile/compressive stress perpendicular to the interface and longitudinal and vertical shear stress parallel to it. In this study, small-scaled specimens were cast together with the box beams and UHPC shear keys of a real bridge and were tested using four different test methods that try to replicate the actual stress conditions. The interface experienced satisfactory bond strength under different stress scenarios even at early age. The cohesion and friction coefficients were determined based on analysis of the experimental data and can be used to estimate the interfacial bond capacity at early age of UHPC. The interfacial bond capacity of a typical bridge was also determined and compared with the stress due to design truck load. The results indicate that the early age shrinkage and thermal load on the interface is more critical compared to the effects of the truck load. When subjected to the design truck load specified by current code, only 4.9% of the bond capacity was used, while the interfacial bond strength during the early age was exceeded. This indicates that the load is not the critical factor that causes bond failure at beam-shear key interface in box beam bridges. Furthermore, the cohesion value is sufficient to resist the applied load and the shear reinforcement can be optimized in the future application of UHPC in box beam bridges. Meanwhile, the early age tensile bond strength was exceeded and therefore the use of shear reinforcement to carry the early age tensile stress is necessary to prevent cracking.

Effects of Temperature Distributions on Thermally Induced Behavior of UHPC Shear Key Connections of an Adjacent Precast Prestressed Concrete Box Beam Bridge

Effects of Temperature Distributions on Thermally Induced Behavior of UHPC Shear Key Connections of an Adjacent Precast Prestressed Concrete Box Beam Bridge

Local Stress Behavior of Post-Tensioned Prestressed Anchorage Zones in Continuous Rigid Frame Arch Railway Bridge

The concrete stress behavior and cause of cracking at the anchorage zones of top and bottom slabs of a post-tensioned prestressed concrete box beam were studied. Based on the complex stress distribution under local anchor problem for the Yichang Yangtze River Bridge, which is the longest continuous rigid frame arch railway bridge in the world, model tests were conducted. Two full-scale specimens of top and bottom slabs were fabricated and gradually loaded based on principle of equivalent stress. The goal was to analyze the longitudinal and transverse stress distributions of cross sections of specimens at various loading cases during the experiment. From the experimental results, it can be concluded that the mechanical behavior of the concrete and steel bars were in good agreement when prestressed tendons were loaded. Tensile stress of concrete in prestressed anchorage zone gradually increased and surpassed the ultimate tensile strength of concrete with the increasing load. Consequently, local longitudinal cracking was formed at the anchorage block. Some recommendations to avoid the concrete at the anchorage zone continuing to crack are summarized in this paper.

Live-Load Moment-Distribution Factors for an Adjacent Precast Prestressed Concrete Box Beam Bridge with Reinforced UHPC Shear Key Connections

Live-Load Moment-Distribution Factors for an Adjacent Precast Prestressed Concrete Box Beam Bridge with Reinforced UHPC Shear Key Connections

Long-term deflection test and theoretical analysis on cracked prestressed concrete box beams

A long-term deflection test is performed for 470 days on two simply supported prestressed concrete box beams under sustained uniform load. The deflection growth rules of the box beams under both cracked and uncracked states are studied. The measured longterm deflection of the cracked beam is 18.4% larger than that of the uncracked beam, whereas the deflection growth coefficient of the cracked beam is 65.3% that of the uncracked beam. The larger long-term deflection of the cracked beam is mainly attributed to the huge value of the instantaneous deflection caused by the crack. Then, the cracks lead to the release of concrete stress, thereby reducing the creep effect. For the uncracked beam, the influences of concrete shrinkage, creep, and prestress loss on the long-term mechanical behavior of components are considered, and then deflection is predicted using the blended method based on the age-adjusted modulus method, the prestressed equivalent load method, and the calculation method for prestress loss. Results show that the theoretical and measured values are in good agreement. For the cracked beam, the crack influence coefficient is introduced to revise its effective elastic modulus by considering the influence of cracks on the long-term deflection of the cracked beam. Then, a formula for calculating the long-term deflection of cracked beams that considers stiffness reduction for instantaneous deflection correction is proposed. The formula exhibits high precision in calculating and analyzing the long-term deflection of the cracked beam. The deviation between the calculated and measured values is within 10%.

Evaluation of Transverse Tie Rods in a 50-Year-Old Adjacent Prestressed Concrete Box Beam Bridge

AbstractAdjacent prestressed concrete box beam bridges are one of the most popular bridges in the United States for short to medium spans. Recently, there has been concern about the structural capacity of these bridges as they age and show signs of deterioration. Unfortunately, limited research has been performed on the transverse ties because they are typically used for pulling the adjacent beam together during construction. Therefore, they are typically neglected in the overall performance of the bridge. Little, if any, information is known of the behavior and contribution of the transverse ties to load transfer and the ultimate capacity after failure of the longitudinal shear key joints. Instrumenting installed transverse tie rods has not been done in the past due to difficultly in accessing the rods, and no technique has been established to perform the installation of a sensor in the tie rods. In addition, instrumenting a tie rod that has already been installed from the fascia beam would only allow th...

Aerodynamic characteristics of a trailing rail vehicles on viaduct based on still wind tunnel experiments

The aerodynamic behavior of rail vehicles subject to crosswind has become one of the hot topics to the Chinese railway community, due to the rapid expansion of the high-speed railway networks in the last decade. To investigate the aerodynamic interference between vehicle and viaduct, models of a typical simply supported 32m pre-stressed concrete box beam viaduct and CRH2 train with scale of 1:25 were tested in wind tunnel experiments. By using simultaneous pressure scanning technique, various tests combining different cases of vehicles on double tracks on the viaduct were carried out. Pressure measurements were performed on the trailing rail vehicle to avoid the three-dimensional effects of train nose. The influences of wind barrier height and porosity on the aerodynamic characteristics of the train were also addressed. The experimental results indicate that the wind pressure distribution on the trailing vehicle is almost uniform along its axial direction, while the aerodynamic influence of vehicles on different tracks (upstream and downstream tracks) is different. Moreover, the porosity and height of the wind barriers are found to require optimization for different configurations.

Shear behaviour of prestressed steel fibre concrete box-beams

Six full-scale prestressed concrete box-beams are tested to study the effects of steel fibres on the increase in shear strength of beams. Beams are cast with no traditional transverse steel reinforcement. The amount of steel fibres and shear span-to-effective depth ratio are the main variables studied. The beams are subjected to concentrated vertical loads up to their maximum shear capacity using two actuators in load and displacement control mode. During the load tests linear voltage displacement transducers (LVDTs) are used to measure displacements at several critical points on the web in the end zone of the beams. Several LVDTs are also placed under the beams at the points of loading to measure the actual total and net displacements of the beams. From the load tests it is observed that the shear capacities of the beams increase with an increase in the amount of steel fibres and decrease as the shear span-to-effective depth ratio increases.

Reliability-Based Assessment of Flexural Strength of High-Speed Rail PC Box Beam in Marine Environment

This paper examines the effect of pitting corrosion of prestressing steel strands on flexural strength of prestressed concrete (PC) beams in marine environment. A reliability-based methodology for the prediction of time to structural failure after corrosion initiation was proposed and probabilities of failure are evaluated using FORM as exampled by a high-speed rail PC box beam. The methodology presented in this paper can be used as a tool for structural engineers and asset managers to assess a corrosion-affected concrete infrastructure and make decisions with regard to its maintenance and rehabilitation.

Behaviors of segmental concrete box beams with internal tendons and external tendons under bending

Precast segmental prestressed concrete box beam bridges have become the preferred construction method for many elevated highway projects in recent years. These beams, which have internal and external tendons, are increasingly popular because the internal tendons can improve the ductility of the beam, and the external tendons are convenient for maintenance. This study experimentally investigates the behaviors of segmental concrete box beams with hybrid tendons. Three scaled specimens with different ratios of the number of internal tendons to the number of external tendons were tested in detail. The experimental results showed that the ratio had a significant effect on the load-carrying capacity, ductility and failure mode of the beams. The opening of gaps between the segments could not be avoided, and the joint nearest to the applied load was determined to be the critical joint. The assumption that a plane section remained planar under bending was suitable for a crack joint produced by the load. The stress increment rule of the external tendons and internal tendons, as well as the variation of the plain bar strain, were determined.

Forensic Examination of a Noncomposite Adjacent Precast Prestressed Concrete Box Beam Bridge

On the evening of December 27, 2005 the fascia beam supporting the east side parapet wall of the third span of the Lake View Drive Bridge failed under the action of dead load. To gain insight into the potential causes of the failure a series of forensic analyses were conducted on the beams decommissioned from the bridge. The study correlates external observations of surface condition with internal chloride profile, depth of carbonation, and existing corrosion. The forensic investigation indicated that strand cover was reduced due to the construction methods of the time. The chloride level in the concrete at the lower layer of strands was high enough that corrosion would be expected. Chloride attack was identified to have come from the leakage of water between beams from the bridge deck surface above. Based on the research findings recommendations are made for visual inspection, and guidelines are provided for condition rating of noncomposite prestressed concrete box beam bridges.

Wallkill River Arch Bridge - Precast Concrete Ensures Bridge Durability

Adjacent prestressed concrete box beams with a composite deck slab provide the superstructure of the open-spandrel Route 52 arch bridge crossing over Wallkill River, about 50 miles (80 km) northwest of New York, N.Y. To create an overall span of 225 ft (68.6 m), precast concrete components are used efficiently and economically in both the substructure and superstructure of the bridge. This article describes some of the innovative design features—including self-consolidating, high-performance concrete with a design compressive strength of 10,000 psi (69 MPa), a calcium nitrite corrosion inhibitor, and grouted splice sleeves—that are used to increase the structure’s durability. The successful completion of the Route 52 bridge demonstrates the triumph of new technologies over traditional methods of construction.

Optimum design of large span concrete filled steel tubular arch bridge based on static, stability and modal analysis

A three dimensional finite element model was established for a large span concrete filled steel tubular (CFST) arch bridge which is currently under construction. The arch rib, the spandrel columns, the prestressed concrete box beam, the cast in situ concrete plate of bridge deck, the steel box beam and the crossbeams connecting the two pieces of arch ribs, were modeled by three dimensional Timoshenko beam elements (3DTBE). The suspenders were modeled by three dimensional cable elements (3DCE). Both geometric nonlinearity and prestress effect could be included in each kind of element. At the same time a second finite element model with the same geometric and material properties excepted for the sectional dimension of arch rib was set up. Static dynamic analyses were performed to determine the corresponding characteristics of the structure. The results showed that the arch rib's axial rigidity could be determined by static analysis. The stability and vibration of this system could be separated into in plane modes, out of plane modes and coupled modes. The in plane stability and dynamic characteristics are determined by the arch rib's vertical stiffness and that of out of plane is determined by the crossbeams' stiffness and arch rib's lateral stiffness mainly. The in plane stiffness is much greater than that of out of plane for this kind of bridge . The effect of geometric nonlinearity and prestress effect on bridge behavior is insignificant.

Chloride Testing of 27-Vear-Old Prestressed Concrete Bridge Beams

This paper discusses chloride testing that was done on five 27-year-old prestressed concrete box beams, 36 in. wide x 27 in. deep (914 x 686 mm), removed from a deteriorated, 54 ft (16.5 m) span multibeam bridge in Connecticut. Limited half-cell testing was also done. Generally, samples from midwidth of the top flanges had low chloride concentrations on the side faces, probably due to water seeping through the grouted shear keys. Some concrete samples had chloride concentrations two to three times the corrosion threshhold level; many other samples had low chloride concentrations. The edge beam, which carried a cast-in-place sidewalk, had chloride concentrations above the corrosion threshold level to a depth of 8 in. (200 mm) below the top surface of the sidewalk. Several locations had chloride concentrations that increased with depth from the surface.

THE BEHAVIOUR UP TO FAILURE OF PRESTRESSED CONCRETE BOX BEAMS OF DEFOR -MABLE CROSS-SECTION SUBJECTED TO ECCENTRIC LOAD.

Keywords UNIVERSIDAD NACIONAL DE TUCUMAN ARGENTIN, HERIOT WATT UNIVERSITY BEHAVIOUR, FAILURES, PRESTRESSED, CONCRETE, BOX, BEAMS, DEFORMATION, LOADS, ECCENTRIC, TESTS, THICKNESS, WEBS, CRACKS, DIFFERENCES, PROPAGATION, BENDING, TORSION, SHEAR, DEFLECTION, ROTATION, FLEXURAL, TORSIONAL, DISTORTIONAL, STIFFNESS, STRAIN, LONGITUDINAL, TRANSVERSE, STRESS, ULTIMATE, COLLAPSE, MECHANISMS, EXPERIMENTAL, TRUSSES, SPACE, SPECIMENS, MODELS, INITIAL... Show All