Precast Concrete Segmental Bridges Research Articles

Shear behaviour and theoretical model of large shear key dry joints in precast concrete segmental bridges using advanced monitoring

Keyed dry joints are commonly utilised in segmental bridges for shear stress transmission. The aim of this study is to explore the shear behaviour and capacity of large shear key dry joints. The considered parameters included key base height, key number and concrete strength. The key base heights were found to have a significant impact on the failure mode and shear carrying capacity. When the key base height is increased by 100%, the shear carrying capacity of the joint is increased by 156%. Digital image correlation (DIC) and distributed fibre optic sensing (DFOS) technologies revealed the characteristics of load transfer in the large shear key, validated the principle of inclined strut column and observed the changing angle of inclined column with the increase in shear key size. Moreover, due to the shear transfer at the large key teeth, there is a trend of separation in the lower contact surfaces of the joint. Based on these findings, an improved calculation method for the shear strength of large key dry joints was established. The calculation results show more accurate predictions for large key dry joints than available calculation methods developed for smaller keyed dry joints.

Experimental investigation on shear behavior of PVA-ECC keyed joints

Keyed joints play a critical role in ensuring the overall behavior of a precast concrete segmental bridges. However, these joints can exhibit poor shear capacity and durability as well as brittle failure. Polyvinyl alcohol fiber-reinforced engineered cementitious composites (PVA-ECCs) exhibit high shear strength and ductility as well as excellent fracture performance, making them attractive for use in the joints of segmental bridges. This study fabricated 16 Z-shaped specimens with number of keys (one, two, or three), concrete materials (normal concrete or PVA-ECC), and types (monolithic, epoxy, or dry) to investigate their failure modes, cracking loads, shear capacities, residual capacities, and shear stress–vertical displacement curves. The results indicated that the keyed joints exhibited shear failure at the root of a shear key, and an increase in the number of keys increased the residual strengths and ductility of both the dry and epoxy joints, but it had a negative effect on the shear strengths. When PVA-ECC was applied instead of normal concrete, the cracking resistance index for all joints improved significantly and the shear strengths and ductility of the monolithic and keyed epoxy joints increased. Generally, the shear strengths of the epoxy joints were 6.3–29.1% higher than those of the corresponding dry joints; however, the ultimate displacements of the epoxy joints were 46.6–72.4% lower. Finally, a method for calculating method of the shear capacities of keyed PVA-ECC joints was proposed and verified to accurately predict the behaviors of previously tested joint specimens.

Experimental and numerical research on the performance of cast‐in‐situ concrete wet joints in closure section in precast concrete segmental bridges under cyclic loading

AbstractThe closure section of precast concrete segmental bridges (PCSBs) usually adopts the wet joint of cast‐in‐situ concrete, the width is generally 10–20 cm, and the regular longitudinal reinforcement is discontinuous, which makes the section the vulnerable part of the bridge. To explore the mechanical property of the wet joint in the closure section of PCSB under cyclic load, six wet joint specimens are tested to investigate the influence of loading mode, interface treatment mode, setting of regular reinforcement, and prestress level. The results show that the failure modes of wet joint specimens have similar characteristics, careful roughening of joint surfaces can improve the bonding effect of the new and old concrete and delay the cracking of the specimen, the cracking load of the specimen increases by 10.3% after careful roughening. When the prestress level increases from 6 to 8 MPa and 10 MPa, the stiffness of the specimens increases obviously, and the fracture development of the specimen in the loading process is improved. The cracking load increases by 21.9% and 32.8%, the shear strength increases by 9.9% and 6.6%, respectively, but the ultimate displacement decreases by 5.6% and 11.4%, respectively. Then, the finite element model of the wet joint was established and verified, the influence of shear key, concrete strength, and wet joint width are selected for parameter analysis. It is found that stress concentration is easy to occur after shear key is set, which has adverse effects on structural flexural resistance. The shear capacity of the model decreases by 22.4% and 21.5%, respectively after the setting of single and double‐shear keys, but the stiffness of the wet joint model before cracking is improved. Compared with C50 concrete model, the ultimate bearing capacity of C60 and C70 concrete models is increased by 11.5% and 24.8%, respectively. Wet joint width has little influence on the mechanical properties of wet joints in the closure section. The research results provide references for design and construction of PCSB wet joints in practical engineering.

A machine learning based method for predicting the shear strength of Fiber-Reinforced Concrete joints in precast segmental bridges

The utilization of Fiber-reinforced concrete (FRC) in the construction of Precast segmental concrete bridges (PSCBs) is progressively increasing. The design of joints among precast members can considerably impact the overall integrity and safety of the structure. Consequently, accurately estimating the shear capacities of FRC joints has become critical for evaluating the safety of PSCBs structures. However, the effectiveness and efficiency of formulas or models intended for prediction of the shear capacities of joints with normal concrete are unknown in predicting the shear capacities of FRC joints. In this study, the machine learning (ML) algorithms are employed to predict the ultimate load of FRC joints, utilizing a database of 192 push-off test results. Three individual models (Lasso, SVM, and KNN) and three ensemble models (RF, GBDT, and XGBoost) were developed for estimating the ultimate load. The GridSearchCV technique was utilized for parameter optimization based on the training set, in conjunction with a five-fold cross-validation method. A comparative study revealed that the XGBoost ensemble model surpassed other models, with a predictive performance ranking as follows: XGBoost > GBDT > RF > KNN > SVM > Lasso. The best-performing XGBoost model achieved performance metrics of R2 = 0.964, MAE = 41.318 kN, RMSE = 56.760 kN, and MAPE = 14.228%. The superior reliability of the XGBoost ensemble model was further validated through comparisons with current design codes and existing models. As ML-based models are typically black-box models, the SHapley Additive exPlanations (SHAP) method was employed to explicitly link the predicted output to the inputs. Based on SHAP results, confining stress (CS), depth of shear key (D), compressive strength of concrete (fcu), total height of joints (H), and height of flat part (Hsm) recognized as the crucial parameters affecting ultimate load.

Shear mechanism and strength calculation of steel shear keyed dry joints in precast segmental bridges

Precast concrete segmental bridges (PCSBs) are prone to weakness at the joints. To ensure accurate positioning and effective force transmission between segments, steel shear keyed joints were designed in the present study. A comprehensive investigation was also conducted into the shear performance of such joints, drawing on existing experimental research and theoretical analysis, so as to facilitate more comprehensive understanding of the shear mechanism and calculation methods involved. The results reveal that the steel shear keyed joint effectively transmitted shear force through the contact pressure between the steel key and concrete, aided by confining pressure. The steel keyed joint was also found to possess high shear capacity and exhibit good ductility. A mechanical model of the steel shear keyed joint was constructed, and the shear mechanism and failure modes were revealed, including shear failure of the steel key, local compression failure of concrete, and tearing failure of concrete. Finally, the present authors suggest that the shear failure of the steel key should be used as the basis for the shear resistance design of steel shear keyed joints, which can be calculated according to the formula ( The strength of concrete around the steel key should also be checked.

Experimental study on the failure process of large shear key joints based on NDT methods

AbstractDry joints with keys are often used in precast concrete segmental bridges (PCSBs) to transfer shear stresses. Large dry joints with keys can often provide greater shear bearing capacity, which can meet the needs of rapid construction and simple assembly. This study focuses on the shear response of super‐sized dry joints with keys under direct shear. Various monitoring methods, including digital image correlation (DIC) and distributed optical fiber sensing (DFOS), were used to systematically study the stress process of large concrete keys. The results show that as the size of the key teeth increases, the shear bearing capacity and ultimate vertical displacement of the specimens also increase. DIC and DFOS techniques provide detailed information on key tooth failure, which is beneficial for subsequent stress analysis of shear keys.

Experimental study on oblique-shear performance of splicing joint for precast ultrahigh-performance concrete segmental bridges

This paper aims to study the effect of the normal stress on the shear performance of splicing joints for precast ultrahigh-performance concrete (UHPC) segmental bridges (PUSBs), an oblique-shear joint is designed to decompose the vertical force into a normal force and a shear force for the joint. The effect of the number, height and inclination angle of the keys on the bearing capacity of the joint is studied by 19 oblique-shear joints. Then, the bearing capacity and failure modes are analyzed significantly. The results show that the failure modes of the joints are shear failure, compression-shear failure and splitting failure, all showing primarily brittle failure. Moreover, the proportion of shear stress in the specimens increases with the increase of the inclination angle of the joint, and the shear capacity of the specimens decreases. Additionally, the shear capacity of the specimens increases with the increase of the height of the keys. After that, we derive a new formula for calculating the shear capacity utilizing Mohr’s stress circle theory and Mohr-Coulomb failure criterion, i.e., the interfacial frictional coefficient is 0.94 and the shear capacity of keys is 0.06. One may find the present formula shows a high guarantee by comparing with those from references. The formula established in this paper may be used to calculate the shear capacity of splicing joint of precast ultrahigh-performance concrete segmental bridges.

Cyclic loading test of self-centering precast segmental concrete high-speed railway bridge columns with UHPC-filled duct connections

Precast concrete high-speed railway (HSR) bridge columns are attractive for standardized HSR bridges, but their applications are rare partly due to a research gap in their lateral behavior. Traditional under-reinforced HSR bridge columns have huge lateral stiffness and poor drift capacity, which means that their prefabrication is not a simple separation-assembly process and requires special research. This study aims to develop a novel self-centering precast segmental concrete (SPSC) HSR bridge column, which is designed to have five major improvements including adopting large-diameter deformed bars as energy dissipation (ED) bars, inter-locking multi-hoops, unbonded post-tensioning (PT) tendons, a cast-in-situ ultra-high performance concrete (UHPC) layer at the bottom joint, and UHPC-filled duct connections. A 1/6 scaled cyclic loading test was conducted on three specimens to validate prefabrication feasibility and assess seismic behavior. The research results show that inter-locking multi-hoops can enable the developed bridge columns to have ductile flexural failure and a drift capacity of up to 5 %. The bridge columns have increased lateral stiffness and strength as well as decreased ductility. UHPC-filled duct connections can cause the strain amplification of ED bars at the bottom joint. The bottom joint opening dominates lateral deformation while the influence of joint sliding can be neglected. The bridge columns have good ED capacity and the equivalent hysteretic damping ratio of about 20 % at the drift ratio of 5 %. The bridge columns have the excellent self-centering capacity to control residual drift ratio in an allowable range before flexural failure. The acceptable drift ratios are suggested to be 3.5 % and 4.0 %, respectively, for the SPSC HSR bridge columns without and with PT force.

Shear behavior and construction method of steel shear keyed joints in precast segmental beams

The joints between segments represent weak points and introduce discontinuity into structures, therefore they are particularly significant in precast concrete segmental bridges. In this study, a new steel shear key was designed, and 6 full-scale tests were conducted. Various shear keys and joint types were taken as experimental parameters to study crack propagation, failure mode, shear slip, ultimate bearing capacity, and the residual bearing capacity of various joints under direct shear loading. The results show that the stiffness and shear capacity of steel shear keyed joints were higher than concrete key joints, and the structural system was more stable than concrete keyed joints at the moment of cracking. Both the concrete key and steel key epoxied joints suffered direct shear failure. However, different to the concrete epoxied joints which experienced brittle failure, steel key epoxied joints demonstrated a large residual capacity. Based on traditional segmental bridges construction, construction methods involving steel shear keyed joints included short-line match, long-line match, and modular methods are introduced. Finally, the feasibility of steel shear keyed joints construction was verified via engineering tests.

Flexural Behavior of Precast UHPC Segmental Beams with Unbonded Tendons and Epoxy Resin Joints

Precast concrete segmental bridges (PCSBs) with hybrid tendons may be the most competitive solution for achieving the advantages of rapid construction and favorable structural performance. Therefore, the flexural behavior of precast concrete segmental bridges (PCSBs) with unbonded tendons and epoxy joints was experimentally investigated in this study, and the effects of the joint types were recorded. Investigations were carried out on the ultimate loads, prestressed strand stresses, deflections, as well as failure modes, while an unbonded monolithic beam was tested for comparison. In addition, the strain measurement proved that the average strains agree with the assumption of plane section, regardless of whether the joints were set. The flexural strengths of prefabricated components were 9~15% lower than those of the monolithic beams with unbonded tendons. Meanwhile, the shape of the joints also influenced the flexural bearing capacity; the bearing capacity of the dual-tooth joint beam was 4.5% lower than that of the single-tooth one, and the bearing capacity of the flat butt joint member was 5.7% lower than that of the dual-tooth joint beam. Moreover, the experimental deflection curve and ultimate bearing capacity of the models with different shear keys showed a good correlation with the FE results. These research outcomes will aid in comprehending the roles of joints in the flexural behaviors of precast UHPC segmental bridges.

Nonlinear Analysis of External Post-Tensioning anchorage of Concrete Segment

Abstract: Precast concrete segmental bridges (PCSBs) have been the most common design technology used in the last decades. In these studies Non-linear structural performances of externally prestressed, precast concrete segmental bridges (PCSB). PCSBs with externally prestressed tendons have become very popular in construction because of economical and safety reasons, fast and practical construction, and outstanding serviceability. External tendons technique is widely used because it allows to inspect the cables and to replace them or to reinforce the tendons in case of damage while such kinds of actions are difficult to be taken in case of internal prestressing. It is widely recognized that segmental bridges have better durability, lower life-cycle costs and higher quality for maintenance than other types of bridges. However, there is lack of reliable computational model for analyzing behavior of post-tensioned PCSBs. Experimental analysis of bridge segment required more cost, time and effort for the analysis and also take cake of quality of material, cast process, curing, and testing. This research presents the results of stress and strain state of the local bearing area caused by a Prestressed cable anchor in reinforced concrete bridge segment. Nonlinear analysis of anchorage and rebar, concrete segment can be carried out by analytical solution calculated with the reference of ACI 318/19. ANSYS software is used for model and analyze the structure. The analysis process was carried out in 3 types : linear elastic analysis, nonlinear elastic analysis, and nonlinear analysis considering the destruction of concrete, and the value is compared with ANSYS software ( static structure).

Experimental study on direct shear performance of prefabricated splicing joints of ultrahigh-performance concrete

Splicing joints are the weak link of precast ultrahigh-performance concrete (UHPC) segmental bridges (PUSBs). Thus, this paper conducts direct shear tests on eight groups of UHPC keyed joints to investigate the shear performance of the interface of the key. The effects of lateral compressive stress (σn) and the number of keys on the shear performance are also examined. In addition, the load–displacement curves, failure modes, cracking loads, and ultimate loads of the specimens with different parameters are presented. After that, the direct shear capacity of the joints is theoretically analyzed based on the test results and relevant specifications, and a formula for calculating the direct shear capacity is derived. The results show that the failure mode of the UHPC keyed joints is primarily brittle failure. Moreover, the failure mode is the direct shear failure along the interface of the key when the lateral compressive stress is low; however, it is the local crushing of concrete in the key when the lateral compressive stress is high. Additionally, the direct shear capacity of the specimens increases linearly with raising the lateral compressive stress. The direct shear capacity of the double-keyed joints is 17.4–29.3 % higher than that of the single-keyed joints under the same conditions. The values calculated by specifications NF P-18 710 and Eurocode 2 2011 are lower than the experimental ones. The experimental data are evenly distributed on both sides of the curve calculated by specification JSCE 2008 when the lateral compressive stress is low, posing potential hazards in this case. The value predicted by specification AASHTO 2003 is also higher than the experimental value. Finally, we derive a formula for calculating the direct shear performance of the UHPC keyed joints utilizing Mohr’s stress circle theory, and it can be applied to engineering design with high accuracy.

Shear strength of steel fiber reinforced lightweight self-consolidating concrete joints under monotonic and cyclic loading

The shear behavior of precast concrete segmental bridges depends on the type of joints between the segments. However, there are few studies evaluating the shear strength of steel fiber reinforced lightweight self-consolidating concrete for application to precast concrete bridges. The purpose of this study is to compare the shear behavior of joints made of general concrete with developed concrete that includes lightweight aggregate and steel fiber under monotonic and cyclic loading. In this study, the push-off shear test was performed in accordance with experimental parameters of different concrete mixtures, key type, confining stress, and application of epoxy between the segments. The tests were carried out to assess the shear strength, shear behavior, crack propagation and failure mode of joints. The test results represented shear capacity of joints decreased 15.2% by replacing normal coarse aggregates with lightweight aggregates but could be enhanced through the incorporation of hooked-end steel fibers. The shear capacities of joints fabricated using developed mixture tended to be underestimated compared to analytically calculated strengths. Furthermore, the normalized stiffness of the joint was decreased with an increased number of load cycles under high-amplitude low-cycle load. The shear resistance through aggregate interlock may gradually decrease with increasing number of cycles resulting in failure at 85% of the failure load of the monotonically tested specimen. An appropriate level of confining stress and application of epoxy shall be considered to prevent sudden failure of joints at high amplitude cyclical loading conditions.

Numerical analysis of precast concrete segmental bridge decks

Precast Concrete Segmental Bridges are nowadays a well-established alternative for bridge construction that presents significative advantages related to the construction process. Numerous bridges have been built using this technology in the past decades and extensive research has been conducted, including the development of different numerical models to study their behaviour. This paper proposes a new Finite Element model for Precast Concrete Segmental Bridge decks capable of reproducing the main characteristics of their behaviour at a reduced computational cost.The model proposed has shown very good agreement with experimental results existing in the literature. After calibration, the influence of different modelling choices has been analysed. The results point out to a high impact of the modelling strategy adopted for the joints in the compression areas, requiring an adequate estimation of the point of contact between the segments. Additionally, consideration of friction of external tendons at the deviators showed limited relevance in the global behaviour of the model but was important for the correct estimation of stress increments in the tendons. Finally, considering or not the presence of epoxy at the joints did not seem to influence significantly the behaviour of the models. The use of shell elements combined with the modelling strategy adopted for the joints offers better accuracy than existing models with a significantly lower computational time.

Experimental and numerical investigations on shear performance of key tooth joints of precast concrete segmental bridge under repeated loading

• Experimental and numerical investigations are conducted on the behavior of adhesive KTJ under repeated loading. • Failure modes for epoxied KTJ specimens of different configurations under repeated loading are analyzed. • Ultimate load-bearing capacity and the stiffness of the KTJ specimen under repeated loading are significantly reduced compared to those of specimen under monotonic loading. • Effects of both reinforcement in single large key and fibers in concrete on the cyclic behavior of KTJ specimens are analyzed. • The finite element modes (FEM) of KTJ specimens under repeated loading are developed and are in good agreement with the experimental results. Precast concrete segmental bridge (PCSB) has developed rapidly because of its advantages of fast construction speed, little environmental impact, easy quality control, and low cost. The key tooth joint (KTJ) is the critical connection part of PCSB. Limited research on performance of KTJ under repeated loading is available. This study includes experimental and numerical investigations on the behavior of adhesive KTJ under repeated loading. Five scenarios of KTJ with different configurations, including geometries of keys, number of keys, reinforcement in key, and steel fibers in concrete, are included. It is found that KTJ with small keys and KTJ with a single large key present similar behavior when the contact areas are kept the same, and the behavior of the large key is stiffer. Compared to monotonic loading, the load-bearing capacity and stiffness of KTJ are significantly reduced under repeated loading due to the damage accumulation in concrete. Adding steel fibers (in concrete) can evidently enhance the ductility of KTJ and adding reinforcement (in large key) can reduce the damage accumulation effects. The developed finite element models of KTJ under repeated loading agree well with the experimental results regarding the cracking development, load–displacement behavior, and load carrying capacity.

Full-scale experimental study on shear behavior of multiple-keyed epoxy joints in precast concrete segmental bridges

Precast concrete segmental bridges (PCSBs) have become a trend in bridge industry, the joint behavior between segments is critical to the mechanical performance of PCSBs. Compared with dry joints, epoxy joints are more widely used in practical engineering, but the researches on epoxy joints are relatively few. In this paper, an experimental investigation of the shear behavior of full-scale multiple-keyed epoxy joints under direct shear are presented, considering the parameters of joint type, confining stress, epoxy thickness, and key geometry. The crack patterns and failure modes of the test specimens were obtained and the influences of the parameters on the shear capacity were discussed. The existing formulas of joint shear capacity were assessed by the test results, and a new analytical prediction model that fully considers the uneven distribution of shear stress in the shear plane was derived based on Mohr’s stress circle, which can accurately predict the shear strength of epoxy joints.

Analysis of Shear Forces and Flaxural Moment at Joints in PCI-Girder Precast Concrete Segmental Bridge (Case Study: Konaweha River Bridge, Southeast Sulawesi)

Analysis of Shear Forces and Flaxural Moment at Joints in PCI-Girder Precast Concrete Segmental Bridge (Case Study: Konaweha River Bridge, Southeast Sulawesi)

Experimental and numerical investigations on shear behavior of large keyed tooth joints

Keyed tooth joint(KTJ) is recognized as the key connection component of precast concrete segmental bridges(PCSB). In this study, the shear behavior of eight scenarios of “Z” type KTJ specimens, including different bonding types, geometries and size of the keys, and reinforcement configurations in the key, is investigated through both direct shear tests and numerical simulation, and the test results are compared with formulas in previous studies. The focus of this study is on the large KTJ (joint with a single large key), which owns the advantages of easy fabrication and configuration of internal reinforcements. Based on the load-slip curve and failure modes of the KTJ specimens under the shear, regardless of key type, the shear capacity of the epoxied KTJ is significantly larger than the dry KTJ without epoxy. With the same contact areas, the shear capacity of the large KTJ is larger than that of the KTJ with multi-small keys. The “direct shear” dominates the failure mode of the plain KTJ specimens. Adding internal reinforcements contribute to strengthening the connection at the joint and converting the dominant failure mode to the “crushing” mode. Further, finite element models(FEM) are established to analyze the shear behavior of keyed joints with different reinforcement and stirrup ratios. Compared to stirrups, adding longitudinal reinforcement is more effective in enhancing the load-bearing capacity and ductility of the reinforced large KTJ specimen under shear. Bakhoum's formula is most accurate in predicting the experimental results. From this study, it is suggested to utilize epoxied joint with the reinforced large shear key in precast concrete segmental bridges.

Shear behavior of steel keyed joints in precast concrete segmental bridges under direct shear loading

AbstractEight groups of “Z” joint specimens were designed for conducting direct shear tests on steel keyed joints. The shape, size, number and joint type of steel keys were taken as experimental parameters, and the cracking load, ultimate load, residual load, and the relationship between vertical loading force and vertical relative displacement of specimens were investigated. The results reveal that the joints relied on the mechanical occlusion between the steel keys and concrete to transmit the shear forces, the load–displacement curve of the joints had a long development course, and the joints could bear large relative displacement. The bearing capacity of steel shear keyed joints increased with the increase in diameter and material strength of the tenon. The ultimate bearing capacity of the epoxied joints with 1 and 2 steel keys were respectively 151.39%, and 69.68% higher than dry joints. Meanwhile, the epoxied joints were found to become brittle and fail in more sudden manner. After direct shear failure, the shear resistance of epoxied joints was completely provided by the steel shear key. The elastic stiffness and bearing capacity of the epoxied joints was not controlled by the number of the steel shear keys, while the dry joints were sensitive with the number of keys. By adding 1 or 2 steel shear keys to a flat joint, the ultimate bearing capacity could be increased by 3.81 and 6.06 times for dry joints, and 43% and 33% for epoxied joints, respectively.

Experimental study on shear behavior of joints in precast concrete segmental bridges

A new shear key was designed in precast segmental bridges, and 12 full-scale specimens were carried out. The types of shear keys (concrete key, steel shear key, inserted reinforcement key), joint types (dry, epoxied), and the number of shear keys (single-key, double-key represented multi-key) were taken as experimental parameters to study the crack development, failure mode, shear slip, ultimate shear capacity, and residual shear capacity of various joints under direct shear loading. The results showed that the stiffness and shear capacity of the steel shear keyed joints are higher than the concrete keyed joints, and the horizontal prestressed system is more stable than the concrete keyed joints at the moment of cracking. There is a local compressive stress concentration in the inserted reinforcement keyed joint, and the load–displacement curve has a long development course, resulting in the large shear slip when the specimen is damaged, which is not suitable as a shear key. The shear slips of steel shear keyed joints are smaller than the concrete keyed joints and inserted reinforcement keyed joints, just are 0.02 ∼ 0.03 mm. The shear capacity of the double-key is 46.66% higher than that of the single-key of steel shear key dry joint. The shear capacity of steel shear key epoxied joints is increased by 69.68%∼118.33% compared with the dry joints. The steel shear key epoxied joints are a direct shear failure, but the mechanical property is similar to the dry joints after direct shear failure, and the ratio of residual shear capacity to ultimate shear capacity is large. Steel shear key has obvious advantages based on mechanical property, simple manufacture, and convenient construction.