Search Results (14)

Integral abutment bridges (IABs) eliminate deck joints by rigidly connecting the superstructure to the abutments, reducing maintenance costs but introducing thermal restraint forces. When only one abutment is made integral, all thermally induced longitudinal movement concentrates at the remaining non-integral end, overloading bearings and concrete elements not designed for this condition. This paper investigates IAB behavior and evaluates two repair options for two, three-span continuous steel bridges on Interstate 635 in Kansas City, Kansas, which sustained progressive abutment damage following a unilateral integral conversion in 2005. A 2D finite element model was developed in LARSA 4D, incorporating composite superstructure elements, shell element abutments, beam element piles, and soil-structure interaction via distributed lateral springs. The model was analyzed under dead, live, braking, and thermal load combinations in accordance with AASHTO LRFD. Full integral conversion generates thermal restraint moments of approximately 813.5 kN-m (600 kip-ft) at the abutments, and pile stresses of 383.9 MPa (55.68 ksi) under Service I and 497.4 MPa (72.14 ksi) under Strength I combinations, both exceeding allowable limits. Elastomeric bearing pads at the non-integral abutment satisfied all stress limits without foundation modification and are recommended as a practical repair strategy for bridges in similar conditions. Full article

Traditional expansion joints in bridge structures are prone to durability problems, such as leakage, corrosion, and high maintenance demands, which can significantly reduce service life. To overcome these limitations, ultra-high-performance concrete (UHPC) link slabs have emerged as an effective jointless solution; however, their mechanical performance and sensitivity to key design and modeling parameters are not yet fully understood. This study presents a nonlinear finite element investigation of UHPC link slabs using the Concrete Damaged Plasticity (CDP) model in ABAQUS. A baseline model, validated against the experimental results, was established with a link slab length of 1100 mm and representative material and detailing properties. A systematic sensitivity analysis was then performed by varying five geometrical parameters (link slab length and thickness, debonding length, reinforcement diameter, and reinforcement spacing) and five numerical/material parameters (non-debonding and debonding interface friction coefficient, UHPC and normal concrete compressive strength, and steel yield strength). For each case, the load–displacement response was examined through initial stiffness (K₀), yield and peak load–deformation values (P_y, Δ_y and P_u, Δ_u), and ductility ratio (μ). The results highlight the dominant role of reinforcement detailing; larger bar diameters and closer spacing substantially increased stiffness and strength while maintaining ductility. Debonding length emerged as a critical tuning parameter, with longer debonding improving ductility but slightly reducing strength. Slab thickness primarily influenced stiffness, whereas overall length showed minor effects on peak capacity. On the numerical side, steel yield strength proved to be the most influential input, affecting all response measures, while the non-debonding interface friction coefficient strongly governed yield capacity. Variations in the debonding friction coefficient, UHPC compressive strength, and normal concrete strength exhibited secondary influence within the tested ranges. Overall, the findings provide practical guidance for both the designing and detailing of UHPC link slabs and the calibration of FEM (finite element modeling) models. By clarifying which parameters most strongly govern stiffness, strength, and ductility, this study supports more reliable structural design and efficient numerical modeling of UHPC link slabs in accelerated bridge construction applications. Full article

In high-speed railways, the reliability of jointless track circuits largely hinges on the operational integrity of compensation capacitors. These capacitors are periodically installed along the track to mitigate rail inductive impedance and stabilize signal transmission. The induced voltage response, referred to as the compensation-capacitor signal, serves as a critical diagnostic indicator of circuit health. Yet it is often distorted by electromagnetic interference and structural resonance, posing significant challenges for robust feature extraction. To address this challenge, we propose a Disturbance-Robust Feature Distillation (DRFD) framework that performs multi-perspective modeling and validation of robust features. The framework formulates a unified multi-objective optimization model that jointly considers statistical significance, environmental stability, and structural separability. These objectives are harmonized through an adaptive Bayesian weighting mechanism, enabling automatic identification of disturbance-resistant and discriminative features under complex operating conditions. Experimental evaluations on real-world datasets collected at a 100 kHz sampling rate from roadbed, tunnel, and bridge environments demonstrate that the DRFD framework achieves 96.2% accuracy and 95.4% F1-score, outperforming the best-performing baseline by 4.2–7.8% in accuracy and 6.5% in F1-score. Moreover, the framework achieves the lowest cross-condition relative variance (RV < 0.015), confirming its high robustness against electromagnetic and structural disturbances. The extracted core features—Root Mean Square (RMS), Peak Factor (PF), and Center Frequency (CF)—faithfully capture the intrinsic electromagnetic behaviors of compensation capacitors, thus linking statistical robustness with physical interpretability for enhanced reliability assessment of railway signal systems. Full article

This paper proposes a steel-ECC ordinary concrete composite continuous bridge deck structure to address the cracking problem of simply supported beam bridge deck continuity. Through theoretical and experimental research, a high-performance ECC material was developed. The ECC material has a compressive strength of 57.58 MPa, a tensile strain capacity of 4.44%, and significantly enhanced bending deformation ability. Bonding tests showed that the bond strength of the ECC-reinforcing bar interface reaches 22.84 MPa when the anchorage length is 5d, and the splitting strength of the ECC-concrete interface is 3.58 MPa after 4–5 mm chipping treatment, with clear water moistening being the optimal interface treatment method. Full-scale tests indicated that under 1.5 times the design load, the crack width of the ECC bridge deck continuity structure is ≤0.12 mm, the maximum deflection is only 5.345 mm, and the interface slip is reduced by 42%, achieving a unified control of multiple cracks and coordinated deformation. The research results provide a new material system and interface design standards for seamless bridge design. Full article

Thousands of multi-span, simply supported beam bridges with short or medium spans have been built in China. They often suffer from problems of cracks in the link slabs over piers, and the deterioration and damage of deck expansion joints at abutments. To address these problems, one approach is to retrofit them by converting the simply supported box beams into continuous structures over the piers and jointless bridges over the abutments. This paper discusses the design methodology and details for retrofitting the Jinpu Bridge in Zhangzhou, Fujian, China, from a simply supported bridge into a semi-integral bridge, in which semi-fixed dowel joints are used to connect the superstructure and the substructure, including piers and abutments. Simultaneously, the finite element software is used to calculate the internal forces and displacements of the structure. The analysis reveals an 11.1% reduction in the maximum positive moment at the midspan of the main beam in the semi-integral bridge compared to the simply supported bridge. However, the shear forces at the interior pier increase by 6.4%. According to the response spectrum analysis, the maximum longitudinal displacement of the semi-integral bridge’s main beam is 11.6 mm, reduced by 80.1% compared to the simply supported bridge under a dead load and earthquake effects. The maximum bending moment and shear force on the pier of the semi-integral bridge are 984.7 kN·m and 312.6 kN, respectively, both below their ultimate bearing capacities. The maximum displacement at the top of the pier is 7.7 mm, which is below the allowable 52.4 mm displacement. The calculated results conform to the design requirements specified by the code. Full article

In jointless bridges, a grade flat approach slab (GFAS) with the same elevation as the pavement can transfer the girder’s longitudinal deformation to the backfill. However, any cracks and settlement of the pavement usually occur at the end of the GFAS. To address this shortcoming, the buried flat approach slab (BFAS) horizontally embedded at a depth in the backfill was proposed. The complicated flat approach slab–soil interaction (FASSI) of the BFAS has not been systemically investigated. To address this gap, the influence of the FASSI on the mechanical performance of the approach slab and the backfill deformation was investigated in this research to understand the mechanism of the FASSI in absorbing one part of the girder’s longitudinal deformation and transferring the rest to the soil. Experimental tests on the FASSI with different embedded depths under longitudinal displacements were conducted. Numerical parametric analyses were carried out by considering the embedded depths and slab lengths as the parameters based on a finite element model verified using the test results. The results show that load–displacement curves of the FASSI comprise three stages: the elastic stage (approach slab’s displacement was absorbed by sand), the elastoplastic stage (sand deformation was observed), and the failure stage (overall shear failure of the sand was found). The longitudinal displacement transfer mode and vertical deformation distribution mode of the sand were affected by the embedded depth and slab length. With an increase in the embedded depth or a decrease in the slab length, the sand deformation decreases, which is beneficial for avoiding pavement crack risks and improving the pavement evenness. Finally, a simplified calculation formula that can be used to predict the load–displacement curves of the FASSI was proposed. This research provides the theoretical basis for the design and construction of the flat approach slab in jointless bridges. Full article

The cracking of link slabs in jointless bridges presents significant challenges due to the complexity of their stress conditions. This study focused on analyzing the transverse stresses in link slabs of jointless steel–concrete composite bridges. Utilizing linear elasticity theory and partial differential equations of plates, the deflection and stress distribution functions for the link slabs were determined. The validity of these analytical solutions was confirmed through comparisons with finite element models and load tests. Results from both the load tests and the finite element model indicate that the upper face of the girder end link slabs experiences maximum tensile stresses in both transverse and longitudinal directions. The stress values obtained from the analytical method align well with these results, showing that the total stress, when considering transverse stresses, reaches 107% of the longitudinal stresses alone. Furthermore, a 40% reduction in longitudinal girder spacing or a 50% increase in girder end length can lead to link slab stresses of 128% and 145% of the longitudinal stresses, respectively. This finding suggests that even loads lower than those designed based solely on longitudinal stresses can result in cracking. Therefore, it is recommended that transverse stresses be considered in the design of link slabs for jointless bridges. Relying solely on conventional longitudinal stress analyses may underestimate actual stress conditions and contribute to the formation of cracks. Full article

Past research has shown that as skewed bridges change temperature, additional lateral movement or forces will occur along with the elongation of the bridge. Even though past research has documented this behavior, lateral movements of semi-integral bridge superstructure associated with temperature effects on bridge skewness have not been well predicted. In this study, the seasonal movements of a 24-year-old semi-integral bridge caused by temperature effects with skewed abutment have been investigated by conducting a series of field measurements on bridges subjected to various environmental climates. The measured data showed that as the bridge heated up, the superstructure tended to move toward the acute corner of the bridge, and the bridge would contract towards its obtuse corner with a negative temperature change. During warm weather, the cracks on the end diaphragm tended to open with a positive temperature change and close with a negative temperature change, which was much more predictable than the cold weather behavior. This behavior confirms that even though the bridge moves linearly with temperature, the end diaphragm response to the temperature depends on the season. Movement of the bridge superstructure from temperature change has caused cracks in the end diaphragm, which are now propagating to the deck. These cracks could damage the bridge enough that it would require repair work in the future. The evidence in this study will help provide a complete picture of seasonal jointless bridge behavior so future semi-integral bridges can be made safer and more efficient. Full article

Water leakage and debris accumulation caused by the expansion joints in a bridge superstructure reduce the service life of the bridge and increase the maintenance costs. A link slab is an effective means to eliminate the expansion joints, providing a continuous deck system. However, the load-caused concrete cracking of the link slab also leads to problems associated with water leakage and rebar corrosion. In order to solve these problems, a new type of steel–concrete composite link slab (SCC-LS) was designed to continuously subject the bridge deck to a positive bending moment and surface concrete compression, which reduced the cracking damage in the link slab. This paper presents the mechanical performance results of the SCC-LS obtained using full-scale model tests. Furthermore, theoretical calculations and finite element (FE) models of the jointless bridge validated the performance based on the experimental results. The results of this study show that the SCC-LS can effectively solve the problem of concrete cracking on the surface of the bridge deck, which has theoretical reference significance and engineering application value for the structural design, maintenance and transformation of continuous simply supported bridge decks and the promotion of seamless bridges. Full article

The semi-fixed dowel joint studied in this paper consists of a steel dowel with rubber sleeves and a rubber pad to connect the superstructure and the substructure and to support the main beam. This type of joint is suitably used in retrofitting a jointed bridge with high-stiffness substructure into a semi-integral bridge. This study aimed to investigate the nonlinear stiffness of the joint, which is the key parameter in the retrofitting design. Taking the real joint in a retrofitted semi-integral bridge as a prototype, tests on full-scale models were carried out, in which the wall thickness of the rubber sleeve and the thickness of the rubber pad were taken as parameters. The test results show that the wall thickness of the rubber sleeve is the main factor affecting the radial stiffness and the flexural stiffness of the semi-fixed dowel joint. With the decrease of the wall thickness of the rubber sleeve, the radial stiffness decreases while the flexural stiffness increases. However, the thickness of the rubber pad has little influence on both the radial and flexural stiffness of the joint, and its main role is only vertical loading-bearing. If the longitudinal deformation of the main beam of a bridge under maximum temperature variation is 10 mm as the allowance value of engineering design, the wall thickness of the rubber sleeve for this joint should not be less than 40 mm. At last, on the basis of experimental research and theoretical analysis, the formulas of radial stiffness and flexural stiffness are fitted; it can be used as reference for practical engineering application, or for formulation of relevant specifications. Full article

The flexural pile foundation is used in integral abutment jointless bridges (IAJBs) in practical engineering to effectively dissipate the horizontal reciprocating deformation induced by the ambient temperature or earthquake loadings. Various types of flexural piles including the H-shaped steel pile (HP), prestressed concrete pile (PC), prestressed high-strength concrete pile (PHC) as well as the reinforcement concrete pile (RC) have been implemented in IAJBs. However, there is a lack of comprehensive studies on the flexural deformation and seismic performances of these piles. In order to investigate and compare their mechanical behaviors and seismic performances, a low-cycle pseudo-static test on several different types of piles was carried out. The test results indicated that the plastic hinge location of piles moved to a deeper pile depth with the increase of reinforcement ratio, buried pile depth and prestressing level, which led to better pile–soil interaction. The crack resistance of a concrete pile was improved as the reinforcement ratio and prestressing level increased. Moreover, the rectangular pile had a better soil–pile interaction and energy dissipation capacity than the circular pile. The inflection point of the pile deformation shifted deeper as reinforcement ratio, buried pile depth and prestressing level increased, which improved the effective length and horizontal deformation capacity of piles. The H-shaped steel pile showed a better elastic-plastic deformation capacity, ductility and energy dissipation capacity as compared to the concrete pile. Moreover, the pile having a higher bearing ratio sustained larger lateral loads whereas the surrounding soil was subjected to higher loads. Finally, new seismic design criteria of three-stage seismic fortification and five damage level for the concrete piles of IAJBs were proposed. Full article

Soil-abutment or soil-pile interactions under cyclic static loads have been widely studied in integral abutment jointless bridges (IAJBs). However, the IAJB has the combinational interaction of soil-abutment and soil-pile, and the soil-abutment-pile interaction is lack of comprehensively study. Therefore, a reciprocating low-cycle pseudo-static test was carried out under an cyclic horizontal displacement load (DL) to gain insight into the mechanical behavior of the soil-abutment-pile system. Test results indicate that the earth pressure of backfill behind abutment has the ratcheting effect, which induced a large earth pressure. The soil-abutment-pile system has a favorable energy dissipation capacity and seismic behavior with relatively large equivalent viscous damping. The accumulative horizontal deformation in pile will be occurred by the effect of abutment and unbalance soil pressure of backfill. The test shows that the maximum horizontal deformation of pile occurs in the pile depth of 1.0b~3.0b of pile body rather than at the pile head due to the accumulative deformation of pile, which is significantly different from those of previous test results of soil-pile interaction. The time-history curve for abutment is relatively symmetrical and its accumulative deformation is small. However, the time-history curve of pile is asymmetrical and its accumulative deformation is dramatically large. The traditional theory of deformation applies only to the calculation of noncumulative deformation of pile, and the influence of accumulative deformation should be considered in practical engineering. A significant difference of inclinations in the positive and negative directions increases when the displacement load is relatively large. The rotation of abutment when bridge expands is larger than that when bridge contracts due to earth pressure of backfill. Full article

The pile foundations below approach slab in a semi-integral abutment jointless bridge (SAJB) that requires high flexibility to accommodate the horizontal cyclic deformation of approach slab generated by the girder’s thermal expansion and contraction as well as earthquake action. In this paper, reactive powder concrete (RPC) and reinforce concrete (RC) micro piles were designed and fabricated. The shaking table tests on dynamic response of micro piles-soil interaction were conducted to investigate the dynamic response characteristics such as the strain time history of pile-soil system, the bending moment, and the deformation of piles. The maximum strain response of piles was observed at the buried depth of 4.2 D (D is the diameter of pile). Meanwhile, the maximum bending moments of RPC and RC piles appear at the depth of 0.64 D and 0.42 D, respectively, under the dynamic load excitation, and the peak horizontal deformation of piles were observed at pile head. It is found that the bending moment and the strain response of the RPC pile are larger than that of the RC micro pile, and increased by 40% and 98%, respectively. The RPC micro pile has better crack resistance, higher ductility, and flexural rigidity than that of the RC pile, and it can be widely used as pile foundations in SAJBs for the earthquake area. Full article

The long length and complex service load form conflicts with the low limits of longitudinal and transverse displacements of jointless bridge design. The longitudinal displacements of the Nanjing Dashengguan Yangtze River Bridge, a jointless steel-truss arch railway bridge, and its girder end reliability are investigated in this article. The time–frequency characteristics of the longitudinal displacements of bearings and expansion joints are analyzed using the empirical wavelet transform. The long-term characteristics of the longitudinal displacements of bearings and expansion joints in the operation period are explored. Furthermore, the relative transverse displacements of the bridge girder end are calculated using longitudinal displacement monitoring data. The mechanical behaviors of the expansion device under relative transverse displacements are studied. The reliability of expansion devices and crossing trains under the effects of relative transverse displacements is studied using kernel density estimation. The main results demonstrate that: (1) The longitudinal displacements of bearings and expansion joints are mainly influenced by environmental temperature. (2) The maximum relative transverse displacement of the expansion joint is close to 1 mm in long-term bridge operation, with the transverse rail deflection at the expansion device approaching 1 mm, which reduces the stability of cross high-speed trains. Full article