In recent years, ship-bridge collisions have occurred frequently, significantly increasing the risk of damage to bridge substructures. To evaluate the safety performance of the damaged double-column pier and determine the optimal reinforcement scheme, the ship collision accident involving Xietang Bridge was used as the engineering case study. Several feasible reinforcement measures were proposed, and the impact resistance of each scheme was compared using finite element simulations. The results show that, among the two impact conditions with different loading states, the peak impact force under the fully loaded condition is 2.68 MN, and the residual displacement on the impacted side of the pile cap is approximately 291 mm, indicating that a collision with a fully loaded standard cargo vessel is the most likely cause of the actual accident. Under the same impact conditions, compared with the unreinforced pier, the pier strengthened using the section-enlargement scheme has a 47.7% higher peak impact force and provides the greatest improvement in the impact resistance of the bridge with double-column piers. The impact angle has a greater influence on the impact duration and the dynamic response of the bridge, thus increasing the risk of overall bridge collapse. This study provides a reference for ship-collision assessment and reinforcement design of bridges with double-column piers.

Ultra-high performance concrete containing different coarse aggregates(UHPC-CA) is highly efficient in suppressing material shrinkage, optimizing some mechanical properties, and saving economic efficiency by mixing an appropriate amount of coarse aggregates into Ultra-high performance concrete (UHPC). Concrete structures are at risk of fire, and investigating the dynamic mechanical properties of concrete after high-temperature is significant for comprehensively assessing the post-fire structural safety of concrete. In this study, two types of Ultra-high performance concrete were selected as the research objects: one without coarse aggregate, referred to as UHPC, and the other with coarse aggregate, referred to as UHPC-CA, five different temperature levels were set, and a Split Hopkinson Pressure Bar (SHPB) apparatus was employed to investigate the dynamic compressive properties of the materials. Thus, the failure mode and mechanical characteristics of UHPC and UHPC-CA were obtained. At a fixed strain rate, the dynamic compressive strength initially increased with temperature, reaching a maximum at 200 degrees C and then decreasing at higher temperatures. After exposure to 800 degrees C, as the strain rate increased, the dynamic compressive strength of UHPC and UHPC-CA decreased by 24.8 %-35.7 % and 30.5 %-37.2 % respectively; The dynamic increase factor (DIF) for UHPC and UHPC-CA is approximately linearly increased; after exceeding 200 degrees C, the temperature has a pronounced weakening effect on strength of UHPC and UHPC-CA; After 600 degrees C, both UHPC and UHPC-CA exhibit a marked increase in their DIF; Through SEM scanning, the microscopic characteristics of concrete are obtained, and the mechanism of high temperature and strain rate on the mechanical properties of UHPC and UHPC-CA is revealed in combination with the results of mechanical properties. According to the ZWT model, the constitutive model taking the effect of temperature on UHPC-CA is proposed, with the values from the constitutive model having good consistency with the experiments.

This study focuses on a novel three-span hybrid continuous beam bridge, analyzing the force performance and key design parameters of the non-cellular post-support plate joint. A finite element model and parametric analysis were used to reveal the stress distribution patterns, the load-bearing characteristics of the connectors, and the load transfer path under negative bending moments. The study shows that the axial force within the joint is equitably shared among three load paths: the top slab concrete (20.7%), the bearing plate (40.1%), and the shear connectors (39.2%). Although interfacial friction contributes approximately 27.1% to the total shear resistance, it is conservatively recommended to neglect this effect in design due to inherent uncertainties. Parametric analysis reveals distinct marginal effects and efficiency thresholds: increasing the bearing plate thickness from 20 mm to 100 mm results in a mere 1.0 MPa reduction in the peak concrete stress, while extending the joint length beyond 1.0 times the beam height renders the central connectors ineffective. Furthermore, reducing the connector stiffness effectively lowers the non-uniformity coefficient from 2.3 to below 2.0. Notably, the first row of web PBLs carries 34.8% to 47.2% of the total shear force, with a stable non-uniformity coefficient of 1.05–1.06, establishing it as the critical control section for simplified design. These findings provide a theoretical basis and practical guidance for the design of similar joints in hybrid girder bridges.

Vehicle-induced quasi-static responses can support in-service assessment of continuous girder bridges; however, natural traffic makes it difficult to separate structural response patterns from traffic-load intensity. This study developed a support-reaction framework for extracting mechanically interpretable indicators from uncontrolled traffic. A resultant-reaction equivalent-beam model was established, and the time-mean reaction was derived under linear-elastic and statistically steady traffic assumptions. The derivation factorizes the response into normalized reaction time mean (NRTM), representing the influence-line-controlled support-reaction distribution, and statistical steady-state equivalent uniform line load (STEUL), representing average traffic-load intensity. Simulations driven by measured traffic statistics verified the conditional factorization. Higher vehicle arrival rates shorten convergence windows; vehicle-statistics and bridge-length analyses show that the terminal NRTM remains insensitive to traffic-load statistics, whereas the terminal STEUL changes with traffic-load intensity. Diurnal, noise-drift, and damage simulations further show that NRTM can be tracked with stability-selected windows, is insensitive to zero-mean white noise, and is sensitive to equivalent stiffness reductions. The framework provides a mechanics-based route for long-term support-reaction monitoring and preliminary damage screening under natural traffic.

This study investigates the seismic and axial performance of prefabricated concrete columns reinforced with a novel comb-shape transverse reinforcement. Unlike traditional closed-loop transverse reinforcements, the comb-shape transverse reinforcement features an open-ended configuration designed to enhance constructability in precast applications. A comprehensive experimental program was conducted, including axial compression tests on eleven column specimens with varying transverse reinforcement parameters and quasi-static cyclic tests on two full-scale prefabricated bridge piers. Results show that comb-shape transverse reinforcements, especially when penetrating the entire section, significantly improve both axial load capacity and ductility. A modified stress–strain model is proposed to account for the unique confinement behavior of comb-transverse reinforcement-confined concrete, showing strong correlation with test data. Furthermore, numerical simulations using OpenSees effectively replicate experimental responses, validating the applicability of the proposed model. The findings demonstrate that comb-shape transverse reinforcements offer both structural and construction advantages, making them a promising solution for enhancing the seismic resilience of prefabricated bridge piers.

A large number of built small and medium-span bridges in China are facing the problem of increasingly degrading structural performance. Therefore, it is of great significance to carry out lightweight intelligent monitoring and realize damage identification and early warning, so as to ensure the safe operation of these bridges. For typical small and medium-span simply supported beam bridges, a damage analysis method based on measured dynamic deflection data was established by combining the influence line theory and mechanical constitutive equations. Furthermore, based on the high-precision monitoring algorithm and instruments of digital image correlation (DIC), the real-time dynamic deflection data of the bridges were obtained. It is shown that typical defects such as sectional stiffness degradation, hinge joint damage and failure, and support performance degradation are effectively identified. The results were applied to the digital transformation project of an overpass in Shanghai, which verifies the effectiveness of the dynamic deflection DIC optical measurement technology and the damage identification method and indicates that the proposed method has good value in popularization and application.

The high temperature from the fire can significantly deteriorate the mechanical properties of concrete, and the cooling process after extinguishing the fire will further change the internal crack evolution and dynamic response of the concrete. Therefore, understanding the dynamic response of concrete after high temperature is crucial for evaluating and analyzing the safety of concrete structures after a fire. This paper takes ordinary concrete as the research object and uses two cooling methods after high temperature: natural cooling and water immersion cooling. Static tensile tests, separated Hopkinson pressure bar (SHPB) dynamic tensile tests, and numerical simulation studies are carried out. The coupled influence of temperature, cooling method, and strain rate on the dynamic splitting tensile performance of concrete is systematically analyzed. The results show that as the temperature increases, the dynamic tensile strength and elastic modulus of concrete generally decrease. When the strain rate is 3.5 s−1, the dynamic tensile strength decreases from 9.54 MPa at room temperature to 3.85 and 4.23 MPa after 600 ℃. Under the same temperature and cooling method conditions, as the strain rate increases, the dynamic tensile strength of concrete significantly increases, and the rate effect is more obvious as the temperature increases. The cooling method has a significant impact on the strength degradation pattern. The maximum increase in dynamic tensile strength of concrete can reach 2.33 times. At 600 ℃, the dynamic tensile strength of the water immersion cooling specimens is slightly higher than that of the air cooling specimens. The numerical simulation results show that the modified K C model can better reflect the dynamic tensile failure mode and stress–strain response of concrete after high temperature, with the peak stress and peak strain errors controlled within 5

Precast segmental bridge columns are commonly used but merely in low-seismicity areas, since their seismic performance is not clear under actual earthquake motions. To evaluate the feasibility of precast segmental columns in high-seismicity areas, it is necessary to investigate the dynamic behavior of such columns under bidirectional seismic excitation owing to multi-dimension characteristics of earthquake ground motions. Two 1/ 10-scaled columns with continuous low-carbonated rebars between segments were designed and reinforced with ultra-high-performance concrete (UHPC) based on a proposed design method. Then, shake table tests of reinforced columns were conducted to investigate the influence of types of seismic motions (near-filed and far-field) and loading direction (unidirectional and bidirectional) on dynamic responses of precast columns. The experimental results showed that minor concrete damage occurred in the bottom segment, and 0.2 % residual displacement was found, which indicated the column had an excellent re-centering capacity. Compared with the column under unidirectional seismic excitation, the column subjected to bidirectional seismic excitations had more serious concrete damage, more obvious fundamental frequency reduction, and larger displacement responses at the column top, residual displacement, and peak stress of tendons. The displacement of the column top under bidirectional loads was twice that under unidirectional loads. In addition, the response of the column under near-field earthquake motions was more significant than that of the column under far-field seismic excitations.

For bridge structures, the mechanical systems in real physical space are high-dimensional, complex, and nonlinear, and the loads that bridges experience are random and time-varying. This makes it very difficult to conduct statistical analysis of the mechanical effects of bridge structures in real physical space. In view of this, this article redefines the P-function and L-function used to describe traffic flow loads through theoretical derivation of statistical steady-state mechanical effects analysis of bridges: The P-function represents the average weight of all vehicles passing through any position on the bridge deck; The L function represents the probability of a vehicle passing through any position on the bridge deck. Furthermore, a digital twin model for traffic flow loads was proposed, which is suitable for mechanical effect analysis under steady-state conditions of bridge structure big data statistics, in order to quantify the big data characteristics of traffic flow loads in physical space bridges. Starting from the traditional traffic flow survey, a measured traditional traffic flow load model was established. Using numerical simulation methods, the conversion relationship and parameter influence relationship between it and the proposed traffic flow load digital twin model were studied, solving the indirect detection problem of the entire bridge deck traffic flow digital twin model. In response to practical engineering problems, the digital twin model of traffic flow load was applied to the statistical steady-state strain effect calculation of actual bridge structures, and the calculation results confirmed the accuracy and effectiveness of the model.

In practical engineering, concrete structures typically undergo high temperatures and fire spray cooling during the process of fire, and high temperatures will cause changes in the microstructure of concrete. Therefore, studying the fracture mechanical properties of concrete after rapid cooling at high temperatures is more in line with the actual engineering situation. This paper sets five temperature conditions (20°C, 200°C, 400°C, 600°C, and 800°C), and after rapid cooling in a water bath, a hydraulic servo machine is used to conduct three-point bending beam fracture tests on plain concrete (PC) and high performance concrete (HPC). The fracture process and mechanism are analyzed using digital image correlation (DIC) and acoustic emission (AE). The research results indicate that the three-point bending unstable fracture load of PC and HPC decreases with the increase of temperature, with the maximum reduction after 800 ℃ high temperature, reaching 87.5% and 82.2%, respectively. After high temperature, the fracture energy of PC and HPC both showed a trend of first increasing and then decreasing. The ductility index of PC and HPC increases with the increase of temperature. The unstable fracture toughness and initial fracture toughness of PC and HPC decrease with the increase of temperature. By combining DIC and AE technologies, the development and fracture mode of cracks in PC and HPC after rapid cooling at high temperature are analyzed. The results showed that the softening effect of concrete is more significant after high temperature, the crack initiation stage is earlier, and the bearing capacity is lower. Furthermore, modern testing techniques are employed to reveal the mechanism of the impact of high temperature and cooling methods on the mechanical properties of HPC from a microscopic perspective. The research results have important reference value for practical engineering.

Over the past decade or so, ultra-high performance concrete (UHPC) has been increasingly used for wet joints of bridge deck panels (BDPs) in bridge superstructures. To evaluate the flexural performance of UHPC wet joints for precast bridge deck panels, a total of seven BDPs were designed, including one monolithic cast-in-place bridge deck panel (MCIPBDP), one precast bridge deck panel (PBDP) with NC wet joints, and five precast bridge deck panels (PBDPs) with UHPC wet joints. The design parameters included reinforcement types (straight bars and Ubars), U-bar lap details (contact lap splice and non-contact lap splice), filling materials (UHPC and NC), and joint widths (150 mm, 200 mm, 250 mm, and 500 mm). Three-point bending tests were performed to evaluate the flexural performance based on the failure mode, load-deflection curve, cracking width in the wet joint region, and stiffness degradation. The experimental results showed that it is feasible to replace 500-mm-width NC wet joints with 200-mm-width UHPC wet joints for PBDPs with U-bars. UHPC wet joints, with a width of 250 mm, effectively prevented straight bars from slipping. As the width of UHPC wet joints decreased, the failure mode shifted from shear failure to bending failure. In addition, the cohesion-friction hybrid model was proposed to simulate the behavior of joint interfaces. The FE analysis results demonstrated that the FE model and modeling method have high accuracy and general applicability. Finally, the flexural capacity calculation formula was developed according to the strut-and-tie model. The theoretical calculation results were in good agreement with test results.

During the service life of bridge structures, they will be affected by various physical and environmental changes, which comprehensively manifest on different time scales. In other words, structural effects will have different variation patterns at different time scales, which will be reflected in the multi-scale characteristics of structural mechanical properties over time. However, most of the existing bridge performance indicators are defined on a time scale corresponding to a single factor. Therefore, it is necessary to analyze, process, and apply bridge monitoring signals differently at different time scales and components of different factors. This article proposes a signal decomposition and reconstruction method that extracts signals of different components from strain monitoring signals of bridge structures. On this basis, different feature extraction and indicator recognition are carried out for different extracted components. Among them, for component A related to bridge vibration, this paper proposes a strain mode identification method based on statistical stability. This method is based on the assumption that the strain mode under random noise has approximate time invariant characteristics, and noise is eliminated through statistical averaging. The component B of the vehicle induced effect is obtained through empirical mode decomposition (EMD) and bandpass filtering, and the lateral collaborative performance of the assembled beam bridge is characterized based on the correlation coefficient of component BA bridge hinge joint damage identification method based on temperature strain is proposed for component C of temperature effect. The effectiveness and feasibility of the above workflow were verified through real bridge data.

Over the past decade or so, ultra-high performance concrete (UHPC) has been increasingly used for wet joints of bridge deck panels (BDPs) in bridge superstructures. To evaluate the flexural performance of UHPC wet joints for precast bridge deck panels, a total of seven BDPs were designed, including one monolithic cast-in-place bridge deck panel (MCIPBDP), one precast bridge deck panel (PBDP) with NC wet joints, and five precast bridge deck panels (PBDPs) with UHPC wet joints. The design parameters included reinforcement types (straight bars and U-bars), U-bar lap details (contact lap splice and non-contact lap splice), filling materials (UHPC and NC), and joint widths (150 mm, 200 mm, 250 mm, and 500 mm). Three-point bending tests were performed to evaluate the flexural performance based on the failure mode, load-deflection curve, cracking width in the wet joint region, and stiffness degradation. The experimental results showed that it is feasible to replace 500-mm-width NC wet joints with 200-mm-width UHPC wet joints for PBDPs with U-bars. UHPC wet joints, with a width of 250 mm, effectively prevented straight bars from slipping. As the width of UHPC wet joints decreased, the failure mode shifted from shear failure to bending failure. In addition, the cohesion-friction hybrid model was proposed to simulate the behavior of joint interfaces. The FE analysis results demonstrated that the FE model and modeling method have high accuracy and general applicability. Finally, the flexural capacity calculation formula was developed according to the strut-and-tie model. The theoretical calculation results were in good agreement with test results.

The GFRP (Glass Fiber Reinforced Polymer) is prospective in bridge and building engineering for its advantageous material property. The connection configuration of hybrid bonded/bolted joint of GFRP is thought superior in mechanical performance compared with the traditional bonded and bolted joints. However, the fatigue issue of this type of joint remains unclear which impedes its engineering applications. The presented work experimentally and numerically investigated the fatigue behavior of the GFRP hybrid bonded/bolted single-lap joints under shear loading. High-cycle fatigue tests on single-bolt, four-bolt, and nine-bolt specimens were conducted to study the failure process, rigidity degradation, failure mode, and fatigue life of the hybrid joints, where the nondestructive monitoring techniques of AE (Acoustic Emission) and 3D-DIC (Three-Dimensional Digital Image Correlation) were adopted, respectively to detect the material damages and overall deformation of specimens. Finite element modelling was further carried out to reveal the fatigue failure mechanism of hybrid joints, in which the property degradation of GFRP plates and adhesive layer were considered. Results showed that the failure process of GFRP hybrid single-lap joints under fatigue shear loading can be divided into four stages: (1) steady and (2) rapid development of adhesive damage, (3) steady and (4) rapid development of GFRP damage, of which the (2) and (4) stages account for less than 3% of the total fatigue life of joint, respectively. Stiffness degradation of 14–35% were read for the tested joints before final failure, and the joints with more bolts performed a superior degradation resistance compared to the less ones. Besides debonding and bolt inclination, the single-bolt joints failed with bearing failure of GFRP material, while the failure mode of multi-bolt joints were dominated by shear failure in GFRP plate with Y-shaped zone. The simulation results well supported the observations in experimental test. Based on the experimental results, the S-N curve of the GFRP hybrid single-lap joints is proposed, which can provide support for the engineering design of this type of joints.

In order to solve the problem of strain modal identification under strain monitoring signals with poor vibration modal information, this paper proposes a strain mode identification method with statistical stability significance. This method removes noise, vehicle-induced effects, and temperature effects from the original dynamic strain signal, retaining only vibration-related components, and obtaining a statistically stable high quality bridge strain power spectrum, thereby identifying high quality strain mode parameters. Furthermore, in order to verify the confidence level of the strain modes obtained by this method, this paper adopts the interval estimation method to estimate the power spectrum, natural frequency, damping ratio, and modal shape after statistical processing. The credibility of strain modes has been estimated by interval estimation. The confidence interval of 95% confidence for each modal parameter is obtained, achieving the confidence-level evaluation of corresponding variable modal parameter identification. In response to practical engineering problems, this paper evaluates the actual bridge data of Tongji Road Bridge in Shanghai, and explains the abnormal phenomena that occurred in the data evaluation based on the measured diseases, verifying the practicality of this method.

The mechanical performance of the GFRP hybrid bonded/bolted single-lap joints under static tensile loading is experimentally and numerically investigated. Static loading tests considering the hybrid joints with single bolt, four bolts, and nine bolts were first conducted to study the failure process and modes of hybrid joints. Finite element (FE) analysis involving the material degradation and failure laws was also performed to reveal the joints’ internal failure mechanism. Based on the verified FE analysis approach, the effects of plate thickness and bolt end distance on the failure capacity and strength of the hybrid joints were further studied, by conducting a numerical parametric analysis. Results indicate that, the loading process of the hybrid joints can be identified into two stages divided by the bonding failure. The failure patterns mainly include the plate slippage, the inclination of bolts, and the tensile fracture of GFRP plate, and their occurrences vary for the joints with different bolt numbers. Additionally, the rigidity and failure load of joint are also significantly affected by the bolt number. As the plate thickness increases, the ultimate capacity of joints would be improved, while the failure strength decreases. With the bolt end distance getting greater, the ultimate capacity/strength would increase. In general, the achievement of this research work can provide references for the design and further study of the GFRP hybrid joints in civil engineering applications.

为探究砂浆-混凝土接缝界面动态受压力学性能,设计混凝土、砂浆以及砂浆-混凝土接缝界面三种不同试件,应用液压伺服试验机和霍普金森杆(SHPB)对试件静动态力学性能展开试验研究,由试验获取不同拼接缝工况下试件破坏形态和力学特征参数.同时,利用CT扫描技术,分析了三种不同试样的动态增强效果,并从细观层面揭示了其作用机理.结果表明:在静态作用下,接缝试件整体抗压强度处于砂浆试件与混凝土试件之间;在动态作用下,三种不同试件抗压强度随着应变率提高逐步增加,混凝土对应变率有更强的敏感性,砂浆的敏感性最弱.相较于混凝土试件,砂浆和砂浆-混凝土接缝试件受压破坏后的完整性显著提升;利用试验数据并基于欧洲混凝土委员会提出的CEB公式优化得到适用于三种不同材料的动态提高因子(DIF)与应变率数学模型,该模型具有较好的适用性.

Monitoring information on bridge structures in service can be used to identify structural damage or to assess the service performance of the structure in general. However, it is a challenging but significant task to use the monitoring information of the structural static effects under the natural traffic conditions during the operation period to identify the structural damage or overall performance. The challenge is to define and identify indicators that characterize structural damage and service performance through monitoring information on static effects under unknown traffic loads. To this end, this paper firstly establishes an analytical model for the support reaction of continuous girder bridges under the action of arbitrary traffic stream loading, and based on this a series of new indicators that can reflect the big data mechanical behavior laws of bridges in the statistically steady state are developed, i.e., the time-average state resultant force of the support reaction and the statistically steady state traffic stream equivalent uniform line load, as well as the normalized indicator of the time-average state support reaction resultant force obtained by extension, with a view to evaluating the service

In this study, shear damage development of four precast bridge columns with different connection design details are first examined via quasi-static test. The short columns are of identical dimension and reinforcement arrangement for both pier and footing segments, and the span-to-depth ratio is 0.85 for shear study. The connection utilizes grouted splice sleeve (GSS) couplers for all four specimens. Different bonding materials are compared, effectiveness of shear keys is investigated, and variation of steel rebar grades is carried out. It is found that epoxy retain lower bond strength than high strength mortar, lower grade of longitudinal rebar significantly reduces shear strength of bridge column, and shear keys are of limited effectiveness on the overall shear damage development. An analytical method for shear strength calculation is then proposed and calibrated based on different test results, which incorporates possible influencing factors for shear strength estimation. Maximum difference between the test results and estimated strength values are less than 10%, and it indicates that the proposed method can be used as a reference for shear strength estimation of short precast bridge columns for seismic strength estimation.