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Fibre-reinforced engineered cementitious composites are increasing being used in construction due to their superior toughness and durability. For composite structural members additionally reinforced with steel bars, the bond–slip relationship between the composite and reinforcing bars is an important parameter for designers. To understand the bond behaviour between Chinese 500 MPa steel bars and composites, pull-out tests were conducted to study the influence of the bar diameter, cover thickness and embedded length on bond properties under tension. The results indicated that the process of the bond–slip failure for 500 MPa steel bars in composites can be divided into three stages: ascent, descent and remnant. The bond strength increased with a decrease in bar diameter, while shortening of the embedment length enhanced the bond strength. Specimens with a larger cover thickness achieved higher bond strength, but the enhancement in bond strength was negligible for specimens with a cover thickness greater than 55 mm. A formula for calculating the bond strength for Chinese 500 MPa reinforcing bars in composites was developed based on the experimental results and a consistent model for the bond stress–slip relationship was also obtained.

Free vibration and bending of laminated plates on Winkler foundations are investigated based on a combination of generalized layerwise theory (LW) for higher-order shear deformation theory (HSDT) a...

A vertical spring had a changeable horizontal stiffness to avoid resonance under a seismic displacement, and a viscous damper had a perfect energy dissipation function to reduce the seismic displacement. They were joined together to achieve a seismic isolation system considerably reducing the seismic acceleration response, however, their displacement should be paid more attentions under an earthquake or in a shaking table test. Because the interface friction in the system affected the scaling process of the system in the shaking table test and the corresponding displacement responses, the system was numerically scaled before a real shaking table test. The comparison between the displacement responses of scaled models and prototype models shows that the spatial friction variation and the gravity distortion are the error sources of the relative and residual displacements of scaled models. The error of scaled relative displacement is reduced by the means of increasing PGA, damping constant, spring constant or reducing vertical spring length with zero stress, however, the error of scaled residual displacement is still chaotic under these means. Only if the error sources above are eliminated fundamentally will the error of scaled models be avoided. The conclusions are validated correct by a real shaking table test.

When the friction pendulum system and shear keys work together to resist the ground motion, which obliquely inputs (non 45°) to the bridge structure, the shear keys in XY direction will be sheared asynchronously, so that the friction pendulum system will have a violent changing direction curve movement on the sliding surface under the earthquake, and there is a strong plane friction coupling effect during this process. In view of this situation, this paper constructs a Spring-Viscous damping-Coulomb friction plane isolation system with XY shear keys, which realizes the detailed and accurate mechanical analysis under the plane friction coupling effect of friction pendulum system, and adopts self-programming to realize the calculation of the time history response. The results indicate that when XY shear keys are sheared asynchronously, on the one hand, it will change the motion state of system, caused the influence of the plane friction coupling, on the other hand, it will cause a sudden change of the structural acceleration at the moment of the shear key sheared. While the shearing force of XY shear keys is small, the plane friction coupling effect will play a leading role, which will reduce the maximum acceleration of the structure. Meanwhile, the plane friction coupling effect caused by XY sheared asynchronously will increase the maximum relative displacement of the structure, and this amplification effect needs to be more importantly considered in the design of structural seismic isolation when the PGA is small.

To evaluate the seismic responses of bundled conductor interconnected electrical equipment, a model of the interconnected system was established. The bundled conductor model was incorporated into the interconnected model, and the electrical equipment was simplified as a 5-degrees of freedom structure. The bending stiffness of the sub-conductor and the constraint effects of the spacer, usually omitted in previous research, are considered in the paper. The iteration method was used to obtain the terminal forces and moments of the bundled conductor. Then, the model was validated by shaking table tests. We investigated the effects of the slackness and bending stiffness of the bundled conductor on the seismic responses of the interconnected system. Considering the bending stiffness of the sub-conductor and the effects of the spacer, the seismic response characteristics of the interconnected electrical equipment were much different from those connected by a flexible conductor without bending stiffness in previous research. Not only the terminal forces, but also the terminal bending moment should also be considered in the seismic performance evaluation of interconnected electrical equipment.

It is generally perceived that ground motion duration has an effect on structural seismic response and damage, despite the neglect of current seismic codes. Based on friction SDOF systems, this paper investigates the duration effect of ground motions on seismic responses and damage of sliding bearings. Ground motions are divided into long-duration (LD) and short-duration (SD) cases, taking the significant duration of 25[Formula: see text]s as the boundary. Each case consists of natural records and spectrally equivalent artificial ground motions to decouple duration from other earthquake characteristics. Results from response history analyses implicate that duration has hardly any effect on seismic responses of the system exhibiting an approximate linear elasticity. Nevertheless, for systems with distinct frictional nonlinearity, selecting LD ground motions as seismic inputs usually leads to a conservative result. By performing incremental dynamic analysis (IDA), nonlinear systems in SD cases bear 10% higher damage risk than those in LD cases without considering the influence of temperature rise. The same is true for systems with a small friction coefficient of 0.005 when earthquakes are in the low intensity range. It was also found that damage exceedance probabilities of these small friction coefficient systems are almost unaffected by the duration as the peak ground acceleration increases to more than 0.6[Formula: see text][Formula: see text]. When the effect of temperature rise caused by friction is considered, the damage exceedance probability in LD cases is higher than SD cases. The damage probability of friction SDOF system under LD earthquake will be underestimated without considering the influence of temperature rise.

The construction of high-speed railways continues to extend in seismic prone areas, but there is limited research on the seismic-induced track irregularities occurred in positions where high-speed railway bridges are involved. Taking a five-span high-speed railway simply supported beam bridge as the engineering example, the corresponding nonlinear system model, with CRTS II slab ballastless track, is established by using ANSYS finite element analysis software. The distribution mode of post-earthquake track residual irregularity is studied, the statistical characteristics of its power spectral density are analyzed, and a representative seismic-induced track geometric irregularity spectrum is constructed. The effects of the site categories and the epicenter distance on seismic-induced track spectrum are also discussed. The results show that after the earthquake, the alignment irregularity is significant, while the vertical, cross-level and gauge irregularities can be ignored. The amplitude of track geometric irregularity, caused by earthquake, increases significantly with the increase of ground motion intensity. The seismic-induced track spectrum obeys lognormal distribution at all frequencies. The track spectra almost coincide for all five site categories, thus, the impact of site categories on the seismic-induced track spectrum of high-speed railway bridges is considered negligible. Due to the pulse effect, the seismic-induced track spectrum of near-field earthquakes is significantly larger than that of far-field earthquakes.

When the ground motion is input into a Spring-Viscous damping-Coulomb friction plane isolation system with XY shear keys along a certain inclined angle, XY shear keys will be sheared asynchronously...

After an earthquake, a track-bridge system may suffer damage and residual deformation, posing a threat for trains passing over a bridge. However, since railway transportation is an important channe...

Railway transportation, as an important lifeline during earthquake relief and post-disaster reconstruction, has an extremely significant role. The study of track irregularity caused by earthquakes is the basis for ensuring traffic safety after their occurrence. In this paper, a finite element model of a five-span simply supported high-speed railway beam bridge with the China Railway Track System (CRTS) II was established and an experimental verification was performed. Eighty arbitrarily selected seismic waves were extracted from the Pacific Earthquake Engineering Research Center (PEER) strong ground motion database and a nonlinear time-history analysis was performed on the finite element model. The frequency–domain distribution law of earthquake-induced track irregularities was studied. A stable target earthquake-induced track irregularity spectrum model was constructed, and its expression was fitted. According to the results, in the case of transverse earthquakes, the rails experienced noticeable alignment irregularity and cross-level irregularity, while the amplitude of the gauge and vertical irregularity were relatively small. The target irregularity spectrum has a higher amplitude in the low-frequency components. When peak ground acceleration (PGA) was low, earthquake-induced track irregularity was not obvious, but the deteriorating effects of earthquakes on track irregularities increased significantly with increasing PGA.

Considering that existing shaking table tests on bridge structures have not taken into account the effect of moving trains, this paper takes a multi-span simply supported girder with a CRTSII slab ballastless track system and a Chinese CRH2C high-speed train as its objects of study, builds a reduced-scale model for the bridge and train using a similarity ratio of 1:10, and constructs an on-bridge running test platform based on a four-array shaking table. A running test under seismic action is preformed to explore the effects of train speed and the vertical component of ground motion on structural responses under the combined action of seismic and train loads. According to the findings of this paper, a higher train speed leads to more intense wheel-rail interactions. Train speed and the vertical component of ground motion have significant effects on the vertical deformation of structures and on the transverse deformation of bearings and piers, but their effects on the transverse deformation of track structures are negligible. The vertical component of ground motion may cause vertical separation between girders and bearings. The train may induce disengaging between track structures in the vicinity of girder gaps.

In the dynamic analysis of railway lines, both lateral and vertical track irregularities should be considered. In addition, uncertainties in the bridge structure and train load will have different ...

At present, specific earthquake motion is often used for analyzing the influence of trains on high-speed railway structure; however, the uncertainty of earthquake motion is rarely taken into consideration. In this study, on the basis of considering the uncertainty of earthquake motion, and taking a simply-supported beam with CRTS II track system and CRH2 high-speed train in China as the research objects, a finite element analysis model of vehicle-bridge coupled model was established and verified by tests. The influencing mechanism of the trains on structural response under the action of uncertain earthquake was analyzed, and the range of the influence levels of trains on seismic response of structure was calculated. The research findings show that under the effect of earthquake, the presence of trains decreases the responses of piers and bearings, while increases the response of track structure. With increasing peak ground acceleration, the effect of trains on the track structure deformation increases, while that on the bending moment of piers, shearing force, and bearing deformation all decrease. The increase in train speed will not significantly affect the seismic response of structures. The ratio of seismic response between the operating conditions with and without vehicles was kept within a certain range, so that the demand range for seismic response under the operating condition with vehicles can be approximately simplified.

The increasing prevalence of simply supported bridges in high-speed railway (HSR) lines has raised concerns about the safety of trains crossing these bridges during an earthquake. As these bridges are typically continuous and long, it is essential to consider the effects of traveling seismic waves on the random vibration of the train-bridge coupled (TBC) system. To address this issue, the new point estimate method (NPEM) is used to analyze the dynamic response and parametric sensitivity of a three-dimensional TBC system subjected to non-uniform ground motion with multiple random parameters. The motion equations of the TBC system are derived using bridge seismic theory under multi-support excitations. The analysis incorporates random variables such as the damping ratio, density, Young’s modulus, and seismic magnitude to capture the influence of traveling seismic waves on the random vibration of the TBC system. Simulation results show that the traveling seismic wave effect can cause changes in the first vibration frequencies of the train and bridge, potentially leading to the first few frequencies reordering. Additionally, considering the traveling wave effect will make the TBC system’s response less apparent than without considering the traveling wave effect. The uncertainty of bridge and seismic parameters can seriously affect the train’s running safety. The sensitivity of the bridge density and seismic magnitude is particularly prominent for bridge responses when the traveling seismic waves effect is strong. This methodology can be used for random and sensitivity analysis of a train running over a long bridge under non-uniform earthquake conditions. Overall, the NPEM can provide valuable insights into the dynamic behavior and safety of TBC systems, enabling more effective design and maintenance of HSR bridges.

Herein, an approach for the dynamic response of a four-beam system with arbitrary boundary conditions when subjected to successive moving loads is proposed. Based on the proposed method, the resona...

Friction pendulum bearing (FPB) is a sliding-based isolator, widely used in the seismic design of the bridge structure. However, there is neither unified standard nor complete evaluation system to evaluate the specific isolation effectiveness of FPB-isolated bridges with different pier heights. In this paper, the prototype bridge finite element models (FEM) of the typical simply supported girder bridges on the double-track railway in China, are established and studied. These bridge FEM differ in the pier height range of 4–60 m. Each FEM adopts two types of bearing: FPB (isolated bearing) and spherical steel bearing (non-isolated bearing). The nonlinear time history analysis is carried out to compare the seismic responses of FPB-isolated and non-isolated bridges. Based on the comparison results, the seismic isolation ratios of FPB are defined and obtained. In addition, a new criterion index is presented to quantifiably measure the effectiveness of the seismic isolation of FPB-isolated bridges with different pier heights, which is beneficial to the further popularization and application of FPB in the seismic design of bridge engineering.

China’s railway network is wide, and some of them cross the seismic zone, and the ratio of high-speed railway (HSR) bridges is high. Therefore, the safety of trains on the bridge may be endangered in the event of an earthquake. Because the response of track–bridge system is sensitive to the randomness of bridge structural parameters during the earthquake, while the train wheelset is directly in contact with the track system, the running safety of train (RST) may be also sensitive to the randomness of structural parameters. In this paper, the model of train–bridge coupled system (TBCS) under earthquake was established, and the accuracy of the model was verified by test results. To efficiently calculate the safety performance of trains considering the randomness of structural parameters, the point estimation method (PEM) was used in this paper, and the applicability of PEM was proved by comparing with the calculation results of Monte Carlo simulation (MCS). Then, PEM was used to discuss the running safety performance of trains under different ground motion (GM) intensities, different train speeds, and different pier heights. Finally, based on the maximum probability, the GM intensity threshold of a bridge based on running safety is determined.

Based on an innovative high-speed railway simply supported bridge (HSRSSB) model, this paper conducts the investigation of potential influence of near-fault pulse-type ground motions on a 49-span HSRSSB. To obtain target conclusion, 85 original records of near-fault pulse-type ground motions are collected and are imposed on the simulation model as excitation, dynamic responses including girder displacement, rail displacement, pier moment, bearing deformation, and residual displacement are gathered as well. Linear regression analysis reveals the relationship between dynamic response results mentioned above and intensity measures (IMs). Moreover, 6 typical ground motions are chosen from the 85 records as prototype for pulse parameter analysis. Through the artificial ground motions synthesis, the effects of parameters consisted with pulse amplitude, pulse period, and pulse number on HSRSSB are investigated and discussed. It is concluded that responses of HSRSSB are sensitive to acceleration-type IMs and have the strongest linear relationship with spectral IMs at fundamental period of structure. For pulse parameter, the HSRSSB dynamic responses show positive correlation relationship with pulse amplitude, but negative correlation with pulse period.

The seismic vulnerability of high-speed railway (HSR) bridges may be overestimated or underestimated when the track structure is oversimplified in a finite element model. Thus, the author establish...