This paper presents a novel type of replaceable shear link with a variable cross-section. The proposed design involves expanding the cross-sectional area and employing fully bolted connections to the non-energy-dissipating components. This design approach not only facilitates the concentration of plastic deformation within the energy-dissipating region but also ensures easier implementation of elastic design due to the bolted connections. To assess the seismic performance of the variable cross-section replaceable link, three distinct section configurations were designed for cyclic loading tests: a low-yield-point (LYP160) specimen without weakening in the energy-dissipating region, a Q235 ordinary steel specimen with an opening in the energy-dissipating region, and an ordinary steel specimen with a long oval opening in the energy-dissipating region. Through the cyclic loading tests, the seismic performance of the replaceable shear link was examined thoroughly. The experimental results indicate that plastic deformation primarily occurs within the energy-dissipating region, with buckling and tearing observed around the openings in this region as the primary failure characteristics. The low-yield-point specimen exhibits an overstrength coefficient exceeding 3.0, featuring a complete hysteresis curve, superior energy dissipation capacity, and a plastic rotation of 0.18 rad. Although the specimen with elongated openings demonstrates significant overstrength coefficient and plastic deformation capacity, its energy dissipation capability is compromised due to the weakened section. The specimens with circular openings exhibit an initial elastic stiffness similar to that of the low-yield-point steel specimens, surpassing the stiffness of the specimens with elongated openings by approximately 84%. These findings provide valuable insights for applying variable cross-section replaceable links.

To study the seismic response and lap length requirements of the simply-supported bridge across faults, an elastic-plastic analysis model of the simply-supported bridge was established. Through dynamic response analysis, elastic-plastic analysis and shear resistance analysis, the influence of slip effect of fault ground motion on the lap length requirement of simple supported beam bridge is studied, and the relation between the relative displacement of pier beam and the permanent displacement of ground before plastic hinge failure is discussed. Research shows that the location of the fault affected the seismic response of the structure, and the closer the fault structure is, the greater the earthquake impact will be. The slip impact effect of fault ground motion increased the seismic response of the structure. The maximum shear strength ratio of the plastic joint area of the pier under fault earthquake action is 0.47. The checking calculation of the shear strength of the pier meets the requirements of the seismic design code. The seismic response of the structure under cross-fault seismic action drifted, resulting in the plastic hinge only developing in the same direction. The residual sum of squares and R² of the polynomial fit are 539.910 and 0.984, respectively. When the permanent displacement of ground is 1.6 m, the relative displacement of pier and beam before plastic hinge failure is 49.5 cm, accounting for about 56% of the calculated supported length. When the peak acceleration is small, the supported length of the simply-supported beam bridge under the earthquake action across the fault meets the requirements of the code.

Since the pulsed wind tunnel balance foundation plays a supporting role in aircraft wind tunnel tests, in order to deeply study the influence of the layered subsoil on the vibration characteristics of the balance foundation, the impedance function of the balance foundation on a layered subsoil under impulse load is derived. A dynamic response equation of the foundation is established by using a simplified model, and the dynamic impedance function of the simplified model is equated with that of the foundation-foundation system. The dynamic response of the balance foundation on the laminated foundation under impulsive wind tunnel loading is obtained and verified by numerical simulation. The results show that the vertical amplitude, horizontal amplitude and slewing angle of the foundation gradually decrease with the increase of the loading frequency. The increase of the loading amplitude leads to the increase of the maximum amplitude of foundation vibration, while the vibration frequency remains unchanged. The increase of the shear modulus of the foundation results in the decreasing of the maximum amplitude of foundation vibration. The increase of the foundation dimensions leads to the obvious decreasing of the maximum amplitude of foundation vibration and the vibration frequency. In addition, the vertical vibration amplitude of the foundation increases with the decrease of foundation layer depth ratio, while the horizontal vibration amplitude and slewing angle decrease with the decrease of layer depth ratio. The increase of foundation shear wave velocity has less effect on the vertical vibration amplitude, while the effect on the horizontal vibration amplitude and slewing angle is more significant.

To explore the coupling mechanism of the time-varying fluid-solid coupling vibration of the medium flowing through the pipeline on the seismic response, the oil pipeline supported on the diagonal spanning structure is taken as the research object. Considering the time-varying characteristics of the dynamics during the medium flowing process through the pipeline and adopting the two-way fluid-solid coupling theoretical model, the theoretical method for calculating the coupling between the medium time-varying fluid-solid coupling vibration and seismic response is proposed, and a finite element simulation model for the coupled medium-pipeline-span system is established. By setting the calculation parameters and boundary conditions of the coupling interface, the simulation is carried out. In the finite element simulation model, by setting the calculation parameters of the medium, fluid, pipeline, crossing structures, and considering the boundary conditions of the coupling interface, simulation calculations were carried out. The displacements and acceleration responses at the end of the bridge platform and the cross-section of the pipeline across the location were extracted for calculations and comparative analysis with the calculation results without considering the medium flowing vibration effects was carried out. The results show that: when the medium flows from the left side of the pipeline to the right side over time, the state changes of different fluids in the pipeline caused by the medium flow and the seismic coupling result in differences in the pipeline displacement response and acceleration response distributions along the pipeline length. When the source of the medium flow reaches about 4/5 of the pipeline length over time, the peak displacement response and peak acceleration response of the media occur all the time. The coupling response of the right half of the pipeline is larger than that of the left half of the pipeline, and the calculation results of the pipe cross-section at six typical locations in the right half of the cross-section reveal the general rules of the medium flowing vibration coupling with the seismic response. Under the same conditions, the displacement coupling response of the pipeline considering the medium flowing vibration effects coupling with seismic response is approximately 2.7 times that without considering the medium flowing vibration effects. It indicates that the fluid-solid coupling vibration considering the medium flowing vibration effects has non-negligible effects on the earthquake response.

The compressibility of reservoir water and the influence of reservoir-bottom silt on the seismic response of the structure are taken into account to establish the high arch dam-reservoir water-foundation system model of Jinping-I Arch Dam, and the feasibility of using the acoustic-solid coupling method to simulate the effect of reservoir water on the dam body is verified by comparing it with the dynamic water pressure calculated by the Westergaard method. The absorption of silt deposited at the bottom of the upstream reservoir is simulated by different reflection coefficients of the reservoir bottom set in the model; seismic records that conformed to the hydraulic code response spectrum were selected as input based on the site conditions, and the response values of dynamic water pressure at the arch crown beam of the concrete dam under the action of vertical-incidence earthquakes with different bottom reflection coefficients were analyzed and studied. The results showed that the magnitude of the bottom reflection coefficient has a significant effect on the dynamic water pressure results at the arch crown beam, and the dynamic water pressure results increase with the increase of the reflection coefficient, and the difference of the dynamic water pressure at the heel of the dam with adjacent reflection coefficients becomes larger.

Seismic isolation technology is an effective means to protect the safety of structures. Taking the friction pendulum isolation structure as an example, a method for calculating the maximum deformation of the isolation layer (MDIL) based on the maximum momentary input energy (MMIE) analysis is proposed. Firstly, the MDIL is verified to be occur simultaneously with the MMIE based on a nonlinear single degree of freedom (NSDOF) model. Secondly, the relationship between the maximum sliding displacement and the hysteretic energy consumption of the isolation layer is derived. The ratio of the MDIL to the maximum sliding displacement of the isolation layer is further determined. Finally, a method for calculating the MDIL based on the MMIE is proposed and verified using the NSDOF model. The results show that there is a high correlation between the MDIL and the MMIE. The ratio of the hysteretic energy of the isolation layer to the MMIE decreases with the increase of the equivalent period of the structure. The ratio of the MDIL to the maximum sliding displacement is about 0.55. Compared to the actual maximum deformation of the isolated structure, the calculated deformation using the energy method is with an error of 10%.

Since there are fewer and fewer high-quality bedrock sites to choose from, it is inevitable that new nuclear power plants will be built on non-bedrock sites in the future. At this time, soil-structure interaction is a factor that must be considered in the seismic fortification of nuclear power plants. In this paper, a three-dimensional finite element model of the site-pile raft foundation-nuclear power plant is established for Hualong One nuclear power plant planned to be built on a non-bedrock site in China. The direct stiffness method and the boundary substructure method are used to achieve oblique incidence seismic waves input, and the difference in the seismic response of the nuclear power structure when SV waves are incident at three different angles is studied. The effect of soil-structure interaction (SSI) on the structural response is further analyzed. The results show that the non-bedrock site of the nuclear power plant will significantly amplify the bedrock seismic waves, and the peak acceleration amplification coefficient at the bottom of the containment can reach 3.6 when the seismic wave is vertically incident. With the increase of the incidence angle of the seismic wave, the horizontal acceleration response decreases and the vertical acceleration response increases, and the horizontal and vertical acceleration response spectra shift towards the long-period direction and the short period direction, respectively. SSI can significantly affect the seismic response of nuclear power structures in non-bedrock sites.

In order to study the mechanical properties of prefabricated thin-walled piers connected by grouted sleeves and the overall seismic performance of the bridge, firstly, the damage morphology characteristics of a group of ordinary cast-in-place thin-walled piers and prefabricated thin-walled piers connected by grouted sleeves were investigated through the proposed quasi-static test, and the differences in the skeleton curves and hysteresis curves between the two types of piers were analysed by comparing and contrasting them. Then, based on ABAQUS platform and the test data of this paper, the numerical simulation of the grouted sleeve connected thin-walled piers is carried out. On this basis, a three-span continuous box girder bridge is selected as an example, the multi-scale finite element dynamic analysis model of the whole bridge is established, and 100 ground are selected for the nonlinear time-history analysis, and the differences in the time-history response of the bridge components and hysteresis curves of the bridges set up with different piers are studied. Finally, the seismic fragility curves of different members were established to analyse the damage characteristics of each member of two types of bridges. The test results show that the damage form of prefabricated thin-walled pier is bending and shear damage, the concrete in the sleeve area is intact, the plastic hinge region is transferred to above the sleeve cross-section, the overall ultimate bearing capacity is slightly increased, the hysteresis curve shape is relatively full, with good plastic deformation capacity, and the hysteresis performance of ordinary cast-in-place thin-walled piers is basically the same. The model can simulate the overall mechanical properties of prefabricated thin-walled piers. The time-history fluctuations of prefabricated thin-walled piers mainly occur in the middle period of earthquakes. The difference in maximum displacement and internal force response between the two types of bridge piers is about 5% and 10%, and the bearing response is less affected compared to the bridge pier. Prefabricated thin-walled pier bearings and blocks are easily damaged components, and abutment bearings and blocks are more easily damaged than bridge piers. Prefabricated thin-walled piers are more easily damaged than ordinary cast-in-place thin-walled piers, but the difference is small. Prefabricated bridge piers can basically achieve the design principle of equivalent cast-in-place.

Due to process limitation, the laying accuracy of the traditional subway track bed is low, and the construction speed is slow, while the construction accuracy and efficiency of the prefabricated track bed are relatively high. In addition, many subway lines often require the addition of vibration reduction measures or an upgrade in the vibration reduction levels after a period of operation. Therefore, it is urgent to develop the prefabricated damping pad floating slab track (PDPFST) with various vibration reduction grades and convenient upgrade options for vibration reduction. Therefore, the PDPFST was developed and applied to three new metro lines in Qingdao. In this paper, the coupled simulation analysis and field tests were conducted on the dynamic performance and vibration reduction performance of the vehicle passing through the PDPFST. Firstly, the structure and construction technology of the PDPFST were introduced. Then, the requirements and evaluation methods for the simulation and test of dynamic performance analysis and vibration reduction effect analysis were presented. Then, a vehicle-floating slab track-tunnel coupled dynamic analysis model was established. Finally, the coupled simulation results were compared with the field test results. Through the above research, the following conclusions are drawn: Compared to the traditional track slabs, the construction progress of the PDPFST is increased by 3 times (approximately 110 meters per day). The simulation results of the dynamic performance and vibration reduction performance of the vehicle passing through the PDPFST are in good agreement with the measured values, and the dynamic performance of the vehicle meets the requirements. When the vibration frequency is greater than times the natural frequency, the floating slab track can exhibit a good vibration reduction effect. The vibration reduction effect of the PDPFST is remarkable. The high vibration reduction effect is approximately 13 dB and the medium vibration reduction effect is approximately 8 dB. The research results can provide a certain theoretical and practical reference for the design and implementation of the PDPFST.

In recent years, metallic bar dampers have been widely applied in structural vibration reduction due to their excellent energy dissipation capacity. To further enhance the mechanical performance of metallic bar dampers, this study proposes a double hourglass-shaped damper made of LYP160 low-yield-point steel, featuring a constant cross-section straight segment LYP160-double hourglass shaped steel damper(LYP-DHSD). To investigate the mechanical properties of LYP-DHSD under shear displacement, two LYP-DHSD specimens were designed. The hysteretic characteristics and fatigue performance of the specimens were studied through low-cycle reciprocating loading tests. A refined finite element model of LYP-DHSD was developed, and parameter analysis of the hysteretic performance was conducted with the outer diameter, inner diameter, and length of the constant cross-section straight segment as variables to further explore the stress pattern of LYP-DHSD under cyclic shear displacement. The results show that under cyclic shear displacement, LYP-DHSD achieves multi-section yielding and exhibits excellent load-bearing capacity, deformation ability, and stable energy dissipation performance, with fatigue performance meeting code requirements. Adjusting the inner diameter significantly influences the structure’s load-bearing capacity, stiffness, and energy dissipation. Increasing the length of the constant cross-section straight segment reduces the load-bearing capacity, stiffness, and energy dissipation of LYP-DHSD. Additionally, increasing the inner and outer diameters improves material utilization efficiency initially, but it subsequently decreases. Modifying the length of the constant cross-section straight segment allows for adjustments in the plasticity distribution region of LYP-DHSD. Based on the analysis results, it is recommended that the ratio of the inner diameter to the outer diameter of LYP-DHSD be set between 0.375 and 0.625, and the ratio of the inner diameter to the length of the constant cross-section straight segment be set between 1 and 2.