Considering factors such as slope excavation quantity and slope stability, RC frame structures supported by foundations with different elevations (FSSFDEs) often occur, resulting in irregular structures and significant torsion. To study the torsional effects and corresponding control measures for FSSFDEs, the reliability of the finite element model was verified using pseudo-static tests and shaking table tests. Sixteen finite element models with varying structural parameters were analyzed using both elastic and elastoplastic dynamic finite element analysis. The study examined the influence of factors such as the total number of dropped stories, the number of spans and the number of dropped stories at the intermediate ground embedding end, and the number of spans at the upper ground end on the torsional effects of the structures. Additionally, the effectiveness of different torsional control measures was compared through case analysis. The main conclusions are as follows: In the elastic state, the torsional effect of RC frame structures with three different ground elevations is significant in the stories at the intermediate and upper ground ends, and it is smaller than that of structures with two different ground elevations. In the plastic state, it is beneficial to improve the torsional effect of the structure by decreasing the size ratio of the part under upper embedding end corresponding to the overall structure. Setting up horizontal grounding components, steel support or viscosity damping in the RC FSSFDEs can improve the torsion resistance. Setting up horizontal grounding components provides the best improvement on torsion effects for structures on rock slope.

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.

For the large yield displacement of the buckling-restrained steel plate wall(BRW), only stiffness and bearing capacity can be provided in the small deformation stage. BRW can not dissipate energy in the small deformation stage. To solve this problem, the wall type friction damper (FD) and buckling-restrained steel plate wall are arranged in parallel in the thickness direction to form a new type of buckling-restrained steel plate wall combined with friction damper (FD-BRW). In the small deformation stage, the friction damper in the composite member slides to dissipate energy. As the deformation increases, the buckling-restrained steel plate wall yields, and the friction damper and the buckling-restrained steel plate wall dissipate energy together. Based on the test results of BRW, FD and FD-BRW, a simplified calculation model was established to simulate the mechanical properties of FD-BRW. The simplified calculation model consists of three springs. The calculation results of the simplified model were basically consistent with the experimental results, which can replace the solid finite element analysis and can be directly applied in the overall analysis of the structure. Based on the simplified model, taking the optimal additional damping as the control index, the reasonable ratio of the sliding friction force of friction damper to the yield bearing capacity of the buckling-restrained steel plate wall (slip-yield ratio) and the recommended value of the height-width ratio of the member were discussed through parametric analysis. The results showed that the height-width ratio is recommended to be less than 1.5, and the reasonable range of slip-yield ratio is 0.07~0.10.

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%.

To study the bearing capacity, lateral stiffness, ductility, and failure mode of high-strength steel composite Y-shaped eccentrically braced steel frames under horizontal loads, pushover tests were conducted on a half-scale three-story specimen. The test adopted three-mass inverted triangle proportional loading, and used OpenSees software to establish a corresponding numerical model for simulation. The results show that under the action of horizontal load, the link begins to yield, and the stiffness of the structure gradually decreases as the load gradually increases. During the test, the plasticity of the link on the second floor of the structure is the most obvious, the inter-story drift is the largest, and the inter-story drift ratio reaches 0.0433 rad. When the structure is finally damaged, it is manifested as the failure of the joints between frame beam and link, and the frame beams and columns are still in an elastic state.When modeling in OpenSees, the connection between the link and the frame beam is adopted using the method of rigid link and rigid section. The pushover curve simulation results obtained by this modeling method are in good agreement with the test results, indicating that the numerical model can be used for the simulation analysis of the seismic performance of the global structure. The parametric analysis results show that the lateral stiffness and bearing capacity of the shear link are better than those of the shear-flexural link.

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 investigate the anti-liquefaction capability of coral sand sites, this study conducted shaking table model tests controlling the degree of saturation to overcome the vague saturation state in general model tests. By comparing the dynamic response and liquefaction behavior of coral sand and quartz sand with similar degrees of saturation, gradation, and relative density, the liquefaction characteristics of coral sand sites were discussed. The experimental results show that both materials are in a liquefiable state under similar degrees of saturation without showing significant differences in anti-liquefaction strength. Before liquefaction, the shear modulus of coral sand is significantly higher than that of quartz sand. If current V_s liquefaction assessment method is directly applied, the site would be judged as non-liquefiable, thereby overlooking the liquefaction risk in the use of coral sand sites. After liquefaction, the shear modulus of both tends to be zero, indicating that the post-liquefaction seismic damage of both types of sites is similar. This study has proven through indoor model tests that coral sand is a liquefiable soil with anti-liquefaction strength similar to that of terrestrial sand, corroborating the results of previous seismic damage investigations. Furthermore, the model saturation preparation method and the degree of saturation evaluation method used in this study can provide technical reference for future coral soil model tests.

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.

The elastic foundation typically exerts a suppressive effect on the vibration response of the supported structure, and the influence of the soil-structure interaction effect on the dynamic characteristics of the structure exhibits typical nonlinear energy sink characteristics. At present, more and more attention has been paid to the dynamic research of elastic foundation beams considering soil motion. Based on the modified Winkler model, the finite-depth elastic foundation is equivalent to the additional mass of the nonlinear energy sink system, and the vibration suppression effect and parameter optimization of the elastic foundation on the finite-length beam supported by it under simple harmonic excitation is conducted. The nonlinear dynamic response of a simply supported beam on an elastic foundation is analyzed using the Galerkin method, the incremental harmonic balance method, and the arc-length continuation method. Furthermore, on the basis of verifying the correctness of the theoretical results by numerical methods, through multi-parameter optimization and analysis, the suppression effect of limited range soil on the dynamic response of its supporting beam is revealed, and the optimal parameter range of nonlinear stiffness and damping of the elastic foundation is proved. The results show that by adjusting the elastic soil parameters to the optimal range by technical means, the amplitude reduction percentage of the finite-length beam can reach more than 96%, and it has a wide vibration suppression frequency band.

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.