To study the comfort level of human-induced vibration of a variable section steel-truss pedestrian bridge and the vibration reduction effect of tuned mass damper (TMD), a steel truss girder pedestrian bridge on the Beijing Hangzhou Grand Canal was taken as the research object. Finite element simulation and on-site measurement were used to study the human-induced vibration response of the steel truss pedestrian bridge. Based on the finite element model, the vibration response of the bridge before installation of TMD was analyzed, the pedestrian comfort level was determined, and the influence of pedestrian density, damping ratio and crowd excitation frequency on the bridge was discussed. In this way, the TMD design parameters were given, and the influence of TMD mass ratio on the vibration reduction effect was analyzed. On site measurements were conducted on the pedestrian bridge after the installation of TMD, and based on which acceleration time history and frequency spectrum analysis were used to study the human-induced vibration response of the bridge under corresponding operating conditions. Comparison of the results shows that before installing the TMD, the acceleration response of the bridge exceeds the specification limit, and the effect of human-induced vibration should be considered. In a certain range, the acceleration response increases with the increase of pedestrian density and decreases with the increase of damping ratio. The vibration response increases significantly when the pedestrian step frequency is close to a certain order of the vibration frequency of the bridge. After the installation of TMD, the measured human-induced vibration response of the bridge is reduced, and its response is consistent with the simulation results. The research results in this paper can provide theoretical support for the study of human-induced vibration of variable section steel truss bridge.

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.

On December 18, 2023, a M_s6.2 earthquake occurred in Jishishan County, Gansu Province, affecting 118 towns including Dahejia Town, Liuji Town and Shiyuan Town. The areas have a relatively low level of economic development, with widespread and severely damaged brick (earth) and wood structures, resulting a significant number of casualties. In view of the large stock of brick-wood buildings in the region and their local characteristics, this study summarizes the architectural and structural characteristics of double-slope brick-wood structures and single-slope high wall brick-wood structures based on the on-site research, analyzes the typical earthquake damage phenomena and mechanisms, discusses the seismic vulnerabilities of existing brick-wood structures, and proposes the corresponding improvement measures in combination with the actual needs of rural construction. The findings indicate that in the epicentral area, most of the brick-wood structures are moderately damaged or severely damaged, and a few are destroyed. Structures with a mix of brick column and earth wall load-bearing and single-slope high-wall structures suffered more severe damage compared to double-slope brick-wood structures. The damage can be classified into four categories including overall or partial collapse, roof damage, wall damage, and other damage. The primary causes of the damage are identified as irrational structural systems, low mortar strength, poor overall integrity, and the absence of effective seismic construction measures. Consequently, this paper suggests targeted improvement measures to enhance the overall integrity, increase the collapse resistance of the walls, and prevent the collapse of roof components. These measures aim to provide a scientific basis and practical guidance for improving the seismic resilience of rural dwellings and optimizing disaster prevention and mitigation strategies.

To identify an efficient and accurate feature selection algorithm for filtering seismic intensity indicators, the performance of four common feature selection algorithms, MIC, ReliefF, XGBoost and Lasso, was compared and analyzed. Based on the incremental dynamic analysis results of single-degree-of-freedom structures and the ground motion features, the feature selection regression model was established, the ground motion features was sorted and screened according to the Euclidean distance, the performance of the feature selection algorithm was evaluated according to the screening results, and the least squares regression model was established based on the incremental dynamic analysis results of the 2-storey, 4-storey, 8-storey and 12-storey reinforced concrete frame structures, and the standard deviation change of residual was used to measure the prediction ability of ground motion intensity measure selected by different feature selection algorithms for structural collapse. The results show that the accuracy of the ground motion features screened by the Lasso regression algorithm is 31% higher than that of other algorithms when used for structural collapse prediction. The results can be used as a feature selection algorithm reference for the selection of ground motion intensity measures in the uncertainty analysis of ground motion in the structural vulnerability analysis under the performance-based earthquake engineering (PBEE) framework, and can also be used as an effective feature selection algorithm reference for the selection of ground motion intensity measure s suitable for structural collapse prediction.

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.

In order to study the seismic performance of ultra-high performance concrete filled high-strength square steel tube (UHPCFHST) columns, this paper uses the hoop factor, length-to-slender ratio, and axial compression ratio as the parameters of study to conduct the low cyclic reversed loading test. The damage patterns of the specimens were observed, and the influence of each parameter on the hysteretic properties, stiffness, ductility and energy dissipation capacity of the specimens was analyzed. The test results show that the damage characteristics of all specimens are similar, and the phenomena of steel pipe buckling and concrete crushing appear at the bottom of the column. With the increase of the hoop coefficient (from 0.55 to 0.98), the ductility of the specimens increased by 8.91% and 21.52%, respectively. The initial stiffness, horizontal bearing capacity and ductility of the specimens decrease with the increase of the length-to-slender ratio, and the greater the length-to-slender ratio, the more significant the weakening of the ductility of the specimens. When the axial compression ratio increases from 0.1 to 0.2, the initial stiffness and horizontal bearing capacity of the specimen increase, while the ductility decreases. At the same time, the load-bearing capacity test results in this paper and the calculated values of each specification are compared and analyzed. The calculation results of the United States ANSI/AISC 360—16 AISC specification for structural steel buildings are lower than the measured values by 48%, which is relatively conservative. The calculation results of the GB 50936—2014 technical code for cencrete filled steel tubular structures are higher than the measured values by 17%, After analyzing the Fujian provincial local standard DBT/T13-51—2010 technical specification for concrete-filled steel tube structures, the calculation is the most consistent with the actual measurement, which provides a reference basis for the design of high-strength square steel pipe ultra-high-performance concrete columns under low cyclic reversed loading.

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.

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.

To study the vibration influence of urban rail transit on buildings along the line, a frame-shear wall structure near a subway was selected as the research object. Under the excitation of rail transit vehicles, vibration monitoring of typical buildings was carried out at the foundation, along the height direction and the horizontal direction of the building, and the evaluation criteria such as 1/3 octave plumb vibration acceleration level, peak acceleration, and plumb fourth power vibration dose value were used for the analysis. The research results indicate that when the structure is 55 meters away from the inner contour of the tunnel, significant subway-induced vibration can still be detected inside the structure, and the relevant evaluation values may exceed the regulatory limits. In addition, the existing regulations do not specify the selection criteria for subway vibration, and the evaluation quantities determined by different value methods may seriously underestimate the impact of subway-induced vibration. Along the height direction of the structure, the vertical vibration response of the measurement points from the first underground level to the third above ground level did not significantly decrease, and there may be amplification at the top. The vertical vibration at the center of the floor slab is significantly amplified compared to the edge of the floor slab. The plumb fourth power vibration dose value at the center of the slab can reach 345% of that at the corner of the slab, and the corresponding maximum vertical vibration acceleration level can increase by 12.9 dB.

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.