The permanent magnet can provide an initial magnetic field for the magnetorheological isolation bearing. A new type of isolation bearing is designed by using the permanent magnet and the electromagnetic coil to form a mixed magnetic field function. The magnetic field generated by the coil adjusts the magnetic field of the permanent magnet to change the stiffness of the magnetorheological elastomer layer, and realizes the variable stiffness performance of the isolation bearing. Using ANSYS Electronics software to simulate and analyze the isolation bearing, simulate the magnetic induction intensity inside the test device under different current intensities, draw its magnetic flux density cloud map and calculate its saturation point. The magnetorheological elastomer with 23% carbonyl iron powder was prepared. The effects of excitation current intensity, shear amplitude and excitation frequency on the shear performance of the isolation bearing were studied. The results show that the stiffness of the isolation bearing decreases in real time with the increase of the control coil current, and the variable stiffness characteristics of the magnetorheological elastomer isolation bearing are realized. Under the condition of stiffness softening, the excitation current intensity, shear amplitude and excitation frequency have significant influence on the equivalent stiffness and equivalent damping of magnetorheological elastomer isolation bearing.

The percussion-based method refers to a detection technique that utilizes a hammer to percuss test structures to produce vibration and sound, and diagnoses any abnormalities in structures based on sound features. Percussion-based bolt loosening detection has been one of the hot research topics in recent years. Most existing studies focus on the issue of single bolt loosening, while multi-bolt connections are commonly used in engineering applications. Therefore, current methods can not meet requirements for multi-bolt loosening detection in engineering. This paper proposes a fast percussion-based multi-bolt loosening detection method, using a single-row multi-bolted steel beam-column joint as the research object. Firstly, characteristic vectors of percussion sound of each bolt within the joint are extracted by short-time Fourier transform and binarization processing. Then, the Euclidean distances between characteristic vectors of each bolt under the loosening cases and under the reference case are calculated to quantify loosening characteristics. Normalized loosening indexes are subsequently constructed by combining loosening characteristic values of all bolts to measure loosening degree of the joint. Finally, the loosened bolts are identified by comparing the difference between loosening characteristic values and baseline value of each bolt. Experimental results show that the proposed method can rapidly and accurately identify loosened bolts in the joint, and further enhance the potential of percussion detection method in engineering application.

In order to improve the refinement level of mechanical parameters of layered structures explored by Rayleigh wave, this study constructed the Rayleigh wave dispersion equation in layered elastic semi-infinite stratum based on the spectral element method. For the two stratum structures of semi-infinite and “upper soft and lower hard”, compared and calculated the dispersion curves of multi-modes Rayleigh wave with spectral element method and fast vector-transfer algorithm. The results show that the relative error between the calculation results of spectral element method and the corresponding results of fast vector-transfer algorithm is under 0.05%, which has high calculation accuracy. On this basis, for the three complex layered structures of “upper hard and lower soft”pavement structure, containing “soft interlayer” and containing “hard interlayer”, this study derived the calculation method of surface displacement based on spectral element method, and established an semi-analytical method to determine the superposition coupling mechanism of multi-modes Rayleigh wave in complex stratum structure by analyzing the contribution of each mode phase velocity of Rayleigh wave to surface displacement energy, which are in good agreement with the corresponding simulation results of velocity-stress finite element method, indicating that it is reasonable and feasible to calculate the dispersion curves of Rayleigh wave and reveal the superposition coupling mechanism of multi-modal Rayleigh wave based on spectral element method.

In order to meet the needs of the rapid development of super high-rise buildings and modern industrialized residential building systems, a new type of plate-reinforced composite (PRC) coupling beam with steel bar truss deck is proposed. The failure mode, bearing capacity, deformation capacity and energy dissipation capacity of PRC coupling beams without considering the effect of floor slab, with ordinary reinforced concrete(RC) floor slab and with steel bar truss deck were studied by quasi-static test. At the same time, ABAQUS software was used to analyze the stress development of concrete, steel plate and steel skeleton of PRC coupling beam with steel bar truss deck under different peak loads. The results indicate that the shear bearing capacity and ductility of the coupling beam can be significantly improved with steel bar truss deck, and the setting of steel bar truss deck can significantly increase the peak load of the coupling beam, and the improvement of the bearing capacity of PRC coupling beam with steel bar truss deck is stronger than that with RC slab. The forward peak load of specimen PRC-S3 is 31% and 18% higher than that of PRC-NS1 and PRC-S2, respectively, but the stiffness degradation of the coupling beams with slabs were more serious after cracks were produced at the junction of beams and slabs. PRC coupling beams with steel bar truss deck have superior energy dissipation capacity, and there are significant diagonal compressive struts in the span of the coupling beams. The main compressive strut and its derivative compressive struts together constitute the truss to bear the shear force. Stress concentration occurs at the bottom of the coupling beam in the upper and lower chord reinforcement of the truss and the longitudinal reinforcement of the coupling beam, and the cumulative energy dissipation corresponding to the failure point of the coupling beam specimen PRC-S3 is 1.39 times that of the specimen PRC-NS1 without slab.

In assembled integral shear wall structures, the quality of sleeve grouting connections is random, that the vertical connection performance of structure and the seismic performance of structure will be affected. According to the pull-out tests of grouting sleeves with different defective degrees, a set of equivalent grouting sleeve defective connection bearing capacity models is established in this paper, and a finite element model of the assembled integral shear wall structure is built based on an actual engineering structure. By considering the randomness of grouting defects, the mechanical connection properties of grouting sleeve joints are given to the corresponding degree of defects, reflecting possible defects in the grouting sleeve. Structural stochastic non-linear response analysis and reliability assessment were carried out by non-linear finite element analysis and combined with probability density evolution method(PDEM). The results show that the structural non-linearity has a significant coupling effect with randomness under dynamic action. The randomness of defects will gradually amplify the effect on the structural response over time, and there will be significant differences in the overall reliability of the structure in different safety domains.

This paper aimed to investigate the seismic failure characteristics of the railway gravity piers with pile foundation under the influence of frozen soil layer and the influence of different influencing factors on the seismic performance of railway gravity piers with pile foundation in the seasonal frozen soil region. Firstly, the seismic damage characteristics of the railway gravity bridge pier with pile foundations in frozen soils were investigated by quasi-static model test. Secondly, a finite element model of bridge pier with pile foundation considering frozen soil effect was established. Then, the influence of the seasonal frozen soil layer thickness, shear-span ratio, axial compression ratio and bearing depth of pile cap on seismic performance of the railway gravity bridge pier with pile foundation was discussed by numerical simulation method. The results showed that the increase of seasonal frozen soil layer thickness in a certain range is beneficial to improve the seismic performance of the railway bridge pier with pile foundations, but if the frozen soil layer thickness increased beyond this range, its influence on the lateral bearing capacity of the bridge pier is weakened and the damage of pile-soil-pier system will be accelerated. Increasing the shear-span ratio and decreasing the embedded depth of the pile cap can significantly reduce the seismic performance of the bridge pier with pile foundations in frozen soils. Increasing the axial compression ratio can increase the lateral bearing capacity of the bridge pier with pile foundations, but it will accelerate the appearance of peak load of the bridge pier with pile foundations and accelerate the damage of the pile-soil-pier system.

Assembly supports and hangers have been widely used in engineering, but there are few researches on their seismic performance. To investigate the failure mechanism, seismic behavior and influence factors of assembly portal supports and hangers under earthquakes, reverse cyclic loading were subjected to two different typologies of specimens to acquire the influence of seismic bracing and joint connectors on their seismic behavior. The results showed that specimens without seismic bracing were easy to fail at the right-angle or channel base connectors, specimens with seismic bracing were easy to fail at the connection of pipe hoop. The seismic performance of the joints connected by interlocking was poor, while the joints connected by bolt-through was superior. The elastic stiffness, ultimate strength, yield strength, strength and stiffness degradation, and energy dissipation of specimens with seismic bracing were better than those of the specimens without seismic bracing. The main reason affecting the seismic behavior of specimens without seismic bracing was the performance of joint connectors, while the main reason for specimens with seismic bracing was seismic connectors. The research can provide reference for the engineering application, quality inspection and standard formulation of supports and hangers.

The steel column-steel plate shear wall coupled structure(SC-SPSW) uses steel coupling beams to connect the steel plate shear wall and the steel columns on both sides. The system can make full use of the coupling effect between steel plate shear wall, coupling beams and steel columns to improve the shortcomings of traditional steel plate shear walls and have favourable seismic performance. This paper adopts plastic design based on energy concept, and derives the design method of SC-SPSW system by combining with relevant codes. Using SAP2000 software, twelve SC-SPSW system cases with different heights and coupling ratios(CR) were designed and carried out by static analysis and dynamic time history analysis to investigate the yielding mechanism and the influence of the coupling ratio on the seismic performance. It is shown that all SC-SPSW systems applying this design method can achieve the ideal yielding mechanism with excellent seismic performance. Suggestions are also made in terms of the appropriate selection of CR for different structural heights.

In order to solve the problem of input ground motion of fault-crossing structure and reveal its seismic response law, based on the physical model of the fault and the equivalent pulse function, this paper constructs a matrix considering the spatial variation characteristics of ground motion. A hybrid simulation method of high and low frequency superposition is proposed to simulate the input ground motion on both sides of the fault. Firstly, based on the established bridge site fault model, the stochastic finite-fault method is used to generate high-frequency ground motion at the target location. Secondly, according to the characteristics of pulse effect and permanent displacement of ground motion on both sides of the strike-slip fault, different equivalent pulse models are used to simulate the parallel and normal low-frequency pulse components of the fault respectively. The Butterworth filter is used for high-pass and low-pass filtering at the cut-off frequency. According to the drilling data, site model and the spatial coherence of ground motion on both sides of the strike-slip fault, a transformation matrix is established to simulate its spatial variability. Finally, the high and low frequency components after matched filtering are superimposed in time domain to obtain the input ground motion on both sides of the fault. The rationality of results is examined in three aspects including time history, response spectrum and structural response. 3D dynamic finite-element model of the actual fault-crossing suspension bridge is established using OpenSees to analyze the seismic response under the simulated ground motions. The results show that the angle and position of the fault-crossing and the amplitude of the permanent displacement have a significant influence on the seismic response of the fault-crossing bridge. The large residual internal force and residual displacement are the important reasons for the damage of the bridge.

To improve the seismic performance of building structures and overcome the shortcomings of traditional passive tuned mass dampers (TMDs) with narrow vibration reduction frequency bands and difficulty in adjusting their own frequencies, a SMA-TMD with frequency modulation capability is presented based on SMA springs made of shape memory alloy (SMA) materials. Through frequency testing experiments, researchers found that the frequency of SMA-TMD increases with the increase of current flowing into the SMA spring. Shaking table tests were designed and conducted to validate the feasibility and effectiveness of the frequency tuning and vibration reduction performance of the SMA-TMD. The experimental results show that compared to a detuned traditional TMD, the SMA-TMD, which retunes with the main structure by adjusting input current, demonstrates a higher vibration reduction rate in controlling the top floor peak acceleration response of the structure. The damping performance can be improved by at least 21.5%. Furthermore, the working stroke of the SMA-TMD is significantly improved compared to that of the traditional TMD, the maximum working stroke under the two sets of experimental conditions can be reduced by at least 46.9% and 39.2%, respectively. This improvement can save installation space, reserve more building area, and broaden the application scenarios by enabling placement in structures with spatial limitations.