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.

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.

To investigate the seismic performance of the monolithic precast concrete wall with concealed steel plate bracing, a two-story monolithic precast concrete wall with concealed steel plate bracing and a benchmark two-story cast-in-situ wall with the same bracing were designed and constructed. The bracings in the precast wall were connected by welded joints at the wall-to-wall and wall-to-foundation connections to fit the larger construction tolerance. Cyclic loading tests were conducted on the walls. The results indicated that the bracings in the precast wall connected by welded joints were able to satisfy the large construction tolerance requirement and transfer the internal force well. The seismic performance of the monolithic precast concrete wall was emulative to the cast-in-situ wall in terms of the lateral strength, stiffness degradation, and energy dissipation. Both of the walls were failed in flexure, but the monolithic precast wall formed an additional plastic zone at the top interface of the post-casting segment.

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.

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.

A recoverable precast shear wall composed of precast RC wall and steel energy-dissipator (RPSW-SE) was proposed and tested under reversed cyclic load. The failure process, shear capacity, hysteretic behavior and degradation characteristics were compared with that for cast-in-place concrete shear wall. Moreover, the damaged specimens were repaired by replacing damage steel member and tested again to investigate the seismic performance including hysteretic behavior, shear resistance as well as energy dissipation capacity, and to discuss the recoverable of RPSW-SE. The results showed that the RPSW-SE had good integrity and shear resistance, and the hysteretic curves were relatively full. The steel-energy connection area yielded prior to RC wall and dissipated a large amount of energy, enhancing the deformation capacity and energy dissipation capacity. The stress distribution and damage evolution of the shear wall was improved, and the failure of the RPSW-SE was caused by the fracture of the short steel-column at the slits of the shear-plate, without obvious plastic damage in the concrete wall. It was analyzed that more than 90% of the energy-dissipation in the shear wall was concentrated in the steel-energy connection area, achieving the controllable damage and energy dissipation. The performance indexes of the repaired RPSW-SE were close to those of original ones, indicating that the RPSW-SE had good recoverability.

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.

After thousands of years, the Archery Tower of the Deshengmen has been damaged in different degrees and types. Through the investigation of the damages, the number, proportion and distribution of the damage types have been summarized and the causes of the typical damage characteristics and its influence on the mechanical performance of the wooden frame have been analyzed. In order to explore the influence of the typical damage characteristics on the mechanical behavior, the comparative analysis on the influence of pulling-out of tenon on the mechanical behavior of the wooden frame is made, and the FEM of the standard frame and the frame in the state of pulling-out of tenon are established. Results show that the damages are mainly concentrated in the column frame layer and the beam frame layer. The damage of the column frame layer is mainly manifested by cracking and inclination. The typical damage of beam frame layer mainly includes pulling-out of the tenon and horizontal crack of wooden beam. Besides, the moment-rotation angle curve of joint has obvious asymmetry. The failure state of the joint is the tearing failure of the cross grain at the variable section of the tenon. When the amount of pulling-out of the tenon is numerical, the amount of pulling-out of the tenon has no obvious effect on the flexural bearing capacity of the frame. When the amount of pulling-out of the tenon increases to a certain level, the flexural bearing capacity of the beam frame will decrease significantly, and the positive peak bearing capacity will decrease significantly relative to the negative loading. The positive decrease rate is 16% ~ 18%, and the negative decrease rate is 9%~15%. The study results can provide important references for the safety protection and repair of traditional wooden structures.

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.

Shaking table test is an effective means to study the complex dynamic characteristics and seismic response of large structures, and it is the key to desigh the scale model structure in the shaking table test due to the limitation of shaker size and load. Based on the dimensional similarity method and elastic similarity law, the geometric similarity ratio of 1∶20 was taken, and the design of the dynamic scale model of key parameters was carried out using a spatial special-shaped arch bridge as the prototype. Firstly, through finite element numerical analysis, the dynamic characteristics, internal forces and displacements of the original bridge model and the scaled bridge model under dynamic action are analyzed to verify the rationality of the scaled model. Under the selection of reasonable seismic action, the structural time history response analysis was carried out. The calculation results show that the scaled model bridge is completely consistent with the first tenth-order mode of the prototype bridge with the frequency error less than 7%, the response error of internal force, displacement and acceleration of the key section has not exceeded 10%, and the scaled model bridge can reflect the dynamic characteristics and response characteristics of the original bridge. This research work can provide technical support for the seismic design of shaking table of space irregular arch bridge, and provide reference for shaking table tests of similar bridges.

With the increase of concrete age and performance degradation, the dynamic response of concrete dam will change significantly. The heightened gravity dam is also affected by the difference between new and old concrete materials. In order to study the influence of the aging of gravity dam materials and the performance difference of new and old concrete in heightened gravity dams, taking the heightened Danjiangkou gravity dam as an example, the seismic dynamic response analysis is carried out by using the ABAQUS finite element analysis software. The demolition and reconstruction (the new material condition) and the construction according to the heightened height (the old material condition) are compared with the heightened condition, analyzing the responses of heightened gravity dams to the displacement of the crest, the stress at key points, and the plastic damage with the aging of the concrete material properties under seismic dynamics. The results show that with the increase of the aging degree of concrete materials, the dynamic response of the heightened gravity dam is generally better than that of the old materials and inferior to the new materials. The damage of the dam body tends to extend downward to the joint surface of the new and old concrete. The heightened gravity dam has the characteristics of strong adaptability, low damage index and high anti-sliding stability coefficient, which improve the comprehensive characteristics of the dam body. Besides, the weak parts such as the new and old joint surfaces should be reinforced and bonded to give full play to the engineering benefits of heightening the gravity dam.

The mass concrete used in gravity dam is easy to lead to inhomogeneity of strength due to its inherent characteristics, construction quality and other reasons. In the current seismic analysis of concrete dams, concrete is generally regarded as a material with uniform strength distribution, but there are few studies on the influence of strength inhomogeneity on dam dynamic damage. Based on the plastic damage theory of concrete and the probability distribution model of Weibull, Python language is used to redevelop ABAQUS. On the premise of considering the plastic damage of concrete, the influence of random inhomogeneity distribution of concrete strength on the damage of gravity dam body and bedrock is studied. The dynamic damage of dam and bedrock, the interaction between dam and reservoir water, and the radiation damping of infinite foundation are comprehensively considered in calculation. The dynamic responses of dam and bedrock after earthquakes, such as damage area distribution, damage area ratio and damage dissipation energy, are compared and analyzed. The influences of inhomogeneity concrete strength on dam and bedrock seismic damage are revealed. The research results can provide reference for the design and construction of gravity dam.

Many steel-concrete composite curved box girder bridges have been built recently, while in these bridge designs, the understanding of vehicle-bridge coupled vibration was limited. Due to the effect of bending-torsion coupled under vertical loading, the change of the reaction force of the relevant support bearing has not been well solved. In this paper, based on the ABAQUS general finite element software, the horizontal curved motion of the vehicle was simulated by the method of Fourier series, which made the numerical analysis of vehicle bridge coupled vibration be possible. The numerical analysis results had verified for its accuracy with the existing experimental and theoretical ones. Taking a steel-concrete composite box girder bridge with four spans as an example, further analysis were carried out considering the influence of the support bearing force of bridge under the case of vehicle on the inside and outside lanes and superelevation . The results indicate that the outer support bearing of the other side of the box girder will appear falling, when the vehicle is driving along the inside or outside lanes of the curved girder bridge. The vehicle speed has little influence on the peak support bearing force, while the bearing separation can be alleviated by the lower vehicle speed. The superelevation has little effect on the support bearing reaction force. When the vehicle is driving along the inside lane, it will be easy to alleviate the falling of some support bearings of the outside box girder. When it is driving along the outside lane, it will aggravate the bearing separation of the inside box girder.

In this paper, the stilted buildings were taken as the research object, and according to the characteristics of unequal height embedded structure, three types of three-dimensional stilted frame structures were designed: non-isolation, base isolation and the second floor column bottom isolation (interlayer isolation). Then elastic response spectrum analysis and elastic-plastic dynamic time history analysis of analysis models were carried out to investigate the influence of different isolation bearing layout on the dynamic response, failure mode, probability of seismic collapse and other seismic performance of stilted frame structures. The results show that the application of seismic isolation technology to the stilted frame structure on slope can control the dynamic response of the structure and improve the safety margin of the whole structure, which provides a new way to improve its seismic performance. The setting of base isolation can improve the non-uniformity of structural stiffness distribution, reduce the difference of shear distribution between stilted columns and improve the safety reserve of the shortest columns. However, there are differences in the deformation of isolation bearings with different levels. Isolation bearings with different lateral stiffness should be arranged in the base isolation model. Compared with the base isolation, the interlayer isolation has better ability to control the structural damage, the deformation of the upper floor is more uniform, and the probability of seismic collapse is lower. However, in the interlayer isolation design, it should be considered to appropriately reduce the difference of lateral stiffness between stilted columns.

A double shell space damping structure is introduced to reduce the vertical accelerations of the containment in the nuclear power plant. Based on the mechanical characteristics of the structure, a simplified three particle and three degree of freedom dynamic model is established, the structural response transfer functions are further given and the parameter analysis was conducted. The influence rules of the structural mass ratios, damping ratios and frequency ratios on the vertical response of the structure are clarified. The scale shaking table dynamic test of the double shell space damping structure is completed. The test results show that the double shell space damping structure can reduce the vertical accelerations of the inner containment, and the damping ratios are 12.23% ~ 27.84%. The theoretical calculation results are in good agreement with the experimental results. The double shell space damping structure can effectively reduce the vertical acceleration response of the containment in the nuclear power plant.

In order to realize the safety protection of floating cultural relics during earthquakes, a nonlinear quasi-zero stiffness isolation system is analyzed. The stiffness model and the motion balance equation of the isolation system were established, and the harmonic balance method and Newton iterative method were used for theoretical analysis, and the fourth-order R-K method was used for numerical analysis of the motion balance equation under harmonic excitation and ground motion excitation. The theoretical analysis results show that the nonlinear quasi zero stiffness of cultural relics of the isolation system under harmonic excitation, outer excitation frequency is low frequency phase, the response of the system is unstable region, therefore, if the rigidity and damping ratio of the system is improved the unstable area and peak amplitude response of the system will be reduced, and make it tend to be characteristic of the linear vibration isolation system. Increasing the damping ratio can reduce the effective initial frequency of the isolation system, but increasing the damping ratio in the effective frequency band will increase the transfer coefficient of the system. Increasing the spring stiffness will increase the effective initial frequency of the isolation system, but reduce the amplitude response of the system in the low frequency stage, but increase the transfer coefficient of the system in the effective frequency band of the isolation system. Numerical analysis shows that there are only two stable solutions in the unstable region, and the response state of the system is related to the initial state of the system. The system can significantly reduce the acceleration response of input ground motion under the action of actual ground motion excitation. The damping coefficient of the isolation system is insensitive to the change of the input peak value of the ground motion with less long period components, but is sensitive to the change of the input peak value of the ground motion with more long period components, indicating that the isolation performance of the system is better for the short period ground motion, which is consistent with the theoretical analysis results under the action of simple harmonic excitation.

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.

On Dec. 18th, 2023, a magnitude 6.2 earthquake hit Jishishan Town of Linxia City in Gansu Province, and caused an unusual mud sliding disaster in Jintian Village and Caotan Village of Zhongchuan Town in Qinghai Province. The mud flowslide resulted in catastrophic consequences as casualties and demolishing and burying of residential houses. Such large mud sliding phenomenon has not been frequently reported in historical earthquakes. Through field investigation, it is confirmed that the underlain soil liquefied and triggered the disastrous phenomenon which has already been termed liquefaction-induced flowslide. Nevertheless, the massive liquefaction-induced flowslide is the first time been reported and verified by field evidence in recent 70 years. The investigation and analytical results demonstrate that the underlain soil layer in the upstream area liquefied, triggering instability and catastrophic flowslide, and the soil and water conditions in the flowing channel potentially accelerated the sliding. It is deduced that liquefaction possibly occurred in many a place, that is, the sliding channel was suspected of liquefying in various spots. The ground shaking intensity in the sliding area maintained relatively high, and that the peak ground-motion acceleration was estimated around 0.4 (±0.1) g. The findings and investigation results are useful to help understanding the mechanism and process of the uncommon flowslide disaster.

The investigation of earthquake damage shows that the lateral spread of gently inclined soil is a common form of foundation failure. As the concrete pile has a high vertical bearing capacity and shear resistance, and the stone column has a high permeability, which can effectively reduce the degree of liquefaction of the surrounding soil, whether the concrete-stone composite pile can be used as an effective engineering measure to deal with the large lateral deformation of liquefaction in gently inclined soil, its feasibility is worthy of in-depth research. Therefore, the numerical model of liquefiable soil-pile foundation is established based on OpenSees finite element platform, then the reliability of the numerical model is rerified. On this basis, the reinforcement effect of concrete-stone composite pile on inclined liquefaction soil is studied. In addition, the effects of area ratio of core pile and thickness of stone shell on dynamic response of inclined liquefaction soil are discussed. The results show that the concrete-stone composite pile has a significant anti lateral displacement effect, which can effectively reduce the lateral displacement of the surrounding soil and the bending moment of the concrete core pile. When the proportion of concrete core of pile body is about 20% and the proportion of stone shell area is 80%, it is the optimal design scheme.

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.

When the lifting platform works at heights in the outside field, river beach and other environments, the dynamic interaction between the soft soil and outriggers of lifting platform will change the dynamic characteristics of the lifting platform system. In this paper, three dynamic models of lifting platform, which are incorporated with three different inerter dynamic vibration absorber (I-DVA) systems defined as SIS, SPIS-1 and SPIS-2, are presented with the consideration of soil-structure interaction. The expression of the amplification factor and the displacement mean square value of the operating platform is derived under harmonic and random force excitation, respectively. The optimal stiffness ratios and damping ratios of the I-DVAs are obtained based on H_∞ and H₂ optimization criteria by genetic algorithm in terms of three different soil foundations. The vibration reduction performance of three I-DVA systems is evaluated under the conditions of their optimal design parameters. The numerical studies show that: SPIS-2 performs the most effective vibration reduction, which not only suppress the resonance amplitude of the lifting platform, but also widen the frequency bandwidth. The soil-structure interaction can reduce the amplification factor under harmonic excitation and the mean square value under random excitation of the operating platform. The soil-structure interaction influences the optimal design parameters of the inerter systems insignificantly under harmonic and random excitation. Therefore, some empirical formulations of the optimal parameters for I-DVAs are fitted in order to provide reference for the vibration reduction design of lifting platform.

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.