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.