By reviewing literature in the field of earthquake engineering, the pulse-component models of earthquake ground motions are collected and organized. The characteristics of various pulse models are compared and discussed. The research significance of these pulse-component models is concluded and organized to form a systematic research framework. According to the existing research results, it is pointed out that the seismic hazard analysis considering the pulse effects in earthquake ground motions is the core in the research framework. Although the pulse models use different mathematical expressions to describe the same pulse characteristics, their performance is similar in structural dynamics. There are similarities between the pulse models with the forward directivity effect and those with the fling-step effect. At last, the details on considering the pulse effects in ground-motion selections for seismic design of structures are discussed.

In order to clarify the differences of wind vibration response of base-isolated buildings calculated by three commonly used biaxial restoring force models of MSS, Casciati and Harvey and Gavin, three models were used to simulate the restoring force of lead-rubber bearing under horizontal uniaxial and biaxial displacement. Comparing the differences of tests or finite element results. The differences in base displacement, top displacement and top acceleration for a numerical example were analyzed using three models. The results show the trends that the restoring forces of three models simulate the lead-rubber bearing in uniaxial cyclic displacement, square and offset square displacement are basically the same. While simulating circular and offset circular displacements, the biaxial restoring force shape of MSS model is different from the finite element results, which cannot simulate the coupling behavior of the bearing accurately, and the error of Casciati model is slightly smaller than that of Harvey and Gavin model. The Casciati model and the Harvey and Gavin model are basically the same in calculating the wind vibration response. For the root-mean-square of the cross-wind response, the differences between the three models are not significant. For the root-mean-square of the along-wind base displacement, top displacement and top acceleration, the MSS model is slightly smaller, while for the peak factors of base displacement in along-wind and cross-wind, the MSS model is slightly larger. For the variation of the peak factor of top acceleration and the ratio of the maximum top acceleration of bidirection to unidirection with wind speed in along-wind and cross-wind, the MSS model differs from others. With the consideration of the simulation of biaxial coupling effect and the difference of wind vibration response, the Casciati model is suggested to consider the influence of biaxial restoring force model on wind vibration response of base-isolated buildings.

The current research on ground motion parameters and fragility analysis of large-span spatial reticulated domes mostly focuses on the superstructure, ignoring the influence of the substructures on the overall structure. In order to select the ground motion parameters suitable for evaluating the response of schwedler single-layer reticulated domes supported by substructure, six single-layer reticulated domes with different rise-span ratios and different substructures were designed. Then, the dynamic characteristics of the reticulated domes supported by substructure are analyzed. After that, incremental dynamic analyses were carried out for reticulated domes supported by substructure on multiple three-dimensional ground motion records. Based on incremental dynamic analysis data, eighteen ground motion parameters are analyzed and evaluated in terms of correlation, efficiency, and sufficiency. Based on characteristic responses at failure state of a large number of arithmetic cases, the seismic damage model of single-layer reticulated domes supported by substructure was established. The results show that the presence or absence of the substructure has a greater influence on the structural fundamental frequency, and the structural fundamental frequency decreases as the stiffness of the substructure decreases. The difference between the fundamental frequency of the structure without support column and the structure with 10-meter support column is as high as 24%. The acceleration spectrum intensity and PGA are more strongly correlated to the seismic responses of reticulated domes supported by substructure，and the efficiency and sufficiency are better than other ground motion parameters, which can be used as ground motion parameters for fragility analysis of schwedler single-layer reticulated domes supported by substructure. At the same time, when the height of substructure is the same, the seismic performance of the reticulated dome structure with small rise-span ratio is better, and the critical load due to the collapse of the structure is greater. The influence of the support height on the seismic performance of reticulated domes is not linear. Therefore, the height of the substructure should be selected reasonably when designing the structure.

Efficient detection of apparent cracks in reinforced concrete (RC) structures can provide evidence for rapid assessment of earthquake-damaged structures. Such work exhibits large and repetitive characteristics in both earthquake sites and laboratory environments, therefore, it is suitable to adopt the computer vision technology to make up the inefficiency and uncertainty of manual methods. Using images from consumer-grade cameras as data sources, a convolutional neural network (CNN) model suitable for concrete apparent crack detection is constructed by integrating U-Net and VGG-16, and the model training and testing are completed based on a multi-type RC component crack image database. Morphological operations and Otsu threshold segmentation are used to further optimize the crack detection results as input data for width measurement. To reduce the measurement error of crack width caused by the non-perpendicularity of the camera axis to the crack plane, perspective error correction is performed on the original image using specific targets. After verification, the average deviation of the crack width measurement after perspective error correction can be reduced up to 25%.

Structural damage identification based on deep learning are mainly realized by capturing the characteristics and internal rules of data. Insufficient training samples and noise interference may lead to the failure of mining effective features and internal laws. It is particularly important to mine information as much as possible from the data for damage identification. To solve these problems, a structural damage identification method based on graph convolutional network (GCN) is proposed. In order to extract more features, considering the correlation between different position sensors and the characteristics of each sensor data, one-dimensional vibration data was converted into graph data by the graph construction method. Subsequently, GCN was used to extract the data features of the graph samples and achieve rapid classification to achieve the purpose of damage identification. The feasibility and reliability of the proposed method were verified by the Qatar University grandstand simulator structure, and the effects of noise level, number of samples, the method of graph construction and convolutional network parameters on the recognition results were discussed. The results show that, compared with 1 dimensional convolutional neural network, the GCN model has higher damage identification accuracy in the case of strong noise and small samples. The method of graph construction and pooling have certain influence on the identification results. The identification results of Path graph and Topk pooling are stable and higher than those of other combination forms.

A structure damage identification network model ( E-DenseNet) that combines empirical mode decomposition (EMD) and densely connected convolutional network ( DenseNet) is proposed. The collected acceleration signals undergo EMD to obtain multiple intrinsic mode function (IMF) components, and then the weakly correlated IMF components with small absolute values of Pearson correlation coefficients are removed. According to the organization of the input data, three types of E-DenseNet models are set. E-DenseNet1 reconstructs the signal using strongly correlated IMF components to establish one-dimensional single-channel input data. E-DenseNet2 treats each strongly correlated IMF component as a channel to establish one-dimensional multi-channel input data. E-DenseNet3 uses all strongly correlated IMF components to form a two-dimensional matrix to establish two-dimensional single-channel input data. The numerical analysis of a simply supported beam shows that: E-DenseNet1 runs quickly with poor damage detection accuracy. E-DenseNet2 is computationally efficient with high damage detection accuracy. E-DenseNet3 provides good damage detection results but is time-consuming. Compared with one-dimensional multi-channel residual convolutional neural network (ResNet) and standard convolutional neural network （CNN）, E-DenseNet2 performs much better in damage detection accuracy. It is thus concluded that E-DenseNet2 ensures both the computational efficiency and the damage detection accuracy. The visualization analysis of E-DenseNet2 exhibits its damage detection process that for different samples of the same damage scenario, a deeper layer outputs more similar features until the fully connected layer provides the most similar output features.

In order to study the damage evolution law of reinforced concrete grid shear wall under earthquake action, the existing two-parameter earthquake damage model of reinforced concrete members is modified, and the earthquake damage model suitable for grid shear wall is proposed. Using the grey incidence method, the test information of grid shear wall is analyzed, the key design parameters are determined, and the formula for calculating the combined coefficient of damage model is given. The effects of shear span ratio, axial load ratio, vertical limb width and transverse limb height on the damage of grid shear wall are studied, and the relationship between the main parameters and the damage evolution of grid shear wall is obtained. Based on the proposed damage model, the damage index of grid shear walls is calculated. According to the damage state of specimens, grid shear walls were divided into five damage levels including basically intact, mild damage, moderate damage, severe damage and collapse failure, and the damage index range of different damage states was calibrated.

A total of 12 seawater sea-sand concrete filled plastic-lined steel tube (SSC-PLST) specimens were tested by flexural loading and finite element modeling. The bending properties of the composite members and the influence of the plastic lining layer on the bending capacity of the composite members were studied. The effect of plastic lining on the load-carrying capacity of SSC-PLST members was investigated. The results show that, the failure pattern of SSC-PLST specimens is similar to that of conventional concrete filled steel tube (CFST) members, namely, the tension zone of steel tube yields and the concrete produces fine and dense flexural cracks, and the compression zone of steel tube buckles and the concrete at the corresponding position is crushed. The bending moment-deflection curve of SSC-PLST members is characterized by three stages, showing good load-carrying and deformation capacities. The contact stress between different components of SSC-PLST member is relatively small and unevenly distributed. The influence of plastic lining on the flexural capacity of SSC-PLST member is mainly related to the thickness of plastic layer, but is less affected by the strength of steel or concrete. Finally, a simplified calculation formula of load-carrying capacity for SSC-PLST flexural members is proposed, which can provide reference for the engineering application of this structural member.

Based on the seismic performance test of one common shear wall and four ultra-high performance concrete (UHPC) prefabricated composite shear walls, the hysteretic properties, bearing capacity, ductility, stiffness, and energy dissipation capacity were studied. The effects of width-to-height ratio, replacement by expanded polystyrene (EPS) and vertical reinforcement connection on the seismic performance were analyzed. The results show that compared with the common shear wall, the UHPC composite wall has excellent seismic performance and the maximum bending capacity increases. The UHPC prefabricated slab and steel truss can work well with the concrete in the cavity. The hysteretic curve, skeleton curve and stiffness degradation curve of UHPC composite wall are basically consistent with the trend of common shear wall. In the range of the ratio of height to width, the smaller the ratio of height to width, the greater the flexural capacity and stiffness of the composite wall of UHPC, and the worse the energy dissipation. Replacement by EPS can improve the energy dissipation capacity of composite shear wall after yield, but reduce the ductility of UHPC composite wall. Only using the vertical reinforcement of the concealed column to connect with the base has little effect on the flexural capacity and energy dissipation of the UHPC composite wall, but it can facilitate the construction greatly.

In order to study the collapse mechanism of simply supported bridges under liquefiable site conditions, this paper combines the actual earthquake damage investigation and carries out a shaking table model test on the widely used simply supported bridge under simulated liquefaction ground. Continuously enhanced white noise and sine wave excitation were used as the input of the shaking table. The collapse mechanism of the simply supported bridge under liquefaction ground is studied. The results show that the liquefaction phenomenon can be reproduced well by the shaking table test. The maximum strain position and the natural frequency of the piles decrease with the increasing liquefaction, and the increasing relative displacement between adjacent piles will lead to the bridge collapse. The damage mode of the experimental results is close to that of the actual seismic phenomena. This paper can provide a significant reference for the study of soil-structural interaction under earthquakes and also accumulate the experimental data for the seismic safety evaluation of existing similar bridges.

Resonance phenomena have been found many times in Wenchuan earthquake damage surveys, and they have been extensively studied in structural engineering, but in-depth research has not yet been carried out in slope engineering. In this paper, the inherent vibration characteristics and resonance response of horizontal layered slopes are studied by shaking table model tests. Firstly, the natural frequency of the slope is obtained by white noise excitation, sinusoidal sweep wave excitation and natural wave excitation, and the advantages and disadvantages of different methods in obtaining the natural frequency of the slope are discussed. Secondly, by entering sine wave excitations of different frequencies and different amplitudes, the dynamic response characteristics of the slope are studied, focusing on the acceleration and displacement response characteristics of the slope at the resonance frequency. The results show that the results of the white noise excitation and sweep tests are relatively close, and the white noise excitation is more sensitive to the change of the natural frequency of the slope, and the determination of the natural frequency is blurred due to the occurrence of multiple peaks in the natural spectral ratio curves. The resonance response phenomenon of slope appears at its natural frequency, showing that the amplification coefficient of peak acceleration and peak displacement of slope will peak in the resonance frequency segment. Compared with the elevation effect, resonance plays a leading role in the amplification effect of slope response, which will aggravate the deformation and failure of slope under vibration. This work helps to reveal the seismic response characteristics of slopes from the perspective of slope resonance, and can also provide ideas for slope seismic mitigation studies.

Passive variable damping and stiffness device is a device that does not require external energy input and feedback control, and has the functions of variable damping energy consumption and variable stiffness limit. By combined with isolation bearings, this device forms a new isolation system that can effectively control seismic waves of different types and intensities. Based on the theory of performance-based design, a design method for composite isolation systems has been proposed. Through this method, the parameter design of passive variable damping and stiffness devices and isolation bearings in the isolation layer can be completed. The study also provided a complete design process and detailed explanation of the design process, and verified the feasibility and effectiveness of the design method through engineering examples. This performance design method can be widely applied in the engineering design field of composite isolation new systems, providing a reliable design method and technical support for related engineering. Through this advanced design method, the structure can better cope with disasters caused by earthquakes, ensuring the safety and stability of the structure.

The influence of frequency content in earthquake wave on the torsional response of the single-story symmetric frame structure is studied in this paper. The dynamic equilibrium equation for the single-story symmetric frame structure subjected to earthquake wave passage excitation is given, and the relative motion method is adopted to solve the equation. The time-domain analytical solutions in series form to earthquake wave passage excitation are given for torsional responses. The peak column shears of the frame to wave passage excitation are respectively calculated for earthquake waves with sufficient and insufficient frequency content, and the influence of the frequency content on wave passage effect is analyzed. Studies show that the analytical solutions of column shears to wave passage excitation are not only related to the natural frequency and excitation frequency, but also related to the time delay and the square of the ratio of structural fundamental frequency to excitation frequency. The earthquake wave passage effect of frame structure is prone to occur for those earthquake waves whose main frequencies of earthquake acceleration amplitude spectra are lower than the structural fundamental frequency. There is not earthquake wave passage effect for those earthquake waves whose main frequencies are higher than the structural fundamental frequency. The earthquake wave passage effect of frame structure depends not only on the time delay, but also on the low-frequency content. The joint action of low-frequency content and time delay can produce the earthquake wave passage effect. The richer the low-frequency content, the more obvious wave passage effect.

In addition to the direct incident body wave at the bottom, the sub-basin in the basin and sub-basin also have laterally propagated surface waves generated by the large basin, which lead to the change of the resonance characteristics of the sub-basins. Based on the explicit finite element method, the effects of sub-basin impedance ratio, large-basin dip angle and half-width on the resonance frequency and amplification factor of two-dimensional trapezoidal basin and sub-basin under the vertical incidence of SH and SV waves are comparatively analyzed. The results show that: affected by the laterally propagating surface waves generated in the large basin, the maximum values of PGV and E_x in the sub-basin are obviously amplified, and the amplification of SV waves is greater than that of SH waves. The sub-basin impedance ratio has a great influence on the maximum PGV, E_x, resonance frequency and amplification factor of the basin and sub-basin, while the dip angle and half-width of the large basin have little effect. Compared with a single small basin, the resonance frequency of the sub-basin increases under the incidence of SV wave and SH wave, with the value of incidence of SV wave greater than that of SH wave under the same impedance ratio. The amplification factor of the sub-basin under the incidence of SH wave is basically larger than that of the single small basin, while the SV wave is lower than the single small basin under the low impedance ratio, but higher than the single small basin and the SH wave incidence under the high impedance ratio. The resonance frequency and amplification factor of the basin and sub-basin are more affected under the incident SV wave than that of SH wave.

In order to study the effect of irregular seismic loads on soil deformation characteristics, systematic dynamic triaxial tests were carried out on sand samples in this study. In the test, four irregular seismic stress time histories with different peak values and constant amplitude cyclic sinusoidal loads with 20 cycles were applied to three sand samples with different densities for comparative study. The results show that the strain growth curves of sand samples are significantly different under the input of seismic loads and constant amplitude cyclic loads, and the load type and load waveform are the main factors affecting the strain time history development characteristics of soil elements. The correction coefficient obtained by considering the load irregularity is affected by the load type and the relative compactness of sand, and is not affected by the magnitude of the dynamic stress amplitude of the input loads and the type of sand. Finally, for the calculation of soil element deformation under seismic loads, an estimation method based on conventional constant amplitude triaxial deformation test is given.

In order to explore the influence of the parameter changes of piles on the near-field active vibration isolation after the concrete row piles were installed in the foundation, a three-dimensional finite element model consistent with the test site was established in the finite element software, and the finite element model was verified by calculation and analysis. The calculation results were verified and full-size finite element model was established with reference to the TB 10621—2014 Code for design of high-speed railway, and the specific influence of the parameter changes of row piles on the vibration isolation effect under the action of the train load was analyzed. The analysis results show that the effect of the pile length parameter on the vibration isolation effect is obvious. As the parameter increases, the vibration isolation effect is more ideal. When the pile length parameter is 10.5, the ratio will continue to increase, and the vibration isolation effect will not improve significantly. The larger the parameter is, the less ideal the vibration isolation effect is, and the smaller pile spacing can achieve the ideal vibration isolation effect. The burial depth parameter has a significant impact on the vibration isolation effect, the larger the parameter, the less ideal the vibration isolation effect. When the parameter is 3.5, the vibration isolation effect will be unsatisfactory, and a shallower burial depth can obtain a better vibration isolation effect.

In view of the shortcomings of the approximate formula in current standards, combining with the structural characteristics of single-story and two-story brick enclosure wall-timber frame ancient buildings, a cantilever analysis model with concentrated mass and continuous distributed mass is constructed to consider the mass and position of the roof and floor, as well as the distribution law of the mass and stiffness of the enclosure wall and timber frame. According to the principle of structural dynamics, the analytical model is equivalent to a single point cantilever model by using the equivalent mass method. The equivalent formulas of the central concentrated mass and the continuous distributed mass and the calculation formulas of the fundamental period are derived. The developed analytical model can well reflect the influence of the large roof, floor and wall on the natural vibration period of the ancient buildings, and the corresponding calculation formula can be used to obtain the transverse and longitudinal fundamental period of the structure. Combined with the experimental study of the dynamic characteristics of three typical ancient buildings, the application method of the calculation formula is introduced, and the calculated value of fundamental period is compared with the measured value. It shows that the analysis method provided in this paper is suitable for the analysis of the fundamental period of the ancient timber frame buildings with different transverse and longitudinal arrangement of the enclosure walls.

Based on the seismic damage data of Wenchuan earthquake, the seismic vulnerability model of entirety and different sections of mountainous tunnel is obtained by regression analysis. The peak ground acceleration (PGA) was selected as the ground motion parameter and the lognormal distribution was selected as the vulnerability model, and the seismic vulnerability curves of the tunnel structure of entirety and different sections (entrance shallow burial section, entrance transition section, ordinary section, fractured section) were obtained by the maximum likelihood estimation, and the vulnerability characteristics of different section and the whole tunnel were compared and analyzed. Under the condition of slight damage, the seismic vulnerability of the entrance shallow burial section is higher than that of other section. With the increase of the degree of damage, the seismic vulnerability of the fractured section is gradually higher than that of other sections of the tunnel. The average loss rate model of the tunnel was established by combining the loss ratio of tunnel structure in a specific failure state. The tunnel vulnerability models and average loss ratio model established in this paper can be used to evaluate the seismic loss rapidly in the event of similar earthquakes in the future.

The seismic damage investigation and analysis were performed on buildings in Moxi Town and Detuo Town in the meizoseismal area of the M_s6.8 Luding earthquake in Sichuan. Buildings with the characteristics of looseness, brittleness, and eccentricity were seriously damaged, while buildings with confined masonry structure and “even” structural layout have performed surprisingly well. Based on deformation saturation theory and the damage of Luding earthquake, the structural layouts of common buildings were divided into five forms: structure with full hard-brittle axis, structure with full weak-brittle axis, structure with full weak-ductility axis, structure with hard-brittle axis and weak-ductility axis ( either uneven or even), and the corresponding seismic damage performance and internal mechanism of each form were analyzed. The results indicated that the structure with full hard-brittle axis, the structure with full weak-brittle axis and the even structure with hard-brittle axis and weak-ductility axis had not reached the deformation saturation, so the seismic damage was extremely light, with almost no visible cracks, while the buildings with other structural layouts were damaged or even collapsed. Finally, it is suggested that the seismic design of structures should have the concept of “even” by using deformation saturation theory.

The seismic damage of rural dwellings in the M_s 6.2 earthquake in Jishishan is explored. The structural characteristics, construction habits and construction techniques of the rural dwellings in the disaster area were summarized. The collapse and typical earthquake damage characteristics of rural dwellings with different structural forms were analyzed. The mechanisms of traditional building practices on the seismic resistance and disaster prevention capability of residential houses were studied. The results of the research and analysis show that the structural systems of rural dwellings are mostly “tiger hugging head” style brick-wood structure, accounting for 50.9% of the total number of researched houses, and there are fewer cases of earthen structure and brick-concrete structure, accounting for 28.2% and 20.9%, respectively. There are many cases of the overall collapse of the earthen structure in the study area, fewer cases of overall collapse of brick-wood structure, and no cases of total collapse of brick-concrete structures. The earthquake damage of brick-wood dwellings mainly consists of cracking at the corners of the gable walls, dislodging at the joints, partial collapse of the gable walls, and cracking of roof laps. The main earthquake damage to earthen dwellings is damage to the corner of the gable wall, collapse of the gable wall, and collapse of the roof. Earthquake damage to brick-concrete structure mainly consists of wall cracking, wall collapse and floor (roof) damage. Bad construction habits such as mud joints, thick-covered loess roofs, and large-weight door decorations exacerbated the earthquake damage to residential houses and should be improved in the subsequent restoration and reconstruction work. Measures and suggestions to improve the earthquake-resistant and disaster-preventive capacity of rural dwellings were put forward with regard to the seismic damage characteristics of different structural systems and construction habits, with a view to providing reference for the construction，strengthening and renovation of rural dwellings in the disaster areas.

The 6.2 magnitude earthquake in Jishishan of Linxia Hui Autonomous Prefecture in Gansu Province occurred on December 18, 2023. The earthquake caused extensive damage and collapse of town and village buildings, resulting many casualties. It is a typical small earthquake and large disaster. This paper summarizes the seismic damage characteristics and patterns of typical village and town buildings surveyed in the epicenter of the Jishishan earthquake, and analyzes typical cases based on the structural type, construction year, and whether seismic measures are used. The reasons for the severe seismic damage in this earthquake are summarized as follows: Some self-build houses have brick columns and adobe walls, but the two parts are lack of effective connections and have poor seismic resistance. This can be seen from the fact that houses with ring beams and structural columns in the same courtyard are basically intact, but houses without seismic structural measures are severely damaged. Some have varying openings on different floors, resulting in discontinuous vertical force transmission. There are many irregular planar arrangements in the structure. Partial structures are incomplete or have weak areas. Rural self-build houses are constructed according to the habits of craftsmen, without considering the stress requirements under earthquake actions, and a quality supervision system mechanism needs to be established.

The M_s6.2 magnitude earthquake that struck Jishishan County, Gansu Province, on December 18, 2023, caused varying levels of damage to different engineering structures in the region, resulting in significant casualties. In order to study the impact on the water supply system, based on the investigation data, the seismic damage characteristics of buildings, structures, facilities, equipments, and water supply pipeline networks were summarized. The study revealed that structures designed and constructed to be earthquake-resistant experienced relatively minor damage, highlighting the effectiveness of China’s earthquake-resistant design standards. The water plant located in the low-intensity zone was shut down as a result of the earthquake, with oil leakage from certain equipment leading to water contamination and a reduction in water supply capacity. Additionally, the water supply pipeline network in the high-intensity zone sustained multiple damages at the connections of the old steel pipelines, resulting in water shortage and reduced water pressure that adversely impacted residents’ lives. Finally, four recommendations for recovery and rebuilding were proposed, including the adoption of seismic isolation techniques for equipments, the use of flexible connections for pipe-equipment interfaces, the selection of water supply pipe materials, and the conduct of a comprehensive leakage survey of the pipe network.