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.