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.

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.

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.

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.

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.

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.

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.

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 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.

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.