A rapid prediction method of seismic-induced damage in high-speed railway ballastless track simply-supported bridge system is proposed based on convolutional neural networks. To obtain more information of seismic motion, one-dimensional seismic motion data is transformed into three-dimensional image through continuous wavelet transform as the input of convolutional neural network. The reliability of the proposed method is validated by comparing with results in damage samples database. The influence of different hyperparameters of convolutional neural networks on prediction results and training duration are analyzed, and a combination of hyperparameters of convolutional neural networks optimized by Bayesian optimization is obtained. The time required for seismic analysis of high-speed railway ballastless track simply-supported bridge system using different seismic analysis methods is compared. The optimized convolutional neural network is utilized to predict seismic-induced damage of different key components in high-speed railway ballastless track simply-supported bridge system. The research indicates that the initial learning rate is the most significant factor affecting the accuracy of network prediction, while the learning rate decay factor, batch size, and number of training epochs have certain effects on the network prediction results. The training duration of convolutional neural network is mainly determined by the number of training epochs and batch size. The proposed method demonstrates high prediction accuracy for seismic-induced damage in various components of high-speed railway ballastless track simply-supported bridge system, and the network structure exhibits high applicability. The optimized convolutional neural network has shorter training time and more accurate prediction for seismic-induced damage in high-speed railway ballastless track simply-supported bridge system. The research findings can provide reference for rapid repair of seismic-induced damage in high-speed railway systems after earthquakes.

In order to explore the feasibility of reuse of waste clay bricks, a series of experimental studies were conducted on hysteretic behavior of 6 brick aggregate geopolymer recycled concrete-filled circular steel tubular (BAGRC-FST) columns. Key parameters including steel tube thickness (4 mm and 6 mm), replacement ratio of brick aggregate (0%, 50%, 100%) and axial compression ratio (0.05, 0.25 and 0.50) were considered. The failure mode, skeleton curves and hysteretic curves of the specimens under reciprocating load were obtained, and the change law of seismic performance indicators such as stiffness degradation, hysteresis behavior, peak bearing capacity, ductility, bearing capacity degradation and energy-dissipation capacity of the components were analyzed. The results indicated that the failure mode of the specimen is characterized by bulging and cracking at the bottom of specimens and the breakage of the core concrete in the area where plastic hinges appear, which is similar to that of ordinary CFST columns. The increase of brick aggregate replacement ratio of brick aggregate and axial compression ratio reduces the bearing capacity of specimens, and the increase of steel tube thickness will increase the bearing capacity of specimens. The hysteretic curves of specimens were plump without obvious pinching effect, implying that the BAGRC-FST columns had desired energy-dissipation capacity. Moreover, increasing the axial compression ratio reduces the deformation capacity of specimens and accelerates the degradation of stiffness and bearing capacity. However, increasing the thickness of the steel tube can improve the deformation ability of specimens. The substitution rate of brick aggregate has limited influence on stiffness degradation, ductility, bearing capacity and energy dissipation capacity of the BAGRC-FST columns.

In order to study the impact of cast-in-place hollow infill walls with flexible connections of PVC joint plates on the seismic performance of reinforced concrete(RC) frame structures, six full-scale specimens were designed and manufactured with hollow concrete walls and PVC joint plates as the main factors, and pseudo static tests were conducted. By comparing and analyzing the seismic performance indicators such as failure characteristics, load displacement curves, skeleton curves, stiffness, displacement ductility, and energy dissipation capacity of cast-in-place hollow infill wall frame structures with pure frame structures, flexible connections with PVC joint plates, and rigid connections without joint plates, it is mainly concluded that the addition of PVC joint plates reduces the improvement effect of hollow concrete infill walls on the lateral stiffness and bearing capacity of the frame structure. The displacement ductility and energy dissipation capacity of the cast-in-place hollow concrete infill wall frame structure have been improved, providing protection for the infill wall. However, the cast-in-place concrete hollow infill wall with flexible connections using PVC joint plates still significantly affects the lateral stiffness and ultimate deformation of the frame structure. When designing the structure, reasonable consideration should be given to its adverse effects on the overall seismic performance of the structure.

High polymer cementitious Gobi soil is made by mixing high polymer with Gobi soil in a certain ratio, which can effectively improve the mechanical properties of Gobi soil. In order to study the dynamic residual deformation characteristics of high polymer cementitious Gobi soils, the effects of high polymer mass ratio, surrounding pressure, consolidation ratio and dynamic stress ratio on the residual shear strain and residual body strain of high polymer cementitious Gobi soils were investigated in this paper using medium-sized dynamic triaxial tests. The results show that the high polymer cementitious materials can effectively reduce the dynamic residual deformation of Gobi soil, and the residual shear strain of polymer cementitious Gobi soil after 30 cycles of loading is 15.0%~18.8% of that of natural Gobi soil, and the residual body strain is 12.1%~22.2% of that of natural Gobi soil. The reduction of residual shear strain was 85.0% and 95.2%, and the reduction of residual body strain was 87.9% and 95.5% for 3% and 12% of high polymer mass ratio. The larger the high polymer mass ratio, the larger the reduction. Projection pursuit regression (PPR) was used to analyze the influence weights of each influence factor on the residual deformation, and the influence weights of the dynamic residual shear strain and residual body strain of the polymer cementitious Gobi soil were obtained as high polymer mass ratio to peritectic dynamic stress ratio to consolidation ratio. An exponential function was used to fit the relationship between residual deformation and vibration times of polymer cementitious Gobi soil, and a modified residual deformation model of high polymer cementitious Gobi soil was established, which can respond to the effect of high polymer mass ratio.

The deep overburden in coastal soft soil areas will magnify ground motion significantly, which will have adverse effects on engineering construction. Based on the frequency domain analysis method of seismic response in one-dimensional horizontal soil layer, inputting different seismic waves, the equivalent linearized dynamic calculation model is used to analyze the shallow site seismic motion characteristics of different site conditions under 7-degree seismic fortification. The calculation results show that the maximum acceleration, the maximum shear stress, the maximum shear strain and relative displacement of the shallow soil layer within 70 m can be significantly affected by the difference of shallow soil layer thickness or seismic wave spectrum. The variation of relative displacement with depth does not conform to the characteristics of cosine function recommended by the code. The cosine curve apparently underestimates the rate of change in displacement (shear strain) at the shallower position and overestimates the rate of change in displacement (shear strain) at the deeper position. In this paper, a fitting relation is proposed to estimate the relative displacement of shallow soil layers within 70 m in coastal soft soil areas under 7-degree seismic fortification. This fitting relation has certain limitations, but can provide reference for seismic response analysis of underground engineering in coastal areas.

In the accelerated process of urbanization, the deterioration of aging buildings, and the rapid climate change in current times, the resilience and sustainability of buildings have become increasingly important. Post-earthquake rehabilitation of buildings often requires significant economic and downtime cost, while also causing severe environmental impacts such as carbon emission. However, it is still lack of reasonable and rapid assessment method for evaluating seismic environmental impact. Therefore, this study proposes an improved building life cycle seismic environmental impact assessment method, using the input-output database and the “ repair cost-ratio”assumption to convert existing seismic economic loss data into environmental impacts, considering the key factors that reduce the feasibility of building rehabilitation due to residual deformation. It quantifies the life cycle seismic environmental impact of buildings under seismic risk through seismic hazard analysis, structural analysis, damage analysis, and loss analysis. Based on this method, the life-cycle seismic environmental impact assessment of steel frame buildings strengthened by self-centering braces (SCB) and buckling-restrained braces (BRB) was carried out. The results show that if the reduction in rehabilitation feasibility caused by residual deformation is not considered, the seismic environmental impact will be seriously underestimated. After considering the residual deformation, compared with BRB, the frame strengthened by SCB shows a significant advantage in reducing the impact of the seismic environment with the minimal residual deformation.

In order to improve the seismic performance of prefabricated frame structures, different types of steel energy dissipation hinged dampers have been proposed that the prefabricated beams and columns are connected with steel hinges and the mild steel energy-dissipating elements are installed on the upper, lower or both sides of the hinges. The structural forms and seismic performance of several energy-dissipated hinged dampers were summarized, and a T-shaped energy-dissipated hinged damper with simple structure and good seismic performance was selected to study the seismic performance and mechanical model. ABAQUS software was used to simulate the test of T-shaped damper, on this basis, 24 finite element models were established to analyze the flange weakening degree and T-shaped section size of the T-shaped energy dissipation element, the different influencing factors were quantified to obtain the skeleton curve calculation formula of the energy dissipation hinged damper, finally, the correctness of the formula was verified. The results show that the T-shaped energy dissipation hinged damper has good bearing capacity, ductility and energy dissipation capacity. The proposed skeleton curve has high accuracy, and can provide reference for the design of this kind of damper.

Seismic(vibration) isolation technology is an effective measure to improve the seismic performance and comfort of over-tracking buildings, and the design methods optimization of such structures has practical significance and urgency. This study proposes an evaluation model based on the ratio of benefit to life cycle cost that suitable for over-tracking seismic (vibration) isolation structures. The effects of key structural parameters such as period ratio, mass ratio, stiffness and damping of the isolation layer on the benefits of the over-tracking seismic (vibration) isolation structures were studied. Based on genetic algorithms, an optimal design method for over-tracking seismic (vibration) isolation structures is proposed. The research results show that the seismic losses of the structure after adding isolation layers are mainly concentrated in the substructure, and the greater the mass ratio of the upper and lower structures, the smaller the seismic losses. The period ratio of the upper and lower structures has a greater impact on the overall seismic losses of the structure. The larger the period ratio, the smaller the seismic losses. The stiffness of the isolation layer is positively correlated with the isolation efficiency. After using the optimization algorithm to optimize the prototype structure, both seismic losses and vertical acceleration vibration levels were reduced, verifying the feasibility of this method and providing reference for engineering design.

Shape memory alloys (SMA) have the characteristic of superelasticity and shape memory property, and are increasingly applied to civil engineering. A novel SMA-based device is proposed, which has the seismic mitigation and displacement limiting capacities. The device connects with the superstructure and substructure of the bridge through axis pins. The novel device not only can restrain the bridge in a safe range, but also can dissipate the seismic energy, and protect the bridge from earthquake damage. This study comments with pseudo-static tests on a single SMA cable specimen and the novel device. The constitutive models of the SMA cable and the novice device are proposed based the test results. A finite element model of a cable-stayed bridge with a main span of 360 meters was established in OpenSeesPy software for investigation. Seven far-field and seven near-field earthquake records were selected to study the seismic responses of the cable-stayed bridge with the novel device equipping 0, 5, 10, 15, 20, 30, 40, 50 SMA cables. The study results indicate that the maximum longitudinal displacement of the girder decreased significantly with the number of SMA cables increased. However, this reduction was accompanied by a slight increase in the average maximum curvature at the base of the main tower. For example, the seismic mitigation device with 10 SMA cables reduced the average maximum displacement of the girder by 51.8% and 36.8% under seven far-field and seven near-field earthquakes, respectively. However, the corresponding average maximum curvature at the tower base increased by 5.1% and 16.0%, respectively. Consequently, the proposed SMA-based seismic mitigation device can effectively reduce the displacement of the girder at the cost of a small curvature increment at the tower base.

To capture the characteristics of faults accurately, considering a typical coal mine as an example, the geological model of fault zone and fault plane is established by the numerical calculation method, and the influence of thickness of fault fracture zone and fault plane on mining of coal mine working face under normal fault condition is studied. The study shows that the smaller the stiffness of the fault plane is, the more time steps need to be calculated for the model balance. Under given conditions for the thickness of the fault zone, the influence of the fault plane gradually increases as the working face advances closer to the fault plane under the conditions of different contact surface stiffness, the stress peak in front of the working face tends to rise with the increase of interface parameters, and the stress peak is the highest when there is no interface, and the vertical displacement of the working face roof increases gradually with the decrease of the interface stiffness. The stress in front of the working face increases with the increase of the thickness of the fault zone under the same interface parameters. The vertical displacement of the roof increases with the thickness of the fault zone. With the increase of the vertical distance from coal seam under different interface parameters, the displacement difference between the two sides of the fault of the high strata is larger than that of the low strata, and the two separate plates is also larger in the high strata. Under the condition of different fault zone thicknesses, the displacement difference between the two sides of the fault increases with the advance of working face. The slip amount of the point with higher strata is larger than that of the point with lower strata in a certain range of vertical distance. The slip amount on the two sides of the fault increases with the increase of the thickness of fault. This study has certain guiding function for coal mining under the influence of faults.