A large number of seismic investigations have shown that the damage caused by nonstructural components could not be ignored, and with the increasing maturity of the response spectrum method, it has become an important method for the seismic response analysis of nonstructural components. However, the current method of generating response spectrum was mostly used for multi-story structures, and the method of generating response spectrum for large-span structures was still not clear. Therefore, this article establishes nine types of single-layer cylindrical reticulated shell structural models on the basis of ABAQUS and Python. Through numerical analysis, the representative nodes of the single-layer cylindrical reticulated shell were identified by comparison, and the spectral characteristics of the three-way acceleration response spectrum were investigated and analyzed, and the fitting form of the node response spectrum was established, and the fitting formula of the three-way acceleration response spectrum of the single-layer cylindrical reticulated shell nodes was proposed. In addition, this article further determined the calculation formula of each characteristic parameter through the fitting analysis, and investigated the relationship between the peak acceleration amplification factor, the peak spectral acceleration amplification factor and the effective distance of the nodes, the structural rise-to-span ratio and the roof mass based on the representative nodes. The research results in this article could be used to approximate the seismic response of the single-layer cylindrical reticulated shell non-structural components, and could provide a valuable reference for the generation of response spectrum for other large-span structures.

In order to improve the seismic performance of reinforced concrete (RC) frames, carbon fiber-reinforced polymer (CFRP) was used to retrofit reinforced concrete frame structures. The effects of CFRP on the failure mode, the energy dissipation characteristics, the lateral stiffness degradation patterns, the ultimate bearing capacity degradation and the ductility of RC columns were investigated by the pseudo-static tests. The results show that the peak bearing capacity, initial stiffness and ductility of the CFRP reinforced model are increased by 43.89%, 39.27% and 30.10%, respectively. Based on the parametric study of the finite element model, the contribution of CFRP to the seismic upgrading effect of RC columns was quantitatively revealed, and the optimized design of CFRP retrofitted was proposed. The results indicated that the peak load, ductility and energy dissipation capacity of the whole structure are improved by using CFRP full-wrap reinforcement and strip reinforcement models with different coverage areas. The damage degree of column decreases, the damage degree of beam increases, and the failure mode changes from “column hinge” to “beam hinge”. Simultaneously, different CFRP reinforcement areas and the distance between strip-shaped CFRP have different reinforcement effects on concrete structures. Based on the investigation results, the recommended ratio of the width of CFRP strip to its spacing is 1.00 to 1.25.

In order to investigate the effectiveness of treatment measures for silt subgrade in high seismic fortification areas, vibration table model tests were conducted on pure silt subgrade and reinforced silt subgrade. Based on a comparative analysis of the failure characteristics and dynamic response laws of the two models, the influence mechanism of reinforcement on the seismic performance of silt subgrade was explored. The experiment shows that after the peak acceleration of seismic load reaches 0.25 g, the experimental pure silt subgrade gradually experiences cracking, fragmentation, and sinking failure. After adding four layers of geogrids on the slope side of the subgrade, the seismic resistance of the silt subgrade can be effectively improved. When the peak acceleration of the seismic load is loaded to 0.35 g, although cracks also appear on the reinforced silt subgrade, the subgrade can still maintain good integrity. Under seismic loads, reinforced silt subgrade and pure silt subgrade have basically the same acceleration and dynamic soil pressure response rules. The acceleration amplification factor increases nonlinearly with the increase of subgrade height, and decreases with the increase of seismic load. Under the same load, the amplification factor on the slope side of the subgrade is larger than that on the centerline side, but the difference between reinforced silt subgrade is smaller. The dynamic soil pressure of both models shows a pattern of “larger on both sides and smaller in the middle” in the height direction of the subgrade. In the direction of the subgrade cross-section, the dynamic soil pressure on the centerline side of the subgrade is greater than that on the slope side. Due to the influence of subgrade structure, the potential fracture surface of reinforced silt subgrade under seismic loads will form at the end of the reinforced body and within the low pressure compaction zone. Reinforcement is an effective measure to improve the seismic performance of silt subgrades. In practical engineering applications, the length of the reinforcement should not be less than 0.65H, and there should also be sufficient anchoring length.

The reactor building is a vital part of the nuclear island. Its floor response spectrum is essential for the design of internal equipment, such as the reactor pressure vessel and steam generator. To study the variation of the floor response spectrum of seismic isolation structures under different seismic inputs, a shaking table test was conducted on a nuclear reactor building model with a geometric similarity ratio of 1∶20. Three sets of seismic motions were generated based on NRC Reg. Guide 1.6. These included unidirectional (X-direction), bidirectional (X+Y directions), and triaxial (X+Y+Z directions) motions. Accelerometers were used to measure the floor responses under each condition, allowing for the analysis of response spectra for key floors. The results indicate that seismic isolation structures have two main peak points in the floor response spectrum, located near the first and second natural frequencies. The first frequency exhibits a lag, while the second frequency has a lead. There is a coupling effect between seismic motions in different directions. Near the first frequency, this coupling reduces the peak response of the upper structure’s floor spectrum. In contrast, near the second frequency, the interaction between vertical and horizontal seismic motions sharply amplifies the response, and this effect increases with height.

Vertical ground motion is more intense in the near-fault zones, which poses a potential threat to the rocking self-centering (RSC) column piers with low seismic damage characteristics. Based on the OpenSees platform, finite element model of RSCs was established, and the accuracy of the modeling method was validated by comparing simulation results with pseudo-static and shaking table test results. Ten near-filed ground motions with pulse-like waves were used as the earthquake inputs, and bidirectional horizontal excitation and the three-dimensional excitation were considered respectively. A research on the influence of vertical ground motion on the seismic response of RSCs, and the continuous beam bridge with RSCs was conducted. The results show that vertical ground motions can increase the maximum axial force of RSCs, and reduce the minimum height of the RSC section, but the changes are not significant on average. Under disadvantageous conditions, the maximum axial force can increase by about 19.55%, and the minimum height of the compression zone of the section can be reduced by about 22.05%. Overall, the vertical ground motion has a minor impact on the maximum displacement at the top of RSCs. Vertical ground motion can greatly change the tensile stress and failure of energy-dissipating steel bars in RSC bridge columns. Therefore, it is necessary to consider the vertical ground motion effects on seismic response estimation of RSC bridge columns and RSC bridge structures.

To overcome the overly conservative nature of uniform hazard spectra and the unconservative nature of conditional mean spectra, the composite spectrum that combines the previous two spectra is proposed. The conditional periods are determined based on specific seismic information of the site (including magnitude, epicentral distance, etc.). This allows for the construction of multi-composite spectra that capture the regional seismic characteristics. A composite spectrum, representing the envelope of the corresponding conditional mean spectrum of one earthquake scenario, is ‘moderately’ conservative. By considering the influence of all earthquake scenarios in the region, the multiple mixed spectra are applicable for seismic analysis of all structures within the region. As illustrated by a specific region, the uniform hazard spectra, seismic parameters, and conditional periods of the region are determined following the seismic hazard analysis, and the method for generating multiple composite spectra is presented. Both the composite spectra and the design spectra are used to select actual ground motions. A case study is conducted on a typical cable-stayed bridge and the seismic responses in the longitudinal and transverse directions are compared. It shows that due to the contribution of higher modes, there exist significant differences in the vibration amplitude of different bridge components. The force response (including bending moments and shear forces) of the tower is more sensitive to short-period ground motions. Using design spectra to select ground motions significantly overestimates the longitudinal seismic response of the cable-stayed bridge. The overestimation is 50%, 23%, 38%, and 19% for the beam displacement, tower top displacement, tower base bending moment, and tower base shear force, respectively. It is suggested that the envelope of the mean seismic responses induced by the ground motions selected from each composite spectrum be used as the design seismic response of the cable-stayed bridge. This approach reasonably assesses the seismic demand of the bridge, thereby reducing the cost of the cable-stayed bridge and improving its economy.

In this paper, an innovative self-centering coupled shear link (SC-CSL) used between the steel brace and brace connection plate in the concentrically brace steel frame (CBF) is developed by combining the coupled shear link (CSL), shape memory alloy (SMA) bars and disc springs. Firstly, the hysteresis performance and failure mode of the SC-CSL are analyzed using the validated finite element method. Then, the seismic performances of CBF with a steel brace, CSL and SC-CSL are analyzed. Numerical results show that the innovative SC-CSL has excellent bearing capacity and low residual deformation. The SMA bars mainly sustain tension while the disc springs static under tension force, and the disc springs sustain compression while the SMA bars are static under compression force. The tension and compression forces of the SC-CSL can be almost equivalent with reasonable SMA bars and disc springs. In addition, the seismic performances of CBF, CBF-CSL and CBF-SC-CSL are almost the same, and no yielding or damage occurs to the steel beams, steel columns and steel braces during frequent earthquakes. The steel brace in the CBF has a severe buckling phenomenon. The CBLs with an elastic steel brace can have excellent bear capacity and deformation capacity. The residual deformation of CBF-SC-CSL visibly decreases during rare earthquakes, which shows good seismic performance and seismic resilience capacity.

To address the significant discrepancy between damage degree and peak values when employing traditional acceleration indices for evaluating seismic damage in loess slopes under large earthquakes at far-field and small earthquakes at near-field scenarios, this study developed a novel evaluation system based on particle vibration velocity theory. Through shaking model tests and numerical simulations, the coupling mechanisms between acceleration and velocity responses during seismic damage evolution in loess slopes were systematically investigated, revealing intrinsic correlations between dynamic parameters and damage states. The results indicate the acceleration amplification effect of loess slopes is obvious. When the peak acceleration is taken as the evaluation index, the calculated intensity of loess slope top in the near field is greater than the actual intensity. A linear correlation was established between peak particle velocity and soil tensile strength. It is suggested that the peak velocity should be used as the evaluation index of failure intensity for loess slope with typical site amplification effect. An innovative five-level seismic intensity evaluation system was proposed in accordance with GB/T 17742—2020 specifications, defining velocity threshold intervals and characteristic failure patterns for each damage level, thereby establishing a quaternion correspondence criterion integrating damage degree, intensity, peak velocity, and seismic damage characteristics. This research provides theoretical foundations and quantitative criteria for seismic damage assessment of loess slopes.

The damping of the primary structure has a certain impact on the dynamic characteristics of the system. However, the damping of the primary structure is often neglected when optimizing the design of DVAs using analytical methods to simplify calculations. This paper employs the perturbation method to derive an analytical solution for the optimized design parameters in negative stiffness-inerter dampers considering the damping of the primary structure under random excitation. Firstly, the governing equation of the vibration system under base acceleration excitation is established to obtain the absolute acceleration response transfer function and the corresponding mean square value. Secondly, the perturbation method is introduced to obtain the analytical solution of the optimal design parameters of the negative stiffness-inerter damper considering the primary structure damping under the H₂ criterion, and the validity of these analytical solutions is verified. Subsequently, through comparative case studies, it is demonstrated that neglecting the primary structure damping can cause significant deviations between the optimal design parameters of the negative stiffness-inerter damper and the actual values when the primary structure damping radio is relatively large highlighting the necessity of considering primary structure damping in parameter analytical optimization design. Finally, the optimal mean square value of absolute acceleration in the frequency domain and the peak value of the time history response in the time domain are compared after installing negative stiffness-inerter dampers and inerter dampers for the primary structure with damping, respectively. The result indicates that reducing the damping ratio of the main structure allows negative stiffness to increasingly improve the damper’s effectiveness. Furthermore, it demonstrates that the negative stiffness-inertance damper is more efficient in controlling the peak time-history response of the main structure.

The main building structure in a thermal power plant houses a large number of mechanical and electrical equipment, which is an essential component of the entire building. In this study, a calculation model for the main building structure considering the interaction between equipment and structure was established. A separate structural model of the main building structure was used as a comparison. Through static push-over analysis, the seismic performance of the structure was evaluated. The seismic fragility analysis based on SPO2IDA was conducted for both models. It was found that the structure-equipment interaction system in the elastic-plastic stage has a higher stiffness. The coal bunker has a significant damping effect on the coal bunker layer and adjacent layers, but it slightly increases the inter-story drift angle on the floor with the maximum inter-story displacement angle. The seismic fragility curve of the structure-equipment interaction system in the main power plant is obtained based on the SPO2IDA method.