A fully precast concrete energy-dissipation frame structure is proposed. It adopts straight threaded sleeve connections and employs viscous dampers to enhance its overall seismic performance. To investigate the seismic performance of the proposed precast concrete energy-dissipation frame structure, pseudo-dynamic tests were carried out on a precast concrete energy-dissipation frame specimen and a precast frame specimen. The research focused on the failure modes, plastic hinge development, hysteretic behaviors, stiffness degradation, ductility, and energy dissipation capacities of the frame specimens. The results indicate that both the precast frame specimens with and without viscous dampers experienced flexural-shear failure, with the damage concentrated near the mid-height of the column joint. Compared with the precast frame without a damper, the precast energy-dissipation framework exhibited a 97% increase in positive ultimate bearing capacity and an 82% increase in negative ultimate bearing capacity. The energy dissipation capacity and stiffness were also significantly improved. Considering the stress state of the framework, the precast framework columns are in a pure shear state at mid-height, which requires high shear resistance and is prone to brittle failure. Therefore, it is recommended to strengthen the shear resistance of the mid-height connection joints, improve the construction quality, and ensure the gripping force of the connection parts.

On December 18, 2023, the Jishi mountain earthquake revealed damage to 750 kV surge arresters. In order to improve the seismic performance of existing pillar-type electrical equipment in substations, the intermediate layer was selected as the isolation part for modification. Two intermediate isolation schemes were proposed: steel wire rope damper and composite seismic isolation bearing. The original surge arrester and isolation structure were modeled using the ABAQUS finite element method. Ten sets of seismic waves were input for finite element analysis, and the stress of bushing root, top acceleration and displacement responses of each structure were extracted to compare and analyze the isolation efficiency of the intermediate layer. The results show that under seismic action, the intermediate isolation structure of the steel wire rope damper can effectively reduce the stress of bushing root and top acceleration of the surge arrester, but it has a significant amplifying effect on the top displacement, which can easily cause wire tension damage. The intermediate isolation scheme with composite seismic isolation bearing can improve the vertical stiffness of the intermediate layer structure, so that the root stress and top acceleration of the original structure bushing decrease by more than 40%, and the peak displacement of the top is only increased by 12.56%, so as to achieve a good seismic isolation effect. The intermediate isolation device with composite seismic isolation bearings exhibits good seismic isolation efficiency and is an effective retrofit measure to improve the seismic performance of existing 750 kV surge arrester.

In order to improve the seismic performance of traditional HDR(high-damping seismic isolation rubber bearings)bearings and their adaptability in simply supported beam bridges in high-intensity seismic zones, a new type of composite seismic bearing was developed based on the rational integration of steel bar dampers and HDR bearings, and its structural construction and mechanical behavior were described. Taking a specific specification product as an example, the vertical compression performance and horizontal hysteresis performance were demonstrated through finite element numerical simulation and experimental research. Then, a 5~20 m concrete simply supported beam bridge in an 8-degree seismic zone was taken as the object, and a finite element model was established using SAP2000 to study its seismic performance. The results showed that the vertical compression performance of the bearing met the standard requirements, and the horizontal hysteresis curve was more full than that of the HDR bearings. The finite element numerical analysis and experimental results were in good agreement with the theoretical skeleton model. Compared with the HDR bearings seismic system, the internal force response of the bridge pier increased to a certain extent after the use of the composite bearing, but it is still within the capacity range, and the displacement of the bridge beam end and the relative displacement of the pier-beam are significantly reduced, which can effectively avoid the occurrence of seismic damage such as beam-falling and collision of adjacent beams.

A load-structure model for the underground interchange utility tunnel was established based on the response displacement method. Transverse seismic analysis was carried out on the underground interchange utility tunnel. The internal force, deformation, and damage responses of an underground cross interchange cast-in-place utility tunnel under seismic excitations along two main axes were analyzed. The results indicate that under major earthquakes, the inter-story displacement angle at the interchange node of the utility tunnel exceeds the standard limit by 167.50%, with tensile damage reaching 0.985, far exceeding the tensile damage limit, which marking it as the weakest part of the interchange utility tunnel. Due to significant differences in stiffness and deformation modes between the interchange node and standard segments, the deformation at joints near the interchange node is the greatest. Under major earthquakes, the deformation at the joints near the interchange node can be up to 20 mm and 18 mm in two directions, respectively. The maximum inter-story displacement angle between layers at the interchange node may not occur simultaneously. Under major earthquakes, the maximum inter-story displacement angle between layers exceeds that between the top and bottom slabs by 19.15%. Consequently, it is necessary to determine the most unfavorable condition based on the maximum inter-story displacement angle between layers. The findings can provide a reference for the transverse seismic design of interchange utility tunnels.

Progressive collapse is a nonlinear dynamic behavior of structural systems. In order to study the progressive collapse resistance laws of reinforced concrete planar frame structures after failure of important members, an important member identification method based on strain energy of members was proposed. The effectiveness of the method was verified by taking a four-bay and eight-story reinforced concrete frame structure as the target. It was found that the method identifies important members with high effectiveness. On this basis, eight reinforced concrete frame structures with different beam spans or total number of floors were designed in accordance with code. Firstly, important members were identified based on the above method and the adverse structural member removal scenarios were formulated. Then, impacts of different total number of floors and structural span on progressive collapse resistance capacity of reinforced concrete planar frame structures were analyzed by adopting the nonlinear dynamic alternate path method. Finally, the approximate functional curve of reinforced concrete planar frame structures between proportions of columns removed from ground floor and degrees of structural collapse was fitted. The results indicate that after removal of center column at ground floor, structures are mainly carrying vertical loads by ground floor frame beams, and frame beams of remaining floors cooperate with ground floor frame beams to support loads. The decrease in total number of floors and the decrease in span can increase redundant load carrying capacity of structures, which has a positive effect on resistance capacity of frame structures to progressive collapse. Frame beam span has a significant effect on degree of structural collapse and total number of floors has a limited effect on degree of structural collapse. The relationship between proportions of columns removed from ground floor and degrees of structural collapse of reinforced concrete plane frame structures can be approximated by a logistic function.

This study analyzes 6 436 offshore ground motion records from 496 seismic events observed by seafloor observation network for earthquakes and tsunamis along the Japan Trench (S-net), aiming to investigate the frequency content characteristics of vertical ground motion components. Using random-effects regression with consideration of key factors like water depth and sediment layer thickness, we developed empirical models for vertical frequency content parameters. Significance tests and the Akaike Information Criterion (AIC) were employed to evaluate parameter validity and model goodness-of-fit. Results show that significant differences exist between horizontal and vertical frequency content distributions, highlighting the significance of the water depth parameter and setting condition. For S-net ocean-bottom stations (water depth: 102~7830 m), vertical frequency parameters shift toward shorter periods at depths less than 1500 m, while longer-period (longer than 0.8 s) records increase significantly at depths greater than 1 500 m. The water depth significantly affects vertical frequency content. Predictions for different tectonic types show consistent differences between vertical and horizontal models. Site terms exhibit significant differences between inner-trench and outer-trench stations, possibly influenced by the propagation paths of seismic waves and the topographical features associated with the outer ridge of the trench rather than sediment layer thickness. This study provides support for understanding offshore ground motion characteristics and assessing offshore seismic hazards.

To enhance the protection of masonry pagodas and improve the damping performance of suspension pendulum damper (SPD), a novel SMA composite pendulum damping system is proposed, integrating shape memory alloy (SMA) into SPD. This system enhances the inertia force generated by the pendulum within SPD by leveraging the super elasticity and high damping characteristics of SMA, thereby improving the overall energy dissipation capability of the damping system. Initially, the study outlines the process of obtaining the equivalent restoring force of SMA through stochastic equivalent linearization. Subsequently, it establishes the SDOF computational model of the SMA composite pendulum damping system by drawing parallels with the SDOF computational model of SPD. The paper elucidates the structure and operational principles of the damping system, followed by an exploration of the effects of two control parameters on its performance. Further, the study applies both SPD and the new composite pendulum damping system to a masonry pagoda. The structural vibration response is analyzed under three distinct seismic excitations following the implementation of the damping system using ABAQUS software. The findings reveal that the SMA composite pendulum damping system outperforms SPD in vibration control under various seismic excitations, demonstrating its superior applicability.

In the current context of increasingly constructed urban built environments, the disaster impacts of functional disruptions in urban buildings hit by earthquakes can quickly propagate and intensify through the social chain. To quantify the functional disruption of earthquake-damaged building complexes, this paper focuses on assessing the functional recovery time of urban building complexes after an earthquake and develops a comprehensive assessment framework. The framework employs a fuzzy hierarchical analysis to quantify the impact of key factors, such as building renovation class, regional economy, climate, and topography, on the recovery process. Additionally, the study divides the rehabilitation process of the urban complex into a preparation phase and a repair and reconstruction phase, and develops a systematic assessment model for each phase. In the preparation stage, the assessment model especially considered the impact of the earthquake emergency period and systematically sorted out the time required for five key recovery preparations under different intensities of effects according to the expected intensity of earthquake effects; the assessment model for the repair and reconstruction stage was constructed based on the damaged area of the earthquake-damaged houses as well as the time required for repairing or reconstructing per square meter. The model preliminarily estimates the reconstruction time per unit area of houses of different building structure types in China through in-depth analysis of the quota data, and takes into account the uncertainties in the construction process by using the Monte Carlo simulation method. And the repair time per unit area of a house is derived by reasonably discounting the reconstruction time based on its damage degree. The research results not only provide new perspectives for the theory of urban disaster management, but also provide good data support for the resilience building of the government and enterprises and the rapid development of recovery decisions after disasters.

A simplified method for calculating the longitudinal movement and cumulative displacement of the stiffening girder in long-span suspension bridges under random traffic flow is proposed. In this method, the suspended stiffening girder system is equivalent to a single-degree-of-freedom (SDOF) vibration system. Based on this SDOF system, the longitudinal vibration equations of the suspension bridge’s stiffening girder under moving loads and random traffic flow are derived. A rapid calculation method for the stiffening girder’s longitudinal vibration response under random traffic flow is proposed. Taking an example of a long-span suspension bridge and using existing traffic measurement data, random traffic flow samples are generated based on the Monte Carlo method. These samples are then treated as random loads on the SDOF system. The SDOF vibration equation is solved, and the results are compared with ANSYS dynamic analysis results. The findings reveal that under random traffic flow, the stiffening girder undergoes longitudinal movement and accumulates a significant displacement. This cumulative displacement consists of both static and dynamic components, with the latter contributing more significantly. Compared to the finite element transient dynamic analysis, the displacement response results obtained from the simplified SDOF system show minimal differences in extreme values and root mean square(RMS) values (less than 5%), although there is a slightly larger difference in cumulative displacement (approximately 13% ~ 19%). This indicates that the simplified vibration model can capture the stiffening girder’s longitudinal movement characteristics under random traffic flow. The proposed simplified method greatly simplifies the analysis of the stiffening girder’s longitudinal movement under random traffic flow, enabling response evaluation and parameter optimization in the preliminary design stage.

In order to expand the application of perfobond leiste (PBL) shear connectors, the low-cycle reciprocating loading tests were conducted on one steel reinforced concrete composite shear wall and four steel plate concrete composite shear walls with PBL shear connectors. The failure mechanism and seismic performance of the specimens were studied. The results show that the failure modes of shear walls under horizontal loads can be divided into two types including bending failure and bending-shear failure. The aspect ratio of the walls, the configuration of steel core plates and the arrangement of the PBL shear connectors are important factors affecting failure modes. PBL shear connectors can facilitate steel core plates working well with the concrete. Besides, the configuration of steel core plates can improve the bearing capacity of the walls. The bearing capacity of shear walls decreases with the increase of aspect ratios, and the vertical arrangement of PBL shear connectors is better than the horizontal arrangement of PBL shear connectors. Based on the design of compression-bending capacity of steel reinforced concrete columns recommended in EN 1994-1-1:2004, a design formula of compression-bending capacity for steel plate concrete composite shear walls with PBL shear connectors is proposed. It is verified that the design formula can accurately calculate the compression-bending capacity of the shear walls with large aspect ratios by comparison.