Probabilistic seismic hazard analysis (PSHA) has been recognized as a reasonable method for quantifying seismic threats. Traditionally, this method ignores the effect of the focal depth, in which the ground motion prediction equations (GMPEs) are applied to estimate the probability distribution associated with the possible motion levels induced by the site earthquakes, but it is limited by the unclear geological conditions, which makes it difficult to provide a uniform equation, and these equations cannot express the non-linear relationship under geological conditions. Hence, this paper proposed a method to consider the seismic focal depth for the PSHA with the example of California and used a back propagation neural network (BPNN) to predict the peak ground acceleration (PGA) instead of the GMPEs. Firstly, the measured PGA and unknown PGA seismic data applicable to this method were collected separately. Secondly, the unknown PGA data were supplemented by applying the BPNN based on the measured PGA data. Lastly, based on the full-probability equation, PSHA considering the focal depth was completed and compared with the current California seismic zoning results. The results showed that using the BPNN in the PSHA can ensure computational accuracy and universality, making it more suitable for regions with unclear geological structures and providing the possibility of adding other parameters to be considered for the influence of the PSHA.

The fragility of concrete-filled steel tubular (CFST) frame structures with buckling-restrained braces (BRBs) subjected to multiple earthquakes is studied in this paper. First, a fiber beam element model with rate-dependent concrete and steel material properties is developed for CFST members and, then, the effect of the strain rate on the seismic response of the CFST frame structure is investigated numerically. The influence of BRBs on the seismic response of the CFST frame structure is then comparatively analyzed. The seismic responses of the CFST frame structure with BRBs under single mainshocks and earthquake sequences are investigated, and the fragility curves are generated using probabilistic seismic demand analysis. The obtained roof displacement and inter-story drift ratio (ISDR) of the structure decreased by 10.2% and 6.9%, respectively, when obtained while considering the strain rate effect, compared with those obtained without consideration of the strain rate effect. BRBs can effectively improve the seismic performance of the CFST frame structure in that the maximum roof displacement and ISDR can be reduced by 45.1% and 43.9%, respectively. Compared with those under single mainshocks, the maximum roof displacement and ISDR of the structure with BRBs under earthquake sequences significantly increase. The fragility of the BRB structure under earthquake sequences is more severe than that under single mainshocks. Therefore, the influences of the strain rate effect and earthquake sequence should be considered to realistically evaluate the seismic fragility of CFST structures.

The effect of aftershocks on the fragility of single-story masonry structures is investigated using probabilistic seismic demand analysis Finite element models of an unreinforced masonry (URM) structure and a confined masonry (CM) structure are established and their seismic response characteristics when subjected to mainshock, aftershock, and the mainshock-aftershock sequence are then comparatively investigated. The effects of aftershocks and the use of confining members on the seismic response are studied. Probabilistic seismic demand models of the structures are built, and fragility curves under various conditions are derived to investigate the effect of aftershocks on structural fragility. The maximum roof displacement and maximum inter-story drift ratio are lower in the confined masonry model than in the unreinforced masonry model; additionally, the probability of exceedance (PE) values of each damage limit state reduced, and those of the mainshock-damaged models subjected to aftershock significantly increase compared to those directly subjected to a same-intensity aftershock. The probability of severe damage or collapse compared with the mainshock-damaged CM model is greater than when each is subjected to a same intensity aftershock. The use of confining members benefits aftershock resistance and reduces the failure probability of the mainshock-damaged structure. The PE values significantly increase with the aftershock scaling factor δ. Therefore, the effect of aftershocks should be considered in the seismic design and analysis of masonry structures.

Based on the concept of environmental protection of solid waste utilization, material testing is conducted to achieve native improvement using coal gangue‐based limestone‐calcined clay cement (LC3). Finite element (FE) models of rural raw‐soil architecture with a colored‐steel roof (RACSR) were established. The effect of modified soil type and seismic character on the vulnerability of single‐story raw‐soil structures was investigated using probabilistic seismic demand (PSD) analysis. The seismic response characteristics of 80 representative sequences were comparatively investigated when subjected to northwest clay (raw soil) of China, fiber and stone‐improved clay (modified soil), and coal gangue‐based limestone‐calcined clay cement (LC3 soil). The maximum interstory drift angle (ISDA_max) was lower in the LC3 soil model and the modified soil model compared to the raw‐soil model. The use of LC3 soil improves structural resistance and reduces the damage probability of a structure, and the influence of different ultimate failure states on the vulnerability of the raw‐soil structure was studied.