Spectra-compatible artificial ground motions are used extensively in the time history analysis of nuclear power plants. Owing to reasons such as the dense controlling frequency points and stringent requirements for the number of small response points, it is difficult for the conventional matching methods to generate artificial ground motions that are highly compatible with multi-damping design spectra. In this paper, to resolve the problems of high precision and robustness, an improved hybrid method for constructing a multi-parameter adjustment curve in the time domain is proposed. Different from artificial intelligence methods, the improved hybrid method is a deterministic iterative method that combines the advantages of the simulated annealing algorithm (SAA) and the time domain adjustment method. The SAA is used to determine the optimal weights of the corrective time histories of all the damping ratios at a specific frequency, which controls the influences of the corrective time histories on the response spectra. Subsequently, based on the optimal weights, the artificial ground motion is adjusted in the time domain to reduce the fitting error of all the damping ratios at a specific frequency. Moreover, the multi-damping design spectra matching problem of frequencies and damping ratios is simplified to a one-dimensional problem of frequencies using the SAA. Numerical examples are presented to demonstrate the versatility of the proposed improved hybrid method.

Fracture mechanics is one of the most important approaches to structural safety analysis. Modeling the fracture process zone (FPZ) is critical to understand the nonlinear cracking behavior of heterogeneous quasi-brittle materials such as concrete. In this work, a nonlinear extended scaled boundary finite element method (X-SBFEM) was developed incorporating the cohesive fracture behavior of concrete. This newly developed model consists of an iterative procedure to accurately model the traction distribution within the FPZ accounting for the cohesive interactions between crack surfaces. Numerical validations were conducted on both of the concrete beam and dam structures with various loading conditions. The results show that the proposed nonlinear X-SBFEM is capable of modeling the nonlinear fracture propagation process considering the effect of cohesive interactions, thereby yielding higher precisions than the linear X-SBFEM approach.