Recycled aggregate concrete-filled square steel tube (S-RACFST) frame has the characteristics of high bearing capacity, good ductility, and superior seismic performance. To propose a displacement-based seismic design of S-RACFST frame, the validity of the design method was verified by a detailed calculation example. Based on the performance requirements, this design method divided the structural performance into five levels: normal use, temporary use, use after strengthening, life safety, and collapse prevention, and suggested specific steps for the displacement-based seismic design of S-RACFST frame using the inter-story displacement angle limit value as the quantitative indicator. The 10-story S-RACFST frame was used as an analytical example for static elasticplastic analysis. The pushover lateral displacement curves of the frame structure at each performance level were obtained and compared with the displacement-based seismic design curves. The results show that the displacement-based seismic design method of S-RACFST frame structures can fulfill the performance level requirements such as "temporary use," "normal use," and "collapse prevention," and the displacement-based seismic design method is one of the effective ways to realize the performance design of S-RACFST frame structures.

The paper proposes a method for analyzing the mechanical properties of flexoelectric materials based on the isogeometric finite element method (IGA-FEM) and polynomial chaos expansion (PCE). The method discretizes the flexoelectric governing equations utilizing the B-spline shape functions that satisfy the continuity requirement to obtain the mechanical properties (electric potential) of the material. To obtain a mechanical property with different input parameters, we choose the truncated pyramid model as the object of study, and use IGA-FEM and PCE to solve different single uncertain parameters, including independent Young’s modulus and uniformly distributed force, and two kinds of flexoelectric constants, respectively. Numerical examples are presented to bear out the accuracy and viability of the proposed methodology.

An efficient method of moments (MoM) based on polynomial chaos expansion (PCE) is applied to quickly calculate the electromagnetic scattering problems. The triangle basic functions are used to discretize the surface integral equations. The polynomial chaos expansion is utilized to accelerate the MoM by constructing a surrogate model for univariate and bivariate analysis. The mathematical expressions of the surrogate model for the radar cross-section (RCS) are established by considering uncertain parameters such as bistatic angle, incident frequency, and dielectric constant. By using the example of a scattering cylinder with analytical solution, it is verified that the MoM accelerated by PCE presents a considerable advantage in computational expense and speed.