A practical method for seismic response analysis of nonlinear soil-structure interaction systems

Soil–structure interaction (SSI) plays an important role in the analysis of seismic structural responses. This study significantly extends an efficient linear SSI analysis method presented previously by the authors and co-workers to realistic nonlinear SSI systems, that is, systems with nonlinear soil, nonlinear structures, and flexible foundations (e.g. single- or multiple-pile foundations). The flexible foundations lying on half-space nonlinear soil are represented by frequency-dependent compliance functions that are fitted numerically instead of obtained by closed-form solution. These functions are then transferred to the time domain using the discrete-time recursive filtering method. A non-iterative algorithm is applied to guarantee the boundary conditions between soil and structure, that is, the displacement continuity and force equilibrium between them. The proposed method is implemented on an open-source FE software framework, called OpenSees. The accuracy and efficiency of the extended coupling method are investigated in detail through the seismic response analyses of typical soil–foundation–structure systems while considering the cases of linear or nonlinear soil, linear or nonlinear structures, and single- or multiple-pile foundations. Results show that the extended coupling method is significantly faster than the traditional FE method and provides acceptably accurate solutions for SSI systems with linear or low-to-moderate nonlinear soil. The paper provides a method for fast evaluation of nonlinear SSI effects in seismic structural response analysis.

Seismic Analysis of Low-Rise Self-Centering Prestressed Concrete Frames considering Soil-Structure Interaction

In this study, the seismic behavior of low-rise self-centering (SC) prestressed concrete frames considering soil-structure interaction (SSI) is presented. For this purpose, a typical 4-story SC concrete frame, with and without flexible foundations, is analyzed through nonlinear dynamic analysis. Ground motion sets with two hazard levels are selected for analysis. A conventional reinforced concrete (RC) frame is also studied, and the structural demands of the RC and SC frames are compared in terms of peak and residual drifts, base shear, residual settlement, and rotation of foundation. The analysis results show that considering soil-structure interaction generally increases the peak and residual drift demands and reduces the base shear and connection rotation demands when compared to fixed base conditions. For the cases with and without flexible foundations, the SC frame is found to have comparable peak story drifts with the RC frame and have the inherent potential of significantly reducing the residual drifts. The seismic analysis results of the frames with flexible bases show that the RC and SC frames can experience foundation damage due to excessive residual foundation rotations after the maximum considered earthquake (MCE).

Plant Cell, Tissue and Organ Culture: The Most Flexible Foundations for Plant Metabolic Engineering Applications

Significant advances in plant cell, tissue and organ culture (PCTOC) have been made in the last five decades. PCTOC is now thought to be the underlying technique for understanding general or specific biological functions of the plant kingdom, and it is one of the most flexible foundations for morphological, physiological and molecular biological applications of plants. Furthermore, the recent advances in the field of information technology (IT) have enabled access to a large amount of information regarding all aspects of plant biology. For example, sequencing information is stored in mega repositories such as the National Center for Biotechnology Information (NCBI), which can be easily accessed by researchers worldwide. To date, the PCTOC and IT combination strategy for regulation of target plant metabolism and the utilization of bioactive plant metabolites for commercial purposes is essential. In this review, the advantages and the limitations of these methodologies, especially regarding the production of bioactive plant secondary metabolites and metabolic engineering in target plants are discussed mainly from the phenotypic view point.