Nonlinear FEA of Soil-Structure-Interaction Effects on RC Shear-Wall Structures

Abstract

Considering Soil-Structure-Interaction (SSI) is essential when evaluating the structural system’s response as it can unveil behaviors that are otherwise not accounted for in fixed-base (FB) systems. Nonlinear Finite Element Analysis (NFEA) is performed on a six-story Reinforced Concrete (RC) shear wall structure to investigate SSI effects. The soil medium in consideration represents site class E soil type in accordance to ASCE7-10 standards. The structural elements including the RC wall, slabs, foundation, and soil continuum are modeled using 3D solid hexahedral elements. Additionally, to further enhance accuracy to the modeling, all steel reinforcement including longitudinal and transverse rebars are modeled as embedded bars within the brick elements. The smeared crack approach is utilized for optimal computational efficiency. Four types of RC walls that differ in reinforcement detailing for varying seismicity design levels are explored. The representative structures are loaded with their tributary gravity loads applied to the corresponding slabs. Lateral load effects are imposed onto the structures through displacement-controlled monotonic as well as cyclic pseudo-static protocols. The systems’ responses from the SSI and FB systems are compared through pushover and hysteretic curves (lateral force versus lateral drift), strain/stress contours, as well as interpretive response quantities such as characteristic stiffnesses and energy dissipation. It was found that all SSI models exhibit higher lateral displacements ranging from an additional 34% to 85%, lesser force demands within the superstructure by around 10%, and higher levels of energy dissipation (on an average of 25%) due to soil compressibility. Furthermore, all FB models experienced higher strain concentrations at the bottom region of the shear walls. Thus, it was found that wall shear reinforcement can be reduced by accounting for SSI effects. Lastly, the reinforcement detailing (special versus ordinary) had a noticeable effect on enhancing the system’s performance.