Investigation of the Seismic Behavior of Framed Tube Buildings Considering Soil Structure Interaction

Abstract

In recent years, the framed tube system has been known as the most efficient structural system for the high-rise buildings. The entire lateral resistance in the framed tube structures is provided by closely spaced exterior columns and deep spandrel beams. A framed tube building suffers from the shear lag effects, which cause a nonlinear distribution of axial stresses along the face of the building so that the axial stress in the corner columns increases while it decreases in the interior columns. Shear lag depends on the perimeter columns size and spacing and flexibility of the spandrel beams. In this study, the influence of soil structure interaction (SSI) on shear lag phenomenon and deformation of reinforced concrete framed tube structures have been investigated and the results of linear and nonlinear analyses have been compared. In addition, P-Delta effects on some of the nonlinear static analyses have been considered and the sequence of plastic hinges formation has been investigated. The influence of SSI, the formation of plastic hinges and P-Delta effects have been determined by analyzing a 50-story reinforced concrete framed tube structure under seismic loading. The results show that SSI decreases shear lag and increases deformations of the structure. It also indicates that the formation of plastic hinges is so effective in deformation of the top stories and distribution of axial stresses in the top half of the building, and how P-Delta effects are important in deformation and strength of the framed tube structures.

Keywords

• shear lag
• framed tube
• soil structure interaction
• p-delta effects
• nonlinear static pushover analysis