Development of an approximate method for analysis of connected buildings considering soil-structure interaction

Abstract

Bridges connecting high-rise towers are becoming popular due to functional, architectural, and connectivity reasons in addition to the structural benefits they provide. Two regular adjacent buildings will become irregular with respect to certain modes when rigidly connected with a reinforced concrete bridge. The analysis of connected buildings for lateral loads is often complicated as it depends on the dynamic properties of the connecting towers and bridge. The design procedure for regular buildings according to earthquake codes will no longer be acceptable for connected buildings. For a realistic solution, the superstructure-foundation-soil interaction must be considered as one compatible unit. The study presents an approximate method developed for the analysis of connected buildings considering soil-structure interaction. The actual building model with 3x3 bays and 10 stories as twin towers, with varying sizes of piles and the bridge, is modeled in ETABS and the structural response is obtained. An approximate model using a single tower with modifications of mass and stiffness coefficients at the level of connection is used to develop an analytical model in MATLAB. In each model, a fraction of the axial stiffness and mass of the bridge is considered from 0 to 20 at a regular interval of 0.5 and the closeness of the structural response to the actual is determined. The contribution of the stiffness and mass to be considered is varied and the closest match is determined. The study is repeated by varying the level of the bridge, diameter of the pile, and the width of the bridge from a single bay to three bays and inferences drawn.