SPTC Project 15.5-03

Development of Novel Analysis Model for Foundations Subjected to Combined Torsional and Lateral Loads Due to High Wind

Abstract

In this study, we perform a nonlinear finite element analysis (FEA) for a circular foundation in an undrained clay under combined loading of a torque and a lateral load. To determine collapse loads, the displacement-controlled swipe loading path method is employed in FEA. Analysis results are presented in the form of failure envelopes as a function of embedment depth ratio for various definitions of ultimate lateral capacity. Results from FEA clearly show that lateral capacity is reduced by the concurrent application of torsion, and the reduction effects are quantified as a function of torque-to-lateral load ratio.Based on the insights gained from FEA, we further develop a novel analysis model through analytical approach. Governing differential equations for a circular foundation, embedded in a layered soil, subjected to a combination of lateral and torsional loads are derived based on energy principles and variational calculus; a total of six, interdependent differential equations are obtained. We develop a numerical algorithm to solve the interdependent differential equations and test the algorithm under individual loading components, which shows excellent agreements with those from previous studies and FEA. A full implementation of the solution algorithm for combined loading case can be done as a future study. Furthermore, the analysis model developed in this study can be regarded as a groundwork for more advanced models such as nonlinear analysis model that considers degradation of soil modulus using a piecewise-linear approach.

Project PI:Hoyoung Seo

 

Researchers:

Junyoung Ko

Suranga Gunerathne

 

Project Duration: 2017-2018

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