Influence of Temperature Variation on Raft Foundation Performance A Combined Analytical and Numerical Study

Thermal expansion and contraction of raft and mass concrete foundations, along with a build up of restrained stresses, are greatly affected by the variation in temperature. The temperature effects are not taken into account in conventional foundation design and may be ignored, resulting in the improper estimation of the distribution of stress, deformation and serviceability performance. This research examines the effects of temperature fluctuation on the behaviour of foundations analytically and numerically. Thermal strain, thermal stress and soil bearing pressure variation were tested under various temperature conditions (5°C, 10°C, 20°C, and 30°C) using a method of manual calculation. A raft foundation was incorporated in SAFE software and a three-dimensional numerical model of a 44 storey building was created. The modelling of the foundation was adopted a shell element with the soil–interaction represented as elastic spring supports, in order to get realistic soil–structure interaction behaviour under thermal loading condition. The findings show that there is considerable thermal deformation and restrained stresses developed in raft foundations due to change in temperature. It is observed that with the increase in the temperature difference, the stress levels and a non-uniform distribution of soil pressure increase as per both analytical and SAFE results. Edge stresses and differential reactions are more visible with higher thermal loads, which may cause serviceability issues and may lead to more cracking. The study finds that the temperature effects are a critical component in the performance of raft foundations and therefore they should be specifically considered in design practice. The analytical–numerical method is useful to provide a reliable framework to evaluate the thermal behavior and to enhance the understanding of the soil–structure interaction under temperature loading. This improves the safety, durability, and prediction of performance of foundation systems for high-rise buildings.