Reinforced Concrete Raft Foundation, Temperature Field, Thermal Stress Analysis And Crack Control

Reinforced concrete raft foundation is a widely used foundation form by industrial and civilian buildings, and large industrial equipments. During the construction period, concrete's hydrate reactions and environmental temperature changes cause the formation of uneven temperature field, for which stress and deformation are formed correspondingly. According practical engineering, taking effective control of such non-loaded deformation has great significance for ensuring its proper work and its carrying safety.This article mainly analysis the uneven temperature field, temperature stress, with the influences of concrete shrinkage, creep and self-constraint. Main contents are as followed:1. From the basic principle of heat conduction, thermal conduction differential equation of reinforced concrete raft foundation is gained; Using the finite difference method, deduced the numerical solution of uneven temperature field under the first and the third boundary conditions; For temperature field under steady or quasi-steady conditions, using Fourier equation could get the solution. Compared to measured data, finite difference method is convenient and highly accurate.2. Through further analysis, it is found that calculation method of temperature stress should consider the influences of elastic modulus variation, creep foundation restraints, and environment temperatures. 3. According to the calculation formula of shrinkage stress deformation and self-constraint stress deformation, deduced some non-loaded stresses calculation formula, which is simplified to shrinkage stress and self-constraint stress, equivalent temperature stress calculation formula by introducing the equivalent temperature. It is very convenient and has highprecision.4. Designed the temperature stress processes in early age, long age or ordinary work (including sudden cold or hot situations), providing basis for temperature control designers. Comprehensive temperature stress calculating processe is gained by individual calculating of temperature stress, shrinkage and self-constraint stress, and the temperature crack conctrol method was analysed.