混凝土与土体非线性对地基梁弯矩的影响

INFLUENCE OF NONLINEAR CHARACTERISTICS OF CONCRETE AND SOIL ON BENDING MOMENT OF FOUNDATION BEAM

采用钢筋混凝土有限单元法研究土体和混凝土非线性对地基梁弯矩的影响。通过对土体和混凝土为线性和非线性4种不同计算模式,指出在考虑混凝土与土体为非线性时,其弯矩明显小于当混凝土与土体均假定为线性时的弯矩。要正确计算地基梁弯矩应同时考虑混凝土与土体的非线性,如不能同时考虑混凝土与土体的非线性,则在计算刚性地基梁时至少应考虑土体非线性,而计算柔性地基梁时则至少应考虑混凝土非线性,此时钢筋用量对设计荷载作用下的弯矩影响不大。此外,给出柔性地基梁弯矩折减系数β的计算公式,该系数定义为考虑混凝土非线性时的弯矩与郭氏表弯矩的比值,利用该系数可方便地由郭氏表弯矩得到考虑混凝土非线性时的弯矩。

The influences of nonlinear characteristics of concrete and soil on bending moment of foundation beam are investigated by the finite element method（FEM）. Four kinds of different calculation modes are considered, in which soil and concrete are taken as linear or nonlinear materials. It is concluded that the bending moment considering the nonlinear characteristics of concrete and soil is smaller than that of assuming concrete and soil as linear materials. Nonlinear characteristics of concrete and soil should be considered in order to obtain a more accurate bending moment; and it is, for the minimal demand, to consider the nonlinear characteristic of soil for the rigid beam and the nonlinear characteristics of concrete for the flexible beam, if it is very difficulty to consider nonlinear characteristics of concrete and soil at some time. The influence of reinforcement ratio on bending moment under design load is not obvious. Besides, a formula of the discount coefficient of the bending moments is presented, which is defined as the ratio of the bending moment considering the nonlinear characteristic of concrete to bending moment from the Guo＇s Tables. Using the discount coefficient, bending moment considering the nonlinear characteristic of concrete is easily obtained by the bending moment from the Guo＇s Tables.