Study on Calculation Method of Raft Foundation Based on Locally Uniform Distribution of Subgrade Resistance
|School||Huazhong University of Science and Technology|
|Keywords||uniaxial ribbed-raft subgrade resistance locally uniform distribution characteristic point MDM CLDM|
Raft foundations are widely used in modern buildings, the distribution of subgrade resistance on the raft plate is influenced by many complicated factors, but in the design of raft foundations, the majority of structural engineers design raft foundation based on uniform distribution of subgrade resistance. When bottom column’s axial force between different axial of the upper structure are different, particularly the difference is vary large, if use the approach, the result don’t match the actual stress state of raft foundation. It has important theoretical significance and practical engineering value to research the distribution law of subgrade resistance and internal force calculation method of raft foundation that bottom column’s axial force is different or column grid isn’t uniform.The paper is aimed at uniaxial ribbed-raft, make basic assumptions according to the upper structural mechanical characteristics, establish raft calculation model based on locally uniform distribution of subgrade resistance, study the subgrade resistance and internal force calculation method of raft. It is called Characteristics Line Dividing Method (CLDM).The core of CLDM is to solve the characteristics point (line) dividing plate to a series of strips, assumes subgrade reaction on each strip is uniform (local equivalent uniform subgrade resistance), deduce internal force formula. The paper assumes that the feature point is strip’s midpoint, it is called Midline Dividing Method (MDM); sets up a quartic equation, which is about the relationship between column axial force and the characteristic point based on the shear at characteristics point (line) of strips is zero; By means of the solution of the quartic equation by Matlab and numerical fitting the simplified equation of the characteristic point be figured out; deduces the equations of moments and shears. Calculate a practical example respectively in ways of CLDM, MDM and Rigid Plate Method (RPM) and analyze the results of comparison. It proves that it’s more accurate to use CLDM and MDM than RPM, and the subgrade resistance is more reasonable.