| The groundwork, and foundation is the base of the building, and belongs to the underground concealed work. The survey, design and construction quality of the foundation is directly related to the safety of the buildings. Reinforced concrete independent foundation under column is widely used in industrial and civil construction of buildings. However, the calculation method of flexural capacity of independent foundation under column by the current Code for design of building foundation (GB50007-2011) may result in some practical problems.Firstly, this dissertation introduces developing history of the flexural capacity calculation method of the independent foundation under column in the previous codes. Based on the force balance analysis, the calculation formulas in the previous codes is derived and compared with the method suggested in Technical code for building pile foundations (JGJ94-2008), where the earth is supposed to be infinite small columns. The distance between the two methods is analyzed.Then, discussion on the calculation method of existing code formula itself is conducted. It is pointed out that the existing formula for calculating introduces the error in the calculation model because it is according to the trapezoidal damage mechanism. On this basis, the plastic hinge line analysis of the independent foundation under column is derived, leading to the ultimate moment capacity of the foundation. According to above analysis, a series of new equations is proposed based on the cross plastic hinge line in the slab to calculate the bending capacity of the independent foundation under column.Finally, the safety of the proposed calculation formula is investigated. Based on the numerical examples, the results using the two calculation formulas are discussed to reveal the distance between the two methods. The threshold of the two methods is deduced, from which the boundary conditions can be draw out to judge the safety of the existing design results. |
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