摘要
桩—梁基础体系因其经济性和工作性能较好被广泛应用于多层砖混结构、框架及框架剪力墙结构的房屋建筑。但桩—梁—地基土共同作用体系非常复杂,体系中各部分共同作用、相互影响,其受力机理和变形特征尚未完全清楚。在我国,每年都有相当数量的建筑采用该类型基础,因此本文专门对桩—梁基础进行了深入分析研究。
通过考虑梁下地基土对基础梁的各向支承作用,引入坐标变换矩阵对任意方向上的基础梁进行坐标变换,使其能适用于格式基础梁(包括非正交格式基础梁)的计算,同时采用荷载修正法修正格式基础梁中基底重叠面积的影响,用刚度修正法修正桩—梁基础中基底重叠面积的影响。
本文通过采用剪切位移法中的应力扩散模型考虑桩与桩之间的应力传递作用;采用Geddes假定确定桩身和桩端的应力分布,推导位移系数,并以此为基础求得柔度矩阵;桩身和桩端的应力分布大小由桩的荷载分配系数控制,通过迭代法可以求出桩的荷载分配系数;在考虑基础梁对桩—梁—地基土共同作用的刚度贡献基础上,提出了桩—梁—地基土共同作用方程,并通过本文作者开发的相应计算程序,经实例计算验证了本文方法的正确性。另外,本文还通过对桩—梁—地基土共同作用体系中荷载分担比、桩顶反力分布、桩沉降、承台内力及其影响因素等进行分析,得出了一些有益的结论和建议。
Pile-beam foundation is widely used in multistory buildings of brick masonry structure, frame structure and frame-shear wall structure due to its good working function and economy. However, this kind of foundation becomes a complex system under the interaction of pile-beam-soil and the behavior of the foundation is still not clearly explained. As this kind of foundation is used in a great number of buildings every year in China, further research on the interaction of pile-beam-soil is needed.
A computing program of crossed foundation beam is developed by using the coordinate alteration matrix and taking into account the action of soil under the foundation beam. Meanwhile, the influence of overlapping area on the beam foundation is modified by means of load amendment, and the influence of overlapping area on the pile-beam foundation is modified by means of stiffness amendment.
By applying the model of stress-spread in shear-displacement method to describe the stress spread between piles and the Geddes hypothesis to determine the stress distribution of pile, a displacement coefficient is deduced to calculate the flexibility matrix and the coefficient for load distribution of pile. Considering the stiffness of foundation beam, the equation of the interaction of pile-beam-soil is established and an analysis program is developed related to the interaction. The reliability and efficiency was tested by an actual example. In addition, factors such as the settlement in pile, pile loads and the stress in the foundation beam have also been analyzed. Some conclusions and recommendations have been put forward.
引文
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