扩展基础冲剪破坏机理分析

Mechanism Analysis on the Shear Failure of Spread Footings

本文通过采用有限元法对基础冲剪试验进行数值模拟,并对计算结果与试验结果进行对比分析。分析表明,基础的破坏方式与基础的边界尺寸有关:当基础宽度B≤b c+2h0时,基础发生剪切破坏,裂缝横贯基础宽度;当基础宽度B>b c+2h0时,基础发生冲切破坏,基底裂缝形态近似为圆形。剪切破坏的基础,剪应力主要分布在基础沿短边方向的柱根处;冲切破坏的基础,剪应力主要分布在柱根四周,柱角处出现应力集中现象。剪切破坏的基础,钢筋应力主要沿长边方向分布,柱根和裂缝处应力较大;冲切破坏的基础,钢筋的应力沿双向分布,柱根和跨中应力较大。通过上述分析,进一步明确冲剪破坏机理,为工程设计提供参考。

The shearing is an important influencing factor in design of reinforced concrete footings. Integrating indoor model test, the method of finite clement is applied to simulate the process of shearing. The comparison analysis is made between the results of calculated and test. The analysis result indicates that the foundation mode failure associates with foundation boundary dimensions. The shear failure occurs on the foundation and crack goes across the width of foundation when the width of foundation B〈〈.b,~ ＋ 2h0 ;the punch failure occurs on the foundation and the fracture shape of foundation base approaches a circle when the width of foundation B 〉 b ＋ 2ho. The shearing strength distributes mainly on the column root of foundation short edge direction for shear failure foundation,the shearing strength distributes mainly around tbe column root for punch failure foundation,the column angle appears stress concentration phenomenon. The reinforcement stress distributes mainly along the long side direction for shear failure foundation, the stress is bigger on the column root and cracks, and the reinforcement stress distributes mainly along the two-way distribution for punch failure foundation, the stress is bigger on the column root and mid-span. The punching shear failure mechanism is further defined through the analysis above and provides reference for engineering design.