窄基塔单桩十字梁自平衡基础极限承载力试验

Experiment on Ultimate Bearing Capacity of Self-balancing Cross Beam Foundation with Single Pile in Narrow-base Tower

提出一种结构简单、整体性能好、施工快捷且经济效益好的新型窄基塔基础——单桩十字梁自平衡基础,在足尺试验及数值模拟的基础上,对新型基础的受力特点和破坏模式进行研究。建立土体-混凝土-钢筋的非线性有限元模型,考虑土体与混凝土的非线性接触,进行模型的加载-卸载分析,并将分析结果与试验结果进行对比;通过分析得到新型基础的极限承载力,并得到新型基础在荷载作用下的破坏形式、薄弱位置及钢筋应力。结果表明:有限元模型的荷载-位移曲线、主筋轴力变化曲线及十字梁基础的裂缝发展与试验结果吻合较好,荷载-位移曲线基本呈缓变型或直线型,十字梁主筋轴力在上拔侧距十字梁底部0.5 m左右位置出现最大拉应力,在受压侧的十字梁与桩体交界面处存在最大压应力,单桩主筋拉应力的最大值出现在距桩顶大约1.95 m处,压应力最大值出现在距桩顶大约0.94 m处;十字梁裂缝从十字梁根部下侧开始发展,受拉钢筋屈服,受压区混凝土发生破坏,所得结论为新型基础的设计提供依据。

A new type of narrow base tower foundation(self-balancing cross beam foundation with single pile)with simple structure,good overall performance,fast construction and appropriate economic benefit was proposed.Based on full-scale test and numerical simulation,the mechanical characteristics and failure mode of the new foundation were studied.The nonlinear finite element model of soil-concrete-reinforcement was established.Considering the nonlinear contact between soil and concrete,the load-unload analysis of the model was carried out,and the results were compared with the test results.Through the analysis,the ultimate bearing capacity of the new foundation was obtained,and the failure form,the weak position and the reinforcement stress of the new foundation under the load were obtained.The results show that the load-displacement curve of the finite element model,the change curve of the axial force of the main reinforcement and crack development of the cross beam foundation are in good agreement with the test results.The load-displacement curve is basically of slow change or linear.The axial force of the main reinforcement of the cross beam has the maximum tensile stress at the position about 0.5 m from the bottom of the cross beam on the uplift side.There is a maximum compressive stress at the interface between the cross beam and the pile on the compression side.The maximum tensile stress of the main reinforcement of single pile is about 1.95 m away from the pile top,and the maximum compressive stress is about 0.94 m away from the pile top.The cracks of the cross beam begin to develop from the lower side of the cross beam root,the tensile reinforcement yields,and the concrete in the compression zone is damaged.The research can provide the basis for the design of the new foundation.