Dynamic Ultimate Bahavier of Reinforced Concrete Hollow Pier under Combined Loads

本研究提出了混凝土空心墩的试验和分析结果，以阐明其在组合荷载下的基本行为。混凝土空心梁的极限位移小于相同尺寸的填充梁，其极限位移能力和耗能能力均趋于较低。在极限状态下，能量耗散比填充梁低20%左右。空心梁达到峰值强度后，其强度衰减迅速。在空心截面的法兰部分存在许多弯曲裂纹。一旦这些裂缝发展到腹板部分，它们就变成了剪切裂缝。这种现象不仅发生在剪切破坏试件上，也发生在受弯破坏试件上。这就是为什么当采用空心截面时，腹板宽度较窄需要仔细考虑其抗剪强度的原因。将桥墩位移分离为弯剪两分量的试验结果表明，即使以弯剪破坏为主，随着循环荷载的增大，剪切的影响也越来越大。由此得出结论，在分析钢筋混凝土空心墩时，仅考虑抗弯性能的分析是有局限性的，因此必须将抗剪性能与抗弯性能结合起来考虑。在高轴向加载时，荷载-位移曲线表明，由于钢筋屈曲和覆盖混凝土剥落，位移能力趋于变差。由此可见，改善结构细节，如提高抗剪配筋率，对提高空心墩在高轴向荷载下的位移能力具有重要意义。

This research presents results from testing and analysis of RC hollow piers to clarify their fundamental behavior under combined loads.1.The ultimate displacement of RC hollow beams are smaller than the same-size filled beam, and the capacity of displacement and energy dissipation tend to be lower than that. At the ultimate state, the energy dissipation is about 20% inferior to the filled beam. After the hollow beam reaches the peak strength, the deterioration of its strength is rapid.2.In the flange part of a hollow section there are many flexural cracks. Once these cracks develop into the web part, they are turned into shear cracks. This phenomenon occurs not only in case of shear failure specimen but flexural failure specimen. This is why the narrow width of the web of the hollow section requires careful consideration on its shear strength, when hollow section is adopted.3.The experimental result of separation of pier displacement into flexural and shear components shows that the influence of shear is increasing when the cyclic load becomes larger even if the flexural failure dominates. This leads to the conclusion that the analysis that deals with only flexural behavior has the limitation when we analyze RC hollow piers, so the shear behavior must be considered in cojunction with flexural behavior.4.When high axial loading is used, the load-displacement curve shows that the displacement capacity tends to become worse because of the rebar buckling and the spalling of cover concrete. From this it follows that inprovement of structural details, such as increasing the shear reinforcement ratio, is important to enhance the displacement capacity of hollow piers under high axial load.