Studies on Method of Limit States Design for Underground RC Frame Structures

地下钢筋混凝土框架结构极限状态设计方法的建立，首先要确定作用在结构上的地震力。地震力的主要部分是水平土压力。在日本现行抗震设计规范中，规定用Mononobe和Okabe公式确定上述动土压力，但这两个公式最初是为挡土墙抗震设计而提出的，因此不一定适用于地下管道等柔性墙地下结构。为此，首先要建立动土压力产生机理的概念，并建立合理的动土压力预测公式，然后在剪切试验装置上对气干岐阜砂模型地基和三个埋有不同刚度模型管道的复合模型进行水平正弦激振 ...更多信息 在振动台上进行了共振频率的dal运动，观测到的管道侧壁沿着动土压力的响应表明，当管道的剪切刚度由低于周围土层的剪切刚度变为高于周围土层的剪切刚度时，在基础运动的同一阶段，管道侧壁动土压力的分布方向相反。在管道刚度较低的情况下，管道底部的反应加速度比自由地面情况下的反应加速度小得多。用有限元数值模型对上述试验进行的模拟显示了与上述相同的行为。综合试验和数值计算结果，阐明了作用在地下管道侧壁上的动土压力的发展机理，导出了动土压力的预测公式，阐明了钢筋混凝土框架的延性特性，建立了延性的估算方法。通过以上研究，可以说建立了一种地下钢筋混凝土管道极限承载力的估算方法。少

In order to establish the method of "Limit States Design for Underground RC Frame Structures" it is most important for us to estimate the seismic forces acting on the structures. Main part of the seismic forces are horizontal earth pressures. In Japanese current aseismatic design standard it is specified to determine above dynamic earth pressures by Mononobe and Okabe's formulae which were, however, originally proposed for the purpose of the earthquake resistant design of retaning wall, so that they are not necessarily fit to such underground structure of flexible walls as underground conduit. Thus, we must establish an idea of mechanism of generating dynamic earth pressures for the first as well as the formula to be able to predict them reasonably.A model ground of air dried Gifu sand compacted in a shear testing apparatus and three composite models at each of which the model conduit of different rigidity was buried in the above same model ground were excited horizontally with sinusoi … More dal motions of resonant frequencies on a shaking table.The observed response dynamic earth pressures along a side wall of conduit show that the distribution of them at the same phase of base motion reverses in its direction as the shearing rigidity of conduit changes from lower to higher than the oneof surrounding soil layer. In the case of lower rigidity of conduit the response acceleration at its bottom is much lower than the one in free ground case. The simulations of above tests with FEM numerical models show the same behavior as mentioned above. Synthesizing both experimental and numerical results the mechanism of development of dynamic earth pressures acting on side walls of underground conduit has been clarified and a formula predicting them has been derived.Besides, the characteristics of the ductility of reinforced concrete frames have been clarified and a method of estimation of it has been established too. With all the results obtained above it may be said that a method to estimate the limit states bearing capacity of underground RC conduit has been established. Less