ABSTRACT

Thin reinforced concrete walls may fail due to out-of-plane instability when subjected to seismic loading. While previous numerical studies on wall instability have focused on the behaviour of members with two layers of vertical reinforcement, this work addresses the response of walls with a single layer of rebars. Such walls are particular prone to out-of-plane failure when subjected to cyclic in-plane loading. The numerical investigations herein performed simulate the aforementioned local behaviour and validate it against experimental measurements. A parametric study on the effect of boundary conditions shows that imposing an out-of-plane displacement or a rotation at the storey height increases the vulnerability to instability. It is also seen that the storey height itself is an influencing variable. The second part of this study proposes an improved equivalent boundary element model for the assessment of wall instability. Existing mechanical models, based on pinned-pinned boundary conditions, represent the boundary element over the height of the plastic hinge. This work shows that such models often underestimate the critical tensile strain triggering out-of-plane failure. A new equivalent boundary element model is proposed where a bilinear axial displacement profile defined a priori is applied. The latter is shown to satisfactorily approximate the vertical strain profile in wall boundary elements and to lead to better estimates of the critical strain triggering out-of-plane failure.

摘要

当承受地震载荷时，薄的钢筋混凝土墙可能会由于平面外不稳定性而失效。虽然以前关于墙体不稳定性的数值研究集中在具有两层垂直钢筋的构件的行为上，但这项工作解决了具有单层钢筋的墙体的响应。当受到循环平面内载荷时，此类墙特别容易发生平面外破坏。本文进行的数值研究模拟了上述局部行为，并根据实验测量对其进行了验证。对边界条件影响的参数研究表明，在楼层高度施加平面外位移或旋转会增加不稳定的脆弱性。还可以看出，层高本身就是一个影响变量。本研究的第二部分提出了一种改进的等效边界元模型，用于评估墙体的不稳定性。现有的机械模型，基于 pinned-pinned 边界条件，表示塑性铰高度上的边界元素。这项工作表明，此类模型通常低估了引发平面外故障的临界拉伸应变。提出了一种新的等效边界元模型，其中定义了双线性轴向位移分布先验应用。后者显示出令人满意地近似壁边界单元中的垂直应变分布，并导致更好地估计触发面外失效的临界应变。