Publication

Abstract : When buildings resist seismic action in a given direction (say, N-S direction), simplified seismic assessment procedures, generally, consider wall panels oriented along the direction of the shaking (i.e., walls along N-S direction) to resist only in-plane loads and wall panels oriented perpendicular to the direction of shaking (i.e., walls along E-W direction) to resist only out-of-plane loads. In short, these procedures for seismic assessment of existing buildings, typically, do not consider the interaction of walls meant to resist in-plane and out-of-plane loads. Therefore, independently verified are the adequacy of walls meant to resist in-plane loads and out-of-plane loads. However, in reality, when walls resist in-plane lateral loads, it deforms laterally in the same direction. Moreover, for buildings with a rigid diaphragm and good wall diaphragm connection, this lateral displacement (in N-S direction) results in relative displacement between the bottom and top part of out-of-plane walls (i.e., walls along E-W direction) (Fig. 1). This relative displacement is due to the displacement compatibility between the walls oriented along the in-plane and out-of-plane directions. This paper presents the effects of the relative displacement between the bottom and top part of the out-of-plane walls on its overall stability and load resisting capacity in the out-of-plane direction. Developed moment-displacement relationships of out-of-plane walls indicate a reduction in the out-of-plane displacement capacity, with an increase in relative displacement between the top and bottom part of the wall. This reduction in the out-of-plane capacity is inversely proportional to the level of axial load on the wall. Unlike the out-of-plane displacement capacity, the developed relationships do not show a significant drop in moment capacity. However, the out-of-plane stability of walls, particularly in the post-peak region, is better represented by the attainment of an ultimate displacement rather than the force capacity. Finally, this paper presents a simple seismic assessment procedure to verify the adequacy of out-of-plane walls.