The high modes of structure effect on the seismic demands of hollow brick partitions

Observations from past earthquakes in reinforced concrete buildings show that the masonry partitions can endanger the life of buildings occupants and lead to significant damage and loss. The most present codes of practice do not consider the effects of nonlinearity and higher modes of the structure and three-dimensional behavior of partitions on the out-of-plane seismic demands of these components simultaneously and the main purpose of this study is to investigate the effect of these cases together. This research involves assessing the seismic performance of partitions made of the hollow brick located in different stories of 3-, 7- and 11-story buildings containing 3D reinforced concrete special moment frames and subjected to a suite of 7 appropriate earthquakes. A finite element program, OpenSees, has been used for nonlinear seismic response history analysis. The average of the peak of responses of partition, under the seismic excitations, was computed for any model and the forces obtained using the analytical method, which some of them verified with existing studies results, were compared with the values from the code. For the majority of the models, the results show that the analytical seismic demands on partitions, in the lower half, are higher than those calculated using the code provisions because of the effect of higher modes of the structures and the peak values is even up to 1.54 times the computed value based on the code. The code provisions are conservative for the partitions in the upper half of the buildings.