The Influence of Deformability of Horizontal Diaphragms in the Distribution of Seismic Loads to Bracing Elements in Rectangular Buildings

Abstract

The operations of a floor, as a significant structural element, have an influence on the stability of the structure when it acts as a horizontal diaphragm. In this study, the in-plane deformability of rectangular floors of single story buildings is examined under the effects of horizontal seismic actions. Therefore, the effects of parameters influencing the behavior of the floor such as size opening and their location, position of shear walls, span-to-depth ratio, and materials constituting the floor were studied. Results suggest that a diaphragm will behave in a flexible manner whether it is classified as rigid or flexible. However, a small opening in the floor can change the behavior of a diaphragm assumed rigid and make it behave like a flexible diaphragm. Additionally, flexible diaphragms can distribute horizontal seismic shear forces to vertical resisting elements due to the relative rigidity of the shear wall. These results are in contradiction with seismic codes such as ASCE/SEI 7-10 [1], FEMA 356 [2], and Eurocode 8[3], further the size of opening that make flexible diaphragm behave like rigid diaphragm was suggested by formula. For the building with a shear wall, the classification of the diaphragm in seismic codes such ASCE is not accurate enough and they need to reform with taking into consideration the location of the opening in the floor.

Keywords

• Earthquake, Rigid Diaphragm, Flexible Diaphragm, Shear forces, Shear wall, Seismic code