Influence of the Floor Diaphragm on the Rocking Behavior of CLT Walls

Abstract

In the design of cross-laminated timber (CLT) buildings in earthquake-prone areas, a crucial role in energy dissipation is played by the panel-to-panel joint. Such a connection, theoretically, could be designed for three different types of behavior: coupled, uncoupled, and monolithic. Coupled and uncoupled behaviors provide a certain amount of energy dissipation, whereas monolithic behavior does not. Currently, no specific design rules to attain a given condition are provided in any code. Furthermore, no information on the dependency of the wall behavior upon other variables, such as the out-of-plane stiffness of the floor diaphragms or the stiffness of other metal connections (e.g., hold-downs and angle brackets) can be found in the literature. In an attempt to fill in this gap, this paper presents the results of numerical analyses carried out using a commercial software package. In these analyses, the influence of the upper floor diaphragms on the rocking behavior of a two-panel wall assembly is investigated. Fully reversed displacement-controlled cyclic tests are simulated, while varying the geometrical properties (aspect ratio of the wall panels), mechanical properties (types and number of connectors used for the panel-to-panel, wall-to-foundation and wall-to-upper floor connections, out-of-plane stiffness of the floor panels), and gravity load applied on top of the assembly. The rocking capacity of the walls is investigated, together with displacements and global behavior of the assembly. The results obtained highlight the important role played by the stiffness of wall-to-floor diaphragm joints, whereas the out-of-plane flexural stiffness of the slab has a negligible effect on the overall response of the assembly.