Experimental Investigation of In-Plane Stiffness of Timber Diaphragms in Traditional Chinese Residential Houses

The in-plane stiffness of timber diaphragms significantly affects the distribution of seismic loads among lateral force-resisting systems and the global response of the whole structure. In this work, the in-plane response of traditional Chinese timber diaphragms and the influence of certain parameters were investigated through an extensive experimental program, which consisted of cyclic tests on two full-scale diaphragms, monotonic tests on six sub-components, and connection tests. The chosen configurations were typical of those found in historic dwelling houses in southern China. Test results confirmed the high ductility and orthotropic nature of traditional Chinese timber diaphragms. The initial stiffness and energy dissipation capacity in the parallel-to-joist direction were found to be only about 50% and 70% of that in the orthogonal direction, respectively. For both directions, configurations with butted floorboards exhibited stiffer behavior than those with continuous floorboards, while the interaction between tongue-and-groove floorboards was shown to make little difference to the initial stiffness. The comparison between experimental results and predictions indicates that the current standards do not apply satisfactorily to traditional Chinese timber diaphragms, and specific provisions considering configuration differences are suggested to be included in the future.