Seismic performance of light timber frame structures with sheathing and cladding: Experimental shake table tests

This paper presents dynamic and seismic tests on a two-storey light timber frame structure with OSB sheathing and additional gypsum fibre board cladding on a biaxial shake table. The work is part of the HELEPOLIS research project on the influence of fire protective cladding on the lateral load-carrying behaviour of light timber-framed walls. The test specimen was investigated with sheathing only and with additional cladding. The experimental programme comprised white-noise and impulse excitations to identify dynamic properties, as well as increasing seismic excitations up to structural failure for the cladded setup. The main objectives were: (i) quantifying the amplitude dependence of the dynamic properties; (ii) identifying the influence of cladding on stiffness and resistance; (iii) characterising the nonlinear response and failure mode of the cladded structure; and (iv) assessing vibration-based indicators for damage detection. The results show that the natural frequencies decrease with increasing amplitudes while damping ratios increase significantly. The additional cladding increases the stiffness of the structure significantly. At the same time, it can lead to higher base shear and hold-down forces, which may critically affect the design of non-ductile elements. The experimental data underline the need to explicitly consider claddings in the seismic design of light timber frame structures. Under seismic excitations incrementally scaled up to a peak ground acceleration of 0.98 g, the failure of the 2nd storey is governed by ductile failure of the stapled sheathing-to-framing connection. The failure is preceded by a marked reduction of natural frequencies. In addition, a comprehensive dataset is provided.