Timber shear walls: numerical assessment of the equivalent viscous damping

The seismic performance of timber shear walls is studied in this work, with focus on the energy dissipation ensured by sheathing-to-framing connections. Timber light-framed constructions present a fairly good earthquake resistance, basically attributable to the high strength-to-density ratio of timber and to the remarkable ductility of joints with metal fasteners, which ensure reduced inertia forces and good energy dissipation, respectively. Generally, timber has a poor dissipative capacity, unless it is properly reinforced, while the steel connections can ensure a good amount of plastic deformation and, as a consequence, a significant energy dissipation. In order to take into account this aspect, the designers can refer to the force-based design method proposed by EuroCode 8, which allows to reduce the demand of the elastic acceleration spectrum by applying a reduction factor. Overall, few efforts have been spent so far to analyze the mechanical behaviour and the energy dissipation of a single wall, and few parametric analyses are available that consider different wall configurations. Therefore, an original parametric FE model has been implemented in the present work by means of the open-source software OpenSees [1]. The numerical model has been validated considering the data carried out from experimental tests presented in Ref. [2]. The SAWS mechanical model, originally proposed by Ref. [3] and developed in Ref. [4], has been calibrated by means of non-classical identification methods, using the available experimental data, and then implemented in order to simulate the behaviour of a single nail. Numerical non-linear analyses are carried out, varying some basic design variables affecting the overall racking capacity of the wall, namely: aspect ratio, nails spacing and number of vertical studs. The equivalent viscous damping has been assessed by estimating the damping factor η through the Capacity Spectrum Method. Keywords: Timber shear walls; racking capacity; energy dissipation; equivalent viscous damping; Capacity Spectrum Method . References [1]    McKenna, F. and Fenves, G. (2001) The OpenSees Command Language Manual: version 1.2, Pacific Earthquake Engineering Center, Univ. of Calif., Berkeley, USA. [2]    Gattesco, N. and Boem, I. (2016) Stress distribution among sheathing-to-frame nails of timber shear walls related to different base connections: experimental tests and numerical modelling, Construction and Building Materials , 122 , 149-162. [3]    Foschi, R. O. (1977) Analysis of wood diaphragms and trusses, Part 1:Diaphragms, Canadian Journal of Civil Engineering , Ottawa, 4 (3), 345–352. [4]    Folz, B. and Filiatrault, A. (2001) Cyclic analysis of wood shear walls, Journal of Structural Engineering , 127 (4), 433-441.