CYCLIC RESPONSE OF LATERALLY LOADED TIMBER FASTENERS ACCOUNTING FOR SHAFT FRICTION

This paper is based on the extension of the program HYST, developed by Foschi for the computation of the cyclic nonlinear response of timber fasteners under lateral loading, to take into account shaft frictional forces. The wood medium is modeled using the Foschi embedment model and shaft friction is simulated with an elastic Coulomb-type friction model. The initial confining pressure surrounding driven fasteners is taken into account by a lateral shift of the wood embedment curve. The model is used to compute the cyclic response of a driven fastener and also that of a bolt connecting three wood layers when subjected to a reversed cyclic displacement history. Results from these two cases show that the value of the initial confining pressure and the coefficient of friction have only a slight effect on the computed hysteretic response. However, for the driven fastener, both quantities were found to significantly affect the computed amount of fastener withdrawal. The model is thus suitable to be used as a basic component in the modeling of shear walls with fasteners that will experience moderate withdrawal under lateral cyclic or earthquake loading.