Seismic design of CLT buildings: definition of the suitable q-factor by numerical and experimental procedures

The paper discusses the definition of the force modification factor (q-factor) in the literature and its relevance to the design of structures in seismic areas. The available methods for estimating the q-factor are based on the verification of the non-linear seismic response of entire buildings by means of experimental full scale shake table tests or numerical simulations. Such procedures are very expensive from cost and computational points of view. This paper proposes a new procedure for the q-factor evaluation based on a proper application of the pushover method to the load-displacement curve obtained through experimental quasi static tests on representative wall elements. That procedure is validated through shake table tests and numerical simulations on Cross-Laminated-Timber (CLT) building systems. An extensive application of the proposed procedure to a number of CLT shearwall systems tested in the CNR-IVALSA laboratory is presented in order to carry out a reliable estimation of appropriate q-factors. Finally the main advantages and limitations of the proposed procedure are presented and critically discussed.