Verification of the behaviour factors proposed in the second generation of Eurocode 8 for cross-laminated timber buildings

Abstract

After 20 years since the publication of the Eurocodes, in 2012, the European Commission gave mandate to the European Committee for Standardization (CEN) to develop a second generation of Eurocodes. Among the different parts of Eurocodes, a substantial revision process has been undertaken for the seismic design rules of timber buildings included in Eurocode 8 (EC8). In particular, a major effort has been made to implement the design rules for Cross-Laminated Timber (CLT) buildings and to define the behaviour factors q for such structural type. The choice of the behaviour factor q for CLT buildings in the new “timber” chapter of EC8 has been made by examining several proposals available in literature. Most of these studies were not referred to any specific design provision and certainly could not have followed the design rules drafted in the second generation of Eurocodes. This paper presents a study aimed to verify whether the proposed values of the behaviour factors q are consistent with the attained seismic performances of CLT buildings designed in accordance with the new “timber chapter” of EC8. Parametric non-linear static (pushover) analyses and a risk-consistent approach, based on the use of Incremental Dynamic Analyses (IDA) and fragility curves were conducted to evaluate the performance of a few selected archetypes. The results obtained from the analyses and the risk-consistent approach showed that the proposed values of q-factor for CLT buildings in second generation of Eurocode, namely 2.30 and 3.20 for a ductility class 2 (DC2) and 3 (DC3) respectively, can be reasonably accepted.