مقررات جدید برای طراحی لرزه ای ساختمان های چوبی در اروپا The new provisions for the seismic design of timber buildings in Europe

1. Introduction Timber structural systems have increasingly become a viable alternative to other traditional structural materials like concrete, steel and masonry, mainly because of their excellent properties related to sustainability, energy efficiency, speed of construction and high seismic capacity. According to [1] the market share of wood-based residential buildings goes from less than 1% in Spain to 12% in Germany, 15% in Austria, 18% in Switzerland and Belgium, 21% in UK and 30% in Ireland, in 2006. A similar percentage (6.4%) has been estimated in Italy in 2014 [2] with an increasing expected growth in the next years. With specific attention to the mechanical behaviour of timber structural systems, several shaking table tests and extensive numerical simulations have been carried out in the last years within international research programmes, showing their excellent structural performances in case of seismic events. A tangible outcome of the obtained results in the research field is given by the increasing number of medium-rise buildings constructed in earthquake-prone areas with different level of seismicity in the last 10–15 years (Fig. 1). The revision process of the structural Eurocodes and therefore of Eurocode 8 [3] began in 2015 with the formal establishment of CEN (European Committee of Standardization) Project Teams tasked to prepare new drafts of the different sections, and the final updated version is expected to be released around 2020. Among the different materials, the Chapter related to the seismic design of timber buildings is probably the one which needs major changes, being the current version rather old and short and considering that the construction practice for timber buildings evolved in the last years much more rapidly and radically than for other materials, especially concerning earthquake design. This paper presents a proposal of modification of the current provisions; the proposal has been partly presented in [4] and it is still under discussion within the CEN/TC250/SC8 committee ‘Design for Earthquake Actions’, sub-group WG3 ‘Timber’ and for this reason it should considered as a draft version, since many changes may occur before its final published version. This manuscript represents the authors’ point of view on the basis of a scientific research background and the design common practice, and it shall be not assumed as the final Standard version.