Impact of Energy Efficient Construction Details on Seismic Resistance of Passive Buildings

Abstract

Recently, an increasing trend of passive and lowenergy buildings transferring from non-earthquake prone to earthquake-prone regions has thrown out the question about the seismic safety of such buildings. The paper describes two most commonly used structural details of energy efficient construction, which could be critical from the point of view of earthquake resistance: i) Foundation of a building on thermal insulation (TI) layers and ii) Fixing of precast balcony element without thermal bridge. The first part of the paper describes the problematics of founding of a building on TI and presents the authors' proposal of seismic fuse assembled out of TI boards and waterproofing (foil) layers, which have been commonly used under the RC foundation slabs of passive buildings. The main idea is to reduce the seismic forces on the superstructure by allowing controlled lateral sliding between the individual layers of the TI boards. The feasibility of the proposed solution has been analysed by means of nonlinear dynamic analyses for selected 2-and 4-storeyed passive buildings founded on TI boards made of extruded polystyrene (XPS). The second part of the paper analyses the seismic response of precast balcony cantilever structural elements, which have been recently developed in seismic non-prone areas in order to prevent the thermal bridge at the point where the cantilever is fixed to the building. Such balcony elements have been made primarily to withstand vertical static loading neglecting the eventual vertical seismic loads in the case of an earthquake. It has been found out that those cantilevers in the case of uplift might not be designed with adequate safety, since they lack sufficient reinforcement on the bottom side. In order to reduce their seismic vulnerability some changes of precast load-bearing TI elements have been proposed.