Seismic performance of Point Fixed Glass Facade Systems through Finite Element Modelling and proposal of a low-damage connection system

Among glazed curtain walls, the growing interest in Point Fixed Glass Facade Systems (PFGFS), simply known as “Spider Glazing”, is mainly due to their aesthetics, architectural attractiveness and high transparency they can provide when compared to more traditional framed glass facades. PFGFS are in fact punctually attached to the structure by using spider arms and bolted fittings. However, some PFGFS solutions have shown an unexpected moderate seismic vulnerability in recent earthquake events, as a consequence of inadequate connection detailing. As part of current seismic design philosophy, high structural and non-structural damage is accepted under a design-level earthquake. This inevitably leads to high post-earthquake losses in terms of both repair costs and business interruption for the damaged buildings. Therefore, nowadays the need for research efforts towards the development of low-damage technologies for the overall building system, including structural and non-structural components, is increasingly recognized. This paper aims at investigating the seismic performance of PFGFS through numerical studies at both localconnection level, by advanced non-linear FEM modelling implemented in ABAQUS software, and at globalfacade system level, through a simplified lumped plasticity macro-model developed in SAP2000 program. Non-linear static (PushOver) analyses have been carried out to assess the overall in-plane capacity of the facade. Based on the numerical outcomes obtained for a PFGFS consisting of traditional connections (i.e., available on the market), a novel low-damage system has been proposed. This solution comprises horizontal slotted holes for the bolted connection of the spider arms to the supporting structure. A parametric analysis, involving the variation of the slotted hole length, has been finally performed to study the effectiveness of the proposed solution. Results highlight the improvement of the in-plane capacity of the PFGFS, specifically an increase of the maximum allowable inter-storey drift ratio from 1.17% for the traditional system to 2.49% for the low-damage connection.