Connection systems between composite sandwich floor panels and load-bearing walls for building rehabilitation

Abstract

The use of advanced composites for building rehabilitation presents several advantages when compared with traditional construction materials. When degraded building floors need to be replaced, composite sandwich panels are a potentially interesting solution, namely for buildings with load-bearing rubble masonry walls. In this paper, connection systems between composite sandwich floors and load-bearing walls are proposed, and their behaviour under vertical loading is investigated. The systems comprise steel angles anchored to the walls, serving as main supports of the sandwich panels, which are then adhesively bonded and/or bolted to the angles. These connection systems are experimentally assessed using sandwich panels made of glass-fibre reinforced polymer (GFRP) face sheets and cores of either polyurethane (PUR) foam or balsa wood, by means of flexural tests on cantilevers, which are also simulated using non-linear finite element models. The structural response of the connection systems is determined, including the rotational stiffness conferred to the floors, the strength and the failure modes. Moment–rotation relationships are obtained for the connection systems and sandwich panel types considered, which provide a wide range of rotational stiffness values, from 60 to 10,856kNm/rad per unit width (m). These are then used to analytically estimate the short-term mid-span deflections of floors with semi-rigid connections and spans ranging between 2m and 5m. It is shown that some of the proposed connections allow significant floor stiffness increases compared with simply supported conditions, with reductions in total mid-span deflection of up to 65% being achieved for a span of 4m. The results obtained for the proposed connections highlight (i) their potential benefits for fulfilling serviceability limit states and (ii) the importance of considering an adequate structural model when designing sandwich floor panels.