Author(s)

ASHRAF OSMAN, MOHAMED G. KHERD

Abstract

This study investigates the lateral behaviour of steel moment resisting frames cladded externally with precast reinforced concrete panels, under the action of both wind and earthquake loads. The aim is to explore the possibility of achieving extra saving in the steel structure weight by utilizing the external cladding to engage in resisting the applied lateral loads. To achieve these objectives, several hypothetical steel moment-resisting frames were initially developed. Then, these frames were analysed using a push-over technique. In performing these analyses and for sake of comparison, the frames were considered as bare steel frames once and in other cases the contribution of the external reinforced concrete cladding panels was included. The structural elements of the analysed moment resisting frames (beams and columns) were modelled analytically using a beam-column element that allow the formation of plastic hinges at elements ends, while the external reinforced concrete precast cladding panels were modelled using equivalent diagonal struts that can yield and possess a criterion for collapse that simulates the possibility of failure of connection between panels and steel frames. For all performed analyses, lateral stiffness, strength, and sequence of plastic hinging were evaluated and compared. It was concluded that utilizing precast concrete external panels’ contribution in designing moment resisting frames against wind loads can improve significantly frames’ initial stiffness and strength, leading to significant reduction in their steel tonnage. For designing against earthquake loads, the panels limited frames’ lateral deformation and reduced their weights which was considered beneficial in resisting minor and moderate earthquakes and limiting the damage to non-structural elements. However, at ultimate state under severe earthquakes, to maximize the contribution of these panels, the connections between the steel frames and the panels needs to be sufficiently strong to ensure engagement of panels in resisting the lateral loads, and frames should be detailed for a strong column– weak beam concept.

Keywords

seismic behaviour, steel moment resisting frames, precast reinforced concrete panels, exterior cladding