Design for improved seismic performance of a light gauge steel portal frame structure

• Main Author: Ahmed, Alia Osman Mohamed
• Published: University of Strathclyde 2013
• Subjects: 624
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.667560

This research work develops a design methodology for improving the earthquake resistance of slender portal frame structures and evaluates the performance of this kind of light gauge steel portal frame structures in earthquake prone areas through the study of designed building using a finite element approach. The design of the building was carried out for a site in Sudan for peak ground acceleration 0.23g according to the Eurocodes 3 and 8 for ductility class "Low". Two analytical techniques (i.e. Static displacement pushover and dynamic time-history), were employed to assess the behaviour of the light gauge steel portal frame structure. A new cyclic column link dissipation device is introduced to protect the structure under seismic loads and prevent buckling of frame rafter components. This link is made of back to back lipped channel cold formed steel section and dissipates energy in cyclic bending. It has a yield strength value less than the frame members, and moment resistance about 2/3 the buckling moment of resistance of the frame rafter members. The column link section is stockier than the rafters; the limiting slenderness of the columns was that for compact section. To accomplish the main objective, the potential benefits (of lightness) of utilising light gauge, steel, slender steel for the construction of portal frame buildings in earthquake prone areas, preliminary analyses of the frame with different types of links were performed using the commercially available finite element software ANSYS. The frame was analysed by nonlinear static horizontal displacements. The inelastic behaviour of the steel elements was considered using the von Mises yielding criterion and the nonlinear gemoetry were considered as large displacement and P-δ effects in the analyses.