Experimental investigation on sub-assemblage frame with cruciform column section

Abstract

This paper presents an experimental investigation on full-scale sub-assemblage frame. The purpose of conducting the full-scale sub-assemblage frame is to visualize and to observe the connection system as close as possible to the actual practical application. Two set of sub-assemblage frames were tested and discussed in this paper. The sub-assemblage frame consists of a built-up hybrid beam section connected to two cruciform column sections using typical end-plate connection. The connections used in this study are the flush and extended end-plate that proposed by the Steel Construction Institute for wind-moment connection but incorporating several modifications. The sub-assemblage frame was tested under monotonic load until failure, and the built-up hybrid beam section is unrestrained against out-of-plane deformation, to control the failure criterion of the beam to lateral-torsional buckling. The structural behavior of the sub-assemblage frame was closely observed and the experimental results were compared to the theoretical model proposed by the authors. The rotational stiffness and moment capacity of the end-plate connection tested in the sub-assemblage frame were predicted using the results obtained from the isolated connection tests. The experiment results showed the failure of the sub-assemblage frame is dominated by lateral-torsional buckling at mid-span of the beam, due to the absence of lateral restraint. Comparison between theoretical and experimental model showed reasonable agreement. The design approach of BS 5950-1: 2000 for beams subjected to bucking moment showed large reserves of strength, which the actual effective length ratio for beams connected using flush end-plate and extended end-plate connection are 0.70 and 0.78 respectively. The extended end-plate connection poses more strength and stiffness to the sub-assemblage frame as compared to flush end-plate connection, and reduced the deflection of the beam significantly. It is possible to predict the behavior of sub-assemblage frame with end-plate connection using the proposed method. The built-up sections used in the study able to reduce the steel weight usage so as the overall construction cost.