Analytical prediction on deformation characteristics of lapped connections between cold-formed steel Z sections

Abstract

This paper presents an analytical method to predict the deformation characteristics of lapped connections between cold-formed steel Z sections. Based on the test results of typical lap shear tests on bolted fastenings between cold-formed steel strips of various strengths and thicknesses, a normalized bearing deformation curve was established. The curve was then adopted to predict the deformation characteristics of lapped connections between cold-formed steel sections where deformations due to global bending and shear actions as well as local bearing were significantly. The predicted deformation characteristics of a total of 26 lapped Z sections with different section sizes and connection configurations up to failure were then compared with the measured results, and comparison is found to be highly satisfactory. Moreover, an empirical formula was also proposed for the moment rotation relationship of lapped connections at large deformations after failure under combined bending and shear. The proposed method is considered to be very important in assessing the structural behaviour of multi-span purlin systems with lapped Z sections, in particular, in determining the effective flexural rigidities of lapped connections over internal supports. Such design data is essential for the establishment of internal force distribution along the entire lengths of the purlin members. Hence, the co-existing shear forces and moments at the ends of lap of the lapped connections are obtained accurately to check against section failure under combined bending and shear.