Fracture Behaviour of Cold-Formed Steel Bolted Connections

Abstract

In this thesis, research into fracture behaviour and capacity of cold-formed steel (CFS) bolted connections is presented based on three independent experimental programs in conjunction with a numerical study using Finite Element (FE) simulation. Current design rules are also discussed and new design models are proposed. In terms of the first experimental program, testing bolted connections with staggered holes under monotonic shear loading was conducted to provide insights into the fracture behaviour and capacity of the connections failing in block shear. Test results are used to propose a new design formula for block shear strength accounting for the combined actions of shear and tension ruptures in the staggered zones which is not available in the current Australian and New Zealand Standard (AS/NZS 4600:2018) and North American Specification (AISI S100:16 (R2020) w/S3-22). A calibrated finite element model (FEM) was then validated against the test results to achieve reliable data using a parametric procedure. The large data set is used for the verification procedure of the proposed formula. In the finite-element (FE) simulation, to study the whole range of deformation of the staggered hole bolted connections (i.e., elastic, plastic and fracture stages), a plasticity model and a ductile damage model are applied to the CFS sheets to represent various stress states in the steel during failure. Reliability analyses are employed to evaluate the capacity reduction/resistance factors of the proposed model for Load and Resistance Factor Design (LRFD) and Limit State Design (LSD).