The behaviour of composite beam-to-column flush end plate connections using blind bolts

Abstract

The numerous advantages achieved by using concrete-filled steel tubular (CFST) columns in multi-storey construction have been appreciated for decades. Tubular sections are more effective than open sections due to higher load carrying capacity, superior seismic capacity, improved ductility and fire resistance. However, the connections to CFST columns are complicated as they require access to the inside of the hollow steel tube. Complicated methods like welding were used to establish connections in the past which were not favourable due to several complications and the exorbitant cost involved. The recent development of the innovative blind bolting technique made it possible to connect beams to CFST columns economically without the need for access within the hollow section. However, the connections developed using this technique remain a concern for engineers due to lack of experience and poor guidelines specifically under cyclic loading. In order to achieve the numerous benefits associated with the use of these connections, it is imperative to investigate different structural components and their response under various loading scenarios.

Two sub-assemblages of cruciform composite beam-to-column joints connected using blind bolts were tested under static and cyclic loading. The test results were used to obtain the load-displacement characteristics of the connection, failure modes and strain development. The test results demonstrated sufficient stiffness and strength of the joints under both loading scenarios. Two finite element models were developed and validated with the experimental data that demonstrated accuracy and reliability. Parametric studies were performed to investigate the influence of various significant parameters on the behaviour of these connections.

Moreover, this thesis presents a useful in-plane structural analysis of low-rise blind-bolted composite frames with semi-rigid joints using ABAQUS software. Analytical models were used to predict the moment-rotation relationship of the composite joints that produced accurate results. Bending moment envelopes of the frames under various loading combination were determined. The analysis suggested that gravity loads governed the frame design and wind loads were found to be more critical in Australia as compared to the earthquake loads. The study provides useful understanding of the complex behaviour of these connections that can be effectively applied in engineering practice.