Behaviour and design of demountable beam-to-column composite bolted joints with extended end-plates

This paper presents a novel structural form of demountable beam-to-column composite bolted joints that can be dismantled at the end of its service life. An experimental programme was conducted to investigate the static and hysteretic behaviour of the demountable composite joints. The initial stiffness, moment capacity and failure modes of the demountable beam-to-column joints were evaluated through experimental results. The demountability of the joints was verified by dismantling the specimens during testing. Finite element models were developed, which incorporated the nonlinear contact interaction, ductile damage and plastic damage. The accuracy of the numerical models was validated with the relevant experimental outcomes. A parametric analysis was thereafter conducted to evaluate the effect of the end-plate thickness, width-to-thickness ratio of the column, bolt diameter and number of bolts on the moment-rotation response. A comparison between the test results and Eurocode was conducted to assess the applicability of the existing design guidance. It is found that the specimens designed with bent reinforcing bars exhibit satisfactory performance, and possess a higher level of hogging moment resistance compared to those with straight reinforcing bars. The designed joints are able to be dismantled readily and all steel components remain elastic when they are loaded up to 40% of the ultimate capacity which is equivalent to the typical service load. The end-plate thickness, width-to-thickness ratio of the column and bolt diameter impose the significant effect on the performance of the bolted joints. Two bolt-rows in tension can improve the moment-rotation response for the joints with extended end-plates. The current design standards are not capable of predicting the behaviour of the demountable beam-to-column joints accurately.