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Abstract
This thesis 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. 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. Moment-rotation relationships of beam-to-column joints were predicted with analytical models aiming to provide accurate and reliable analytical solutions. Among this, initial stiffness of beam-to-column joints was derived on the basis of Timoshenko’s plate theory, and moment capacity was derived in accordance with Eurocodes. The predictions were validated with relevant test results prior to further applications. Frame analysis was conducted by using Abaqus software with material and geometrical nonlinearity considered. Variable lateral loads incorporating wind actions and earthquake actions in accordance with Australian Standards were adopted to evaluate the flexural behaviour of the composite frames. A wide range of frames with the varied number of storeys and bays were thereafter programmed to ascertain bending moment envelopes under various load combinations. Results from experiments suggest that the proposed beam-to-column joints have capacity to provide sufficient stiffness, strength and ductility for the moment-resisting structures. The joints can be demounted in an economical and convenient manner to achieve the high potential of reuse and recycling of steel materials. Numerical analysis is demonstrated to have a good agreement with the test result. Theoretical analysis provides a straightforward way to estimate flexural performance in terms of initial stiffness and moment resistance. Frame analysis highlights that the wind action is a critical parameter that influences the moment-resisting response more significantly than earthquake action in Australia. The composite frames with demountable beam-to-column joints can be designed simply without moment reversal provided that cross-section properties of beams and column are selected properly.