The wide-beam reinforced concrete moment resisting frame structure is widely used worldwide due to its architectural aesthetics, less space occupancy and construction simplicity. Nevertheless, the vulnerability of the beam-column joints in wide-beam frame structures has raised concerns about its application in seismic zones. Currently, experimental investigation and analytical modelling on the wide beam-column joint are scarce compared with the conventional beam-column joint. Furthermore, current seismic design codes of practice simply extend the design rationale from the conventional beam-column joint to the wide beam-column joint so the adequacy and reliability of their applications in seismic regions are questionable. As a result, there is an urgent need to conduct more inves...[ Read more ]

The wide-beam reinforced concrete moment resisting frame structure is widely used worldwide due to its architectural aesthetics, less space occupancy and construction simplicity. Nevertheless, the vulnerability of the beam-column joints in wide-beam frame structures has raised concerns about its application in seismic zones. Currently, experimental investigation and analytical modelling on the wide beam-column joint are scarce compared with the conventional beam-column joint. Furthermore, current seismic design codes of practice simply extend the design rationale from the conventional beam-column joint to the wide beam-column joint so the adequacy and reliability of their applications in seismic regions are questionable. As a result, there is an urgent need to conduct more investigations on the seismic behaviour and strength of wide beam-column joints to enrich the existing experimental database and to provide more rational and reliable guidelines for the seismic design.

In this thesis, a systematic investigation is presented, comprising both experimental research and analytical modelling on the seismic behaviour and strength of reinforced concrete exterior wide beam-column joints. Eight large-scale exterior wide beam-column joints were designed, constructed and tested under reversed quasi-static cyclic loading. The specimens were divided into four series, emphasising on the effects of beam reinforcement ratio, joint transverse reinforcement, column depth and spandrel beam reinforcement, respectively. Four modes of failure were observed among the specimens: beam flexural failure, joint shear failure after beam yielding, premature joint shear failure and premature spandrel beam torsional failure. The detailed analysis showed that the shear strengths of wide beam-column joints can be larger than those of conventional beam-column joints if properly designed. It was further indicated that less beam reinforcement, larger column depth and sufficient spandrel beam reinforcement can significantly improve the seismic performance and strength of wide beam-column joints, while the improvement by using more joint transverse reinforcement was insignificant.

An analytical model is developed to predict the strengths of exterior reinforced concrete wide beam-column joints. In the proposed model, the shear strength of the joint core is determined by the softened strut-and-tie concept and the torsional strength of the outer joint is derived by the thin-walled tube space truss analogy. The model demonstrates superior accuracy through experimental verification. A simplified version of the model has also been proposed to prevent excessive iterative computation and enable easy application in practical design.

The findings prompt a re-thinking of the rationale for the design of earthquake-resistant wide beam-column joints. Based on the comprehensive experimental investigations and mechanics-based analytical model, refurbished design recommendations are proposed to improve the reliability and accuracy of the existing design specifications.