Shaking table tests on the response of reinforced concrete frames with non-seismic detailing

• Main Author: Yavari, Soheil
• Language: English
• Published: University of British Columbia 2011
• Online Access: http://hdl.handle.net/2429/32155

Reinforced concrete frames constructed before the introduction of modern seismic codes have performed poorly during past earthquakes. Such frames have primarily been designed for gravity load effects, leading to light transverse reinforcement in the columns, unconfined beam-column joints, and generally a lack of seismic details required for ductile post-yield behaviour. It has been demonstrated in literature that light transverse reinforcement in a column may result in shear and axial failure. Furthermore, lack of confinement may cause shear failure at joints. However, interaction of vulnerable components and their contribution to the collapse behaviour of existing reinforced concrete frames is not well understood. This research project was initiated to provide a better understanding of the factors contributing to collapse of the frames with non-seismic detailing. In the experimental phase of this study, four 1:2.25 scale, two-bay-two-story specimens were designed with non-seismic details and tested on a shaking table. The target failure mode was intended to be damage leading to collapse that would enable examination of gravity load redistribution during the test. The tests provide unique benchmark data for both qualitative and quantitative assessment of the factors influencing the behaviour of reinforced concrete frames up to the point of collapse. Based on the results from the shaking table tests, this dissertation will evaluate the influence of axial load on shear and axial behaviour of non-ductile columns and the effects of unconfined joints on overall behaviour of a frame near the point of collapse. The analytical phase of the research included evaluation of existing models for predicting shear and axial failure of non-ductile columns and collapse of frames. The currently available models for shear and axial failure of non-ductile columns are mainly drift-based. The results of the current study suggest that these models should be refined using the column ends rotation demand. While results from comprehensive nonlinear models of the four specimens were compared with the test data, simplified models that can be easily employed in engineering practice for assessing existing frames were also evaluated. A refinement to provision from ASCE-41 on column effective stiffness was also proposed in this dissertation.