The critical sections of columns in a framed structure subjected to earthquake loads are invariably adjacent to the beam-column joints or the footings. External restraint provided by the heavy elements alters the column behavior. The improvement of flexural strength in the critical column sections may not always prove conservative for the columns designed according to "strong-shear-weak-bend" seismic design philosophy. Sheikh and Khoury reported that a heavy footing provided additional confinement to the adjacent section and the failure thus moved to a section away from the footing where the restrain effect is minimal. However, no model is found to be able to simulate this phenomenon accurately. In this paper, a mechanic model which can simulate this phenomenon is proposed.
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