Experimental evaluation of strength assessment procedures for R.C. elements with sub-standard details

Today the vast number of older reinforced concrete buildings that do not meet modern seismic provisions are faced with uncertain predicament in terms of expected performance in earthquake events. This has motivated the need for development and proofing of methods of seismic assessment and strengthening and has fueled significant activity in that front over the past 20 years. A Rapid Seismic Assessment system (RSA), which uses capacity prioritizing concepts in order to estimate the failure load of columns as the lowest strength from among several competing mechanisms of resistance (such as flexure, shear, anchorage or lap–splice) is demonstrated experimentally in the present paper. A series of fifteen reinforced concrete prismatic members with substandard details, representative of former construction practices, have been tested under reversed cyclic lateral displacement reversals. Detailing of the specimens was provided so as to develop all the known modes of column failure, thereby illustrating the underlying mechanistic models for strength estimation where reinforcement arrangement is the driving consideration. It was also shown that load history can play a determining role both in the prevalence of strain-controlled modes of failure (compression reinforcement buckling) and in terms of attainment of the available deformation capacity of the structural component. The experimental evidence served as proof-test of the RSA procedure, indicating that it is possible to capture the onset of column failure with relatively simple practical tools.