Estimating plastic strain and residual strain capacity of earthquake-damaged steel reinforcing bars

Modern seismic codes are based on capacity design and the hierarchy of strength philosophy that allows inelastic response in case of severe earthquakes. Thus, in most traditional systems, earthquake damage develops at well-defined locations in reinforced concrete (RC) structures. Plastic hinges form in beams, in coupling beams, and at the base of columns and walls. There is a perceived strong demand from government and industry to develop techniques for assessing damage to steel reinforcement bars embedded in cracked structural concrete elements of earthquake-damaged buildings. Although some studies have been conducted recently, a validated methodology to quantify the level and extent of plastic deformation and residual strain capacity has yet to be widely accepted. In this paper, a damage assessment methodology is proposed based on empirical relationships between hardness versus strain and residual strain capacity that accounts for the effects of strain aging. The method has been applied to buildings damaged in the 2010/2011 sequence of earthquakes in Christchurch, New Zealand.