Design Deformation Limits for Damage Control in Reinforced Concrete Frame Components across Ductility Classes

Current design deformation limits in building codes (e.g., NZS 3101:2006) target life-safety performance objectives. With the intent of promoting post-earthquake functional recovery, there has been a drive towards defining deformation limits that target damage control and increased repairability (i.e., reduce the probability of requiring post-earthquake performance-critical repair) following design level events. To address this gap, first, this paper develops a database of cyclic tests on reinforced concrete beam and column specimens with Ductile Plastic Hinge Region (DPR), Limited Ductile Plastic Hinge Region (LDPR) and Nominally Ductile Plastic Hinge Region (NDPR) in accordance with NZS 3101:2006. Second, formulations for predicting the repairability deformation limit, defined in the paper as the deformation capacity at the lateral strength loss (LSL), was explored in terms of chord rotation, plastic rotation and curvature ductility. Analysis showed that the current curvature ductility limits for DPR (K _d = 19), LDPR (K _d = 11) and NDPR (K _d = 3) implied 60–80% probabilities, 40–60% probabilities and 5–10% probabilities of exceeding the deformation at LSL, respectively. This study proposes new design limits that target a uniform 10% probability of exceeding the deformation at LSL across all frame components. Finally, two multi-storey buildings in New Zealand were redesigned using the proposed deformation limits to examine their impact on the cross-sectional sizes of beams and columns. For both buildings, it is demonstrated that the proposed design limits increased the beam and column cross-sectional area by 20% and 45%, respectively, relative to the current NZS 3101:2006 design limits.