Predicting Damage to Steel Rebar in Reinforced Concrete Structures Subjected to Earthquake Loading

Leslie G. Ramos, & Maha Kenawy

Published August 16, 2021, SCEC Contribution #11600, 2021 SCEC Annual Meeting Poster #054 (PDF)

High-intensity ground shaking can cause significant damage to civil structures and interruption of community functions. Structural components, such as reinforced concrete (RC) columns, deteriorate and accumulate damage during high-intensity shaking. The recent reauthorization of the National Earthquake Hazards Reduction Program (NEHRP) by Congress focuses on the recovery of communities after earthquake events. Consequently, there is a need to understand and predict the extent of damage a given structure may be subjected to. By developing advanced numerical tools to simulate damage and extreme limit states of RC structural members, structures can be retrofitted or built to withstand substantial damage and minimize interruption of function. Commonly used nonlinear structural analysis tools can be deficient in predicting inelastic behavior and accumulation of damage to RC structures due to the mesh sensitivity associated with finite element modeling of material damage. As a result, prediction of the nonlinear behavior of steel reinforcement in columns, specifically buckling of steel rebar, remains a challenging task. Calibrating the numerical models used to represent the behavior of steel reinforcement is difficult due to the sparsity of experimental test data and idealizations associated with structural models that keep them practical and inexpensive. In this study, we present and calibrate a mesh-independent structural analysis model that is capable of representing the effect of steel buckling in RC structures subjected to extreme loads. The numerical model utilizes the nonlocal continuum theory to represent the buckling of steel rebar as material softening in a mesh-objective fashion, and is calibrated using available test data in the literature. Our findings show that predictions of the deterioration of the load-carrying capacity of RC columns, when subjected to cyclic and seismic loading, are sensitive to the steel buckling model and associated material softening parameters. The agreement between the results of the numerical simulation models and experimental tests on RC columns subjected to cyclic lateral loading can be improved using the proposed buckling model for steel. The proposed model is implemented in OpenSees, an open-source structural analysis platform, and can be used by structural engineering researchers and practitioners to model the buckling of steel and predict the degradation of RC members under extreme earthquake events.

Key Words
structural damage, reinforced concrete, extreme loads, steel buckling, mesh sensitivity, OpenSees, finite element analysis, cyclic loading

Citation
Ramos, L. G., & Kenawy, M. (2021, 08). Predicting Damage to Steel Rebar in Reinforced Concrete Structures Subjected to Earthquake Loading. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Engineering Implementation Interface (EEII)