Modeling recommendations for RC and CFST sections in LS-Dyna including bond slip

Abstract

Modeling of reinforced concrete (RC) and concrete filled steel tube (CFST) sections is complex, because the model must be capable of capturing degradation of the concrete strength and stiffness in compression, confining effects, the response of the interface of the steel (either reinforcing bar or tube) and concrete. When RC and CFST are connected, (e.g., RC column-to-CFST pile connections or RC slab to CFST column connections), accurate and validated modeling is required for the steel tube, reinforcing steel, concrete fill, confined and unconfined concrete, bond between reinforcing bars and concrete, and bond between the tube and the concrete fill. To advance understanding and design of structural systems using RC and CFST components, a research study was undertaken to evaluate the accuracy various modeling approaches using LS-Dyna, which has a large library of concrete models and advanced modeling capabilities for bond. Large-scale experimental data was used to validate different modeling approaches for the RC and CFST components and their connections. Four concrete models were compared and evaluated using the test data; the new concrete damage plasticity model is found to provide the most accurate simulation of the cyclic behavior of concrete. The bond-slip behavior between steel and concrete was modelled using the cohesive material model. Model validation included comparison of the damage pattern and measured hysteresis curves. A summary of the recommended modeling parameters for use in future research and engineering practice is provided.