The reinforced concrete beam-column joint exhibits different properties under dynamic loading when compared with that under quasi-static loading, due to the effect of strain rate. However, the majority of previous studies are focused more on the rate effect of concrete and reinforcement, but less on beam-column joints. Based on the former considerations, the seismic behavior of 15 cruciform specimens subjected to various strain rates is studied in this paper, aimed at attaining a better understanding of the effect of strain rates on beam-column joints. In terms of the effect of different strain rates, the failure mode, carrying capacity, stiffness degradation, and energy dissipation of beam-column joints are discussed in detail. An empirical equation to predict the dynamic increase factor of horizontal shear carrying capacity of beam-column joints under different axial compression ratios and strain rates is also proposed through multiple linear regression analysis. Finally, four adjustments for the softened strut-and-tie model are made to get better predicting of the test results. It has been proved that predicted results by the improved softened strut-and-tie model are in good agreement with the test results.
The dynamic mechanical properties of 15 interior beam–column joint specimens subjected to various axial compression ratios are studied. Failure patterns of beam–column joints and development of cracks are predicted by a softened strut-and-tie model and binomial logistic regression model. According to the Coulomb failure criterion and Mohr's circle theory, a model to calculate the shear strength of concrete is derived under the shear compression state. In terms of the effects of different strain rates and axial compression ratios, the carrying capacity, stiffness and carrying capacity degradation, energy dissipation, displacement ductility, bond slip and failure mode of beam–column joints are discussed in detail. Finally, different building codes are selected to compare the results. It is found to be unsafe to substitute the dynamic strengths of concrete and reinforcement bar directly into the quasi-static design formulas to calculate the shear carrying capacity of the beam–column joint, because the shear carrying capacity of the joint is overestimated. To make a more reasonable assessment of the effect of strain rate and axial compression ratio, an empirical equation to predict the dynamic increase factor of horizontal shear carrying capacity of beam–column joints under different axial compression ratios and strain rates is proposed through multiple linear regression analysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.