Empirical Model Of Unreinforced Beam-column RC Joints With Plain Bars

Teresa De Risi Maria*, Ricci Paolo, Verderame Gerardo Mario
Department of Structures for Engineering and Architecture, University of Naples Federico II, Naples, Italy

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© 2018 De Risi Maria et al

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Structures for Engineering and Architecture, University of Naples Federico II, via Claudio, 21 - 80125, Naples, Italy; Tel: +39 0817683341;



Nonlinear behaviour of beam-column joints might significantly affect seismic performance of typical existing buildings, especially in the case of poor structural detailing, as the lack of an adequate transverse reinforcement in the joint panel or deficiencies in the anchorage details. A very limited number of studies deals with beam-column joints reinforced with plain hook-ended longitudinal bars, widespread in Mediterranean building stock, or with the analysis of local aspects, such as the evaluation of joint shear strain capacity. The almost totality of the models proposed in the literature for simulating the cyclic behaviour of RC joints was calibrated by means of tests performed on elements with deformed bars. Such models may be not suitable for elements with hook-ended plain bars, due to their peculiarities in terms of failure mode and concrete-to-steel interaction mechanisms.


An empirical macro-modeling approach is proposed in this work for exterior unreinforced joints with hook-ended plain bars, suitable for extensive nonlinear analyses.


A dedicated database of experimental tests is first collected. Based on this dataset, a shear strength model is developed. The joint panel constitutive parameters are also defined to reproduce the cyclic experimental joint shear stress-strain behaviour.


The whole modeling approach is validated through the comparison with the collected experimental data. It well reproduces the global response, in terms of elastic stiffness, global deformability, softening stiffness, unloading and reloading stiffness degradation and pinching effect for all the investigated tests.


The proposed model thus results reliable for the investigated typology of beam-column joints.

Keywords: Reinforced concrete buildings, Exterior unreinforced joints, Plain bars, Empirical model, Shear strength, Hysteretic behaviour.