RESEARCH ARTICLE


Key Mechanisms of the Seismic Behaviour of External RC Wide Beam–column Joints



Giuseppe Santarsiero*, Angelo Masi
Scuola di Ingegneria, Università della Basilicata, via dell’Ateneo Lucano, 10, 85100 Potenza, Italy


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© 2019 Santarsiero and Masi.

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: (https://creativecommons.org/licenses/by/4.0/legalcode). 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 theScuola di Ingegneria, Università della Basilicata, via dell’Ateneo Lucano, 10, 85100 Potenza, Italy;
E-mail: giuseppe.santarsiero@unibas.it


Abstract

Background:

Reinforced concrete beam-column connections provided with wide beams are widely used in the European residential building stock. Several seismic codes indicate some limitation to be applied to this kind of reinforced concrete buildings due to their reduced performances with respect to those provided with conventional beams.

Objective:

The paper is focused on improving the knowledge of wide beam-column joints, highlighting the key degradation mechanisms affecting them, mainly related to slip phenomena of beam rebars, especially the rebars placed outside the column width.

Methods:

The behavior of wide beam-column joints has been evaluated by means of both experimental tests under cyclic loading and accurate nonlinear finite element analyses. The FE models predicted satisfactorily experimental results, thus enabling to carry out additional numerical analyses aimed at checking the effect of the longitudinal reinforcement amount in the beam member.

Results:

Experimental results show that wide beam-column joints conforming to the Italian seismic code do not exhibit a sufficiently ductile behavior due to damage in the non-confined concrete region, where beam rebars external to the joint core are anchored. Numerical simulations allowed to monitor bond slip of beam rebars as a function of the applied global displacement, showing differences between bars placed inside and outside the column width.

Conclusion:

Numerical simulations showed that different behavior is expected in case additional beam rebars are placed either inside or outside column width. In the first case, higher peak load and ductility values can be achieved, provided that the amount of beam reinforcement is not high enough to shift damage towards the column or cause high shear stress to the joint core and its consequent fragile failure.

Keywords: Cyclic tests, Finite element, Numerical analysis, Reinforced concrete, Wide beam-column joint, Seismic behaviour.