Traditional and innovative reinforced concrete beam-to-column joints with and without floor slab
At LMSSC, Paris, March 5th 2020, 1 p.m.
Doctorate, Department of Civil Engineering (DICIV), University of Salerno (UNISA), Italy
Recent seismic events pointed out that the reinforced concrete (R. C.) structures designed before the current seismic codes are able to exhibit a certain lateral resistance provided by secondary elements, such as masonry infilled walls or floor deck. The present work is focus on the investigation of the "secondary" contribution of R.C. structures (mainly in the beam-columns connections) designed according to the current seismic European code (Eurocode 8 – EC8). In the beam-column Hierarchy Criterion (EC8) there are no mentions to the deck contribution, which could improve the beam resistance.
This study: (i) investigates the effects of the floor deck in the common traditional beam-to-column joint and, (ii) proposes an innovative solution which is aiming to reduce the joint resistance, by computing the existence of the deck contribution. The idea is based to the Reduced Beam Section concept, proper of the steel connection design. As in the steel RBS connections part of the beam, the flanges, is cut in order to create a localized plastic zone, also in the R.C. beam, a cut was made in order to reduce the section effective width and, consecutively, the resistance of the joint. It also assures that the plastic hinge will develop far from the column, thus avoiding any undesired partial collapse mechanism.
The work is divided into two parts, the experimental study and the numerical modelling. The experimental set up was conducted in the STRENGTH laboratory of the University of Salerno, in Italy. In total, 12 full scale specimens were tested in quasi-static analyses, 6 of them belongs to the traditional beam-to-column joints with and without floor slab, while the other 6 belongs to the innovative beam-to-column joints with and without the existence of the floor slab. The 3D finite-element model (with the software Abaqus) of the RC joints reproduce the actual geometry of the experiments, as well as the same boundary conditions and loading as in the experimental program. The numerical investigation is carried out through an extended comparative parametric study and is focused on the quantitative influence of certain simplified modelling assumptions and several critical modelling parameters on the response of the system. A further goal is to investigate the dynamic response of the traditional and the innovative joints, as well as, the effects of the floor deck with the use of finite element reduced order model in order to minimise the computational time.