Influence of Axial Load on the Seismic Behavior of RC Beam-Column Joints with Wide Beam Angelo Masi 1,a , Giuseppe Santarsiero 1,b , Antonello Mossucca 1 , Domenico Nigro 1 1 University of Basilicata, via dell’Ateneo Lucano, 10, 85100 Potenza, Italy a angelo.masi@unibas.it, b giuseppe.santarsiero@unibas.it Keywords: Reinforced Concrete, beam-column joint, wide beam, experimental tests, seismic behavior, axial load. Abstract. Beam-column joints can play a key role on the seismic behavior of reinforced concrete buildings. Until now studies and experimental investigations on this topic have been mainly focused on beam-column joints with stiff beams, i.e. beams with height larger than the thickness of the adjacent floor slab. However, especially in the European residential building stock, frame structures are often equipped with wide - therefore rather flexible - beams. However, not many studies have been devoted so far to this type of connection, therefore an experimental investigation on full scale beam-column joints with wide beam was planned at the University of Basilicata and is currently in progress. In the present paper the main results of two cyclic tests are reported and discussed specifically analyzing the role of the axial load applied to the column on the joint performances and damage mechanisms. Test results highlights that the axial load value has a significant influence of on deformation capacity and ductility behavior. Introduction A large experimental program is currently in progress at the Laboratory of Testing Materials and Structures of the University of Basilicata to analyze the seismic performance of full scale external beam-column joint specimens. Twenty-six specimens were designed and constructed to simulate the typical connections of existing Reinforced Concrete (RC) frame buildings designed either with or without seismic criteria. The main results of tests on the fourteen joint specimens having stiff beam are reported in detail in Masi et al. [1, 2]. Twelve specimens, provided with wide (flexible) beam, that is beams having height equal to the thickness of the adjacent slab and width larger than that one of the connected column, are currently under test. The choice of including this type of beam-column joint in the experimental program was suggested by its frequent presence in the RC framed buildings in Europe. Therefore, it was considered worthwhile performing studies on the role of this beam type when designing or assessing RC building structures. While the seismic behaviour of beam-column joints with stiff beams has been extensively studied by many authors (e.g. [3-5]), less attention has been so far devoted to exterior [6, 7] or interior [8] beam-column connections equipped with wide beams. Poor performances were noticed especially in terms of energy dissipation due to the bad anchorage conditions of the beam rebars out of the column width and, therefore, poorly confined. In fact, severe pinching effects were found in the shear-drift envelope [7]. As a consequence, severe damage occurred at the beam wings outside the column width where high tensile principal stresses were attained. Therefore, the seismic behavior of wide beam-column joints is significantly related to its geometric characteristics that influence the joint performances if compared to subassemblages provided whit stiff beams determining significant reductions of both strength and deformation capacity. In [6] the first results of three cyclic tests on wide-beam-column joints designed according to a previous Italian seismic code, substantially consistent with the current code NTC2008 [9] and with EC8 [10], are reported and analyzed in order to point out the influence of the adopted earthquake resistant design (ERD) level. Test results showed remarkable differences in the seismic behaviour of the joint specimens under study as a consequence of the different ERD level. These first tests were carried out Applied Mechanics and Materials Vol. 508 (2014) pp 208-214 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.508.208 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 79.55.155.196-10/01/14,16:23:34)