Vol.:(0123456789) Bulletin of Earthquake Engineering https://doi.org/10.1007/s10518-019-00723-z 1 3 ORIGINAL RESEARCH On the fbre modelling of beams in RC framed buildings with rigid diaphragm Francesca Barbagallo 1  · Melina Bosco 1  · Edoardo M. Marino 1  · Pier Paolo Rossi 1 Received: 8 May 2019 / Accepted: 21 September 2019 © Springer Nature B.V. 2019 Abstract The development of an accurate numerical model plays a key role for the proper assess- ment of structures. To this end, fbre modelling is widely considered as one of the most rigorous tool for an accurate evaluation of the seismic response of RC framed buildings. However, it has been noted that the interaction between fbre modelled RC beams and the rigid diaphragm adopted to simulate the concrete slab, typical of RC buildings, may cause the development of unintended fctitious axial forces in beams. These axial forces may lead to an overestimation of the resisting bending moment of beams cross section, thus altering the distribution of yielding in the structural members and the collapse mechanism. The goal of this paper is to overcome this drawback by introducing at one end of each beam a simple additional element, named axial bufer element. This element allows the axial deformation of the beam, prevents the development of fctitious axial force and does not invalidate the transmission of shear force and bending moment. The paper investigates the infuence of the presence/lack of the axial bufer element on the seismic response of a set of RC buildings representative of real structures. For this purpose, incremental nonlinear dynamic analysis and nonlinear static analysis were conducted. Keywords Existing buildings · RC frames · Beam/slab interaction · Rigid diaphragm · Nonlinear analysis 1 Introduction Today, a number of diferent numerical models can be used to simulate the seismic response of RC building structures. Out of the available models, those that use one-dimen- sional elements with nonlinearity distributed on a fnite length region and fbre discre- tization of cross-section represent a very appealing choice. Indeed, they can simulate the spread of the plasticity in the structural members. Furthermore, this modelling approach is considered particularly suitable for RC structures, because it allows a more precise * Edoardo M. Marino emarino@dica.unict.it 1 Department of Civil Engineering and Architecture, University of Catania, Via Santa Sofa, 64, 95123 Catania, Italy