Please cite this article in press as: Ascione, L., et al., Macro-scale analysis of local and global buckling behavior of T and C composite sections. Mech. Re. Commun. (2013), http://dx.doi.org/10.1016/j.mechrescom.2013.10.004 ARTICLE IN PRESS G Model MRC-2791; No. of Pages 7 Mechanics Research Communications xxx (2013) xxx–xxx Contents lists available at ScienceDirect Mechanics Research Communications j o ur na l ho me pag e: www.elsevier.com/locate/mechrescom Macro-scale analysis of local and global buckling behavior of T and C composite sections Luigi Ascione, Valentino Paolo Berardi ∗ , Antonella Giordano, Saverio Spadea Department of Civil Engineering, University of Salerno, Italy a r t i c l e i n f o Article history: Received 14 June 2013 Received in revised form 4 October 2013 Accepted 7 October 2013 Available online xxx Keywords: Fiber Reinforced Polymer Thin-walled beam Buckling Finite element analysis a b s t r a c t Buckling modes of pultruded Fiber Reinforced Polymer (FRP) beams are analyzed in this paper. The study is performed on the basis of two mechanical models recently proposed by the authors with regard to global and local buckling of composite thin-walled beams. These models are developed within the theory of small strains and moderate rotations and they take into account the contribution of shear deformation. The constitutive law here adopted is based on the homogenization of the material properties at the macro scale level. With regard to local stability, the junctions are considered as semi-rigid connections, whose stiffness is strongly influenced by the microstructure of the material. A discussion on the effects of the beam geometry and on the failure modes is presented. They may consist in local or global buckling as well as in material failure. Further, the global buckling may be torsional or lateral. The discussion is supported by non-dimensional diagrams which can be useful in design involving “T” and “C” sections subject to axial and bending loads. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction The use of FRP materials, as an alternative to conventional materials, has rapidly increased in the last few decades due to their reasonable durability, high specific strength and stiff- ness. In particular, pultruded composite elements are currently employed in pedestrian bridges and bridge decks, as well as, more recently, in building structures (Clarke, 1996; Chambers, 1997; CNR DT-205/2006; Bank, 2006). Many different types of FRP profiles available on the market are typically characterized by a thin-walled cross-section due to the shape optimization required to reduce manufacturing costs. With reference to the micro-scale level, pultruded composite materials are based on reinforcing fibers (monofilament with a diameter of about 10 m) all oriented in the longitudinal direction of the members and embedded in a polymeric matrix. Homogeniza- tion techniques based on the rule of mixtures allow us to consider the composite as a homogenous transversely isotropic material at a macro-scale level. On the other hand, the micro-structure of the material can strongly influence the mechanical behavior of the junctions, thus a proper characterization needs to be introduced in order to capture the actual behavior of the beams. ∗ Corresponding author. Tel.: +39 089964084. E-mail addresses: l.ascione@unisa.it (L. Ascione), berardi@unisa.it (V.P. Berardi), angiordano@unisa.it (A. Giordano), sspadea@unisa.it (S. Spadea). Over last few years, several studies have focused on the struc- tural behavior of FRP thin-walled beams, dealing with the analysis of the axial and flexural buckling modes. It is well known that due to the thin-walled sectional geometry and the relatively low stiff- ness of composite materials, the design of FRP pultruded members is generally governed by deformability and stability requirements rather than strength. In particular, the failure of pultruded FRP beams and columns may be characterized by either local or global instability. The studies available in literature on global buckling have indi- cated that the shear strain on the middle surface of the beam may significantly affect the FRP ultimate behavior, due to the consid- erable influence of shear deformability in such members (Kabir and Sherbourne, 1998; Brooks and Turvey, 1995; Turvey, 1996; Sapkás and Kollár, 2002; Mohri et al., 2002; Lee and Kim, 2001; Lee et al., 2002; Roberts and Al-Ubaidi, 2001; Roberts, 2002; Machado and Cortínez, 2005; Minghini et al., 2008; Feo and Mancusi, 2010; Ascione et al., 2011; Fraternali et al., 2013). In the past, the local buckling behavior of FRP pultruded beams has been investigated by means of either 3-dimensional FEM analyses (Di Tommaso and Russo, 2003; Pecce and Cosenza, 2000; Turvey and Zhang, 2006; Nguyen et al., 2013) or by modeling the beams as a set of plates mutually constrained by flexible junctions (Bank and Yin, 1996; Nguyen et al., 2013; Rhodes, 1996; Qiao et al., 2001, 2003; Kollar, 2002; Shan and Qiao, 2005; Qiao and Shan, 2005; Mittelstedt, 2007). Both approaches may overestimate the buckling load for the follow- ing reasons: in the 3D FEM approach a rigid behavior of junctions is typically considered, although experimental investigations have 0093-6413/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.mechrescom.2013.10.004