New beam design using filament winding

To minimise the cost of the beam, a pultruded GFRP box profile, available off the shelf , is chosen. Thin-walled box sections are very efficient for beams and have a high resistance to lateral torsional buckling. 

To address the inherent lack of stiffness of hybrid beams, the CFRP laminate is not designed to fail first to give a warning of imminent failure (Chakrabortty etal., 2011). Instead, its primary role is to provide the required stiffness for the beam. As snch, there is no upper limit on its thickness. Therefore, the stiffness of the beam can be tailored. The warning of imminent failure is hoped to be achieved through the crushing of the concrete. 

The addition of the filament-wound outer laminate serves two purposes. Its principal role is to provide some form of confinement to the concrete block-pultmded profile system so as to ensure a composite action, thus eliminating the risk of debonding failure. The lack of composite action between the concrete and the laminates was reported as a serious shortcoming of these sections (Canning et al., 1999 Correia el al., 2007). Finally, with fibres oriented at +45°, its second role is to improve the shear strength of 

The subsequent experimental results reported in Chakrabortty et al. (2011) revealed that the filament-wound wrap induce a beneficial confinement to the concrete. What is not clear, however, was the extent of this confinement. Using finite element analysis, this effect is investigated in the following sections. 

According to Lam and Teng (2003a) and Csuka and Kollar (2010), confined concrete displays different stress-strain curves according to the amount of confinement as shown in Fig. 8.12. When the concrete is fully confined 

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