STEP LENGTH BASED ON CONVERGENCE OF ENERGY RELEASE RATE FOR MULTI-LAYERED CFRP BOUNDED STEEL TUBES UNDER PURE BENDING

Abstract

 Most of the studies on CFRP bonded steel tubes have been based on FE analysis, and there is insufficient research related to the shear lag theory and the energy release rate for adhesive debonding at the CFRP end. This study proposed a design method for the energy release rate and the step length at which the energy release rate converges for multi-layered CFRP bonded steel tubes. The relationship between the step length and the energy release rate at the bonded end is summarized by numerical analysis of shear lag theory solved using eigenvalues analysis under multi-layered CFRP bonded steel tubes. In addition, the equation for the step length required for convergence of the energy release rate was derived and an approximate solution was given. By applying the proposed method to the design of the end steps of CFRP, the energy release rate can be calculated using a simple equation derived from the strain energy of the entire structural system.