Stress Concentration Analysis of the Corroded Steel Plate Strengthened with Carbon Fiber Reinforced Polymer (CFRP) Plates

Abstract

The purpose of this study is to investigate the stress concentration of a corroded steel plate strengthened with carbon fiber reinforced polymer (CFRP) plates. An accelerated corrosion experiment was first executed to acquire corroded steel plates, and then surface profile measurements were conducted to obtain 3D coordinate data of the corroded steel surface. Finite element models considering the surface morphology of the corroded steel plate and the interfacial bonding properties between the CFRP plate and the corroded steel plate were established to investigate the stress concentration of the corroded steel plate strengthened with and without CFRP plates. The reliability of the numerical modeling method was verified based on a mesh convergence analysis and a comparison of the fatigue test, 3D morphology scanning, and numerical analysis results. Specimens with five levels of corrosion damage, six kinds of CFRP-strengthening stiffness, five kinds of adhesive thickness, and five levels of CFRP prestress were numerically modeled. The primary indications consist of features of stress distribution, and the stress concentration factors Kt and Ktg were analyzed. Results showed that the features of stress distribution and the stress concentration factor Kt of the corroded steel plate strengthened with and without CFRP plates are only related to the shape, size, and position of rust pits, but not to the degree of uniform corrosion or the reinforcement parameters. The value of Kt for the corroded steel plate with a corrosion duration of 6~18 months and a weight loss rate of 9.16~21.78% was approximately 1.199~1.345. The converted stress concentration factor Ktg has more practical significance than the stress concentration factor Kt in describing the influence of corrosion and CFRP reinforcement on the peak tensile stress of the corroded steel plate. The value of Ktg increased linearly with the increase of the weight loss rate of the corroded steel plate and decreased appreciably with the increase of the strengthening stiffness and prestress level of the CFRP plates, and it presented a very small increasing trend with the increase of the adhesive thickness.

Fatigue Crack Propagation Prediction of Corroded Steel Plate Strengthened with Carbon Fiber Reinforced Polymer (CFRP) Plates

“…The line elastic constitutive model was adopted for the CFRP plate with an elastic modulus of 165 GPa and Poisson’s ratio of 0.3. The real constant of the spring element COMBIN39 (i.e., the F - D curves), which reflect the bond–slip relationship of the bonding interface between CFRP plate and corroded steel plate, was calculated according to the interfacial bond–slip model of CFRP plate externally bonded to corroded steel plate reported in the authors’ recent study [ 35 , 36 , 50 ]: where F was the force of the spring element COMBIN39, D was the displacement between the nodes at both ends of the spring element, τ and s were the interfacial shear stress and relative slip, respectively, and was the area covered by individual springs. The real constant (FSLIDE) of the bilinear force-deformation element COMBIN40 was calculated according to the maximum static friction force of the CFRP plate in the anchorage zone: where is the tensile force of the high-strength bolt in the anchor device (see Figure 1 , and more details can be found in [ 14 ]); is the static friction coefficient between CFRP plate and steel plate; is the compression area of CFRP plate in the anchorage zone.…”