Modelling crack propagation in structures: Comparison of numerical methods

Abstract

SUMMARYCrack propagation in concrete structures is a very complicated process, and the distribution of cracks may significantly affect the behaviour of the structures under time-dependent loading. If enough damage or extensive cracks exist in a structure, strengthening or repair using external carbon fibre-reinforced polymer (CFRP) reinforcement may be needed. Therefore, an understanding of the influence of the CFRP strengthening system on behaviour is crucial for the proper design of a structural reinforcement strategy. In this paper, we compare three major methods: the discrete crack method, the smeared crack method and the element-free method. By using these methods to study the fracture pattern of a beam with dapped ends, we can compare the capabilities and efficiencies of the three methods. When modelling the crack formation in reinforced concrete structures, the smeared crack approach gives better results than the discrete model in terms of crack spacing and regularity, however, it does not follow the crack growth well. The element-free Galerkin method seems to be superior to the other methods in the sense that it deals with the irregular cracks well and is very efficient in saving computing time. The preferred choice of method depends on the type of problem and the solution accuracy required, and this also depends on a certain balance between the accurate tracing of individual cracks and the computing efficiency. In addition, new algorithms are required for the efficient simulations of dynamic crack propagation, especially in the case of pre-cracked structures strengthened with prestressed CFRPs .

Mechanical Performance Evaluation of Concrete Beams Strengthened with Carbon Fiber Materials

“…However, Figure 3(a) shows that the dominant separation mode at the central crack of the concrete beam should be mode I crack. The term of shearing force and of shear displacement Δ can disappear in (5), only the terms for opening force and displacement leave in the equation. Meanwhile, in Figure 3(b), both opening and shearing effects must be taken into account when calculating SERR for the crack failure that occurred at the interface between concrete and CFRP and the failure at the bottom of CFRP.…”

“…So far, many researches [5][6][7][8][9][10][11] have been conducted to investigate the mechanical properties of the retrofitted members externally bonded with CFRP. It can be concluded that the bonding of the CFRP plates has a significant effect on enhancing the overall performance even for plates with a relatively low modulus of elasticity.…”

“…The strengthening technology externally bonded with CFRP can considerably increase the strength at bending, reduce the deflections as well as crack width in area of tension, and also change the mechanical behavior and failure pattern during service. The researches [5,[8][9][10] demonstrated that the cracking moment in reinforced concrete beams with CFRP can significantly increase by 218%, from 12% to 230%. They also found that in strengthened flexural members, cracks are seen in bigger numbers and closer to each other; however, they are narrower than in beams without strengthened reinforcement.…”

Non-linear time-dependent analysis of cracked reinforced concrete bar

“…The first one consists of the numerical models related to the discrete crack concept. Here, the crack is considered as a discontinuity in geometry section of a bar; the crack width and its location follow from the chosen failure criterion of concrete (see Abrishami and Mitchell, 1996; Dias-da-Costa et al, 2009; Kuutti, 2012; Manfredi and Pecce, 1998; Yang and Chen, 2005; Yang et al, 2008; Yankelevsky et al, 2008). The second class of models relies on smeared crack concepts, where cracking (or softening) of concrete is described by the crack band model.…”

“…The second class of models relies on smeared crack concepts, where cracking (or softening) of concrete is described by the crack band model. There it is assumed that the impact of the crack is smeared over a finite, yet limited crack band length of the reinforced concrete element (see Bažant and Pijaudier-Cabot, 1989; Bažant and Planas, 1997; Bratina et al, 2004; Kim and Lee, 1992; Kwak and Kim, 2002; Yang et al, 2008).…”