Relative behaviour of premature failures in adhesively plated RC beam using controllable and existing parameters

Abstract

Retrofitting of RC beam by gluing a steel plate at the soffit has been a widely adopted technique due to its ease of use, calculations and having minimal variations on structural aesthetics; hence, a large number of such retrofitted structures exist today. However, such structures have also failed frequently due to the formation of premature failures such as peeling and debonding. The further investigations conducted in literature indicated that such undesirable failures can be effected by a large number of geometrical and material parameters. Although, the characterisation and relative influence of such parameters on modes of failures remain unknown; as the past studies have been largely case sensitive or focussing on a small set of parameters. Therefore, to address these issues, a simple but focussed numerical model has been validated through literature for multiple modes of failures over wide range of possible parameters. Further, targeting the response of beam and its critical locations, the authors of this study suggest that the understanding of relative impact of effective parameters, in terms of beam capacity and brittleness of modes of failure, can be broadly utilised to re-evaluate the cause(s) of failure(s) through case studies, or to predict the future of retrofitted structures/beams.

Bond parameters for peeling and debonding in thin plated RC beams subjected to mixed mode loading – Framework

“…Narayanamurthy et al (2012) have summarised key models to signify the importance of interfacial stresses that are responsible for debonding, over the stresses responsible to cause peeling rip-off failure. Others (Chen et al, 2006, Khan, 2018Khan et al, 2017b;Oehlers, 1992;Oehlers and Moran, 1990;Oehlers and Seracino, 2004) have identified the possible interaction between flexural cracks and interfacial cracks.…”

“…As discussed before, peeling being a direct consequence of flexural crack at plate-end, therefore, it depends on the properties of concrete in tension as demonstrated by Khan et al (2017b). This required us to directly correlate the tension behaviour of CDP model with xFEM cohesive model.…”

“…Studies (Macdonald and Calder, 1982;Oh et al, 2003b) have suggested that the modulus of elasticity of adhesive has the direct impact on crack formations (both transverse and flexural), where Khan et al (2017b) have specifically identified that the stiffness greater than 1 GPa/mm would not show noticeable changes in the rate of stress transfer at interface. The effect of stiffness can be directly reflected on the development of transvers strains in plate, for example, Figure 4.…”

“…Where IS: 456 (2000) has completely ignored the contribution of tensile strength. Studies (Khan et al, 2017b;Zhang et al, 1995) have identified that the tensile strength is a key parameter that effects the capacity and failure type of plated beam.…”

“…Studies (Charif, 1983;Jones et al, 1985;Jumaat and Alam, 2008;Khan et al, 2017b;Macdonald and Calder, 1982;Oh et al, 2003b) signify on the fact that, including adhesive properties, a number of other beam parameters also directly influence debonding and peeling simultaneously. As discussed, although both are premature failure, but their impact on the main structure is different; peeling is relatively destructive to main structure than debonding, and accordingly requires different maintenance services.…”