SHCC repair overlays for RC: Interfacial bond characterization and modelling
| Autor: | Stander Hj, Van Zijl Gpag |
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| Zdroj: | Scopus-Elsevier Concrete Repair, Rehabilitation and Retrofitting II ISBN: 9780429103599 |
| Popis: | Bonded overlays are increasingly used in concrete and reinforced concrete repair and rehabilitation applications. Fibre-reinforced concrete (FRC) and various classes resorting under FRC, ranging from Ultra-High Performance Fibre-Reinforced Cements (UHPFRC) to fibre-reinforced Strain-Hardening Cement Composites (SHCC) present interesting options for such overlay repairs. These materials also present other structural application possibilities, but here the focus is on repair overlays. In particular, the modelling and characterization of SHCC and its bond with concrete or Reinforced Concrete (RC) as substrate, are presented. An interface model based on multi-surface plasticity is proposed for Finite Element (FE) modelling of the interface region of an overlay repair system. It enables realistic modelling of the physical processes of interfa- cial delamination and shear-slipping along a SHCC-RC interface. The model incorporates a Coulomb-friction material law, bounded by a tension cut-off, as well as a compressive cap. After the initial thresholds have been reached in these different stress regions, softening is activated, leading to reduced limit surfaces in tension and Coulomb-friction. Due to the pronounced nonlinearity in compression before the peak resistance, strain- hardening is considered, effectively increasing the compressive limit surface, until the peak is reached, after which softening follows with associated reduction of the limit surface. To capture other sources of non-linear- ity, a material model which captures the nonlinear behaviour of SHCC enables the realistic consideration of the overlay cracking. SHCC exhibits increased resistance in tension, shear and flexure at deformation levels beyond those causing first cracking. This is induced by effective crack bridging by fibres, whereby multiple cracks are formed successively at matrix flaws, but controlled to small widths by well distributed fibres, despite relatively low fibre volume proportions (up to 2%). In this paper physical laboratory experiments to character- ize the parameters of the interface and the SHCC material models are described. Case studies are performed by laboratory experiments and comparative FE analyses to verify and validate these models and the characterized parameters. It is argued that these models enable a predictive capacity of the mechanical behaviour of overlay strategies, by accurately capturing mechanical mechanisms of degradation. |
| Databáze: | OpenAIRE |
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