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An analytical modelling approach is developed in this article to simulate the pull-out behaviour of a single straight/hooked end fibre that is embedded in concrete matrix. The partial-interaction model is used to simulate the interfacial bond between the fibre and matrix along the entire fibre length throughout all stages of loading where additional axial and frictional forces due to straightening a hook is incorporated by simulating it as plastic hinges at the apex of bends. The analytical model is presented in a concise matrix form that helps to minimise the number of solution steps for the involved individual cases and provides a monolithic simplified implementation. A significant advantage of the approach is that it does not require fitting of a smoothing polynomial to show the full-range of fibre load-slip behaviour as it simulates the forces for straightening the fibre as it pulls through a bend and directly couples this to the interfacial bond forces. [ABSTRACT FROM AUTHOR]

This article presents a comparison of the bond behaviour between palm oil fuel ash (POFA)-derived geopolymer and conventional cement-based normal weight and lightweight concretes. A total of 16 variables were tested, which includes concrete cover (50 and 100 mm), bar diameter (12 and 16 mm) and types of concrete (POFA-based geopolymer normal/ lightweight concrete and cement-based normal/lightweight concrete). Results showed that the bond strength of cement-based concretes had higher critical bond stress and ultimate bond strength as well as lower slip at the ultimate bond strength compared to the corresponding POFA-based geopolymer concretes. The cement-based and geopolymer lightweight concrete specimens also exhibited greater bond strength than the normal weight concrete specimens. All of the concrete specimens generally exhibited similar bond stress-slip curves. Besides that, bond strength models proposed in the past predicted satisfactory match (difference of up to 35%) to the experimental ultimate bond strength values in the case of cement-based normal weight concrete and geopolymer concrete whereas a difference in the range of 16–138% was found for the case of lightweight concrete. [ABSTRACT FROM PUBLISHER]