Ali A. Abbas

Statically-Indeterminate SFRC Columns under Cyclic Loads

The present study is aimed at examining the structural response of steel-fibre-reinforced concrete (SFRC) columns under reversed-cyclic loading, which were investigated by means of non-linear finite-element analysis (NLFEA). The focus was on investigating the potential of steel fibres in compensating for reduction in conventional transverse reinforcement [and thus the spacing between shear links was increased by 50% and 100% while the fibre volume fraction (V f ) was increased to 1%, 1.5%, 2% and 2.5%]. This is useful in situations where the latter is required in significant amounts (e.g. in seismic design) leading to congestion and practical difficulties in placing the links. The critical factor in the seismic response is the cyclic nature of the load, which is examined in the present research work. An interesting feature of the present research work is the consideration of statically-indeterminate SFRC columns, information on which is rare as previous research studies have focused on simply-supported beams. To address this, both indeterminacy and axial loads were considered in the present investigation. Calibration work was carried out using existing experimental data and good correlation was established between numerical and test results. Subsequently, parametric studies were carried out using the practical range of fibre dosages, which provided insight into how the steel fibres can help reduce the amount of conventional shear links.

FE modelling of SFRC beams under impact loads

The present work aims at investigating the structural behaviour of steel-fibrereinforced concrete (SFRC) beams under high-rate loading conditions mainly associated with impact problems. A simple, yet practical non-linear finite-element analysis (NLFEA) model was used in the study. The model is mainly focused on realistically describing the fully brittle tensile behaviour of plain concrete as well as the contribution of steel fibres to the postcracking response. The constitutive relations were incorporated into ABAQUS software brittle-cracking concrete model in order to adjust the latter to allow for the effects of fibres. Comparisons of the numerical predictions with their experimental counterparts demonstrated that the model employed herein, despite its simplicity, was capable of providing realistic predictions concerning the structural responses up to failure for different SFRC structural configurations. In the present study, the previous work is extended in order to numerically investigate the structural responses of simply-supported SFRC beams under impact loading. Data obtained from drop-weight tests on RC beams (without fibres) indicates that the response under impact loading differs significantly from that established during equivalent static testing. Essentially, there is (i) an increase in the maximum sustained load and (ii) a reduction in the portion of the beam span reacting to the impact load. However, there is considerable scatter making it difficult to ascertain the effect of loading rate on various aspects of RC structural response. To achieve this dynamic NLFEA is employed which is capable of realistically accounting for the characteristics of the problem at hand, a wave propagation problem within a highly non-linear medium. Following validation, a further study was conducted to assess the effect of steel fibers (provided at a dosage of Vf = 1%) on key aspects of structural response such as maximum sustained load, load-deflection curves, deformation profiles and ductility) under different rates and intensities of impact loading. The predictions reveal that steel fibers can potentially increase the maximum sustained load, ductility, toughness exhibited by SFRC members under impact loading compared to their RC counterparts. Pegah Behinaein, Ali A. Abbas and Demetris M. Cotsovos