A. Aziz Saim

Shear capacity of composite slab reinforced with steel fibre to that of fabric reinforcement in concrete topping

Abstract This paper presents the experimental result on the shear capacity of composite slab reinforced with steel fibre concrete topping. Experimental test is carried out on 75 composite slab specimens reinforced with various steel fibres volume fractions in the concrete topping. The type of steel fibres is varied to determine the suitable type to be applied in the concrete topping. This includes HE0·75/60, HE0·75/50 and HE0·55/33 referred to as SF60, SF50 and SF33, respectively, in this paper. The test parameters are fibre aspect ratio, volume fraction and fibre reinforcing index. Control specimen using prefabricated welded steel mesh in the concrete topping is also tested for comparison. The test results show that by replacing prefabricated welded steel mesh with steel fibre in the concrete topping increased the shear capacity of the composite slab. However, the increment depends on the type of steel fibre, where the optimum increment for SF60 and SF50 started at Vf = 0·75% whereas for SF33 at Vf = 0·25%. Even though the percentage increment is small from the whole capacity of the composite slab, but the steel fibre is able to arrest cracks once the propagation started to reach the concrete topping zone during the post-cracking development. This is important especially to members subjected to high shear load, where steel fibres can create an additional shear carriage capacity by preventing them from sudden failure.

Performance of Grouted Splice Sleeves with Tapered Bars under Axial Tension

Many structural failures in precast concrete buildings are initiated by connection failures. To avoid such failures, the connections should have enough strength to join the reinforcement bars between precast concrete panels. This paper presents the structural performance and behaviour of a proposed splice sleeve connection using generic steel pipe. The connection consisted of steel bars with tapered nuts confined in grouted steel pipes. The connections were subjected to increasing axial tension until failure. The results show that the use of smaller pipes gives better confinement effects and provide higher bond strength. A short embedment length of about 10 times rebar diameter is able to provide full tensile strength of the connected rebars. As compared to long embedment length of conventional lapping of steel bars, the proposed connection is able to provide structural continuity with short embedment length.

Noise Exposure among Machine Operators on Construction Sites in South Johor, Malaysia

Machines operators expose to excessive noise in the workplace that may lead to hearing damage. This study investigates construction machine operators noise exposure levels for eight hours or time weighting averages (TWAs), relationship TWA with machine noise emission level, the practices of using hearing protection devices (HPDs) and working in a closed machine cab. Heavy and non-heavy machine operators at five construction sites involved with excavation and piling activities were selected and measured by using dosimeters. 68% of operators were exposed to TWA of 85 dBA and 18% of the operators exceeded the permissible limit. 40% of operators work inside a closed machine cab, 18% wear earplugs and only 16% practiced both. Both operators of heavy machines (except excavators) and dump trucks are exposed to TWA > 90 dBA if they work in open machine cabs. The TWAs were found well correlated (r=0.41) with the machine noise emission, which ranged between 84 dBA to 125 dBA. Furthermore, this study proposes the type of HPD for the operators of typical machine to minimise the risk of hearing loss.