Fracture evaluation of multi-layered precast reinforced geopolymer-concrete composite beams by incorporating acoustic emission into mechanical analysis

In this study, a multi-layered steel reinforced composite beams which are composed of geopolymer concrete section at tensile zone and Portland cement based concrete at compression are investigated. The beams were tested to failure to compare the toughness, post peak behaviour and failure mode based on the variation of the depth of layers. The mechanical analysis incorporated into acoustic emission technique showed that the geopolymer beam endured more deflection than the ordinary Portland cement based beams, however their ultimate load carrying capacities were quite similar. Further, the composite beams, resulted in transition of failure mode of shear to a flexural

Geometric effects of sustainable auxetic structures integrating the particle swarm optimization and finite element method

The development of new materials based on industrial wastes has been the focus of much research for a sustainable world. The growing demand for tyres has been every year exacerbating environmental problems due to indiscriminate disposal in the nature, making a potentially harmful waste to public health. The incorporation of rubber particles from scrap tyres into polymeric composites has achieved high toughness and moderate mechanical properties. This work investigates the geometric effects (thickness, width and internal cell angle) of auxetic structures made of recycled rubber composites based on experimental and numerical data. The response surface models integrated with the swarm intelligence and finite element analysis were proposed in order to obtain a range of solutions that provides useful information to the user during the selection of geometric parameters for reentrant cells. The results revealed the cell thickness ranges from 39-40 mm and 5.98-6 mm, and the cell angle range from -0.01 to -0.06º maximize the ultimate strength. The same parameters were able to optimize the modulus of elasticity of rubber auxetic structures, excepting for the angle factor which must be set between -30º and 27.7º. The optimal Poisson's ratio was found when the cell angle ranged from -30º to -28.5º, cell width ranged from 5-5.6 mm and 2 mm in thickness

State-of-the-art review on the design and performance of steel pallet rack connections

Steel pallet racks (SPRs) are used in the industrial buildings, warehouses and superstores for storing a multitude of different kinds of goods. Because of changing needs over the years, it is often desirable that such installations be readily demountable and capable of reassembly. Therefore, the beam-to-column connections (BCCs) used in SPRs are boltless in nature. SPR BCCs govern the stability of the frame in the down-aisle direction. The design of SPR BCCs is one of the problems for designers that cannot be handled routinely within the existing design specifications available for bolted and welded connections. Moreover, the studies on the considerations necessary for the design and performance of SPR BCCs solely are rarely available. It is therefore, essential to bring to light the factors that play significant role to improve the design and performance of SPR BCCs. A critical review of the research performed over the last few decades into the global stability of SPR structures in the down-aisle direction only is presented in this paper. The information about the design methodologies and testing procedures defined in the literature and design codes as well as the factors governing the performance of boltless connections are identified. The major failure modes are highlighted. The characteristics of the main elements constituting SPRs are also succinctly discussed. Based on the findings, the limitations of current study are highlighted and future research areas are identified

Response of oil palm shell concrete slabs subjected to quasi-static and blast loads

© 2016 Elsevier Ltd. All rights reserved. A series of quasi-static and blast tests was conducted to investigate resistance capacity of concrete slabs in which conventional crushed granite aggregates were wholly replaced with oil palm shell (OPS) as a coarse aggregate. A control specimen using Normal Concrete (NC) using conventional aggregate of similar strength was also prepared and tested for comparison. Two types of OPS concrete (OPSC) slabs were developed-with and without steel fibres (SF) and tested. LVDTs, pressure transducers and accelerometers were used to record data of response of the slabs subjected to quasi-static load and blast loads of 1, 5 and 10 kg TNT. The recorded data were then analysed and compared and conclusions were made on the effectiveness of OPS as a coarse aggregate. It has been found that OPSC outperformed NC slab when subjected to 10 kg TNT as the ductile OPSC panel was intact and had no shrapnels. Through the ductility behaviour of OPSC, it exhibited multiple cracks and the impact resistance of OPS through its energy absorption due to fibrous content within OPS itself was visible both in crack pattern and in its propagation. Though OPS is of organic nature, its resistance to blast waves was observed as the huge fire ball created due to blast had no or little effect on the OPSC panels. The OPS Fibre Reinforced Concrete (OPSFRC) also exhibited blast resistance characteristics, but uneven distribution of fibres and harsh mix with 3% of steel fibres resulted in larger crack width and fibre pull-out failure. Overall, the behaviour of OPSC in blast resistance characteristics is noteworthy and further tests are required to envisage the use of appropriate fibre content in OPSC