Ahmad Beng Hong Kueh

Maximum local thermal effects carpet plot for symmetric laminated composite plates

Maximum local thermal effects carpet plots for symmetric laminated composite plates used in the design and optimization for material under heat loads are produced and demonstrated. The independent variables considered in this paper are the proportions of 0, 45, and 90 degrees ply orientations in the laminates. The carpet plots are presented in such a way that when the failure stress or strain of a composite lamina is known, all possible safe ply orientation proportion can be determined. In addition, the dependency of the carpet plots in correspondence to the temperature change is investigated. It is found that the shapes of both thermal stress and strain plots are practically identical.

Bending Response of Cross-Ply Laminated Composite Plates with Diagonally Perturbed Localized Interfacial Degeneration

A laminated composite plate element with an interface description is developed using the finite element approach to investigate the bending performance of two-layer cross-ply laminated composite plates in presence of a diagonally perturbed localized interfacial degeneration between laminae. The stiffness of the laminate is expressed through the assembly of the stiffnesses of lamina sub-elements and interface element, the latter of which is formulated adopting the well-defined virtually zero-thickness concept. To account for the extent of both shear and axial weak bonding, a degeneration ratio is introduced in the interface formulation. The model has the advantage of simulating a localized weak bonding at arbitrary locations, with various degeneration areas and intensities, under the influence of numerous boundary conditions since the interfacial description is expressed discretely. Numerical results show that the bending behavior of laminate is significantly affected by the aforementioned parameters, the greatest effect of which is experienced by those with a localized total interface degeneration, representing the case of local delamination.

Silver Nanoparticles in the Water Environment in Malaysia: Inspection, characterization, removal, modeling, and future perspective

The current status of silver nanoparticles (AgNPs) in the water environment in Malaysia was examined and reported. For inspection, two rivers and two sewage treatment plants (STPs) were selected. Two activated carbons derived from oil palm (ACfOPS) and coconut (ACfCS) shells were proposed as the adsorbent to remove AgNPs. It was found that the concentrations of AgNPs in the rivers and STPs are in the ranges of 0.13 to 10.16 mg L−1 and 0.13 to 20.02 mg L−1, respectively, with the highest concentration measured in July. ACfOPS and ACfCS removed up to 99.6 and 99.9% of AgNPs, respectively, from the water. The interaction mechanism between AgNPs and the activated carbon surface employed in this work was mainly the electrostatic force interaction via binding Ag+ with O− presented in the activated carbon to form AgO. Fifteen kinetic models were compared statistically to describe the removal of AgNPs. It was found that the experimental adsorption data can be best described using the mixed 1,2-order model. Therefore, this model has the potential to be a candidate for a general model to describe AgNPs adsorption using numerous materials, its validation of which has been confirmed with other material data from previous works.

Characterization of shear bond stress for design of composite slabs using an improved partial shear connection method

AbstractEurocode 4 design provisions specify two methods for the design of composite slabs, namely the m-k and the partial shear connection (PSC) methods. Currently, the m-k method includes the concrete thickness and the shear span of the slab as variables while the PSC method does not. This has resulted in a better accuracy for the m-k method when slabs with varying dimensions are considered. It is demonstrated in this paper that the horizontal shear bond stress varies with the ratio of shear span to effective depth of slab, defined as the slenderness. To include such an effect, a linear shear bond-slenderness equation is proposed. Using the proposed relationship, a linear interpolation of shear bond strength based on two configurations, determined from the outcomes of the bending tests for compact and slender slabs, has been satisfactorily performed. The shear bond strength obtained from this interpolation can be used in collaboration with the existing PSC method, such that the accuracy of the predictio...

Finite Element Modeling of Laminated Composite Plates with Locally Delaminated Interface Subjected to Impact Loading

This paper investigates the effects of localized interface progressive delamination on the behavior of two-layer laminated composite plates when subjected to low velocity impact loading for various fiber orientations. By means of finite element approach, the laminae stiffnesses are constructed independently from their interface, where a well-defined virtually zero-thickness interface element is discreetly adopted for delamination simulation. The present model has the advantage of simulating a localized interfacial condition at arbitrary locations, for various degeneration areas and intensities, under the influence of numerous boundary conditions since the interfacial description is expressed discretely. In comparison, the model shows good agreement with existing results from the literature when modeled in a perfectly bonded state. It is found that as the local delamination area increases, so does the magnitude of the maximum displacement history. Also, as top and bottom fiber orientations deviation increases, both central deflection and energy absorption increase although the relative maximum displacement correspondingly decreases when in contrast to the laminates perfectly bonded state.

Compressive strength of ground waste seashells in cement mortars for masonry and plastering

For environmental protection and sustainable development, many research studies have been carried out on the utilization of waste materials in construction such as fly ash, mine tailings, slags, construction and demolition waste, wood sawdust, rice husk ash, crumb rubber and etc. In this study, two types of waste seashells; green mussel and cockle were tested experimentally to replace fine aggregate in cement mortar. The compressive strength of the cement mortar with seashells were compared with those of a control mortar that was made of a conventional river sand. The main parameter of this study was the proportion of ground seashells used as sand replacement (25%, 50%, 75% or 100% by weight). Incorporation of cockle in cement mortar resulted in higher compressive strength as compared to conventional mortar up to 110 percent. However, incorporation of green mussel resulted in decrement in compressive strength by 67 percent. The results indicate that ground seashells can be applied as a sand replacement in mortar mixes and may improve the compressive strength of rendering and plastering mortar.

Stability of triaxially woven fabric composites employing geometrically nonlinear plate model with volume segmentation ABD constitution

We examine numerically the uniaxially compressed stability of triaxially woven fabric (TWF) composites employing a proposed geometrically nonlinear finite composite plate element model with volume segmentation ABD constitutive relation, taking advantage of greatly reduced degrees of freedom. From satisfactory agreement with results from literature, numerous boundary conditions are explored for various aspect ratios in the buckling analysis. High dependencies of post-buckling patterns on plate aspect ratios are observed, from which a computationally time-saving characteristic equations have been defined before the occurrence of post-buckling state for practical convenience, best described on the basis of logarithmic critical buckling load and stiffness factor. These buckling characteristics have a direct general correlation to TWF’s aspect ratios and boundary rigidities.

FIRE RESPONSE OF A 3D MULTI-STOREY BUILDING WITH BUCKLING RESTRAINED BRACES

THIS PAPER INVESTIGATES THE PERFORMANCE OF A THREE-DIMENSIONAL MULTI-STOREY STRUCTURE WITH BUCKLING RESTRAINED BRACE SYSTEM (BRBS) UNDER FIRE CONDITION, USING A SEQUENTIALLY COUPLED NONLINEAR THERMAL STRESS ANALYSIS. EFFICIENCY OF USING BRBS IN ENHANCING THE STRENGTH AND STIFFNESS OF A STRUCTURAL FRAME IS COMPARED WITH THAT OF ORDINARY CONCENTRICALLY BRACING SYSTEM (OCBS) UNDER VARIOUS FIRE SCENARIOS. THE PROPOSED NUMERICAL MODEL IS VERIFIED BY A SERIES OF FULL-SCALE FIRE TESTS CARRIED OUT ON AN 8-STOREY STRUCTURE AT CARDING-TON. THE RESULTS INDICATE THAT THE VERTICAL MOVEMENT OF HEATED (BUCKLED) COLUMN IN THE STRUCTURAL FRAME WITH BRBS IS LESSER THAN THAT WITH OCBS. CONSEQUENTLY, THE TENSILE FORCE AND BENDING MOMENT OF THE BEAM ADJACENT TO THE BUCKLED COLUMN IN THE FORMER IS LESSER THAN THE LATTER. ALSO, BRB ELEMENTS CAN PERFORM BETTER IN REDISTRIBUTING THE LOAD SUSTAINED BY HEATED COLUMNS WITHOUT ANY BUCKLING OCCURRENCE IN THE BRACING MEMBER, IN COMPARISONS TO THE ORDINARY SYSTEM. IN GENERAL, IT IS OBSERVED THAT BRBS MANIFEST AN IMPROVED PERFORMANCE IN RE-STABILIZATION OF STRUCTURAL FRAME AGAINST FIRE FOR A LONGER PERIOD OF HEATING TIME, SUCH THAT A BETTER FIRE RESISTANCE IS OFFERED TO THE WHOLE BUILDING AS COMPARED TO OCBS, DUE TO A HIGHER RESTRAINT PROVIDED ONTO THE STRUCTURE.

Dynamic response of composite footbridges under running pedestrian load

In this paper, a numerical model to assess the vibration characteristics of an existing slender composite footbridge induced by human running load is presented. The aim is to evaluate the serviceability requirement of the structure against the current design standards. The footbridge vibration response is investigated using the finite element software SAP2000 through a series of analyses in terms of critical acceleration, displacement and velocity. For model verification, the first natural frequency acquired in this investigation has shown good agreement with the value reported in literature. It is found from the current study that the maximum acceleration of composite footbridge due to an average one person running excitation load is 0.15%g. Moreover, the maximum vertical displacement at the mid span is obtained as 0.5495mm, which is much lesser than the standard displacement limit (22.5mm). In other words, the current study has shown that the investigated structure offers human safety and comfort against vibration due to load induced by human running.

Experimental investigation of end-plate connection with cruciform column section

This paper presents an experimental investigation on typical end-plate connection with reduced beam-to-end plate welding, connected to cruciform column (CCUB) section. The study aims to reduce the cost of fabrication and materials. Two tests were conducted to study the behavior of the proposed connections and evaluate the failure modes, moment resistance, initial stiffness and rotational capacity of the connections. The experimental results indicated that the failure mechanisms for the tested specimens begin with the end-plate yielding followed by bolt slippage that was limited to the tension region of the joint due to the tension forces exerted through the top bolt rows. The experimental results will then be used to validate the theoretical model for the T-stub idealization of the tension zone.