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This paper discusses the derivation of a set of dynamic load factors for calculation of walking response on the basis of measurements made during a biomechanics research carried out with young adults. Firstly, a quite large number of experimental data on single footstep force were collected. The single footstep forces were then superimposed to generate the force time history for a continuous walk. This was followed by the transformation of the resultant force to the frequency domain from which the dynamic load factors for the first ten harmonics of a pacing rate can be extracted. A statistical analysis was employed on the dynamic load factors to acquire their design values in terms of the 90-th or 95-th percentile. The waking force function recommended by various design guides and that developed in the paper were then used in a comprehensive finite element model to predict the vibration level of a building floor. Current design guides on floor vibration normally suggest using four harmonics in the walking force whereas load factors for ten harmonics were developed in this paper. The acceleration response of the floor was found to increase by 5-33% when walking harmonics beyond the fourth harmonic were considered. The inclusion of higher harmonics would therefore lead to a more conservative estimation of the floor response.

This paper outlines a novel approach for simulating general nonlinear circuits in the time-domain. The proposed approach can be considered as the generalization of the numerical inversion Laplace transform (NILT) which has been used for circuits with only linear elements. The new approach enables the well-known advantages of NILT such the guaranteed numerical stability and the high-order approximation, to be carried to the domain of nonlinear circuit. A numerical example is given to demonstrate the validity of the proposed method.

The modified numerical inversion of the Laplace transform (dubbed NILT) has been recently proposed as a fast and provably stable numerical simulation for general circuits. Although it has enabled increasing the simulation time step, it highlighted the need for robust approach that can recover the full waveform in between the time points generated by NILT. This paper presents a new approach that addresses this challenge. The proposed approach leverages the NILT framework from a high-order approximation paradigm that computes points on the circuit waveforms to a methodology that computes high order derivatives of the waveforms at the same points. Using those derivatives, an interpolation approach based on Hermite interpolation is used to construct the circuit waveforms on dense points. Numerical experiments are presented to demonstrate the accuracy of both approaches.

This article presents a new approach to construct reduced-order models for large nonlinear circuits excited by periodical or quasi-periodical sources. The key feature in the constructed reduced model is that it enables, through solving a much smaller system, tracing the variations in the periodical steady-state response of the original circuit with regards to variations in selected design parameters. The proposed approach is based on the notion of using discrete empirical interpolation to project the nonlinear operator of the circuit equation onto a smaller subspace. In addition, the original system equations are projected onto the subspace spanned by the first few derivatives of the solution with respect to the selected design parameters. Computational savings are made possible through solving a reduced system of equations instead of the full system. Numerical examples are presented to validate the accuracy and efficiency of the proposed approach.

Finite element analysis (FEA) has been used as a successful supplement to experimental testing in various studies for simulation of anchorage behaviour. Throughout the years, researchers have employed different modelling techniques in various FEA packages to capture the behaviour of post-installed anchors. However, the vast amount of knowledge accrued is yet to be reviewed. This article critically reviews all aspects of FEA from pre-processing to post-processing and provides a comprehensive review of published literature on FEA studies for predicting the behaviour of post-installed anchorage systems. Most current efforts focus on investigating failure mechanism of anchors in uncracked concrete under tensile loading. Findings show that developing finite element model for post-installed anchorage in concrete is very challenging due to complex geometrical configuration of anchors, difficulty in modelling concrete–anchor interface and lack of reliable information on selecting material properties and parameters. The analysis identified key gaps in research related to the effect of geometrical simplification, anchor subjected to dynamic loading and anchor performance in cracked concrete which needs attention in future research. This review article is a valuable resource in facilitating future research on assessing the performance of post-installed anchorage in concrete with FEA.

Reliable performance of the electricity distribution networks is critical to avoid outages and disruptions which may lead to substantial economic losses. Some of the important components of the electricity distribution networks include overhead cables, utility poles, cross-arms, substations, and transformers. These components are subjected to deterioration with aging and pose risks of failure creating safety concerns, specially under extreme weather conditions. Efficient maintenance and the use of accurate condition assessment techniques to monitor the integrity of the aforementioned components are key factors to be considered in managing the electricity distribution assets. This article presents a review of different condition assessment techniques employed for monitoring the electricity distribution infrastructure. The conventional inspection techniques and advancements in non-destructive testing methods are discussed outlining the relative advantages and disadvantages. Other than the normal failures of distribution infrastructure due to component ageing, unexpected and less frequent extreme weather events can have significant impacts on the resilience of the electrical power infrastructure. Thus, the effects of extreme weather conditions on the reliability of the electricity distribution networks and the failure rates of assets are reviewed in this study. Further, the maintenance and decision-making approaches implemented in the power distribution networks are also discussed.

Torque as a tightening method is a simple technique that can be used to tighten a bolt to a given pre-load. Therefore, it is important to theoretically derive an accurate torque vs tension relationship for threaded fasteners as this would enable the industry to achieve a reliable pre-load. Various attempts were made to develop a complete theoretical relationship between torque and tension. Due to the thread angle there exists a nut dilation force causing the nut to expand radially out wards. This effect is more prominent in nuts with smaller height (Style 0 hex nut, refer ISO 4035 1 ). This nut dilation force creates a combined frictional effect with the drive torque thus affecting the torque tension relationship. This paper proposes a novel 3D formulation for torque tension relationship taking into consideration the nut dilation effect. This paper further develops new formulae for tightening and loosening torque, retaining torque, tension vs nut rotational angle relationship as well as formula for nut dilation force for both tightening and loosening.

Timber utility poles are widely used in power distribution and telecommunication networks. Wood is subjected to deterioration with time, and routine condition assessment works are carried out for i...

This article presents a new algorithm for time-domain circuit simulation based on numerical inversion of Laplace transform (NILT). The proposed method, labeled NILT $n$ , shows that for the same computational cost of the conventional NILT, referred to as NILT0, the approximation error is reduced by a significant factor, permitting time-marching with much larger time steps and, consequently, saving significant computational cost per time step. Numerical experiments are presented to demonstrate the efficiency and accuracy of the proposed approach.

There is a need to improve the Australian conformance practice for construction products. This paper presents an overview of the current operating environment of Australia and discusses the differe...

Reinforced concrete (RC) walls subject to in-plane lateral loads are essentially subject to axial compression and tension forces in the respective end regions of the wall. The tension forces initially result in elastic tensile stresses in both the concrete and longitudinal reinforcement. Cracking occurs after the maximum tensile stress of the concrete has been exceeded and results in the reinforcement providing the sole tensile resistance at each crack location. The mechanical interlock between the reinforcement and concrete means that a portion of the tensile stress in the reinforcement at each crack is transferred back into the concrete between adjacent cracks. This mechanism stiffens the concrete in tension and is referred to as tension stiffening. This paper presents a generalised tension stiffening model developed for limited ductile (i.e. lightly confined) RC walls. However, it is also applicable for lightly confined RC elements generally. The model was validated against 14 boundary element prism specimens subject to cyclic loading, with very good correlation observed between the theoretical model and the experimental results. This model can easily be adopted into a sectional analysis procedure to account for tension stiffening in both the elastic and inelastic regions of response in an RC wall.

A State-of-the-Art Guide for Post-Installed Reinforcement provides comprehensive coverage on installation, design, and assesment guidelines for post-installed reinforcements. Previously published in Hong Kong, this Malaysian edition includes new EOTA technical reports and European Assessment Documents, fundamentals for post-installed reinforcements, design proposals, and unique design examples, all of which are specifically tailored to the Malaysian context.

To produce plastic parts of high geometrical quality and dimensional stability through injection moulding process there are several key variables that must be considered. These include processing parameters such as packing time, cooling time, packing pressure, melt temperature, mould temperature and the intrinsic melt flow characteristics of polymeric materials used to produce the part. The challenge of producing high quality part is further compounded if the input polymer material is of reclaimed waste streams with inherent inconsistency in their nature. In this work, significant number of simulation-based studies are conducted using Autodesk Moldflow software to delineate the contributing issues pertinent to the part quality and achieve topological optimization by reducing critical parameters of shrinkage and warpage while ensuring overall cycle time viable for industrial production rates. Key simulation variables were obtained through experimental characterization of flow and thermal properties of the recycled olefin plastics. Different gate locations were simulated, and the best gate locations were selected for a two-gate system. These gates were provided with gate valve controllers for controlling the polymer flow to create cascaded injection moulding scenarios. Such scenarios were iterated with the objective of reducing the pressure required for cavity filling and thereby reducing the clamp force required. Optimized melt and mold temperatures of 245 °C, 20 °C were used for all the simulations performed. The result obtained from the most optimized simulation showed an average cycle time of 10.42 secs, volumetric shrinkage of 5.08%, warpage of 1.05 mm and clamp force of 79.81 tonne would be required to produce a part of 200 mm*100 mm*1.5 mm dimensions. Following a cascaded injection setup, it was shown that the clamp force could be reduced by 60.57%.

This article investigates the development of the following material properties of concrete with time: compressive strength, tensile strength, modulus of elasticity, and fracture energy. These properties were determined at seven different hydration ages (18 h, 30 h, 48 h, 72 h, 7 days, 14 days, 28 days) for four pure cement concrete mixes totaling 336 specimens tested throughout the study. Experimental data obtained were used to assess the relationship of the above properties with the concrete compressive strength and how these relationships are affected with age. Further, this study investigates prediction models available in literature and recommendations are made for models that are found suitable for application to early age concrete. Results obtained indicate that the relationship between the splitting tensile strength and concrete compressive strength can be approximated with a power function between 0.7 and 0.8, and this correlation is not affected by age. Fracture energy of the concrete and modulus of elasticity values obtained in this study correlate well with the square root of the compressive strength and it was found that this relationship holds true for all hydration ages investigated in this paper. Inverse analysis on the wedge-splitting test was conducted to determine the direct tensile strength. Values of tensile strength obtained from the inverse analysis have been validated numerically by carrying out finite element analysis on the wedge split, and anchor pull-out tests. The ratio of the tensile strength obtained from the inverse analysis to the splitting tensile strength was found to be in the range of 0.5&ndash, 0.9 and 0.7 on average.

Stress wave propagation can be effectively used as a non-destructive testing technique for the condition assessment of timber utility poles. Stress waves can be generated by applying a transverse impact close to the ground level of the pole, within the comfortable reaching height of the inspectors. The material behaviour of timber, the presence of natural imperfections and soil-pole interaction generate complexity in the propagation and reflection of generated transverse stress wave. Furthermore, the nonstationary nature of the reflected stress wave creates difficulties in identifying the defect features (i.e., location and severity of the defect) in the time domain. However, the time–frequency representation (TFR) can reveal local features of a reflected stress wave signal in both time and frequency domains simultaneously and hence, it can be effectively used to extract information to assess the health of timber poles. This paper presents a review of widely used TFR techniques in structural health monitoring and evaluates the applicability and efficiency of those methods in the context of structural health monitoring of timber utility poles. The signals collected from laboratory pole experiments and in-situ poles within power distribution networks along with numerical simulations were used to evaluate the performance of different TFR. A numerical simulation of the pole-soil system with different defect types and levels was carried out using the finite element method. Finally, the effect of different defect types, locations and applied impacts on the performance of different TFRs were evaluated.

Collapse prevention is the primary objective of earthquake-resistant design of structures; hence, the probability of collapse should be taken as a crucial performance indicator for risk-based desig...

This article presents a new approach to construct parameterized reduced-order models for nonlinear circuits. The reduced model is obtained such that it matches the variations in the DC operating point of the original full circuit in response to variations in several of its key design parameters. The new approach leverages, through the use of circuit moments with respect to the design parameters, the discrete empirical interpolation approach developed in a model reduction in other domains and enables its efficient application to the problem of DC operating point in nonlinear circuits. Utilizing the idea of rooted trees, the proposed approach constructs orthogonal bases that are used in projecting the full equations of the large original nonlinear circuit onto a reduced system of nonlinear equations in a space with a much smaller dimension. The variations in the DC operating point of the full circuit are then obtained by solving the reduced system of equations, yielding significant computational savings. Numerical examples are presented to demonstrate the efficiency and accuracy of the reduced model in predicting the change in the DC operating point of the original circuit.

Expansive soils (also called reactive soils) undergo heave and settlements due to moisture changes and could result in differential movements in light weight structures. Hence, an estimation of potential ground movement is essential for designing footings for such structures. Shrink-swell index (Iss) is commonly used as a measure of soil reactivity and it is used in Australian standard of residential footing design to calculate ground movement. The shrink-swell test estimates the strain change per unit suction of an undisturbed soil sample; assuming the strain is independent of the insitu moisture content. In this study, 14 undisturbed soil samples were collected from an expansive soil site at different times over a two-year period. The sample locations were very close to each other. The samples had different insitu moisture contents varied from 22 to 37%. Test results indicate that increase in insitu moisture within that range resulted about 50% increase in Iss. Similar increment was observed in a set of samples obtained from another expansive soil site. The impact of insitu moisture content on Iss could lead to incorrect site classification. Consequently, the results of this study indicate that if the site is tested during different times of the year, it will result in different footing recommendations.

Precast concrete building cores are a widely used lateral load resisting system in low and mid-rise multi-storey buildings. However, despite their widespread use in countries like Australia or New Zealand, a very little research or experimental testing has been undertaken to assess their lateral drift behaviour. This article will present the findings and observations of a recent experimental testing programme into reinforced concrete precast building cores, which included three large-scale ‘box-shaped’ precast building core specimens. Adjacent panels in each specimen were connected together using welded stitch plate connections and then connected to foundation blocks on the top and bottom using grout tube connections. The results of the testing showed that the welded stitch plate connections were too flexible to allow full composite action to be developed in the cross-section, which meant the precast building core specimens were around 25% more flexible than an equivalent cast in-situ version. The testing also highlighted common detailing and construction deficiencies that can severely inhibit the ductility of the core.

Timber utility poles are significantly used in power and telecommunication infrastructures all over the world. The deterioration of timber with time is common due to various factors including termi...

Timber utility poles represent a significant part of the power distribution and telecommunication infrastructure. Weathering, decay induced by fungus, and termite attacks deteriorate the condition of timber poles, causing a loss in their strength and toughness. Routine inspections are carried out to assess the condition of poles using conventional inspection techniques. However, the reliability of these techniques is in question. This paper proposes the stress wave propagation (SWP) technique for condition assessment of timber poles and the direct application of the artificial neural network (ANN) pattern recognition algorithm for signal classification. A Fourier-based signal decomposition method has been adopted and the frequency domain statistical features of the decomposed subcomponents were extracted to be used as the inputs for the ANN. Experiments were conducted using both intact and defective timber poles subjected to stress wave propagation. Different ANN models have been developed to classify the signals, and several controlling parameters were evaluated to obtain the best performance model. Further, the support vector machine (SVM) and k-means clustering algorithms were employed to classify the stress wave signals from intact and defective poles. Finally, the results of developed ANN models, SVM classifiers and k-means clustering models for pole classification were compared. The obtained success rates of the ANN model, the SVM classifier and the k-means clustering algorithm were 92%, 87% and 81%, respectively. Further, the trained ANN model was used to predict the health status of in-service poles, which were uprooted and subjected to full-scale bending tests after performing the stress wave propagation.

Due to space limitations, screw anchors may be used closer to the edge of the substrate than distances recommended by manufacturers, e.g. to connect bottom plates, base plates or handrails in resid...

Screw anchors are widely used in applications such as fastening base plates in steel and metal construction, formwork and bracing, structural steel applications, railings and handrails. At present, researchers and design engineers rely on the Concrete Capacity Design (CCD) method to predict the strength of screw anchors under the tensile loading as the only method available in literature. In CCD method, the underlying assumption is that the concrete cone and combined concrete cone and pull-out failure modes are the main failure mode for anchors, whereas, previous studies have demonstrated that pull-out is also a very common failure mode of screw anchors. In this paper, experimental results of more than 180 tests on one particular type of screw anchors are studied to better understand their behaviour under tensile loading. Experimental results are classified based on the observed failure modes. New equations are proposed to predict the tensile capacity of this particular type of screw anchors associated with each of the above mentioned dominant failure modes for the first time. The experimental results are compared with the predicted values by the CCD method and specifications provided by the anchor manufacturer. It is also shown that in majority of cases, the CCD method overestimates both the experimental results and the specifications given by the manufacturer.

This letter presents a new approach for finite-element time-domain electromagnetic analysis. The new method combines the property of high-order approximation in the time domain with the crucial property of unconditional stability. The proposed method has been used in circuit simulation and relies on employing a specific formulation of the numerical inversion of the Laplace transform. The method is validated using one- and two-dimensional scattering from a dielectric object.

Behaviour of low rise cold-formed steel-framed residential structures when subject to lateral loading (e.g. wind and earthquake loads) is significantly influenced by both structural and non-structural elements. The ceiling is normally considered as a horizontal diaphragm for the distribution of such lateral loads to the bracing walls. In Australia, the ceiling diaphragm, in single and two storey cold-formed steel-framed houses, is made of plasterboard lining fixed to ceiling battens which in turn are screwed to the roof trusses. Determination of the stiffness and strength of the ceiling diaphragm is crucial for accurate distribution of the lateral load to the lateral resisting elements (e.g. bracing walls). This paper presents experimental results from tests of typical ceiling diaphragms. Further, a detailed finite element model is described which was validated against the experimental results. The model is capable of reproducing the initial stiffness, non-linear deformation and ultimate strength. The finding from this work would assist engineers in designing the lateral load resisting system for houses.

This paper presents a new approach aiming at simulating the steady-state response of dc–dc switching power converters. The proposed method uses the main concept behind the harmonic balance (HB) to compute the amplitudes of the harmonic content in the steady-state waveform. The proposed approach extends the basic HB to enable its efficient implementation to the power converter circuits, through developing equivalent frequency-domain-based stamps for ideal switching elements. The new technique is formulated to yield, along with the amplitudes of the harmonics, the switching times in the ideal switching elements, resulting in the convergence of the Newton method being obtained within few iterations. A major advantage in the proposed method is that it enables removing the control circuitry, which reduces the size of the circuit and significantly contributes to the efficiency of the method. Experimental results show significant speedup over commercial SPICE-based simulators.

The application of hysteretic damper has gained major attention in seismic resistant design of buildings. It provides an efficient and cost-effective solution to reduce the level of damage induced on the building due to seismic excitations. The efficiency of the damper is influenced by parameters such as yield strength, yield displacement and brace-damper assembly system stiffness. The premise of this paper is to investigate the effect of the uncertainty associated with the hysteretic damper design parameters on the probabilistic seismic performance of steel buildings. Two steel buildings which are designed in accordance with the European Standard design code are evaluated. The uncertainties associated with the damper design parameters are incorporated using the Optimised Latin Hypercube sampling method for different confidence levels. The building response is obtained by conducting nonlinear time history analyses in OpenSEES. The annual frequency of exceeding a damage limit state, which is quantified by integrating the seismic fragility curves and hazard curves, is computed for the steel buildings with and without consideration of the design parameter uncertainties.

The stress wave propagation technique can be effectively used to assess the condition of timber utility poles. However, reliable detection of damage based on the reflected wave within the time doma...

The project ‘Cost-Effective Mitigation Strategy Development for Building Related Earthquake Risk’ under the Bushfire and Natural Hazards Cooperative Research Centre (BNHCRC) aims to develop knowled...

This paper presents the tensile behaviour of individual Double Headed Anchored Blind Bolts (DHABBs) which are anchored within Concrete Filled Square Hollow Section (CFSHS) tubes. The DHABB consists of a conventional Headed Anchored Blind Bolt (HABB) with one additional middle head, between the existing end head in the embedded region and head next to the tube wall. A series of experiments were conducted on the pull-out of single DHABBs under monotonic and cyclic loading using different tube sizes, bolt sizes and concrete types. Detailed results from the experimental work are presented in this paper. A comprehensive three dimensional finite element model was developed and the results were compared with full scale pull-out test results. A good agreement was obtained between the FE and experimental results.

In this paper, the cyclic behavior of groups of double-headed anchored blind bolts (DHABBs), which are anchored within concrete-filled square hollow sections (CFSHSs), is investigated. The ...

Crossarms are widely used in power distribution and telecommunication sectors to support overhead cables. These structures are horizontally attached to the top of vertically erected utility poles and are essential elements in connecting overhead cables to the poles. Timber is the dominantly used material type for crossarms in the existing distribution networks. Nevertheless, there are alternative crossarms made from steel, composites, polymers, and even from concrete. This paper reviews the studies on the condition assessment of timber crossarms considering the aspects of decay identification and flexural strength assessment. The limitations and shortcomings of the conventional inspection techniques for crossarms are presented. Then, the studies on the developments of non-destructive test methods to address these issues are reviewed. Further, the results from the experimental work conducted to assess the structural capacity of in-service crossarms are presented and analysed. In addition, the possible future advancements of alternative crossarm types are also discussed, considering the mechanical strength, durability performance, and sustainability aspects. This paper aims to highlight the advantages and disadvantages of different condition assessment techniques for crossarms, indicating the importance of an integrated approach combining both the conventional and non-destructive testing techniques.

One of 2019's biggest scientific challenges is the coronavirus disease (COVID-19). The current COVID-19 epidemic is still a point of interest of all researchers from every field in the hope of finding a way to have it under control. COVID-19 vaccine development is a lengthy procedure that requires several clinical studies to prove its efficacy and overcome the virus mutations. Personal Protective Equipment (PPE) as masks and gloves are essential for moving the battle out of one's body. Developing a highly efficient PPE is crucial, not only to reduce the spread of virus, but also to protect people who work at the frontline. Virus infection is one of the most serious public health problems facing the world today. Between now and then, several antiviral medicines have been tested to determine their effectiveness as prospective COVID-19 treatments. The rise of viral resistance, as well as the adverse effects associated with antiviral medications, are posing further hurdles, resulting in a decrease in their efficiency as antiviral treatments. This opens the possibility for developing an alternative antiviral material that is both safe and effective. When it comes to their potential to destroy a wide range of viruses, silver nanoparticles (Ag-NPs) laden fiber mats have emerged as a novel antiviral platform, according to the findings of the current study. In the past, Ag-NPs have been extensively examined for their antibacterial properties against a wide range of microorganisms. Their ability to combat hepatitis B and HIV has also been demonstrated to be encouraging, as has their ability to inhibit other viruses such as herpes simplex, monkey pox, and respiratory syncytial virus. Here, we tested the potential effect of silver nanoparticles as an alternative antiviral therapeutic based on their unique properties. When compared to imitative antivirals, elemental silver nanoparticles have the ability to attack many virus sites, reducing the likelihood of the virus developing resistance. Our group has been developing silver nanoparticles loaded on toilet paper seat sheets, cellulose membranes, polymer dressings, and cotton textiles in response to the persistent issue. The new generation of fiber mats will be thoroughly described and tested against SARS-CoV-2 virus. SEM, EDS, TEM, and DLS will be utilized to identify the shape of our fibers and estimate the particle size of the embedded nanoparticles.