Simulation of impulsive loading on column using inflatable airbag technique

The purpose of this study was to simulate impulsive loading on columns by an innovative lab-based experimental technique that utilises inflatable airbags. Mild and stainless steel hollow sectioin columns with effective lengths of 955mm and under simply supported condition were used in this study

Effect of biochar on desiccation of marine soils under constant and cyclic temperatures

Biochar has recently been gaining increasing attention as a stable and sustainable soil amendment material. However, the effect of biochar amendment on the desiccation behaviour of coastal soils has not yet been examined. Consequently, the present study primarily investigated the effect of exposing biochar-amended marine soil (BAS) to constant and cyclic temperatures on its swell–shrink, evaporation and desiccation cracking characteristics. Biochar contents of 1%, 2%, 4% and particle size ranges of PS-1 (600 μm \u3c D ≤ 2000 μm), PS-2 (300 μm \u3c D ≤ 600 μm), PS-3 (D ≤ 75 μm) (D: biochar particle diameter) were employed. It was revealed that the absolute volumetric shrinkage of both unamended and biochar-amended specimens increased as the number of thermal cycles increased. Under continuous heat exposure, 4% (PS-3) BAS in compacted state achieved the maximum reduction in volumetric shrinkage which was 42%. Moreover, under continuous heat exposure, 2% (PS-1) BAS in slurry state achieved the highest reduction in desiccation cracking, which was 73%. The present study highlights the importance of identifying the most effective combination of biochar content and particle size required to achieve a desired outcome, in order to gain the maximum benefit of biochar as an amendment material at the lowest possible cost

An Evaluative Review of Recycled Waste Material Utilization in High-Performance Concrete

The disposal of waste materials and their adverse effects on the environment have become a worldwide concern, disturbing the fragile ecological equilibrium. With growing awareness of sustainability in the construction industry, it is of great importance to recycle waste materials for producing high-performance concrete (HPC). This aligns with the twelfth Sustainable Development Goal (SDG) of the United Nations, emphasizing responsible production and consumption, especially concerning the production of HPC using waste materials and energy-efficient methods. The review evaluates the purposeful utilization of recycled waste materials to improve the engineering characteristics of HPC, taking into consideration pertinent literature. It encompasses a comparative evaluation of strength development, water absorption, microstructures, and x-ray diffraction (XRD) analyses of HPC manufactured with different types of recycled waste materials. The key result of the review showed that using incinerated bottom ash (IBA) below 25% and incorporating 40% copper slag can enhance HPC’s mechanical performance. Additionally, recycled coarse aggregate (RCA) can replace up to 50% of conventional aggregate in self-compacting HPC with minimal impact on durability properties. In HPC cement substitution research, fly ash, silica fume, and metakaolin are prominent due to their availability, with fly ash showing remarkable durability when used as a 15% cement replacement. This thorough review offers valuable insights for optimizing the utilization of recycled waste materials in the development of environmentally friendly HPC. Doi: 10.28991/CEJ-2023-09-11-020 Full Text: PD

Influence of SiO2, TiO2 and Fe2O3 nanoparticles on the properties of fly ash blended cement mortars

This study explores the effects of different types of nanoparticles, namely nano-SiO2 (NS), nano-TiO2 (NT), and nano-Fe2O3 (NF) on the fresh properties, mechanical properties, and microstructure of cement mortar containing fly ash as a supplementary cementitious material. These nanoparticles existed in powder form and were incorporated into the mortar at the dosages of 1%, 3%, and 5% wt.% of cement. Also, fly ash has been added into in mortars with a constant dosage of 30% wt.% of cement. Compressive and flexural strength tests were performed to evaluate the mechanical properties of the mortar specimens with different nanoparticles at three curing ages, 7, 14, and 28 days. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) tests were conducted to study the microstructure and the hydration products of the mortars. To elucidate the effects of nanoparticles on the binder phase, additional experiments were performed on accompanying cement pastes: nanoindentation and open porosity measurements. The study shows that, if added in appropriate amounts, all nanoparticles investigated can result in significantly improved mechanical properties compared to the reference materials. However, exceeding of the optimal concentration results in clustering of the nanoparticles and reduces the mechanical properties of the composites, which is accompanied with increasing the porosity. This study provides guidelines for further improvement of concretes with blended cements through use of nanoparticles

Development of a high performance protective barrier utilising non-composite steel-concrete-steel panels

This study investigates the response of axially restrained non-composite steel-concrete-steel (SCS) panels under static, impact and blast loading conditions. This type of panels shows promising economic and technological characteristics as protective barriers for critical infrastructure protection. Axially restrained non-composite SCS panels have high strength and ductility, which enable them to withstand extreme loading such as impact and blast. The concrete core mass provides inertial characteristics which are beneficial for resisting impulsive loads. The primary resisting mechanism in this type of panels is based on dissipation of imparted energy by axial stretching of the steel faceplates (membrane resistance) and crushing of the concrete core. No hazardous projectiles will be generated since the concrete core is confined by the steel faceplates. The overall cost of construction is reduced by not providing shear connectors between the steel faceplates. Comprehensive experimental investigations have been carried out on axially restrained non-composite SCS panels under static and impact loading conditions. The experimental results have demonstrated that the panel resistance combines the flexural resistance at the initial stage, followed by the tensile membrane resistance of the steel faceplates under large deformation. The tensile membrane resistance of steel faceplates at large deformation could be significantly higher than the flexural capacity of non-composite SCS panels, and it is the main energy dissipation mechanism in this type of panels. The static resistance function of axially restrained non-composite SCS panels has been derived from the results of quasi-static monotonic loading tests. The finite element (FE) modelling techniques for the non-composite SCS panels have been developed and validated against the impact test results of the panels. Using the validated FE modelling techniques, the response of axially restrained non-composite SCS panels subjected to blast loading has been investigated. It is observed that the response of non-composite SCS panels under blast loading can be simulated by simplified model of the thin steel sheet catcher systems. During blast loading, the front faceplate is separated from the concrete core and bounces back before the panel reaches its maximum displacement. Therefore, the energy dissipation by the front faceplate can be neglected, while the rear faceplate dissipates about 80% of the kinetic energy in the panel through membrane stretching. A simplified engineering-level model of the panel has been proposed that considers only the rear faceplate as a catcher system for resisting the impulse delivered by the fragmented concrete core. The response of a barrier composed of non-composite SCS panels and steel posts subjected to blast loading has been studied using numerical simulations. It is found that a certain amount of kinetic energy in the panels is transferred and dissipated by the steel posts due to panel-post interaction. The failure modes observed from the simulations are bending failure of the posts and fracture failure of the rear faceplate of the non-composite SCS panel. From the comparison between the response of a reinforced concrete blast wall and the barrier utilising non-composite SCS panels, it is found that the barrier with non-composite SCS panels could reduce the wall thickness by about 60% when similar amount of steel is used in the construction of both walls. Therefore, the barrier utilising non-composite SCS panels is an economical alternative to the reinforced concrete blast walls in resisting close-range detonation of high explosives. As part of this study, an instrumented falling weight impact (IFWI) test rig is developed to investigate medium strain rate effects on stainless steel. The test results of the stainless steel specimens in this study are significantly lower than the theoretical prediction using the existing Cowper-Symonds coefficients. From comprehensive literature reviews, it is found that the stress level, prior work hardening, heat treatment condition and microstructure of the stainless steel will affect the strain rate effects. Therefore, the Cowper-Symonds coefficients should be used with care. Improved Cowper-Symonds coefficients have been proposed for the stainless steel Grade 304 used in this study

Thermal Response of Mortar Panels with Different Forms of Macro-Encapsulated Phase Change Materials: A Finite Element Study

This paper presents a numerical investigation of thermal response of mortar panels, incorporating macro-encapsulated paraffin in different forms. Two types of macro capsules were fabricated and tested in this study using an instrumented hot plate device. The experimental results show that macro encapsulated paraffin reduced the temperature and increased time lag in the mortar panels due to the latent heat capacity of paraffin. Finite element models adopting the effective heat capacity method to model phase change effects were able to capture the overall thermal response of panels incorporated with paraffin well. Then, a parametric study was conducted using the validated finite element (FE) modelling technique to investigate the effects of different forms of macro capsules, the quantity of paraffin and the position of macro capsules. It was found that the tube and sphere macro capsules showed similar thermal responses, while the plate shaped capsules may cause a non-uniform temperature distribution in mortar panels. The quantity and position of paraffin have significant effects on the thermal response of the mortal panels. A higher paraffin content results in a significantly longer temperature lag and a lower temperature during the phase transition of paraffin. Furthermore, placing the paraffin away from the heating face can cause a longer temperature lag on the other face, which is desirable for building façade applications

Response of rigid polyurethane foam-filled steel hollow columns under low velocity impact

This paper presents the results of experimental investigations on rigid polyurethane foam-filled steel hollow columns under dynamic loading conditions

Numerical simulation and validation of impact response of axially-restrained steel-concrete-steel sandwich panels

Steel-concrete-steel (SCS) sandwich panels are an effective means for protecting personnel and infrastructure facilities from the effects of external blast and high-speed vehicle impact. In conventional SCS construction, the external steel plates are connected to the concrete infill by welded shear stud connectors. This paper describes a programme of research in which the non-composite SCS panels with axially restrained connections were studied experimentally and numerically. High fidelity finite element models for axially restrained steel-concrete-steel panels subjected to impact loading conditions were developed using LS-DYNA. The simulation results were validated against the dynamic testing experimental results. The numerical models were able to predict the initial flexural response of the panels followed by the tensile membrane resistance at large deformation. It was found that the strain rate effects of the materials and the concrete material model could have significant effect on the numerically predicted flexural strength and tensile membrane resistance of the panels

Thermal Properties of Concrete Incorporated with Shape-stable Phase Change Material

There has been an ever-increasing interest in concrete incorporated with shape-stable phase change material (SSPCM) in recent years for its outstanding thermal performance. In this research, PCM was incorporated into porous lightweight aggregate, namely exfoliated vermiculite to form SSPCM. SSPCMS were integrated with concrete to study their effects on thermal behaviour. Thermal testing was performed using both hot plate and KD2Pro. From the obtained results, it was observed that thermal conductivity and diffusivity reduced by 29% and 63% respectively whereas specific heat capacity increased by 40% with inclusion of SSPCMs. It was concluded that the implementation of SSPCM technology can be seen as a feasible and economical solution for energy efficient buildings

Numerical simulation of high-perfromance SCS panels under static and impact loading conditions

Incorporating Sustainable Practice in Mechanics of Structures and Materials covers a wide range of topics, from composite structures, via fire engineering and masonry structures, to timber engineering. Valuable reference for academics, researchers and practicing engineers working in structural engineering and structural mechanics. Summary Incorporating Sustainable Practice in Mechanics of Structures and Materials is a collection of peer-reviewed papers presented at the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21, Victoria, University, Melbourne, Australia, 7th – 10th of December 2010). The contributions from academics, researchers and practicing engineers from 17 countries, mainly from Australasia and the Asia-pacific region, cover a wide range of topics, including: • Composite structures • Computational mechanics • Concrete structures • Dynamic analysis of structures • Earthquake and wind engineering • Fibre composites • Fire engineering • Geomechanics and foundation engineering • Masonry structures • Mechanics of materials • Shock and impact loading • Steel and aluminum structures • Structural health monitoring • Structural optimisation • Sustainable materials • Timber engineerin