Keynote

Session Chair – Prof Priyan Mendis

• Metaconcrete Material and Metatruss Structure for Impact and Blast Resistance - Prof Hong Hao (Curtin University)

  Curtin research center for Infrastructure Monitoring and Protection (CIMP) conducts a number of research projects on developing sustainable, multi-hazards resistant and resilient structures. The current research activities span from modelling accidental blast loadings, quantify dynamic material properties and development of comprehensive constitutive models for traditional and new construction materials, modelling structural responses to impact and blast loadings, and development of engineering solutions with either new materials or new structural forms or both for effective structure protections.

  In this presentation, we will briefly introduce our work on development of metaconcrete and meta-panel for impact and blast resistance of structures. Results obtained in the last three years from theoretical derivations, numerical modelling and experimental tests will be summarized and presented.

Session 1

Session Chair – Prof Alex Remennikov

• Current Research at Swinburne Impact Engineering Laboratory - Prof Guoxing Lu (Swinburne University)

  The construction industry has faced severe challenges over the past two decades. Spiralling costs of building materials and construction have made housing less affordable. In addition to that, the frequency and intensity of disasters have been steadily increasing in the last decades due to climate change. Many critical infrastructure as well buildings are particularly vulnerable, evidenced in the prevalence of floods, cyclones, and bush fires in recent years, exacerbated by populations heavily concentrated in cities and regional centres. Innovative designs, lightweight and high performance composite materials, and new construction techniques are urgently needed for producing sustainable, resilient, smart and cost-effective structures. Prof. Tuan Ngo’s presentation will highlight the key challenges, benefits and opportunities in using the Integrated Computational Materials Engineering (ICME) for developing high performance materials and structures for these extreme events. His talk will also cover new innovations in high performance composite materials, building systems, and construction techniques for resilient and sustainable infrastructure.

• Integrated Computational Materials Engineering (ICME) for designing resilient buildings and infrastructure against extreme loads - Prof Tuan Ngo (University of Melbourne))

  The construction industry has faced severe challenges over the past two decades. Spiralling costs of building materials and construction have made housing less affordable. In addition to that, the frequency and intensity of disasters have been steadily increasing in the last decades due to climate change. Many critical infrastructure as well buildings are particularly vulnerable, evidenced in the prevalence of floods, cyclones, and bush fires in recent years, exacerbated by populations heavily concentrated in cities and regional centres. Innovative designs, lightweight and high performance composite materials, and new construction techniques are urgently needed for producing sustainable, resilient, smart and cost-effective structures. Prof. Tuan Ngo’s presentation will highlight the key challenges, benefits and opportunities in using the Integrated Computational Materials Engineering (ICME) for developing high performance materials and structures for these extreme events. His talk will also cover new innovations in high performance composite materials, building systems, and construction techniques for resilient and sustainable infrastructure.

• Cladding Safety Victoria’s Risk-based Approach Towards a Safer Victoria - Dr Kate Nguyen (RMIT) and Mr Ashley Hunt (Cladding Services Victoria)

  The incorporation of combustible cladding, like Expanded Polystyrene (EPS) and Aluminium Composite Panels (ACP), in building wall systems elevates the fire risk posed to building occupants and users. The primary approach to mitigating cladding fire risk across multiple jurisdictions world-wide has been to require the removal and replacement of combustible cladding. The removal and replacement of cladding is both costly and time consuming, imposing a burden on building owners and occupants that in many instances is likely to be disproportionate to the risk posed by the cladding.

  Through the work of Cladding Safety Victoria (CSV) in Victoria, Australia to assess cladding risk and fund cladding rectification work on hundreds of multi-storey class 2 residential buildings, CSV has developed a unique and detailed knowledge of cladding risk. This institutional knowledge is being combined with international research findings and applied research expertise to provide an evidence base for the acceptance of cladding rectification solutions that supports the interest of fire safety without imposing undue stress and cost burden on building owners, residents and users.

  There is a growing appreciation that the removal and replacement of combustible cladding is not always the optimal way to make a building safe. Where cladding fire risk is rated unacceptable, the best approach remains to remove cladding. However, where the cladding risk is lower, the steps taken to make a building safer need to be proportionate to the cladding risk present. It is incumbent upon governments and regulators to ensure that enforcement, with its attendant costs and other implications for owners and residents, is not disproportionate to the cladding risk. An evidence base is being designed and developed that will enable a building to be deemed ‘cladding fire safe’ in a situation where some cladding is retained on a building façade provided that other specific fire safety measures are in place.

  It is the contention of this research that, for buildings with a lower cladding risk, the threat to life posed by a cladding fuelled fire can be mitigated by a range of targeted interventions designed to reduce the probability of cladding being ignited and once ignited, the probability that a cladding borne fire will lead to injury or death. The targeted interventions are designed to improve the detection of fire, the alerting of building occupants, the transition of fire and smoke between compartments and the protection of egress paths to support safe and timely egress from a building.

  The methodology involves the review of a cohort of lower cladding risk buildings referred to CSV to develop a set of discrete parameters that can be used to evaluate how effectively 12 risk mitigation interventions function to reduce the risk of cladding fires with respect to four primary ignition sources.  A quantitative foundation for risk reduction will be developed for many elements using expert led published data, fire safety analysis and simulations utilising multiple numerical tools including advanced computational fluid dynamics and artificial intelligence/machine learning. Should this project prove successful, it may enable the development of a new approach to cladding rectification of buildings with lower cladding risk. This approach is anticipated to have applications internationally and proportionately to the associated cladding risk, potentially reducing the time frames and costs of risk reduction.

• Pilot Study for Assessing Blast Risk - Dr Ken Dale (Geosciences Australia)

  Since 2009 Geoscience Australia (GA) has developed and hosted an Australian Government capability for estimating insured losses due to blast in Australia’s state capital cities. The capability has been developed in collaboration with the Australian Reinsurance Pool Corporation.

  The current GA workplan includes a pilot study of risk in an Australian central business district (CBD). The pilot will build upon and extend existing blast scenario analyses, and will feature expert workshop activity in estimating local threat likelihood. Factors to be considered in estimating the local likelihood are expected to include human exposure, building values, the presence of iconic buildings and Government offices, and device accessibility or restrictions to street precincts.

  This presentation will describe the pilot framework and discuss progress to date.

• Research works of the Resilient Infrastructure - Prof Chi-King Lee and Dr Damith Mohotti (UNSW Canberra)

  This presentation summarizes research work in the areas of fire, impact dynamics and blast effects on structures currently carrying out by the newly formed Resilient Infrastructure research group.

  In the areas of fire research, a fast yet accurate numerical tool to simulate the impact of fire enhanced wind on the structures downstream of the fire is being developed. The advanced modelling code FireFoam is selected as the base model and enhanced with Adaptive Mesh Refinement technique to account for the details and implications of heat transfer modes in different fire regimes.

  In the area of impact dynamics, a study to understand and compare experimentally, and numerically various bullet-proof fabrics treated with different spray coatings to increase friction between fibres for ballistic performance enhancement is being conducted. In this study, numerous studies on the shear thickening fluid (STF)-impregnated fabric have been conducted.

  In the area of blast effects on structure, a study exploring the advantages of using computational fluid dynamics (CFD) explosion models for medium to far field blast wave predictions, including more accurate estimates of the energy and resulting pressure of the blast wave and the ability to evaluate non-symmetrical effects caused by realistic geometries and gas cloud variations, is being conducted. This study aims to understand and compare the capability/limitations of ANSYS FLUENT CFD commercial code in predicting shock wave propagation.

Session 2

Session Chair – Prof Tuan Ngo

• Simplified Calculation of Airblast Variability for Spherical Air Burst and Hemispherical Surface Burst Explosions - Prof Mark Stewart (The University of Newcastle)

  There can be significant uncertainty and variability with explosive blast loading. Standards and codes of practice are underpinned by reliability-based principles, and there is little reason not to apply these to explosive blast loading. This presentation describes a simplified approach where regression equations may be used to predict the probabilistic model of airblast variability and associated reliability-based design load factors (or RBDFs) for all combinations of range, explosive mass and model errors. These models are applicable to (i) hemispherical surface bursts, and (ii) spherical free-air bursts. The benefit of this simplified approach is that the equations can be easily programmed into a spreadsheet, computer code, or other numerical methods. There is no need for any Monte-Carlo or other probabilistic calculations. Examples then illustrate how model error, range and explosive mass uncertainty and variability affect the variability of pressure and impulse, which in turn affect the damage assessment of residential construction.

• Research Project Overview and Current Capabilities of the National Facility for Physical Blast Simulation - Prof Alex Remennikov and Dr Edward Gan (UOW)

  The National Facility for Physical Blast Simulation (NFPBS) was established and commissioned at the end of April 2018 at the University of Wollongong. This facility is designed for systematic experimental studies of blast wave propagation and loading regimes, blast damage of elements of civilian and military infrastructure, blast injury protection, and other important blast related areas of research. The NFPBS is currently home to one of only two Advanced Blast Simulators (ABS) in the southern hemisphere. ABS’ are able to intrinsically replicate the wave-dynamics of actual free-field explosive blast. The large ABS at NFPBS has a test section of 1.5 x 2 m and is unique in its ability to generate highly adjustable blast waveforms and to provide flexible blast-testing configurations including full-reflection wall targets, diffraction model targets, behind-wall, and blast-ingress scenarios. The research facility also accommodates a smaller 0.3 x 0.3 m ABS intended for studies of reflective panel targets, scaled diffractive models, and free-field blast environment caused from propagating blast wave from tunnel exits. This presentation aims to provide an overview of the research projects performed at the NFPBS and to highlight its current capabilities.

• Recent advances in auxetics: applications in cementitious composites - Prof Yan Zhuge (UniSA) and Dr Tatheer Zahra (QUT)

  Auxetic materials, possessing negative Poisson's ratios (nprs), have the ability to shrink (or expand) in the lateral direction under an axial compressive (or tensile) force respectively. Due to this unique feature, anauxetic material is found to sustain high energy absorption capacity, fracture toughness and shear resistance, and thus regarded as one of the future materials in the field of impact protection. However, civil engineering applications of auxetic structures or materials are minimal due to miscellaneous restrictions on NPR effects. Accumulative developments in auxetics, have facilitated their applications in cementitious materials in recent years. This presentation will provide an overview of recent advances in the development of auxetic cementitious composites and analyses and summarises their mechanical properties under different loading conditions. Prior to extensive finite element (FE) simulations, more attention has been given to the limited experimental results.  Particular attention is paid to the expansionary feasibility of the parent material to introduce auxetic behaviour, with precise identification of the limitations, innovative composition methods, and facilitation of auxetic features. Finally, the presentation outlines the recent research activities of our research team on application of cementitious auxetic fabric composites as protective render and geometrically modified auxetic foams as filler in impact mitigation of masonry structures through numerical modelling. The effectiveness of mortar-auxetic fabric render was studied for mitigating the damage of brick masonry walls under low and high velocity impact forces in terms of energy absorption characteristics and prevention of impactor penetration. Whereas polyurethane foams were modified by embedding re-entrant shaped tubes and fibres to have NPR properties, which were then employed as filler in hollow masonry walls and found effective in resisting the impactor intrusion into the masonry walls.

• Progressive Collapse Research at Griffith University - Prof Hong Guan and Dr Chunhao Lyu (Griffith University)

  This presentation will cover the key findings from the progressive collapse research undertaken at Griffith University, with the primary aim of investigating the collapse resistance and load redistribution of RC flat plate structures and post-and-beam mass timber buildings under various column removal scenarios. For flat plate structures, five 2x2-bay substructure specimens were tested to large deformation stages. Numerical models were developed and validated to simulate the flexural, punching shear, and post-punching failure behaviours of the physical tests. Critical design parameters influencing the failure behaviours were also examined. Results suggest that continuous integrity rebars going through the columns are detrimental to activate tensile membrane action thereby enhancing post-punching capacity in progressive collapse events; concrete strength and slab thickness only affect the slab flexural capacity, whereas reinforcement ratio governs the post-punching capacity through tensile membrane action. On average, 90% of applied load is re-distributed to the nearest adjacent columns, hence increasing the risk of subsequent punching failure. Therefore, risks of both direct (initial damage) and indirect (subsequent) consequences must be considered in design practice. For post-and-beam mass-timber buildings, 11 static and 25 dynamic tests were first performed on 1x2-bay substructures. The ability of commonly used beam-to-column connections to develop catenary action was evaluated and an understanding the dynamic response of such systems, including failure mode and Dynamic Increase Factors (DIF), was gained. Five 2x2-bay substructure specimens were then tested to large deformation stages. Results showed than continuous Cross-Laminated Timber (CLT) floors, by creating alternative load paths, are important design elements to robust mass timber buildings. Other alternative load paths usually not considered in design were also found to carry a significant portion of the applied load.

• Advances in Protective Structures Research at University of Technology Sydney - Dr Jun Li (UTS)

  Research progress on Portland cement- and geopolymer- based ultra-high performance concrete (PC-UHPC and GP-UHPC) in structural protective design are briefed in this presentation.

  PC-UHPC has been proved to be blast/impact resistant thanks to its superior mechanical strength and damage tolerance. Its application, however, is limited by the raw material cost and lack of guidelines. After introducing hybrid fibre reinforcement in PC-UHPC, high flexure strength and fracture energy were characterized. Hollow cross-section design and alternative reinforcement in PC-UHPC were observed to be more cost-effective considering its high compressive and flexure/shear strength. PC-UHPC was also studied as retrofitting/strengthening material. After PC-UHPC overlay strengthening, punching shear could be significantly mitigated in the RC components under dynamic impact loads.

  PC-UHPC is a cement rich material and features a very dense microstructure. Under elevated temperature, it is prone to thermal spalling and its strength deterioration is more obvious than conventional concrete. UTS team developed a fire-resistant GP-UHPC which contains ternary pozzolanic material and a hybrid steel-polypropylene fibre reinforcement. The developed GP-UHPC retained approximately 60% of its original compressive strength after exposed to 800 ºC temperature. Uniaxial and triaxial strength tests were performed under/after elevated temperatures, and the results were used to establish constitutive model for this new material. Effect of cooling regimes (water cooling and air cooling) on the dynamic mechanical properties of GP-UHPC was studied. Application of this GP-UHPC in projectile penetration and field blast tests was demonstrated.

Session 3

Session Chair - Prof Guoxing Lu

• Behaviour of Blast Waves Resulting from Multiple Detonations - Dr Amir Zaghloul and Prof Brian Uy (The University of Sydney)

  Over the past decades, many engineering societies issued design guides to calculate blast loads on structures. While such guides can be successfully used to assess blast loads due to single detonations, the effects of multiple detonations are often overlooked. In this study, the enhancement in blast parameters resulting from simultaneously detonating multiple charges is investigated, emphasising the interaction of blast waves with narrow targets. A parametric CFD study was performed, where the number of charges, their arrangement, and the scaled stand-off distances were changed. It is found that, when detonated simultaneously, multiple charges return much higher pressure and impulse values compared to an equivalent single charge. Moreover, an arced arrangement of multiple charges is more efficient than a flat arrangement in enhancing blast wave parameters. Such enhancement is beneficial in scenarios involving demolition.

  A number of RC columns with different sizes are subjected to blast loading from single and multiple charges, and the resulting damage is evaluated in each case. The analysis is performed using a two-step process: first, CFD analysis is conducted, and the reflected overpressure and impulse are computed from the blast simulations. In the first step, Viper::Blast is used to compute the blast effects. The second step is to apply the blast loads to the RC columns in LS-DYNA. The output from LS-DYNA is then processed to evaluate the damage inflicted on the columns from each blast scenario.

• An update on DSTG work on Protective Structures - Dr Vanessa Pickerd (Defence, Science and Technology (DST) Group)

  Modern warships operate in extreme environments which include low temperature waters, risks of collision and exposure to explosive loads. A warship is essentially a transportable city, but unlike regular city infrastructure, a warship requires a light protective structures to enable it to meet weight requirements. Research conducted at Defence Science and Technology Group (DSTG) investigates the level of protection afforded by warship structures, from a material level through to construction, by use of experimental testing and modelling, enabling Defence to be a smart buyer of warships.

  Typically ships are constructed of various grades of steel, with structures fabricated from different thickness steel plates. Consideration is given to the type of steel used in specific areas of the warship to ensure the most practical level of protection is achieved. One measure of determining the performance of steel is to assess the fracture toughness under high strain-rate loading. The fracture toughness is assessed by testing the steel at different temperatures to characterise its ductile-brittle transition behaviour. To further understand the level of protection a steel offers for extreme environments DSTG uses an explosion bulge test procedure, which simulates what a warship might undergo from a blast loading event.

  Whilst the fracture toughness of the steel is a very important consideration for warships, the steel itself is not the only factor in protective design. As a structure is a welded construction, DSTG also asses the resistance to fracture of the weld joints. This is achieved by explosion bulge testing welded plates and internal detonations within full structural configurations. Data obtained from both material level and structural level testing are being used to enhance the development of modelling capabilities to increase the understanding and ability to predict failure of protective warship structures.

• National Drop Weight Impact Testing Facility - A/Prof Amin Heidarpour (Monash university)

  The performance of structures subjected to impact loading has received worldwide attention. The catastrophic failure of construction materials caused by extreme impact conditions, such as natural disasters and man-made hazards, has justified the need to carry out comprehensive research in order to develop future infrastructure with new, innovative, cost-effective and environmentally friendly materials.

  The National Drop Weight Impact Testing Facility (NDWITF) was launched at Monash Civil Engineering Department in last December 2020. This facility has the capacity to assess the structural safety of high-risk infrastructure, including railway networks, tunnels and bridges, buildings and construction materials, as well as road safety barriers and protective equipment.  The NDWITF also supports research in the broader research community on construction, mining, geo-mechanics, energy and the environment. Fields of application and interest include construction materials under high strain loading, structural dynamics and engineering, mining excavation and rock fragmentation.

  The NDWITF can drop up to 2000kg impact mass and has the capacity to create an impact energy of up to 200,000 J and impact velocity of up to 18m/s. Impact loading can be applied to specimens with a width of up to 1m and length of up to 2m. All displacements recorded within each test is captured by an optical 3D photogrammetry system.

  The NDWITF provides economic, environmental and social benefits to Australia as it will undertake research in resilient, cost-effective and environmentally friendly impact engineering applications. This presentation focuses on the technical aspects of this facility. Moreover, some of the recent tests conducted by this facility will be presented.