Tuan Ngo

A close-range blast event can cause severe damage to building structures due to its ability to produce very high localised impulsive loads. Such events can result from explosives that are attached to the critical elements of a structure, backpack and suitcase explosives, and vehicle or parcel bombs targeting the key structural elements of buildings and bridges. Steel hollow sections are among the most commonly used prefabricated structural element types that are widely used in Australia. Therefore, adopting the necessary precautionary measures in the design of such elements against close-range blast is worthwhile to explore. This paper focuses on an experimental and numerical study performed on concrete-filled and hollow square tubular columns (100 x 5 mm SHS Grade C350) made out of cold-formed structural steel hollow sections (SHS) that were subjected to highly explosive TNT charges. The charges were placed above the top surface of the column at two different scaled stand-off dista...

In this study, a new turning rapid diffuser has been developed using CFD analyses. Typically the diffuser angle should be less than seven degrees, to avoid flow separation. This angle requirement cannot be satisfied when the diffuser length is restricted, such as in the design of a wind tunnel circuit, as a result of its overall dimension. A parametric investigation using ANSYS CFX 10 has found that the diffuser angle can be much larger, without creating flow separation, when the flow is diffused in a circular turning path. With this turning rapid diffuser, the flow has been shown to attach to the diffuser’s sidewalls, even when the diffuser angle is as large as 12 degrees. Flow separation still occurs from the inner surface in the turning direction, however further CFD analyses have indicated that this separation can be reduced by the addition of guide vanes along the turning flow path. The CFD results have been validated with a physical model before being used successfully in the construction of a closed circuit boundary layer wind tunnel at the Institute of Building Science and Technology (IBST) in Vietnam

This paper describes the blast loading trials on steel tubular members with and without concrete infill. The standoffs considered in this trial were selected to demonstrate the response of these steel sections to contact and very close-range detonations of high explosive (HE). The main objective of the trials was to investigate the effects of contact and near-field explosions on steel square tubular members and to demonstrate the effect of standoff variation on the mode of response and failure of steel square sections. The experimental data collected during these trials can be used for verification of theoretical and numerical models of response of steel tubular columns subjected to contact and close-range blasts. Due to difficulties with collecting quantitative data (displacements, blast pressures etc.) in the close proximity of a detonating HE charge, analysis of the steel tubes in this paper is confined mostly to qualitative assessment based on visual observations of the structur...

ABSTRACT Flood damage assessment (FDA) is a key component of risk-based method for flood management. In the current FDA approaches, generally the uniqueness of the building is disregarded in the analysis. Therefore, they are unfit for detailed applications in which case-by-case analysis of building damage is an essential requirement. This limitation is compounded by the use of incomplete and often low quality data inputs about the building and the assumptions and approximations made regarding the geometry and materials of its components. Such shortcomings may result in an incomplete and uncertain outcomes. Considering the benefits and increasing use of 3D urban modeling and BIM in various urban management processes, in this paper, an integrated framework for utilization of detailed 3D building models for the assessment and 3D visualization of flood damage to building according to its distinct behavior against flood is presented. A proof-of-concept demonstration of the framework in a case study underlined the feasibility of implementation of the framework which can potentially benefit a variety of users and be used as a complementary approach to the current FDA methods for improving the resilience of the community towards floods and their adverse impacts.

The duration of blast pressure is significantly important along with its magnitude for dynamic response of concrete elements. Pressure-Impulse (PI) diagrams which include both blast pressure magnitude and duration are often used in concrete damage assessment. Available ...

... This study is continuing at the University of Melbourne. Acknowledgments The data preparation for this study by Mr. Denny Teo is greatly appreciated. References ... 105, No. 11, November 1979, pp. 2243-2260. [3] MENDIS, P., and NGO, T., (2002) “Assessment of tall buildings ...

This paper reviews current understanding of fluid-structure interaction effects that may be associated with Tsunami waves impacting on structural forms. Force models for wave-structure interaction currently adopted by coastal engineers for analysis and design of coastal structures are presented and their relative merits, shortcomings and applicability discussed in the context of Tsunami wave force effects on structures. In addition, the

Progressive collapse of a building can be triggered by damage to certain critical load-carrying elements immediately following a blast. The initial damage can be followed by a chain of events which progressively destabilize the building. The modelling of progressive ...

The energy required for space cooling could be reduced by using ground as a heat sink depending on the weather conditions and the ground characteristics. In this paper the theoretical performance of a closed loop ground coupled cooling system for a commercial building in Hanoi has been investigated as an alternative to the conventional air-to-air cooling system. A theoretical computational model for the prediction of the cooling system performance has been developed. It was found that the ground-coupled cooling system performs better (approximately 30% energy saving) than a conventional air-to-air cooling system.

Flange edge stiffeners increase the ultimate moment capacity of cold-formed channel sections. At the same time, they cause complexity to the buckling failure mode of the section. There is a lack of experimental research on the failure mode of sections with a partially stiffened element, such as channel sections with edge stiffeners, in which a distortional buckling mode can be observed. The focus of recent studies is mainly on the behaviour of the whole section as one member under bending without any concern about the relationship between the web and flange ratio. In this study, an extensive experimental analysis of 42 cold-formed channel sectionswas used to explore the failure behaviour of cold-formed channel sections under pure bending. The sections were made from cold-formed G450 steel with a nominal thickness of 1.6 mm. The results of the pure bending experimental investigations are used to describe the relationship between the web and flange ratio and the failure deformations. ...

High-strength concrete (HSC) is becoming very popular around the world due to its many advantages over normal strength concrete (NSC). There are significant behavioural differences between HSC and NSC, most notably the brittleness and sudden spalling under elevated temperatures, whereby pieces of hardened concrete explosively dislodge. The spalling of high strength concrete walls in fire has generally been ignored by the designers and the fire-resistance of walls has been calculated using the rules specified for normal strength concrete. Major design codes including the Australian Code do not cover spalling adequately. After a brief discussion on the status of research, general observations on spalling are summarized. Relevant results from a comprehensive study conducted at the University of Melbourne are briefly discussed. This is the first systematic testing program covering the fire behaviour of NSC and HSC walls exposed not only to standard fires but also hydrocarbon fires. It i...

Conventional structural materials such as steel and concrete cause structures to be comparatively heavy and interest on lightweight materials has been ever increasing. Metal-elastomer composite systems can be considered as a novel alternative for existing light armour. This paper discusses on the penetration of high velocity projectiles through aluminium–polyurea composite layered plate systems. An analytical model has been proposed to predict the residual velocity of polyurea–aluminium composite plates, and validated with both experimental and numerical investigations. Full metal jacket (FMJ) projectiles (5.56 mm × 45 mm), corresponding to NATO standard SS109, were fired at the aluminium–polyurea composite layered plate systems from a distance of 10.0 m at a fixed velocity of 945 m/s. Four different composite plate configurations were used with thicknesses varying from 16 – 34 mm. Each configuration consisted of six specimens. Residual velocities for each individual test were recor...

ABSTRACT Flood damage assessment (FDA) is a key component of risk-based method for flood management. In the current FDA approaches, generally the uniqueness of the building is disregarded in the analysis. Therefore, they are unfit for detailed applications in which case-by-case analysis of building damage is an essential requirement. This limitation is compounded by the use of incomplete and often low quality data inputs about the building and the assumptions and approximations made regarding the geometry and materials of its components. Such shortcomings may result in an incomplete and uncertain outcomes. Considering the benefits and increasing use of 3D urban modeling and BIM in various urban management processes, in this paper, an integrated framework for utilization of detailed 3D building models for the assessment and 3D visualization of flood damage to building according to its distinct behavior against flood is presented. A proof-of-concept demonstration of the framework in a case study underlined the feasibility of implementation of the framework which can potentially benefit a variety of users and be used as a complementary approach to the current FDA methods for improving the resilience of the community towards floods and their adverse impacts.

ABSTRACT The excellent mechanical properties of nacreous composites are partly attributed to its staggered microstructure, which is made of multiple layers of mineral tablets bonded through a soft protein matrix. An important parameter that could affect the load sharing mechanism in nacre is the waviness of aragonite tablets. In this work, a continuum model of nacre composite is developed, which takes into account the waviness factor. The tablets are subjected to tensile loading and are initially modeled to have dovetail shapes with varying slopes. The load sharing efficiency of nacre is evaluated through displacements, stresses and strain energy density (SED) of the unit cell. The SEDs of unit cells, tablet and matrix are presented for different overlapping lengths and inclination angles, from which maximum SEDs and optimum overlapping lengths are determined. Parametric studies show that larger inclinations of nacre tablets result in higher energy absorbing capacity. A more general case is also presented, where nacre’s platelet is modeled to have sinusoidal waviness of different wavelengths. By varying the wavelength while maintaining the periodicity of the unit cell, stresses, SEDs and displacements are obtained and compared. Analytical results on the optimum waviness of designed unit cells are validated with observed nacreous microstructures.