Cammelli S.,BMT Fluid Mechanics |
Vacca L.,Robert Bird Group |
Li Y.F.,BMT Fluid Mechanics
IABSE Conference, Guangzhou 2016: Bridges and Structures Sustainability - Seeking Intelligent Solutions - Report | Year: 2016
The unsteady wind pressure fields deriving from the atmospheric boundary layer interacting with the aerodynamics of a tall building can be represented as spatially-correlated multi-variate random processes. Due to its random nature, the fluctuating pressure field can be considered as the superposition of a large number of independent partial pressure fields related to particular mechanisms of the excitation. It is within this context that Proper Orthogonal Decomposition (POD), a powerful statistical tool particularly suitable to deal with a large number of random variables, can be used to enhance the understanding and help with the interpretation of the physical phenomena that can drive the wind-induced dynamic response of tall buildings. The main purpose of the work presented within this technical paper, which makes use of wind pressures measured on a scaled wind tunnel model of a prismatic 180m tall building, was to identify hidden physical phenomena embedded within chaotic wind pressure fields with the idea of potentially simplify the analysis work and reduce the increasing demand for wind tunnel data storage. More specifically, this paper will show how complex fluctuating wind pressure fields - driving the response of tall buildings in both the along- And the cross-wind direction - can be approximated by a few dominant standard modes of the pressure field itself.
Thambiratnam D.P.,Queensland University of Technology |
Perera N.J.,Queensland University of Technology |
Abeysinghe C.M.,Queensland University of Technology |
Huang M.-H.,Queensland University of Technology |
De Silva S.S.,Robert Bird Group
Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE) | Year: 2012
Human activity-induced vibrations in slender structural sys tems become apparent in many different excitation modes and consequent action effects that cause discomfort to occupants, crowd panic and damage to public infrastructure. Resulting loss of public confidence in safety of structures, economic losses, cost of retrofit and repairs can be significant. Advanced computational and visualisation techniques enable engineers and architects to evolve bold and innovative structural forms, very often without precedence. New composite and hybrid materials that are making their presence in structural systems lack historical evidence of satisfactory performance over anticipated design life. These structural systems are susceptible to multi-modal and coupled excitation that are very complex and have inadequate design guidance in the present codes and good practice guides. Many incidents of amplified resonant response have been reported in buildings, footbridges, stadia a nd other crowded structures with adverse consequences. As a result, attenuation of human-induced vibration of innovative and slender structural systems very ofte n requires special studies during the design process. Dynamic activities possess variable characteristics and thereby induce complex responses in structures that are sensitive to parametric variations. Rigorous analytical techniques are available for investigation of such complex actions and responses to produce acceptable performance in structural systems. This paper presents an overview and a critique of existing code provisions for human-induced vibration followed by studies on the performance of three contrasting structural systems that exhibit complex vibration. The dynamic responses of these systems under human-induced vibrations have been carried out using experimentally validated computer simulation techniques. The outcomes of these studies will have engineering applications for safe and sustainable structures and a basis for developing design guidance.
Thambiratnam D.P.,Queensland University of Technology |
Perera N.J.,Queensland University of Technology |
Perera N.J.,Robert Bird Group
Australian Journal of Structural Engineering | Year: 2012
Structural framing systems and mechanisms designed for normal use rarely possess adequate robustness to withstand the effects of large impacts, blasts and extreme earthquakes that have been experienced in recent times. Robustness is the property of systems that enables them to survive unforeseen or unusual circumstances (Knoll & Vogel, 2009). Queensland University of Technology with industry collaboration is engaged in a program of research that commenced 15 years ago to study the impact of such unforeseeable phenomena and investigate methods of improving robustness and safety with protective mechanisms embedded or designed in structural systems. This paper highlights some of the research pertaining to seismic protection of building structures, rollover protective structures and effects of vehicular impact and blast on key elements in structures that could propagate catastrophic and disproportionate collapse. © Institution of Engineers Australia, 2012.
Fraser J.,Foggo Associates |
Seel D.,Robert Bird Group |
Chadwick J.,Robert Bird Group |
Valambhia K.,Laing ORourke |
Offiler A.,Laing ORourke
Proceedings of the Institution of Civil Engineers: Civil Engineering | Year: 2012
This paper describes the design and construction of a dramatic 50 000 m2 'air-rights' development above Cannon Street main-line and underground station in London and a scheduled ancient monument. The complex building structure includes two 21 m deep cantilevered wings, requiring a 38-stage structural analysis and full-height precambering of façade structures. Careful phasing and meticulous planning were required to segregate and shield passengers from construction activities. The challenges were successfully overcome by fully integrating design and construction, permanent and temporary works designs, and working in a truly collaborative environment.
Al-Harthy A.S.,Sultan Qaboos University |
Stewart M.G.,University of Newcastle |
Mullard J.,Robert Bird Group
Magazine of Concrete Research | Year: 2011
The paper reviews previously reported predictive models on corrosion-induced crack initiation and propagation and presents new additional results of ongoing accelerated corrosion tests conducted at The University of Newcastle. In addition to eight concrete specimens previously tested, six new specimens were tested to study the effect of reinforcement confinement, concrete strength (24 and 8 MPa), cover (10 and 20 mm) and reinforcing bar diameter (16 and 27 mm) on corrosion-induced cracking. Time-dependent crack widths were measured for different reinforced concrete slabs for corrosion rates up to 169 μA/cm2. It was foundthat predictions of time to crack initiation are highly scattered and can differ by as much as two orders of magnitude. It was also found that crack initiation and propagation times increase with increasing cover and decrease with increasing reinforcing bar diameter and compressive strength. In addition, the rate of crack propagation is 10-50% higherfor reducedreinforcement confinement such as at the edge of a slab or corner of a column. The experimental results are compared with existing crack initiation and propagation predictive models allowing for the accuracy of existing models to be assessed and showingpotential areas for further research. © 2011.
Mullard J.A.,Robert Bird Group |
Stewart M.G.,University of Newcastle
Applications of Statistics and Probability in Civil Engineering -Proceedings of the 11th International Conference on Applications of Statistics and Probability in Civil Engineering | Year: 2011
Corrosion of the reinforcing steel can cause cover cracking and eventual spalling of Reinforced Concrete (RC) surfaces resulting in costly and disruptive repairs. The paper presents a probabilistic reliability analysis which is used to predict the likelihood and extent of corrosion-induced cracking to RC structures. A spatial time-dependent reliability model has been developed where concrete properties, concrete cover and the surface chloride concentrations are treated as random fields. This allows for the calculation of the probability that a given extent of damage will occur for any time period. Three primary maintenance strategies will be considered: i) patch repair, ii) preventative repair, and iii) complete rehabilitative overlay. Incorporated into each of the above maintenance strategies are two repair efficiency factors which take into account varying time to corrosion initiation and corrosion rate of the repair material. These maintenance strategies and repair efficiencies are incorporated in a Monte-Carlo event-based simulation analysis. Results are presented for a RC bridge deck subject to a marine environment. The Life-Cycle Cost analysis considers construction, repair and user delay costs. This predictive capability enables the extent of future repair costs to be more realistically estimated and the optimal maintenance strategies determined © 2011 Taylor & Francis Group, London.
Fragiacomo M.,University of Sassari |
Batchelar M.,Mark L Batchelar Consulting Engineers |
Wellington C.,Robert Bird Group |
Buchanan A.,University of Canterbury
11th World Conference on Timber Engineering 2010, WCTE 2010 | Year: 2010
The pull-out performance of steel rods glued into timber is well documented, and short-term tests by many researchers have demonstrated reliable strength. The behaviour of glued-in steel rods in moment-resisting beam-column joints is much more complex, so that interactions of bending moments, axial and shear forces and the possible effects of creep and stress concentrations all need to be considered. These connections are often used as knee joints in timber portal frame structures. This paper describes the results of a series of long-term load tests on moment-resisting joints between glue-laminated timber members, together with separate load tests on the various joint components. Measurements were recorded to identify time dependant stress redistribution within the test joints and possible crushing of the timber-to-timber bearing surfaces leading to excessive joint rotations. Local deformation of timber loaded in compression perpendicular to the grain was found to contribute to excessive joint deformations in tests where the steel rods were not glued over their full length. The research developed a prediction model for the long term deformations and rotations in a knee joint utilising epoxy grouted steel rods.
Raggett T.,Robert Bird Group
Structural Engineer | Year: 2012
Synopsis Some of the challenges faced by Robert Bird Group and The Design Team during the design and construction of the Olympic and Paralympic Village are summarised. The Olympic and Paralympic Village consists of 2818 apartments in 11 plots and were built to accommodate over 17 000 athletes as part of the London 2012 Olympic and Paralympic Games. After the Games the plots will be converted into a residential community, which will contribute to the overall regeneration of the Stratford area of London. The production of an efficient design solution to enable configuration of the development in two modes; the Olympic and Paralympic Village and subsequently, private and social housing units, was key to the successful delivery of this project. This process occurred during the Global Financial Crisis in 2008, which lead to specific implications for design and procurement.
Mullett P.J.,Robert Bird Group |
Moragaspitiya H.N.P.,Robert Bird Group |
Ward J.,Robert Bird Group
Proceedings of the Institution of Civil Engineers: Engineering and Computational Mechanics | Year: 2013
This paper describes the practical application of computational analysis to the design of a reinforced concrete structure subject to blast loading from a vehicle-borne improvised explosive device. The structure includes a protective slab designed to provide a barrier between the blast load and a densely occupied commercial floor. The blast load derivation was carried out using commercially available computational fluid dynamics (CFD) (hydrocode) software to predict shock wave propagation, reflection and refraction effects. Pressure-time histories were extracted and applied to the mesh of a decoupled finite-element (FE) model of the structural system. The structural analysis was carried out using a commercially available explicit dynamic solver, incorporating non-linear material representations of the primary structural components including the protective slab and supporting columns, beams and walls. The analysis methodology was based on a macro level of structural detail commensurate with the design objectives, with column and beams represented with line elements and walls and slabs represented with thin shell elements. The computational analysis successfully confirmed the adequacy of the proposed design for the specified threat level. The paper concludes that the performance of a reinforced concrete structural system can be cost-effectively assessed for blast loading, to a level appropriate for design purposes, using existing commercially available CFD and FE tools.