Tall buildings. wind engineering & architectural aerodynamics. London Hong Kong Kuala Lumpur Abu Dhabi Dubai Shanghai Houston

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1 Tall buildings wind engineering & architectural aerodynamics London Hong Kong Kuala Lumpur Abu Dhabi Dubai Shanghai Houston

2 Tall and Supertall buildings due to their overall scale and increasing complexity in architectural shape and sophistication are highly wind sensitive structures in terms of their technical feasibility and cost effectiveness. Sustainable design approaches are dictating design BMT Fluid Mechanics (BMT) operates a highly specialised solutions for tall buildings that are energy efficient and resourceful tall building group that provides designers and efficient in their consumption of building material. with a comprehensive portfolio of consultancy services For sustainable, cost efficient, and safe design these for structural, serviceability and environmental design structures now commonly require specialist wind studies based on substantial in-house capabilities and experience to provide design guidance from concept to final design for boundary layer wind tunnel testing and numerical stages and beyond, to provide on-site performance modelling. validation of key building parameters. Key Services Key benefits Wind Climate Analysis cont Where required, generic wind models are complemented through detailed modelling of non-synoptic wind patterns using approaches such as topography modelling and Mesoscale models. Wind climate studies are accepted throughout the world by local building departments and regulatory bodies and deliver a robust basis for reduction of inherent conservatism in design codes. Mesoscale Model Wind climate analysis Structural load analysis Building motion / dynamic response analysis Auxiliary damping system configuration Pedestrian wind comfort analysis / environmental impact assessment Façade pressure analysis (wind and blast) Cost-effective structural design Cost-effective façade design Optimised occupant comfort External microclimate control Iterative design optimisation Interactive solution development Efficient and safe design for blast scenarios Wind Climate Analysis Non-synoptic Wind Profile Synoptic Wind Profile The specification of design wind speeds for structural, serviceability and environmental design requires careful analysis of long-term wind statistics. BMT has access to global wind record databases, which provide longterm wind statistics for extreme wind events including synoptic and non-synoptic wind patterns including e.g. Typhoon, Shamal, Thunderstorm and Monsoon winds. By application of sophisticated industry standard wind models of the atmospheric boundary layer, and extreme value statistical analysis of storm records, site-specific wind climate models are generated for each development that can also provide detailed resolution of wind directionality and probability of occurrence. Hurricane NOAA/SCIENCE PHOTO LIBRARY Design Wind Speeds Wind Frequency Data

3 Dynamic Response / Building Motion Analysis The design requirement to constrain wind-induced These analysis techniques allow iteration between key building sway to levels that are acceptable from an performance parameters of the structural system such occupant comfort point is often the driving criterion in the as building stiffness, mass and damping and dynamic design of the lateral stability systems of tall and super wind responses to progressively derive the optimum tall buildings. High frequency force balance and high configuration. In cases where auxiliary damping systems Flow Visualisation High Frequency Force Balance Model Pressure Model frequency pressure integration testing techniques can deliver accurate quantification of peak building sway and are required to limit building sway, full aeroelastic modelling may be employed to validate the performance Structural Load Analysis provide an assessment of acceptability relative to industry standard comfort criteria. of these damping systems. Dynamic wind loading is a governing parameter in the design of the foundations and the superstructure of tall buildings. Cost efficient design of these components requires reliable quantification of these wind parameters. Boundary layer wind tunnel testing based on high frequency force balance (HFFB) and high frequency pressure integration (HFPI) techniques allow accurate determination of critical loading scenarios accounting for the structural stiffness of the building and structural coupling of multiple tower arrangements. BMT operates state-of-the-art multiple simultaneous dynamic force balance systems, as well as a custom built 1152 channel simultaneous low-range pressure scanning system, that allow complex geometries and linked towers to be comprehensively studied. BMT are able to interactively employ force balance testing technology coupled to sophisticated on-line data analysis software, which allows designers, at an early stage in the design, to interactively and cost-effectively support architectural form-finding and structural concept studies through accurate wind loading analysis for all design arrangements. It has become increasingly common to apply these technologies in wind loading workshops, in which the geometry can be varied and instantaneously analysed, giving best value to the design team. Webcoupled digital video monitoring and data presentation systems allow remote client interaction removing the need for travel to the test facility. Wind tunnel data can be reanalysed iteratively for different structural parameters as the design evolves eliminating the need for repeat testing allowing for efficient tuning of the structural system. Peak Acceleration Criteria Peak Accelerations Facade Pressure Analysis For simple geometries that are exposed to wind in isolated conditions it is often possible to derive safe design wind loading for façade systems by application of code methodology, which is limited to rather simple shapes. However, in most practical applications strong aerodynamic interference effects from adjacent buildings and architecturally complex external shapes, application of code methodology often leads to highly conservative estimates of wind pressures. Using wind tunnel testing technology, cladding pressures on glazed facades and façade features such as clad parapet walls and canopies can be accurately measured using detailed small-scale wind tunnel models instrumented with a large number of pressure taps. Internal pressures including stack effects can be quantified using computational internal air flow models. Block Zone Diagram Force Spectra Dynamic Base Loads

4 Facade Pressure Analysis cont Pedestrian Wind Comfort Analysis cont Sophisticated 3D contouring software allowing automated on-line presentation of surface pressure data for complex external building form allows the façade pressures to be effectively displayed in a way that is easily digested into cost effective façade design by façade contractors. International building regulations in some cases require designers to design building facades and key structural support elements to withstand bomb blasts. A number of codified engineering methods exist to assist designers in this task, though, these are rather simplified. To support performance based design approaches through more sophisticated numerical modelling of blast impact on building facades, BMT has developed in-house capabilities for blast modelling than can be applied to complex building arrangements to derive accurate dynamic loading and consequence scenarios. Cladding Pressure Contours BMT s interactive approach to pedestrian wind comfort studies allows designers to develop wind mitigation schemes and validate these for effectiveness through time and cost efficient iterative wind tunnel test workshop days. BMT s technical and interpretative reporting structures are commensurate with formats required by planning authorities for Environmental Impact Assessments (EIA). Downdraft Pedestrian Wind Comfort Analysis Generating controlled external microclimate in the vicinity of tall buildings by purposeful development of wind mitigation schemes that protect from the unfavourable action of downdrafts and ground-level wind funnelling is key to the commercial success of external recreational spaces and key to ensuring user comfort. BMT operates multiple channel wind speed sensing systems that allow the wind speed up to be quantified in severity and spatial extent in key pedestrian areas, including balconies and roof terraces, and for pedestrian wind comfort to be defined in terms of suitability for planned uses. Comfort & Safety Rating For Pedestrian Wind Environment Suitability Criteria Wind Mitigation Scheme

5 For further information contact: BMT Fluid Mechanics Limited, 67 Stanton Avenue, Teddington, Middlesex, TW11 0JY, UK