Tall buildingswind engineering & architectural aerodynamics

London | Hong Kong | Kuala Lumpur | Abu Dhabi | Dubai | Shanghai | Houston

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.

Tel: +44 20 8614 4400 Fax: +44 20 8943 3224 Email: enquiries@bmtfm.com Website: www.bmtfm.com

sustainable design approaches are dictating design

solutions for tall buildings that are energy efficient

and efficient in their consumption of building material.

For sustainable, cost efficient, and safe design these

structures now commonly require specialist wind studies

to provide design guidance from concept to final design

stages and beyond, to provide on-site performance

validation of key building parameters.

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.

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 long-

term 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.

Bmt Fluid mechanics (Bmt) operates a highly specialised

and resourceful tall building group that provides designers

with a comprehensive portfolio of consultancy services

for structural, serviceability and environmental design

based on substantial in-house capabilities and experience

for boundary layer wind tunnel testing and numerical

modelling.

Key services

• 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)

Key BeneFits

• cost-effective structural design

• cost-effective façade design

• optimised occupant comfort

• external microclimate control

• interactive solution development

• iterative design optimisation

• efficient and safe design for blast scenarios

Wind Climate analysis Cont

Wind Climate analysis

Design Wind Speeds Wind Frequency Data

Non-synoptic Wind Profile Synoptic Wind Profile

Mesoscale Model

Hurricane noaa/sCienCe PHoto liBRaRy

the design requirement to constrain wind-induced

building sway to levels that are acceptable from an

occupant comfort point is often the driving criterion in the

design of the lateral stability systems of tall and super

tall buildings. high frequency force balance and high

frequency pressure integration testing techniques can

deliver accurate quantification of peak building sway and

provide an assessment of acceptability relative to industry

standard comfort criteria.

these analysis techniques allow iteration between key

performance parameters of the structural system such

as building stiffness, mass and damping and dynamic

wind responses to progressively derive the optimum

configuration. in cases where auxiliary damping systems

are required to limit building sway, full aeroelastic

modelling may be employed to validate the performance

of these damping systems.

dynamiC ResPonse / Building motion analysis

FaCade PRessuRe analysis

Peak Acceleration Criteria Peak Accelerations

Block Zone Diagram

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.

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. web-

coupled 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.

stRuCtuRal load analysis

High Frequency Force Balance Model

Force Spectra Dynamic Base Loads

Pressure ModelFlow Visualisation

Tel: +44 20 8614 4400 Fax: +44 20 8943 3224 Email: enquiries@bmtfm.com Website: www.bmtfm.com

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).

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.

FaCade PRessuRe analysis Cont

Cladding Pressure Contours

Wind Mitigation Scheme

Downdraft

Comfort & Safety Rating For Pedestrian Wind Environment Suitability Criteria

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.

PedestRian Wind ComFoRt analysis

Tel: +44 20 8614 4400 Fax: +44 20 8943 3224 Email: enquiries@bmtfm.com Website: www.bmtfm.com

For further information contact: Tel: +44 20 8614 4400 Fax: +44 20 8943 3224Email: enquiries@bmtfm.com Website: www.bmtfm.com

BMT Fluid Mechanics Limited, 67 Stanton Avenue, Teddington, Middlesex, TW11 0JY, UK