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High rise in Docklands
North Quay is a mixed office and hotel development in London Docklands.
The building form is regular, but it is close to surrounding tall
buildings, so BRE was called in to measure the cladding loads, overall
structural loads and the wind environment.
Testing
A static model of the tower and surrounding area was constructed in
BRE's Boundary Layer wind tunnel, at a scale of 1:300, with more than
500 pressure taps.
Ordinarily, a building of this shape would be standard in terms of
wind loading, however the tall buildings upwind of North Quay have
a significant effect on the wind loads, which means the Code does
not apply.
Results
Wind tunnel testing found that wind loads on the east façade
of the tower corresponded with Standards, however the wind loads on
the west façade were much higher than the Standards (over 100%
higher in places). This was due to wake buffeting from the adjacent
taller buildings.
Conclusions
The design could be adjusted to reduce the overall loads by up to
20%, resulting in large potential savings in the cost of the structure.
It also gave the client confidence in the design of the structure
and the reliability of the cladding system. Wind tunnel testing therefore
led to a safer and more serviceable design.
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New development in an
urban area
BRE is currently advising on a new development in a borough that has
been declared an Air Quality Management Area (AQMA). Therefore pollution
emissions to the local environment need to be controlled and the ingress
of external pollution minimised.
As the development is to house internet servers, a high electrical
output of 35 MW is required. This is to be generated using an on-site
combined heat and power plant. This process emits large amounts of
nitrogen dioxide and particles, especially if standby diesel generators
are used.
The project therefore falls under the authorisation of the Environment
Agency and a full IPPC application had to be submitted with the planning
application. The local authority also had to be involved because the
development was in an AQMA.
Testing
A desk study was carried out to determine the heights of chimneys
required to effectively disperse the pollutants.
Results indicated that nine stacks of 100 m in height were required.
However this was not acceptable both in terms of aesthetics and because
a height restriction of 90 m was in place in the area.
To resolve the potential conflict between the planners and Environment
Agency, the client asked BRE to undertake wind tunnel tests to determine
the minimum stack height that will be acceptable.
The wind tunnel tests will also be able to model and determine pollutant
concentrations over the complex urban area in which the development
is to be built.
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Smoke analysis in an international
airport
The main issue was whether the proposed open-plan design for the arrival/departure
area and the retail atrium space would be safe in the event of fire.
It was proposed to use minimal compartmentation and structural fire
protection, and to leave the HVAC system running in 100% replacement
mode.
Coupling a study of smoke and heat transport with predictions of human
behaviour, BRE was able to provide the client with a complete integrated
smoke movement and evacuation analysis. This was used to inform the
design of the smoke extraction system.
The fire scenario used for the modelling studies was based on a luggage
fire test undertaken at BRE. Using this data as the source term in
JASMINE* computer simulations, BRE was able to demonstrate that the
smoke layer in the departure/arrival area and retail atrium space
would not cause a problem to the evacuating people, and that the structural
elements would not be damaged by the heat.
The integrated smoke movement and egress simulations confirmed the
original design concept.
* JASMINE is a fire special-purpose CFD code developed by FRS/BRE.
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