Nov 03 2012
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New regulations for Dubai high-rises soon
The new rules are to take into account the increased number of high-rise constructions in the emirate. In such environment, different standards are required when it comes to wind and seismic design, explains Moawya Safarina, engineer at the Permit Section of Dubai Municipality 's Building Department.
Wind not only affects structures in different intensities, but a new structure also alters the wind flow. An architect designing a building for an area where more than 15 per cent of the terrain is covered with structures taller than15 meter will have to take into account different requirements than when designing a building for an open area without any obstacles.
"In city centers (...) when calculating wind loads on tall structures surrounded by shorter structures, the blocking effects of surrounding structures are accounted for...", explains the new Code.
Elsewhere it elaborates on the specific requirements for structures that are spatially irregular, very tall, or flexible, structures that are susceptible to vortex shedding, galloping, or wake buffeting, structures that are susceptible to wind-induced human discomfort, and structures whose wind response requires a more accurate estimation.
These structures need to undergo wind tunnel testing.
Although the code is still under review, its current draft is commented on for the adopted 'basic wind speed for design in conjunction with wind tunnel testing'.
As Moawya explains, this is the value of the average wind velocities within 10 minutes periods and measured at 10 meters height, likely to be exceeded once in 50 years.
Recorded at Dubai International Airport for the past 25 years, this is set at 108 km/h; a figure higher than the currently accepted figure for design in conjunction with wind tunnel testing.
"This implies that almost every tall structure wind tunnel tested in Dubai to date would need to be classified as "under-designed" after the introduction of the new code. Is DM considering to allow the use of a lower and more realistic basic wind speed for design in conjunction with wind tunnel testing?" comments BMT Fluid Mechanics Ltd., one of the parties involved in the review of the Code.
The Code has been under development since 2009 and is currently in the final review stage, expected to be implemented next year.
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