The wind-load design basis for steel structures in Dubai

Two documents, read together

Clause F.7.12.1 asks the engineer to calculate wind effects for strength, for life safety, and for serviceability, where building movement affects cladding or occupant comfort. The calculation is to be based on ASCE/SEI 7-16 together with the supporting information and additional rules the Code gives for Dubai.¹

ASCE/SEI 7-16 is also Part F’s general loading reference. Loads are defined in accordance with ASCE/SEI 7-16 and Part F, and are factored and combined in accordance with its Chapter 2.² Part F lists ASCE/SEI 7-16 among its essential references.³

Part F also asks that calculations, drawings, specifications and basis-of-design reports state the adopted codes and standards by number, title and version, and where Part F and a referenced standard conflict, the more restrictive requirement governs.⁴

What the Dubai provisions change

Clause F.7.12.2 states that the wind speeds of Table F.10 are used instead of the wind maps in Section 26.5 of ASCE/SEI 7-16.¹

Table F.10 gives reference speeds for a 3-second gust at 10 m height in open terrain. Each row pairs a mean recurrence interval with an application: two serviceability rows, one for occupant comfort and one for displacement; a row reserved for concrete design under Clause 5.3.5 of ACI 318-19; and four strength rows for risk categories I to IV as defined in Clause 1.5 of ASCE/SEI 7-16.¹

For strength, the reference speed rises with the risk category, from 44 m/s at a 300-year recurrence interval for risk category I to 53 m/s at 3,000 years for risk category IV; risk category II uses 47 m/s at 700 years. The displacement check uses 30 m/s at 10 years. Table F.10 also gives the occupant-comfort and concrete-design rows, and the table is the place to read any other value.¹

The same clause sets a minimum design wind pressure of 1 kN/m² that applies in all cases, and requires the directionality factor K_d to be taken as 1.0 where wind tunnel testing is used with up-crossing or storm-passage methods.¹

Strength and serviceability are separate checks

For serviceability, clause F.7.12.4.1 calculates overall building displacement and inter-storey drift using 10-year return wind pressures and compares them with the limits in Table F.11. The stated purpose is to control movements that could overstress, fatigue or reduce the effectiveness of cladding, partitions and other non-structural components.⁵

Clause F.7.12.4.2 then assesses accelerations of the uppermost occupied floor at 1-year and 10-year return periods against recognised criteria such as ISO 10137.⁶

Those clauses are written for buildings, but Part F’s performance section makes the general point for structures within its scope: the basis of design covers strength, deflection control, building movement due to wind and vibration as distinct items.⁷

When calculation alone is not enough

Clause F.7.12.3.1 requires wind tunnel testing for buildings taller than 120 m, buildings whose height is more than five times their average width normal to the wind direction over the top of the building, and buildings of unusual shape or surroundings not covered by ASCE/SEI 7-16 or other reliable published data that cannot be designed safely with conservative wind loads. Testing follows Chapter 31 of ASCE/SEI 7-16, and the Authority might require a peer review of wind tunnel testing for unusual buildings or where the results are not readily comparable to codified values.⁵

The note to F.7.12.1 adds that the rules are intended for the kinds of buildings a code of practice envisages; unusual constructions may need additional studies.¹

Scope and limits

• Part F applies to buildings and to structures or appurtenances connected to a building. Villas and townhouses are designed in accordance with Part K, which this guide does not cover.⁴
• The Code does not apply to certain structures, including tents, cranes, storage racks, scaffolding, formwork and falsework. That is a scope statement, not an exemption from design or approval under other rules.⁸
• Loads during construction are a separate question. Part F lists ASCE 37, design loads on structures during construction, among its references.³ Dubai Municipality’s safety guide asks the contractor to measure wind on site and to suspend work on exposed steel in high winds.⁹