Wind Engineering
Understanding and designing for the forces wind puts on structures.
Quick Answer
Wind engineering is the study of how wind acts on buildings and other structures, and how to design for it. Engineers estimate wind pressures from site wind speeds, terrain exposure, and building shape, usually following ASCE 7. For unusual or very tall buildings, wind tunnel testing may refine the loads.
The Full Picture
Wind loads act as pressure on the windward face, suction on the leeward and side faces and roof, and sometimes as dynamic effects that cause a building to sway or vibrate. Wind engineering sets out how much force to design for and how that force travels through the structure to the foundation. It involves meteorology, fluid mechanics, and structural analysis.
For most buildings, engineers use the procedures in ASCE 7. Inputs include a mapped basic wind speed that depends on the building's Risk Category and location, an exposure category that reflects surrounding terrain such as open country or dense urban areas, and factors for topography, building height, and enclosure. The standard separates loads on the main wind force resisting system from higher local pressures on components and cladding, such as roof edges, corners, windows, and wall panels.
Very tall, slender, or unusually shaped buildings, or those with sensitive cladding, may call for wind tunnel testing, where a scale model is tested to measure pressures and dynamic response. Guidance on such tests is provided in ASCE/SEI 49. Hurricane-prone regions add requirements for windborne debris protection and, in some areas, special envelope provisions.
For contractors, wind design affects roof attachment, cladding anchorage, glazing selection, and temporary works. Construction-phase wind matters too, since partially complete structures, crane operations, and unbraced walls face wind loads before the final lateral system is in place. Precon teams look for wind-driven requirements in the specifications and the structural, architectural, and envelope drawings.
Real Examples
Common Misconceptions
People assume: Wind only pushes on a building from one side.
Actually: Wind creates positive pressure on some surfaces and suction on others, and the roof edges and corners often see the highest local suction.
People assume: Wind design is only a concern in hurricane zones.
Actually: Every building must be designed for wind loads. Coastal regions have higher design speeds and added provisions, but wind governs the design of many structures inland too.
Frequently Asked Questions
What standard governs wind loads in the US?
ASCE 7 sets the procedures for wind loads, and the International Building Code adopts it by reference. Local amendments may add requirements.
What is an exposure category?
It describes the terrain around a site, from open and flat to dense urban, which affects wind speed and pressure near the building. ASCE 7 defines Exposure B, C, and D.
What is the difference between MWFRS and components and cladding?
The main wind force resisting system is the structural system that carries overall wind loads. Components and cladding are individual elements, such as windows or roof panels, designed for higher local pressures.
When is wind tunnel testing needed?
It is considered for tall, slender, or irregularly shaped buildings, and where code procedures do not adequately capture the wind behavior. The engineer of record decides when it is warranted.