The History of Wind Design

The Evolution of Wind Design in Structural Engineering

Wind design in structural engineering has undergone a dramatic transformation—from rough estimations to refined, risk-based methodologies. Here’s how it developed over the past century:

🔹 Pre-1950s: Uniform Pressure Assumptions

Early building codes, such as the 1927 Uniform Building Code (UBC), applied simplified wind pressures:

  • Buildings < 40 ft → 10 psf

  • Buildings > 40 ft → 20 psf

These pressures were conservative and uniform, with no consideration for building location, height variation, or dynamic effects.

By 1932, the UBC introduced slightly refined pressures and allowed a 33% increase in allowable stress when wind acted in combination with other loads.

🔹 1960s–1980s: Introduction of National Standards

The 1961 UBC adopted provisions from ANSI A58.1-1955, marking the beginning of national standard influence. However, wind design was still relatively prescriptive, with minimum pressures that could be adjusted by the building official.

By 1982, ANSI A58.1 incorporated a more detailed approach, including:

  • “Fastest mile” wind speed averaging

  • Mean recurrence interval (MRI) of 50 years

  • Approx. five pages of wind design provisions — a significant step forward

This represented a move from static pressures to more data-informed velocity-based design.

🔹 1995: Shift to 3-Second Gust Speeds

ASCE 7-95 was a milestone in wind design:

  • Replaced the fastest mile wind speed with the 3-second gust — more representative of damaging wind events

  • Introduced a clearer separation between Main Wind Force Resisting Systems (MWFRS) and Components & Cladding (C&C)

This change aligned wind load determination more closely with actual wind behavior and damage mechanisms.

🔹 2010: Alignment with LRFD Philosophy

ASCE 7-10 integrated wind design into the broader Load and Resistance Factor Design (LRFD) framework:

  • Eliminated ASD-level pressure tables

  • Wind speeds increased (by √1.6) to maintain equivalent forces under the new load combination

  • Resulted in a more consistent reliability across different load types

It was a major shift in both philosophy and practice, requiring recalibration of past expectations.

🔹 2016: Risk-Based Wind Mapping

In ASCE 7-16, a significant conceptual change occurred:

  • Removed the Importance Factor, I, from wind design

  • Introduced four distinct wind speed maps based on Risk Category (I–IV), with MRIs of 300 to 3,000 years

This allowed for more precise and performance-aligned design, particularly for essential facilities, without overloading standard occupancy structures.

🔹 2022: Tornado Loads and Resilience

ASCE 7-22 added:

  • Chapter 32: Tornado Load Provisions, applicable to Risk Category III & IV structures

  • Expanded focus from just hurricanes and synoptic winds to tornadic events, driven by resiliency goals

Tornado-resistant design is still in its early stages but marks a new chapter in addressing extreme wind phenomena.