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.

Shallow Frost Protected Foundation Design

Conventional Roof Structural Design

Nails Nails Nails!!!

Using the wrong nail is Common and can put you in a real tight Box and turn your project into a Sinker. Every hanger, shear wall, and framing connection deserves the right nail and without direction from your structural engineer you could be losing crucial capacity out of your connection.

The first step is understanding the different type of nails…

Common Nails - The first choice for many framing, construction and carpentry uses. The heavy shank provides sturdy support for framing and other rough work where strength and function are more important than appearance, because the round head is visible on the surface.

Box Nails - Look similar to common nails but have thinner shanks, making them less likely to cause splitting when driven into thinner pieces of wood. The thin shaft also means they aren't as strong. They are often galvanized to help prevent corrosion. 

Sinker Nails - Sinkers" are thinner than common nails, have a smaller, flat nail head and are often coated so they can be easily driven flush, or even counter-sunk.

Each type of nail has its own size per pennyweight and is best to ask the engineer to label the nail by diameter and shank length. As you can see in the chart below, provided by Simpson Strong Tie, the wrong nail can have major implications in the hanger capacity. If the wrong nail is used there can be a reduction as much as 64% if the nail is acceptable at all.

COVID-19 and Remote Office

Hope everyone is safe and healthy. Glenn Frank Engineering has temporarily transitioned into a remote office since March 16th, 2020. Although the remote office is new to us, we are working diligently to help our clients to the best of our abilities. We have and we continue to organize client meetings online where possible. Construction is ongoing in Boulder County and we are responding as such by making ourselves available for any essential site observations. However, the safety and well-being of our employees is our utmost priority so if a site observation is required, we would highly appreciate a call to discuss social distancing at the site.

Sincerely,
Glenn Frank Engineering Team