By Bodhi Goswami, PE, Project Engineer, Okamoto Structural Engineering
It is a well-known fact California witnesses frequent earthquakes leading to its stringent seismic design requirements for new and retrofit buildings. But is it equally well known that for smaller retail buildings and many residential buildings, wind load still governs the structural design? And such buildings can be constructed with much lesser cost thanks to the code cycle in effect since 2020. Per the new code ASCE 7-16, wind loads across most of western coastline have reduced significantly (up to 15%). Moreover, if you are planning to build your own small hill-top house and wake up to beautiful scenic beauties every morning, you are in luck. The new ASCE 7-16 code considers the reduction in air density at higher elevations leading to even lesser wind loads and more economic constructions. As an instance, a house in Big Bear will be subject to wind loads up to 20% less than a house in Irvine. There has never been a better time to build a tiny hill-top house! Check out our blog on the Tiny House Movement to know more about the new trend of tiny family homes in America.
The latest code cycle in effect since 2020 was based on completion of an updated study by more than a thousand weather recording stations across the country. The study included a detailed analysis of likelihood that a particular region would see a robust hurricane or thunderstorm in the near future. Though certain parts of the country were found to be more probable to see a hurricane resulting in increase in wind loads, fortunately the western coast proved to be subject to lesser winds per the hurricane model leading to this code change. This would cut the lateral forces on diaphragms and shear walls of many buildings across California leading to cost-reduction in construction.
Not only smaller buildings, but even large retail buildings can also benefit from this update in 2018 IBC. Installation of roof screens and upper-level storefront systems are very common tenant improvements that require structural supports and justifications. The higher the elevation of these elements, the more the wind load to be applied per code requirements. These elements will also need to be designed for much lesser loads as compared to the previous code cycle. This makes tenant improvements an economic solution as well.
It is no surprise that a preliminary design of a multistory residential building or a tenant improvement requiring a new storefront completed prior to 2020 can now be constructed much more economically. Though California witnesses the occasional windy days, especially at the coast, we are geographically located such that it does not favor many hurricanes and thunderstorms as compared to other parts of the country. As structural engineers who thrive to provide economic solutions to our clients, we appreciate the efforts of the team involved to bring forward a more accurate hurricane model separating parts of the country who are not expected to see a hurricane/thunderstorm in near future.