November 8, 2018
Wind of change
There was a significant change to the way wind speeds were implemented in the ASCE7-10 standard which is referenced in some recent codes. Most notably, the wind speeds shown in the wind maps were increased; however, the new code has a 0.6 reduction factor for wind pressures in the load combinations. When these reduction factors are applied, they result in very similar wind pressures at 115 mph for ASCE7-10 as compared to the 90 mph wind speed as referenced in ASCE7-05. This change in wind map numbers is a change in how the engineering equations are put together, but the resulting forces are essentially unchanged.
Throughout Stageline’s current documentation, wind speeds listed are actual speeds (service level), which would be measured or reported by forecasts. In contrast, ASCE7-10 uses factored wind speeds that apply directly to engineering equations. In this case, a 90 mph actual wind corresponds with a 115 mph factored wind as used in ASCE7-10.
If all these equations and technical lingo look like Chinese to you, don’t worry you are normal! But hey, we have a full team of people playing with similar equations every day that are available to help and jump on a call.