In the August 2013 SE University session, Scott Walkowicz, PE, from Walkowicz Consulting Engineers discussed bracing masonry walls under construction, and provided reasons why it is important for structural engineers to know about masonry bracing. One of the reasons discussed during the session is that it is important for the structural engineer to understand the issues and potential danger when visiting a construction site. During this session, Scott highlighted changes made in the 2012 Standard Practice for Bracing Masonry Walls Under Construction. Two of the changes include the definition of the “Restricted Zone,” and how the wind speed is measured on the job site.
Restricted Zone
The Restricted Zone is a limited access zone located around a masonry wall which remains in place from the time the wall is greater than 8 feet tall, until the final lateral support is in place for the wall. With the 2012 Standard, the restricted zone is equal to the height of the wall plus 4 feet, and the length of the wall plus 4 feet. The restricted zone can be set based on the final height of the wall, or can be started based on the current height, and extended outward as the wall height is increased.
The restricted zone should be evacuated during the initial period when the wind exceeds 20 MPH, and during the intermediate period when the wind exceeds 35 MPH.
Measurement of Wind Speed
Starting with the 2012 Standard, visual methods are no longer allowed in determining the wind speed. While in the past, visual methods like the Beaufort Wind Scale could be used, an Anemometer is now required, and is used to measure the wind near the walls under construction.
If you are visiting a job site, make sure to understand the location of the Restricted Zone in order to remain safe when wind speeds exceed the evacuation speeds.