[Music] erecting long span trusses is a difficult job trusses are awkward to maneuver and extremely unstable until secured the work is often performed at dangerous Heights in all types of weather and every year workers are seriously injured when a trust system [Music] collapses last year the WCB wrote 26 orders on projects with dangerously installed trusses how dangerous on one job site the whole bu building collapsed Engineers report that trusses collapse because of inadequate temporary bracing until all trusses are properly braced it might only take a gust of wind to cause the whole system to collapse
this video won't show you how to brace your trust project but we will show you the basic rules rules that if followed will keep you from having a trust system collapse before you begin the installation all exterior walls must be braced before the crane arrives consider where it will set up its swing radius must be out inside the limits of approach of any power line if you can't find a safe position contact the power [Music] company on trusses longer than 30 feet you should use an engineered spreader bar when hoisting trusses must be handled carefully
damaged trusses must be repaired and recertified or replaced in this example we'll install temporary bracing to the trusses on a pitched roof spanning 40 ft before the first truss is hoisted strong backs are secured to the side of the building the first truss is then hoisted and secured to the strong backs the crane must always hold the truss until all bracing is in place and the truss is secure the second truss is hoisted and braced to the first the top cord bracing must be spaced no more than 10 ft apart the bottom cord bracing is
then secured matching the top cord bracing the third truss is hoisted and braced back to the second cross braces are now installed on the first three [Music] trusses the cross bracing is placed on the webs of the trusses as close to the top and bottom cord bracing as possible I this creates a rigid unit from which the next trusses are [Music] supported continue installing trusses and bracing this example only shows the top cord bracing the bottom cord bracing is installed in the same manner diagonal top cord bracing must be installed at least every 20 ft
and at each end of the building after installing your first unit of three trusses with cross bracing you must continue installing cross braced units at least every 20 ft on some projects it may be impractical to brace the first truss to the side of the building here's an alternate method Hoist the first truss into position then using prefabricated braces secure the truss at no more than 10 ft intervals [Music] the second truss is placed into position along the end wall and braced back to the first truss install the third truss and Brace to the first
now cross brace the first three trusses and continue the installation remember unless you have the approval of an engineer you can't store material on the installed trusses on some construction sites it may be safer and more practical to pre-build sections of a truss system on this site the contractor has laid out all the trusses for the complete completed roof the trusses have been grouped together in units of four these units are braced and ready for installation the crane then hoists the solid unit of four trusses into position one of the benefits of this method is
that it shortens the amount of time workers spend at dangerous Heights erecting trusses will always present hazards but by following correct procedures for temporary bracing you and your crew can reduce the risk of a truss system collapse [Music]
