Saturday, December 10, 2011

RE: Jacking System Detailing

I have had to do this myself some years ago.  The pros in the industry are Patent Scaffolding.
They will develop what you need, and you rent the scaffolding.  You can focus on the platform at the top to serve as a base for the hydraulic jacks.  Lifting a truss is a delicate process. Use load cells to determine the actual load you are applying. 
I once worked on a bomber plant and was reviewing the shop drawings that were dated early December 1941.  There were half a dozen sheets approved on Dec. 4, 5, etc.  On December 8, 1941 over 150 sheets were approved with no exception.  ....interesting. 

Regards, Harold Sprague
> Subject: Jacking System Detailing
> Date: Fri, 9 Dec 2011 12:25:47 -0500
> From:
> To:
> I am designing a shoring and jacking system for a damaged heavy timber truss. The truss is a WWII vintage multi-ply truss with split ring connections, etc. As is often the case with such trusses, the subject is suffering from a tension chord rupture. One of the two bottom chord plies has completely ruptured, and hence the remaining bottom chord ply and its split ring connections have assumed the full tension load.
> In order to repair the damage, the first step is to support and minimally raise the truss to relieve the presently overstressed members and connections. My intent is to design a structural steel frame to pick up the truss at the structurally appropriate locations, and use bottle jacks supported from shoring platforms to gently raise the frame. I am comfortable with the design of the shoring platforms; however, I would like to know of any references that might be helpful in detailing the support assembly consisting of the bottle jacks and steel frame. My primary concern is stability at the bearings of the steel frame on the jacks.
> Thanks in advance for your assistance,
> Brian Felker, P.E.
> Design Manager/Structural Engineer
> 9742 Maryland Ave, Bldg Z-140
> Norfolk, VA 23511-3095
> (p) 757.341.2047
> (f) 757.341.2095