efsinc
Structural
- Jun 1, 2008
- 68
My client has a roof structure over a busy retail store with existing 6x16s at 8' o.c. Spanning 30' in southern California which does not know how to spell snow. He wants to add HVAC loads to the roof.
The underside of the roof is very congested with ducts and conduits etcetera such that a system to sister strengthening members to the existing beam seems undesirable.
I have heard of engineers using some kind of post tensioning system to increase capacity in this condition.
As explained to me, a kind of Simpson hold down is attached up onto the bottom face of the beam at each end, a kind of "chair" is attached up onto the bottom face of the beam at midspan, and a cable is run from hold down to hold own over the chair and tensioned such that an upward force is induced at midspan at the "chair".
Is this system sound? Any advice on design procedures? I'd sure appreciate your comments on this.
The underside of the roof is very congested with ducts and conduits etcetera such that a system to sister strengthening members to the existing beam seems undesirable.
I have heard of engineers using some kind of post tensioning system to increase capacity in this condition.
As explained to me, a kind of Simpson hold down is attached up onto the bottom face of the beam at each end, a kind of "chair" is attached up onto the bottom face of the beam at midspan, and a cable is run from hold down to hold own over the chair and tensioned such that an upward force is induced at midspan at the "chair".
Is this system sound? Any advice on design procedures? I'd sure appreciate your comments on this.
