Bearing stress in truss bottom chord

[AELLC]

What I have is ordinary light metal plate prefab wood trusses (mostly 2x4 members) spaced at 2' centers with 3 bearing points, and the interior bearing point is a 2x4 stud wall, and of course I can't change the wall to 2x6 because of the architect.

The truss calculations say the bearing length needs to be about 5", much more than the 3.5" actual. I calculate the bearing length required to be about 3.8".

Am I missing something? Is the bearing stress combined with the tension stress in some ratio?

I calculate reaction divided by allowable bearing stress to get required bearing area on the bottom edge of the truss bottom chord, and Load Duration Factor is not applicable. All working stress design.

 

[AELLC]

Mike-

Agreed. It is not a problem with full custom houses because I can specify anything necessary, but this case is a 10-year old design for a standard tract home which is being semi-customized for an owner, and I am working for the construction company. They don't tolerate changes to a design they assumed was good for 10 years. The original design was done by someone else and I didn't detect this wall problem at the time - and the truss calculations were not submitted to me until the plans checker noticed bearing overstress of the truss chords.

 

[AELLC]

dhengr:
No that would be too expensive - I am replacing the H2.5's with TBE4.