IBC 2009 Chapter 34
IBC 2009 Chapter 34
(OP)
I don't know why I am always having questions with Chapter 34 of the IBC but I do.
I was asked to look at an existing wood structure that was built in 1951. The existing structure has a hip roof formed out of plywood plate trusses with conventional framing at each hip end. There is some concern about an addition that is going onto the building and the additional loading the additional framing will be placing on the existing structure. We have been asked to submit a proposal to investigate the structure to make sure the roof is acceptable, if not, propose a fix for the roof to support the new loads.
The problems comes up because the GC has all of the original drawings from when the structure was built (amazing). At the end of each hip, the structure was suppose to have a double truss. A field visit reveals that there was only 1 truss installed. It has been this way for the past 60 years and there is no sign of distress in the roof.
We planned on trying to use section 3403.3 of the IBC (the 5% allowable increase) but now we are not sure if we can. What do others think?
I was asked to look at an existing wood structure that was built in 1951. The existing structure has a hip roof formed out of plywood plate trusses with conventional framing at each hip end. There is some concern about an addition that is going onto the building and the additional loading the additional framing will be placing on the existing structure. We have been asked to submit a proposal to investigate the structure to make sure the roof is acceptable, if not, propose a fix for the roof to support the new loads.
The problems comes up because the GC has all of the original drawings from when the structure was built (amazing). At the end of each hip, the structure was suppose to have a double truss. A field visit reveals that there was only 1 truss installed. It has been this way for the past 60 years and there is no sign of distress in the roof.
We planned on trying to use section 3403.3 of the IBC (the 5% allowable increase) but now we are not sure if we can. What do others think?






RE: IBC 2009 Chapter 34
If these are pre-fab, the shop may have value engineered the design and got 1 to work.
RE: IBC 2009 Chapter 34
RE: IBC 2009 Chapter 34
My suggestion, analyze the truss. If underdesigned, do not add load unless you take care of it by strenthening. If the truss is %50 percent underdesigned, I would not feel comfortable making the situation worse, the "straw that broke the camels back".
RE: IBC 2009 Chapter 34
Are the force per nail reasonable?
If you need to, you can download the 1944 NDS from http://www.awc.org/standards/nds.html. At the lower right of the page. Click on the “NDS Archives + Historical Design Values” button.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.