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Building Alteration Question

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I have an existing building that requires some modifications, one of which affects the seismic load resisting system.  The building is tilt-up with a wood roof/diaphragm and was probably built in the late 1960’s to early 70’s.  There are 8 panels that make up one of the walls that resist the lateral loads for the building and in one of the panels that has an opening in it, the owner would like to increase the opening size.

 

According to IBC 1614.3 Alterations: “Alterations that increase the seismic force in any existing structural element by more than 5% or decrease the design strength of any existing structural element to resist seismic forces by more than 5% shall not be permitted unless the entire seismic-force-resisting system is determined to conform to Sections 1613 through 1623 for a new structure.” 

 

I can’t modify the opening size of the panel without reducing the panel strength by more than 5%, but I can modify the panel and keep the loads in other panels from increasing by more than 5%.  If I retrofit the panel to replace the strength lost by increasing the opening, it will likely become cost prohibitive for the owner.

 

The panels are connected to one another 3 times along the height, so my question is, what constitutes an element according to the IBC provision; is the whole wall (all 8 panels together) an element or are the individual panels elements?  Since a tilt-up system is somewhat discontinuous (depending on the rigidity of the connections), I am inclined to define the individual panels as the elements, but at the same time, I don’t want to be too conservative.  Any thoughts?

 

Thanks,

 

Greg

 

 

 

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Civil Engineering  •  Structural Engineering