huangyhg

can you modify structrual cross bracing?
can you modify the structural cross-bracing in a building in order to add an exit door?
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not without analyzing the building for the new brace configuration per the currently applicable bldg code.
this could be very difficult or impossible because the lateral force resisting system might've been designed under an older bldg code. newer bldg codes sometimes require much larger forces and/or more stringent detailing requirements.
might wanna look at other options if at all possible.
in agree with 271828.
you can modify it if you ensure the structure is not compromised.
i disagree in principle with 271828 on this one. unless your code specifically prohibits changes to an existing building without bringing the whole structure up to current standards, the general rule is that modifications should not adversely affect the existing structure. therefore, if you replace the capacity lost by a bay of cross bracing by e.g. adding equivalent bracing in a different bay which is designed to resist the same load and take it to the ground, i think you would be acting responsibly.
i should add a caveat that modifications of this sort should only be done if you assess the building as competent with reliable load paths, whether strong enough to meet modern codes or not.
you need to check both the structural framing and foundation, especially in the areas where you are removing the brace and adding others, to ensure the bracing mods do not adversely affect the stability of the building.
hokie66, i guess we'll just have to disagree on this one, lol!
i think i will plan a different option and leave the cross bracing as is. thanks for your help.
271828,
i don't disagree that the struts, columns, and footings have to be checked. i just have found that it is often possible. many times the other structural elements are not controlled by the bracing.
yeah, i agree with you. my original "re-analyze the whole bldg" was too broad.
when i read a question like that, i envision somebody either removing the brace and not doing anything or just moving the brace over a couple of bays and not analyzing anything.
if you live in a location like i do (wisconsin), where the old building code required that everything had to be designed for 20 psf wind load, most of the time bracing can be completely removed, or modified, because the ibc only requires 10 psf wind load. just make sure you justify by calculation what you are doing.
daveatkins
dave,
i believe that it would be wrong and unprofessional to so what you are suggesting. don't care what your code says, 10 psf is not enough wind anywhere on the face of this earth. and the code will probably change again in the other direction at some stage.

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