The threads I have read here on IEBC interpretation pretty much cover all extremes - some say that if the lateral demand does not increase more than 10% over the already 1000% utilization ratio, it is OK - others seem to stick with never letting it exceed 110% of material capacity as well as the 10% increase. Regardless, I wanted to ask this question as I think it is slightly different to other discussions.
I have an IEBC Alteration Level 2 building with unreinforced CMU walls and flexible diaphragm that is basically one large open rectangular space with perimeter walls. Although it is a simple structure, it is very large, so the diaphragm cannot span the 160ft between two end shear walls. One of the end walls has notable cracking for a variety of reasons: tall unreinforced parapet, potential foundation settlement, large retrofit rollup door openings, etc. There will be no alterations/modifications to the structure that will affect the loading of this wall. What I am struggling with is where it falls in the code:
1) My opinion is that this falls into the repair category. Although the damage is not "substantial", there is no way to repair it without doing a substantial retrofit. The state of the wall is ultimately the reason I feel the need to address it, not because of any alterations.
a) So if I retrofit it, I have to bring it up to reduced IBC EQ force capacity, and it certainly will not work as is. This means a new steel braced frame with wall girts or complete tear down and replace (it cannot be sawcut and reinforced for a variety of reasons); will also need huge new foundations. But what about the attachment to the diaphragm? 601.2 says repair should not be less conforming than before, which it will not be, but the building will still not comply with reduced IEBC EQ forces.
2) What about a voluntary LFRS alteration? 807.6 says capacity does not need to meet IBC, but then one of the requirements is that engineering analysis show that new structural elements are detailed and CONNECTED to existing structural elements as required by IBC. Since this would be a lateral force resisting element, it seems as though I have no way of connecting to the diaphragm per code requirements.
So is it basically not feasible to fix this wall without adding interior lateral force resisting elements to help the diaphragm out? (Enter typical complaint about how everywhere I go there are existing buildings being renovated with what seems like no concern for any loading event and I will another client for overdesigning).
I have an IEBC Alteration Level 2 building with unreinforced CMU walls and flexible diaphragm that is basically one large open rectangular space with perimeter walls. Although it is a simple structure, it is very large, so the diaphragm cannot span the 160ft between two end shear walls. One of the end walls has notable cracking for a variety of reasons: tall unreinforced parapet, potential foundation settlement, large retrofit rollup door openings, etc. There will be no alterations/modifications to the structure that will affect the loading of this wall. What I am struggling with is where it falls in the code:
1) My opinion is that this falls into the repair category. Although the damage is not "substantial", there is no way to repair it without doing a substantial retrofit. The state of the wall is ultimately the reason I feel the need to address it, not because of any alterations.
a) So if I retrofit it, I have to bring it up to reduced IBC EQ force capacity, and it certainly will not work as is. This means a new steel braced frame with wall girts or complete tear down and replace (it cannot be sawcut and reinforced for a variety of reasons); will also need huge new foundations. But what about the attachment to the diaphragm? 601.2 says repair should not be less conforming than before, which it will not be, but the building will still not comply with reduced IEBC EQ forces.
2) What about a voluntary LFRS alteration? 807.6 says capacity does not need to meet IBC, but then one of the requirements is that engineering analysis show that new structural elements are detailed and CONNECTED to existing structural elements as required by IBC. Since this would be a lateral force resisting element, it seems as though I have no way of connecting to the diaphragm per code requirements.
So is it basically not feasible to fix this wall without adding interior lateral force resisting elements to help the diaphragm out? (Enter typical complaint about how everywhere I go there are existing buildings being renovated with what seems like no concern for any loading event and I will another client for overdesigning).
