NinerStruct
Structural
- Nov 5, 2012
- 36
I have a project where we are adding to an existing building and adding on, for all structural intents, an ICC-500 rated shelter. The construction of the shelter is 12" CMU exterior walls, grouted solid, and 12" hollow core planks with 4" composite topping, all designed for 250 mph wind loads.
Because of the area requirements of the existing building, there needs to be a 2 hour firewall between the new shelter and the existing. Along most of the separation, the shelter wall is constructed parallel to the adjacent existing 8" CMU (grouted at 48" o.c.). We do have a corridor on the south side of the existing building that abuts the shelter. The fire door is located in the shelter wall as it crosses the corridor and there is no structural connection from the corridor to the shelter.
I've attached a sketch of the scenario.
The owner's rep has raised an issue with the fact that, because the original wall wasn't designed as a firewall and because of the non-shelter side of the corridor doesn't have a firewall, the shelter wall is the sole firewall. As such, because of the heavily reinforced connection at the roof (because it's a tornado shelter), if the shelter were to collapse due to a fire, it would pull down the firewall exposing the corridor to the fire. Therefore the building does not meet code.
Our argument is that the code 706.2 requires that the firewall be constructed to allow collapse on either side "under fire conditions" and because the construction of the shelter is all rater for at least 2 hours, if not more, it will not collapse during a two-hour fire event, so it doesn't have to be structurally independent, but still meets code. He says that he is unaware of any such exception.
I am just looking to get others' opinions on whether or not the current design meets code.
I appreciate the input!
Because of the area requirements of the existing building, there needs to be a 2 hour firewall between the new shelter and the existing. Along most of the separation, the shelter wall is constructed parallel to the adjacent existing 8" CMU (grouted at 48" o.c.). We do have a corridor on the south side of the existing building that abuts the shelter. The fire door is located in the shelter wall as it crosses the corridor and there is no structural connection from the corridor to the shelter.
I've attached a sketch of the scenario.
The owner's rep has raised an issue with the fact that, because the original wall wasn't designed as a firewall and because of the non-shelter side of the corridor doesn't have a firewall, the shelter wall is the sole firewall. As such, because of the heavily reinforced connection at the roof (because it's a tornado shelter), if the shelter were to collapse due to a fire, it would pull down the firewall exposing the corridor to the fire. Therefore the building does not meet code.
Our argument is that the code 706.2 requires that the firewall be constructed to allow collapse on either side "under fire conditions" and because the construction of the shelter is all rater for at least 2 hours, if not more, it will not collapse during a two-hour fire event, so it doesn't have to be structurally independent, but still meets code. He says that he is unaware of any such exception.
I am just looking to get others' opinions on whether or not the current design meets code.
I appreciate the input!
