ljk80oze
Structural
- Aug 29, 2007
- 12
- 0
- 0
Hi
I have recently observed a number of precast tilt-up buildings with secondary flexible fire ties between panels. The ties seem to be used on every join and i am a bit confused about the intent - i was hoping someone would be able to sort me out
I understand that the purpose of these ties is to prevent the panels collapsing on would be fire fighters due to panel distortion and subsequent bolt failure. It makes sense that a fire source inside the building would result in the panels bowing inwards and trying to rotate the connections at the top and bottom of the panel depending on the fixity. What i don't understand is why these types of backup measures are required at 'pinned' connections. For example i am designing a simple precast structure with tilt up concrete walls with a steel roof structure providing a diaphragm and transferring all bracing forces to the return walls. This seems to be the standard form of tilt up construction going around. The purlins fix into the side of the walls with a continuous raking angle. The connection is definitely defined as 'pinned' from the wall perspective. If this brace offers no rotational restraint to the wall how can it fail before the steelwork (ie by sudden bolt failure)? I haven't yet calculated the lateral force induced in the bolts by the thermal distortion but it seems improbable that this would govern (sounds like famous last words....beginning to regret not checking it
Anyway this tie is common practice for this type of construction so it is clear that i am off track somewhere... Any suggestions?
Many Thanks!
LJK
I have recently observed a number of precast tilt-up buildings with secondary flexible fire ties between panels. The ties seem to be used on every join and i am a bit confused about the intent - i was hoping someone would be able to sort me out
I understand that the purpose of these ties is to prevent the panels collapsing on would be fire fighters due to panel distortion and subsequent bolt failure. It makes sense that a fire source inside the building would result in the panels bowing inwards and trying to rotate the connections at the top and bottom of the panel depending on the fixity. What i don't understand is why these types of backup measures are required at 'pinned' connections. For example i am designing a simple precast structure with tilt up concrete walls with a steel roof structure providing a diaphragm and transferring all bracing forces to the return walls. This seems to be the standard form of tilt up construction going around. The purlins fix into the side of the walls with a continuous raking angle. The connection is definitely defined as 'pinned' from the wall perspective. If this brace offers no rotational restraint to the wall how can it fail before the steelwork (ie by sudden bolt failure)? I haven't yet calculated the lateral force induced in the bolts by the thermal distortion but it seems improbable that this would govern (sounds like famous last words....beginning to regret not checking it
Anyway this tie is common practice for this type of construction so it is clear that i am off track somewhere... Any suggestions?
Many Thanks!
LJK
