Effective Moment of Inertia - Precast Stairwell
Effective Moment of Inertia - Precast Stairwell
(OP)
Lets say you have a stairwell, made out of 4 precast walls. These walls are connected at the corners with welded steel connections, designed for the forces experienced at the joint interfaces.
What would the effective moment of inertia of the box be in this case? If I compare the above system to a solid cast-in-place concrete monolithic box, I would guess that the precast system would have an effective moment of inertia somewhat less than the CIP option. This is due to the fact that the connections would be designed to yield under the ultimate loads, and then they would allow relative displacements between the members.
To calculate the forces on the connections, I would assume you need to look at Vq/Ib. So then you need to know what the moment of inertia "I" is to get a force, but you don't really know what "I" is until you design a connection??
What is normally done for this type of situation?
What would the effective moment of inertia of the box be in this case? If I compare the above system to a solid cast-in-place concrete monolithic box, I would guess that the precast system would have an effective moment of inertia somewhat less than the CIP option. This is due to the fact that the connections would be designed to yield under the ultimate loads, and then they would allow relative displacements between the members.
To calculate the forces on the connections, I would assume you need to look at Vq/Ib. So then you need to know what the moment of inertia "I" is to get a force, but you don't really know what "I" is until you design a connection??
What is normally done for this type of situation?






RE: Effective Moment of Inertia - Precast Stairwell
The Moment of Inertia is not affected by the connections.
Design the connections for the Moment of Inertia.
Don't forget to check the bearing resistance of the concrete, as the bolts bear on the concrete, as well.
HTH
VOD
RE: Effective Moment of Inertia - Precast Stairwell
The shear connectors need to be designed assuming that full section (all elements in the box) will contribute to moment of inertia.
RE: Effective Moment of Inertia - Precast Stairwell
RE: Effective Moment of Inertia - Precast Stairwell