Moment restraint offered by floor slabs

[ItsOnlyDirt]

Hi All

Can anyone give me any pointers on how I begin to estimate the values of moment restraint offered by floors slabs.

The situation is I am looking at a large diaphragm wall for a cut and cover tunnel. The floor slabs will be installed to accomodate the tunnel ventilation fans etc.

I am carrying out a WALLAP analysis and need some inital values to see how the wall behaves before looking into it in more detail.

Units as I understand them are kN/m/m run of wall/rad which I dont quite get either, so if anyone could point me in the right direction that would be great.

Cheers

 

[hokie66]

Floor slabs would serve as pinned supports for the diaphragm walls, but the connections of floor to wall should not be considered as moment connections. kN/m of wall length would be the units for the uniform reaction on the floor slab, but "/rad" means nothing to me.

 

[ItsOnlyDirt]

The floors will act as moment restraints with units kN/m/radian. Connections are not important to me as I'm looking at the wall deflections only not the structural connections.

Cheers

 

[hokie66]

As I said, the floors should not be considered as moment restraints. Without moment connections, they are not moment restraints. kN/m/radian is not a unit of moment.

 

[ItsOnlyDirt]

That much I do know.

It is a rotational restraint the software is trying to model, or moment spring, which must be related to the flexural stiffness of the floor slab, no?

 

[hokie66]

Just model the slab it as a pin support.

 

[ItsOnlyDirt]

i.e. a rigid support ??

I suspect all that will do is create huge bending moments in the wall lower down as the remainder of the wall flex's during construction.

No worries I'll grab one of our Structural guys.

 

[ItsOnlyDirt]

Ok I have it sus'd, pin support (i.e. no moment fixity) is the way to go for the level of detail I need.

Thanks for your help

 

[hokie66]

You are welcome.