CMU Stair Tower

[TKIL53]

We are looking at analyizing an existing cmu block stair tower to potentially add two more stories to the structural. The existing tower is 8" reinforced cmu block and is roughly 30' tall. In running some preliminary numbers we are having a hard time getting the original structure to work from a lateral standpoint nevermind adding more stories. Is there a specific way of checking a stair tower like, we looked at it as individual shear walls to start, that we may be missing that could bring our design more in line with the original design intent?

 

[minorchord2000]

Are you accounting for wall bracing provided by the stair structure?

 

[mijowe]

Is the stair only supporting itself laterally, or is it helping laterally support additional parts of the building?

 

[JAE]

The shearwalls could be using "flanges" - the intersecting walls at either end of the shear wall. You can use 6t of the wall for this, where t = wall thickness.

 

[BAretired]

You do not supply enough information for an intelligent response. Please provide a plan view.

BA

 

[TKIL53]

The stair tower is only supporting itself laterally. We have not tried looking at the flanges yet but will. we also have not accounted for the stairs framing at this point as we are trying to figure out how to quantify its benefit.

 

[dik]

I've sometimes encountered where there is not enough load on the stair shaft to overcome tension. Is this the case?

Dik

 

[TKIL53]

The tension is the issue we are seeing at this point.

 

[jike]

TKIL53:

I thought that you said that it was reinforced? I assume that you meant vertically. What kind of reinforcement?

 

[Bagman2524]

Are the landings integral with the building floor/supported by the building floor? or are they supported by the CMU tower?

 

[TKIL53]

The walls are reinforced. We are in the process of determining what the reinforcing is as the original drawings are not available to us yet, so we have made assumptions to see if we are even in the ballpark.

The stair are supported off of the cmu walls.