I have a simple situation but not s

[Lutfi]

I have a simple situation but not sure what experience everyone had with it. I am designing mechanical pipe rack supports that will be installed on hollow core concrete slab roof.

I want to attach the base of stub column to directly to the hollow core using expansion bolt type system. Here are my questions:

a) Does Hilti or other suppliers make anchors that are exclusive for use with hollow cores? If so, I would like to know the model number.

b) Is it better to use thru bolts and anchor them from the top and underside of the hollow core slab?

c) Any words of wisdom such as to avoid cutting the strands?

Thanks

 

[dlew]

Lufti,

Hollowcore slabs have the prestressing wires concentrated at the top and bottom of the webs. Any drilling must be done through the voids.

Unless the uplift force in the anchor bolts is so small that you can use toggle bolts, it would be better to install thru-bolts and put a anchor plate under the slab.

Regards

AEF

 

[jheidt2543]

Here are a couple more things to think about:

1. Make sure the precaster is made aware of the size and location of your pipe supports, they are a concentrated load at that point.

2. Through bolting is a much surer way to go, with a plate washer on the bolt at the slab underside to distribute the load over a wider area.

 

[Lutfi]

Guys,

You all are great. It is my conculsion to use thru bolts and plate washer on the bottom of the hollow core. I found out that the existing hollow core to web is only 1.25 inches thick which is not much to resist any uplift.

The gravity load is less than few hundred pounds and it should be no issue.

Thanks alot gang