Point Loads On Hollow Core

[Alexk2]

I need to put a small dunnage frame for some condensing units on the roof. The roof is 8" hollow core plank. Each leg has about 600 pound reaction. Are there any guide lines for point loads on hollow core plank?

 

[BSVBD]

How many legs and what is their proximity? What are the base plate dimensions?

What is going to be their location throughout the span? Close to bearing? Near mid-span?

Assuming (4) legs for a total of 2,400 LBS, depending on the proximity of the legs, the location throughout the precast span and considering the length of span, with this relatively "small" load, i would use "judgement" on whether the precast plank can support the load.

Consider the current existing loads, what will the shear be at existing precast bearing?

Do you have existing drawings specifying the psi of the plank? Do you know who the manufacturer / supplier of the plank is?

If i know the manufacturer / supplier / designer of the precast plank, i typically contact them and they tell me whether or not the plank can support the newly imposed load.

 

[cooperDBM]

The PCI Design Handbook (or CPCI Manual in Canada) provides a method for determining the effective width (load distribution) for point loads on hollowcore. You'll also need to consider punching shear or the local distribution of the load at each leg to get the bearing pressure down.

 

[jike]

Spancrete has done testing on this many years ago and has a data sheet on guidelines on how to design for point loads. Call your local rep. They should be able to help you.

 

[thaidavid40]

Not said above, but probably implied, is that I would center the post legs over the webs between cores of the hollow core planks, and not put them directly over the cores.
Dave

Thaidavid