One way or two way design. 1

[insajn]

If I have a parking lot to design with hollow core slabs I have the dimensions in the attached file.

If the panel is 12 X 12.6 m and I placed the direction of the hollow slab parallel to the 12 m span and supported at the 12.6 m span beam. should I design it as a one way or a two way ?

I know it's supported on two parallel beams only but after putting the screed over the slab and beams wouldn't it behave as a two way ?

So I believe I should design it twice, considering first one way only to design the 12.6 m beams and then use the two way load distribution to design the 12 m beam ?

Am I right ?

 

[jayrod12]

Hollowcore slabs are a one way spanning element only.

 

[KootK]

My vote:

- Design the beams supporting the hollow core as though it's one way framed.

- Design the beams parallel to the hollow core as though it's two way framed in acknowledgement that you'll get some of that effect.

Just like you said.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[cliff234]

I would not use hollowcore plank for a parking deck. The cores will be conduits for water and the joints between the plank may eventually leak. There was a collapse several years ago of a plank-framed parking deck at the Algo Mall in Canada. That failure was discussed on this website. Google it.

With regard to the beams running parallel to the plank, what are those beams doing? The plank will probably have camber and there may be a gap between the top of those beams and bottom of the plank. Are these beams provided to tie all of the columns together, or for moment frames?

Will the plank be exposed to weather on the upper deck? Will de-icing salts be used?

 

[hokie66]

One way, and I agree with cliff234. Hollow core plank is a poor choice for parking decks.

 

[insajn]

Clif234

It's for a moment frame yes.


For the details of construction I know little about, this design is only just practicing new designs.

I will consider your opinions both, I think you are right maybe a waffle slab be better.
Thanks

 

[JLNJ]

If you stick with the hollow core planks, be careful with the loading, especially in shear. Without two-way action the wheel loads can start to be problematic.

I am traveling tomorrow to look at some planks cracked near the supports. I believe it is due to mid-sized trucks using the deck (not specifically part of the 100 psf live load design criteria) and the wheel loads near the supports overloading the planks in shear. Intuitively, the 100 psf should have been plenty of capacity, but you don't get much two-way action on a concentrated load near the supports.