parking garage

[Zulak]

I'm designing a two-story underground parking garage using precast tees, and exterior cast-in-place walls. My first thought was to design the exterior walls as restrained walls at the base, second level and the roof. But is it possible to introduce an axial load into the precast floor tees? Can the precasters accomodate this loading?
If this can't be done, I'll design the walls as a retaining wall with butresses, but would rather not.

 

[phuduhudu]

I would have thought it was easy enough to design the precast tees to take an axial load. The detailing of their fixing would need to take into account this axial load. Also the temporary condition would need to be taken care of before the Tees are in place. Carl Bauer

http://www.bauerconsultbotswana.com

 

[JAE]

Zulak
We just finished a parking garage design which sunk into a hillside creating the need for the precast girders and tees to take axial load (in the diaphragm of the deck) to resist lateral earth loads. At first, the precaster we were working with tried to avoid this, preferring to just design his members without axial. Eventually, they did accommodate it...we carefully indicated the earth loads on our plans for their use.

The connections between girders, cast walls, and double tees may have to be altered to take these forces into account.

 

[ishvaaag]

The problem with most of the big span structures I see mainly in too few vertical supports...this may have caused the failure at some parking in the Northridge earthquake. But most surely is more worrying the hammering of the floor mass on the supporting columns (here some walls as well) than the feasibility of their (beams') buckling.

In this case I would also consider the vertical unloading of the floors under seismic loads...it might create a unsafe condition.

 

[JAE]

ishvaaag,

I've been to a short seminar about Northridge where the speaker indicated some examples of failed parking garages. These apparently failed because the designer did not take into account second order Pdelta forces from the interior columns which were heavily loaded.

 

[RMPE]

JAE, out of curiosity how long was the garage out of the hillside? I've seen some bad problems with such an animal primarily due to expansion/contraction and bad details.