Suspended slab for trucks - Surface Drainage suggestion 2

[DNC Consulting Engineers]

Hi all,

I am currently working on a project to build a Bondek suspended slab over a storage area with warehouses above. The suspended slab should be able to withstand trucks driving over.

I came up with the following ideas, can someone suggest any issue or have any recommendations:
1. Build the warehouse slab 100 to 150mm higher than driveway slab (structural slab)
2. Trench grate drainage in the middle (my main question is can I have the trench grate above the structural slab or it has to be flush with the top of the structural slab as this would be the lowest point?)
3. Install asphalt to create fall from the warehouse slab toward the trench grate.

The issue I have is if I have the trench grate embedded in the structural slab then it will weaken the slab as it is 90deg to the bondek direction but if I have it above the structural slab then water might pond under the asphalt pavement. (option 1 in the attachment)

https://files.engineering.com/getfi...7-ab2c6bc10ac8&file=TRENCH_GRATE_OPTION_1.jpg

https://files.engineering.com/getfi...&file=TRENCH_GRATE_OPTION_1_CROSS_SECTION.jpg

Also, my understanding on the asphalt pavement is it need to be minimum 60mm (is it sufficient for truck driving above)?

I have also had another option (option 2) by running the trench grate parallel to the bondek, doing this, I will only weaken the bondek locally so it is not so bad. Same question, do I need to have the trench grate embeded into the structural slab?

https://files.engineering.com/getfi...a-292c1ad97ddd&file=TRENCH_GRATE_OPTION_2.jpg

Thank you so much !

 

[HTURKAK]

My suggestion would be ;


1. Build the warehouse slab 100 to 150mm higher than driveway slab (structural slab)
- Build the warehouse slab 150mm higher than driveway slab

2. Trench grate drainage in the middle (my main question is can I have the trench grate above the structural slab or it has to be flush with the top of the structural slab as this would be the lowest point?)
- Provide gullies at every 4-5 m in the middle drainage ditch and a common header drain pipe under the driveway slab,
3. Install asphalt to create fall from the warehouse slab toward the trench grate.][/quote]
- Install asphalt to create fall from the warehouse slab toward the center ditch but provide min. asphalt thick. say 50 mm

My opinion only.

..


He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[JAE]

Asphalt will eventually dry out and crack - becoming less and less impermeable.

Option 1
What I've seen and done in the past is construct the lower structural slab, then a waterproof membrane, then a drainboard, then a topping slab which is sloped to various strategically located drains.
Then the drain plumbing would be suspended below the structural slab.

The drains are fitted such that the membrane flashes over flanges that sit on top of the structural slab.

Topping slab is sawcut with joints and sealed similar to any other pavement slab.

Option 2
Alternatively, you could simply build the structural slab and have the contractor slope its top surface to area drains and then use a traffic-bearing waterproof elastomeric membrane on the exposed surface, flashed into the drains.

Option 1 is nice because if your topping slab gets weathered and cracked you can replace it - not interfering with the structural slab.
Downside is that if the membrane leaks somewhere (and it probably will someday) it's hard to determine exactly where that leak is and you have to begin removing topping slab to repair it. Somewhat expensive.

Option 2 is nice because the waterproofing is visible - and inspectable - allowing you to react and repair any leaks immediately.
Downside is that it is a bit more difficult for initial construction - sloping a structural slab - but it can be done.

You didn't say what was below the slab - occupied space or a crawlspace etc. If occupied and you need to insulate there are systems out there that combine the intersitial membrane with rigid insulation and drainboards.

 

[DNC Consulting Engineers]

Thanks Jae !

I spoke to one of my concreter who has done a few jobs like this before and he suggested to do a slope slab instead. Having a topping slab can be a problem due to delamination between the 2 slabs (even asphalt unless it is very thick). Also, if there is a cracks in the slab, it is actually difficult to identify for repairing. So I ended up using option 2.

This is actually a large suspended slab (6000m2 with underground storage compartments and industrial warehouses above). I am still in the conceptual stage but planning to use bondek, bandbeams over concrete columns. Dont mind the location of the Movement joint because it is my next question. I am planning to locate them between grid CD, FG (roughly 1/6 away from any beam), that would make my maximum spacing for the MJ is approx. 25m max (slab is 350mm thick). However, for the East-West, I only placed them at gid 5 which is a step down in the slab. That would make maximum slab panel to 45m which is quite far apart. Do you have any recommendation on the MJ for thermal expansion for slab with this size?

https://files.engineering.com/getfi...2&file=Suspended_ground_floor_slab_layout.pdf

Much appreciated !