3/8" diamond plate at 4' centers--not enough for a 9000lb forklift? 1

[SaMoSteps]

Hi,

I work in a building with a steel frame loading dock.
It is 12'x12' with four 8x13 I-beams (48"OC) and two posts (per beam, also the same 8x13 I-beams) at 5' and 12' from the building.
Each beam is tied to the building.

It has 3/8" diamond plate for the deck.

We have an opportunity to buy a 9000lb forklift (cheap) but from reading some posts here I think the 3/8" plate is not strong enough to support the forklift.

Is it possible to buy another 3/8" plates to cover the existing (and stitch weld) to use the forklift?
Or, weld in ribs/joists across the the 48" spans?

Thanx in advance.

CM

 

[thaidavid40]

You need to check out the load paths from the floor plate all the way to the footing (ground). There is much more to this than just the plate span. And you'll get more bang for the buck with intermediate filler beams than adding more and more heavy plate weight. Get someone structurally qualified to look at this in detail, as there is too much potential liability here to do this half-heartedly.
Dave

Thaidavid

 

[Ron]

Agree with Dave!

 

[SlideRuleEra]

I also agree with Dave. There is another side of your question that you must address:

Get the specs for the forklift. When a forklift is in use weight distribution to the axles is nowhere near equal. With a load at or near rated capacity the majority of the combined weight of the forklift plus the weight of the load is on the front axle. In other words, do the calcs to find the center of gravity of the loaded forklift and determine the weight distribution.

If the specs are not available, perform a simple test before purchase. Have the forklift pick up a heavy load while the front axle (but not the rear axle) is on a truck scale.

http://www.SlideRuleEra.net

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[SaMoSteps]

Thanx for the replies.

The foundation is three grade beams total (2 parallel to building and one tied to building at 90d and intersecting the two parallels), 18" wide and 24" deep,
The "feet/pads" below each post is 12"x12"x1/2"--four bolts at corners into concrete.

As stated, the beams and posts are 8/13s i-beams. Posts are set at 5' and 12 feet from building. Greatest span is less than 7'.

The diamond plate is stitch welded around all circumferences on the 4x8' plates (and one 4x4').

To the non-structural-trained eye, the framing is massive, and according to charts online the beams can hold 19800lbs with an 8' span.

It's the 3/8" plates that appear to be the weakest link.

I cannot even find a structural guy to come out and look in this area. They say they're too busy for such a small job! I'm still trying. Angie's list is worthless so far.

Thanx again. Must keep trying.

 

[oldestguy]

Is there the possibility of removing the existing plates, adding support members for smaller spacing? Certainly you can assume some width of "beam" and check the stresses as a start.

 

[SaMoSteps]

Oldestguy (quite an assumption! (-: )

The plates are stitch welded all around the circumferences, but yes, with time and lots of grinding wheels we can pull off the 3/8" plates.

I looked at charts (online) and "think" 4/9.5s I-beams at 24"oc should be more than adequate.

This is a bike shop. Our heaviest load doesn't come close to maximums. It would never be more than 1000lbs. The weight of the forklift is 9000lbs. At 10,000lbs total, I realize it's WAY better to be safe than sorry.

Can anyone recommend a structural guy in the Long Beach, CA area??

Again, thanx for your replies!

 

[oldestguy]

It's called a cutting torch for removal. Perhaps a reciprocation metal cutting saw would work also.

 

[SaMoSteps]

lol... thanx.

I was afraid of all that heat put into the beams and posts... not a concern?

 

[canwesteng]

I wouldn't look at the foundation for loads this small, and depending on the building probably not even check the columns. Judgement call though. I would say the cheapest thing to do is toss some grating over the checker plate, then check the beams for the extra weight of grating + the forklift. It's a cleanout nightmare though, so depending on your occupancy (warehouse vs mill) this may be a no go. If you access to the area below to add beams without chopping the plate that's option 2. Do what you can to avoid chopping up plate and replacing it, that would be the most costly option.

 

[SaMoSteps]

Canwesteng-

Yes, we can access underneath easily. That's how we determined the beam and post size: the painting/markings are all intact underneath.

We were thinking that (just adding cross beams from underneath) a better option than all the time spent removing the diamond plate.

-- 4/7.7s standard size is rated at 10,000lbs with a 4' span. This seems WAY more than adequate at 24"oc to support the 3/8"...

It's a warehouse--so other than dust and cobwebs, pretty clean all around. No limits/conflicts with time/space/downtime.

 

[SaMoSteps]

Check this out! (picture)

Because of boss's concerns Forklift Owner sent us a pic of the forklift ON a 3/8" diamond plate.

There is a 2x4 centered between the 96" span--just like the frame of existing dock.

We're going over later to check it out--see if the plate bends up at all.

 

[canwesteng]

If you want to proof test the plate, I'd load up the forklift such that you have a factor of safety of no less than 1.5, and make sure the grade of the tested plate lines up with the grade of existing.

 

[SaMoSteps]

Excellent points! Thanx!

 

[JLNJ]

As SRE said, be VERY careful with the front axel load calculations.

My Clark catalog as a 9000# capacity lift at >20,000# on the front axle!

It shows dual front wheels, but the contact patch is still going to be quite small.

3/8 plate is pretty skinny for such an operation.

 

[SaMoSteps]

Thanx, JLNJ,

The weight of the FL is 9000# as per tag on vehicle (not the lifting capacity).

The capacity to lift is (I think) 4500#. But we'd never use it for over 1000#--bike components. Our heaviest load to date was shy of 800 pounds.

 

[oldestguy]

For saving some bucks do the added reinforcing underneath in treated timber, sitting on sufficient concrete blocks to minimize deterioration. In frost country set the blocks as deep as convenient, not necessarily frost depth.

 

[3DDave]

There is a change in rigidity going onto and off the plate which can cause higher loads than you may expect.

The most likely case is that the fork truck is worth having around and any bracing will also be worth it.

 

[thaidavid40]

If you can't find a structural engineer in CA who is willing to look at this for you, then try to find a professor or semi-retired PE who would help you out. Many of these people take on little jobs like this on the side, and can do that for a very reasonable fee. Even if they do not take the job all the way for you, you can at least solicit some good ideas from them - after they have looked at the situation onsite, that is.
Dave

Thaidavid

 

[SaMoSteps]

Thanx again, all.

Looked at the plates for markings of what weight or capacity...nothing. Same with the plates the F L owner used as a demo.

He had a 4x8 plate set off the ground by 2x4s-- two 4' squares. F L didn't bend the plates noticeably (I mean, maybe by mm, but could not see with naked eye). And the demo isn't welded.

We're going to hire a certified welder to come in and brace the underside with 4/7.7s i-beams to create 4' squares (it's a 12'x 12' deck).

I'll report back in a bout two weeks.

Again, thank you! I love these boards!