Compression strength of concrete cube 3

[edison123]

We want to tilt a 100 ton vertical generator rotor to horizontal position by placing it on 40 inch x 40 inch x 40 inch rebarred concrete cube.

The rotor will be hung from a crane at the top and it will be turned on its coupling flange till it is horizontal.

Will this concrete cube hold the 100 ton weight ?

What I am worried about is the pressure at the point of contact of the coupling flange with the concrete block. The whole weight, at least for some time, will be concentrated at this line contact.

 

[SlideRuleEra]

Having the line of contact being directly on the concrete cube is not a good idea. However, if you have a suitably sized steel base plate installed on top of the cube, and have the line of contact on top of this steel plate, it should work. Best to get your civil/structural engineer involved to design the base plate and to ensure that whatever the cube sits on is adequate for the load.

http://www.SlideRuleEra.net

 

[edison123]

Thx SlideRuleEra.

If I place a 10 inch x 10 inch dry, solid wood along the axis of tilt, will it distribute the load over the block ?

 

[Ron]

If you had the load distributed evenly across the cube face, your contact stress is only 125 psi. Depending on the dimensions of the flange, the actual contact stress could remain low or be very high.

Assuming your 10x10 piece of wood is 10x10x40, you would have a contact stress of 500 psi, still relatively small.

If your contact face of the wood is 10x10, then your stress goes to 2000 psi, still not enough to locally fail the concrete in compression; however, you are skirting with overstressing the wood!

Since the cube is reinforced, shear would not be a big deal as your shear area is large and the rebar will help.

We load test concrete piles to 100 tons routinely. They typically range in butt size from 10x10 to 24x24 or are 12 to 20 inches in diameter. About the only time we fail the concrete is when there is an anomaly in the concrete, usually near the top of the pile.

In short, use SlideRuleEra's suggestion of a steel plate for load distribution and you'll likely be OK. Even a 1/4" thick steel plate will help you considerably.

 

[edison123]

Thx Ron.

I will use a 1/2" steel plate on top of the block and then on top of this plate, a 10" x 10" x 40" solid wood.

Hopefully this would distribute the load.

Will let you know how this works.

 

[cvg]

it seems like the steel will distribute the load, you don't need wood also

 

[TFL]

i think the wood is probably to protect his machinery. could be worng though

 

[cvg]

10" x 10" wood will help protect the machinery, but 40 inches thick as stated above is overkill. I would suggest a steel base plate with a 2" x 10" or 4" x 10" wood member on top

 

[edison123]

Thx cvg & TFL

Yes, the wood is to protect the shaft and it is 10" x 10" which is 40" long to suit the top surface of concrete block.

Sometime today, I should have a picture of this arrangement and will post it here.

 

[edison123]

The framework for holding the steel plate (20 mm thick) and the wooden block is getting ready. It should be done by tomorrow.

What do you think is the best wood for this application (high compression)?

 

[itsmoked]

#1 Teak
#2 Oak

 

[edison123]

Thx itsmoked. I see that you are curious about this.

Now that you are here (???), I wanted to ask you how got those pictures directly (not through links) into your posts.

I should be ready with the pictures of my arrangement soon and I realised that despite my brave words, I didn't know how to post them here.

 

[itsmoked]

Hi edison123!

We have to stop meeting in here... People will talk.

I wrote the following faq just for posting stuff.
faq238-1161

 

[edison123]

Thx once again itsmoked (you used to be an electrician ???).

Point 8 of your faq was good. I always goof up on my posts.

One more star for you and what a place to pick it up.

I should have the jig (and the jpg) ready in another 4 hours.

Don't wait up too long.

cheers.

 

[edison123]

You can see the pictures directly in

thread238-140877

 

[edison123]

Now I learnt the tricks, you can see the pictures here also.

The 1st one shows the concrete block in white. On top of it is the the 20 mm steel plate and the newly made angled brace to retain the 10" wooden sleepers.

The 2nd one below shows the wooden sleepers in place with the groove in front where the coupling rim will sit during tilting.

Will this work ? The crane operator is very good.

 

[edison123]

Thx to all MVP's here, the job was done today.

Here is the sequence (I have RF'ed by previous pictures) to reduce the thread download time).

But for the damned wood crushing, it would have been "picture perfect" ending.

Thank you all once again for your valuable tips and advice.

 

[itsmoked]

edison123 thanks for the hassle of putting in the pics. There great!

That is one big muther!!

I would expect and personally desire some crushed wood. It totally limits sliding and helps reduce rolling.

Hey where did you say your job site is?

 

[edison123]

Yeah, it is a 100 ton monstress (???) and I get to 'do her' three times in next one year. It is in Malaysia.

You could put a +ve spin (half glass full) on the crushed wood, I guess. That wood is a goner anyway.

I am now having a coupla' beers for having got thru' the day without killing anyone.

 

[itsmoked]

HA! CHEERS.