Ship bow supporting blocks

[valkyrie77]

Hi all,
Does anyone here know what kind/type of concrete used for the bow supporting block in dock yard?
If I'm going to use a 1m x 1m x 1m cube block,what type of concrete should I used?

Thanks all!

 

[Ussuri]

Will it be submerged for any significant design? Use a marine grade of concrete. Durability

You have already decided what size block you want, you surely know the weight of the vessel so you can work out the required compressive strength.

If you don't really have much of a clue, contact the quarry/mix supplier who will design a suitable mix for you.

You will also need to consider your requirement for reinforcement, which will be dependent on load and any requirements to control cracking (large cracks will allow water ingress and cause reinforcement corrosion). You may find pure mass concrete is suitable.

 

[valkyrie77]

Dear Ussuri,
Thanks for your advise.
The blocks are used to support ships during works in dry dock,so, they are not submerged for any significant design. However, you've enlightened me about the issue. I will find out more about it.The blocks will only be in the water for a short period of time (say an hour or so).
I am new in this field,so, I really appreciate any useful reply here.
As far, the suggested load capacity of the block is 2500 metric tons (can consider it as static load). I'm not sure if pure mass concrete would be suitable?

Thanks in advance!

 

[cvg]

concrete can handle some very large loads, but you will need to distribute the point load. This would be an iterative procedure. You may also want to distribute the load to your dock. Use the strongest concrete you can reasonably obtain and then begin your design. You may want to get a structural engineer involved with this.

 

[civilperson]

Any strength of concrete will suffice. Try lightweight mix design for ease of handling. Use a little reinforcement to keep the face cracks small.

 

[cvg]

I'm not a structural engineer, but I believe the stated load of 2,500 metric tonnes is approximately 5.5 million pounds which if distributed uniformly over the entire 1-square meter block would be over 3,500 psi. If not distributed uniformly, a concentrated load would be much greater than this value. IMO You should not be using light weight concrete and frankly I would not skimp on steel reinforcement either.

 

[hokie66]

Yes, sticking with metric, that is 25 MPa. So using say 50 MPa concrete is appropriate, and reinforce well for load concentrations if you don't want the block to split.

 

[Ussuri]

Probably not an issue, but you may want to check that whatever your block is placed on is also strong enough. No point having a block that is strong enough in compression, sitting on a foundation that is too weak.

 

[valkyrie77]

dear all,
thanks for all your kind response!
though i've found a suitable design,grade of concrete and etc... the job has been cancelled. a big blow, but look at the bright side: i've learned a good experience and skills..
(i've even finished the design for the molds).

again, i thank you all for the supports/ infos given!