Design of Cleat

[teguh62]

Dear all,

I need some information about design of cleat such as codes or books.

Does anyone know?

Thank you in the advance

 

[MikeDB]

You will have to help me. What is a cleat?

 

[civilperson]

An attachment point on docks, wharves, ship decks for securing lines. Usually in a horizontal configuration with two external members for wrapping the line in a figure eight pattern. Use 125% of the largest line strength for design. Castings are available in every conceivable size and material that are certified. Why design and build your own?

 

[transmissiontowers]

Since this is the transmission tower forum, I doubt the cleat teguh62 was asking about was for ships. In a tower subgrade stub angle, they have angles welded to the main leg angle to act as shear keys to transfer the leg load into the concrete foundation.

Is that what you had in mind teguh62?

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I have been called "A storehouse of worthless information" many times.

 

[teguh62]

Dear all,

Thanks for all replies, really sorry, i have not get on line for e few weeks.

Cleat that i have meaned is exactly like transmissiontowers defined, but i do the joint between stub angle and cleat angle by bolt.

May i have further info, references or others?

Thank you

 

[transmissiontowers]

I would take the total uplift or compression in the tower leg and divide it by the number of bolts and size the bolt shear for that load.

A reference for this is ASCE 10 in section 7.2.3 The latest revision is 1997 but it is being updated right now and should be out soon.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[MikeDB]

The physical size of the cleat(s) would be a function of the strength of the concrete and the bearing area. ACI-318 could be used for allowable bearing on concrete.

Regarding the shear on the bolts, might be good to use a larger than normal safety factor to account for prying action.

For smaller loads, I have just used bolts thru the stub angle without a bearing angle or "cleat".

 

[teguh62]

Dear,

Thank's tranmissiontower and MikeDb.

I've been designing foundation for 275kV tranmission tower.
Regarding to soil report, i use pile foundation. For angle shear connector / "cleat angle", it needs 8 level of "cleats". 4 of them on pilecap and the others on column or chimney. Are there any considerations for chimney design regarding to 4 of "cleats" that lay down on it? like minimum concrete thickness/cover from edge of cleats or others?

Thak you

 

[MikeDB]

What is meant by "column or chimney"? Is this a concrete column above the pilecap? If so, wouldn't a base plate and anchor bolts in the pile cap be cheaper.

That seems like a lot of cleats. I would think that the load would not be evenly distributed and that the top cleat would have the largest load.

I assume that tension or uplift on the tower leg will control the concrete design, which will be a function of the amount of rebar and the area of the concrete. From a construction view, with 3" of cover on the rebar, say 1.5" for hoops and vertical rebar and a couple of inches clearance for the cleats, you would need a minimum horizontal cover of 6 to 8" to the cleat. You will need enough vertical cover to develop the tension capacity of the rebar, so depending on the size of rebar, you may need 24 to 36" of concrete above the top cleat in the column.

 

[teguh62]

Thank's MikeDb.

I look the same for distribution of tension force along the cleat, so i'am afraid of that is something that i've forgot to consider. I hope that i won't need that thick concrete above the top cleat, i used 130x130x10mm for stub angle and 110x110x10mm for the angle cleat, with these angle section, i will need about 950x950 mm concrete. If i used 1% for the rebar, i think i will have more rebar than its requirement for tension force so i can reduce the development length. Is it permissible?

For discussion, i've tried to calculate bearing stress on concrete along the cleat. I used perimeter of angle cleat and divide it by maximum allowable concrete stress(ACI, punching shear clause) and so i have very many cleats (more than 8 level). Is there anything wrong with the calculation?


Thank you

 

[MikeDB]

If more rebar is provided than required, I think that ACI does allow the development length to be reduced.

I don't think punching shear will be a limiting factor for you. Check the units on your math. Perimeter is in mm, stress is in mm^2. Do you need to multiply the perimeter by the depth of concrete in the direction of the force?

I don't do well in metrics, but your stub angle does not seem that large, so I am very surprised by the size and quantity of cleats. Bearing on concrete should be a function of the area of the cleat and the compressive strength of the concrete. With a cleat that is only 10mm thick, the bending stress on the angle will limit how large of an angle can be used.

 

[transmissiontowers]

We use drilled piers and stub angles with the cleats welded to the leg angle. Your 130x130 is around our 5"x5" angle and I haven't designed stub angles in many years but 4 cleats on each of the 2 outside faces does not sound too excessive.

If you are using driven concrete piles with a square pile cap, you might take MikeDB's suggestion and consider anchor bolts cast into the pile cap with a base shoe on the leveling nuts. If you are not familiar with a "base shoe", it is a length of angle welded to a big thick base plate with a full penetration weld. The plate is designed for bending and the centroid of the anchor bolts should coincide with the centroid of the leg angle.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[transmissiontowers]

Attached is a JPG of one of our old stub angles with 10 cleats on a 5x5x3/8 angle. The tower was designed in 1964 when I was still in high school.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[transmissiontowers]

Here is a detail of a base shoe for the same tower.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[teguh62]

Thank you MikeDB & transmissiontowers (really helpfull image)

 

[teguh62]

MikeDB,
Yes, I devide tension force by perimeter of cleat angle and by maximum allowable Vc (ACI, punching shear clause), so i have the depth of concrete.
About bearing on concrete, is it 5((f'c)^0.5) (ACI, plain concrete clause)?

transmissiontowers,
Thank you for the image, i can imagine it. May be I will attached my pic if i go with it.

Thank's for discussion