Coefficient of Friction for Steel on Concrete 9

[dik]

A recent project has a small structure with equipment constructed on a steel 'skid'. I have to design restraints to keep it in place. I'm thinking that the coefficient of friction for the steel to concrete would be in the order of 0.2 to 0.25. I'll apply a FOS to this value. Does anyone have a reference for a coefficient of friction?

Thanks in advance.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[KootK]

I've been using this for a while now which suggests 0.45 instead of the commonly assumed 0.55: Link

 

[flight7]

Another link at AISC which may support 0.55 to 0.7 but you should read the whole article: Link

 

[dik]

Thanks, gentlemen (binary term)... 0.2 including a FOS seems more correct.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Lomarandil]

I think there's a substantial difference between concrete which is cast against steel, and presumably remains in a somewhat dry condition (for which the 0.45 range seems defensible), and for steel surfaces against previously placed concrete, potentially not clean or dry, for which I tend to also use 0.15-0.2

 

[dik]

thanks...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[LittleInch]

Can it get water or ice under it?

Or oil of any form?

Then even 0.2 might be optimistic?

does the skid move on the concrete? Can it smooth away any bits of sand or aggregate?

Friction is an unreliable friend - never there when you need them...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BAretired]

Friction is an unreliable friend.

Words to live by.

 

[HTURKAK]

Eurocode (EN 1993-1-8: 2003) Suggests the coefficient of friction between the base plate and grout layer a value of Cf.d = 0,20 for sand-cement mortar and a value of Cf.d = 0,30 for special grout.

But this is for base plate grouted after erection.. ( LI) has a valid point .. In case of equipment skid located on finished concrete surface , the friction will not be reliable...

I will suggest you to provide some post installed anchors etc..















Don't underestimate a nail. A nail saves a horseshoe, a horseshoe saves a horse, a horse saves a commander, a commander saves an army, an army saves a whole country.. GENGHIS KHAN

 

[dik]

Done... with load conditions and anchorage, friction was not part of the solution. Thanks very much gentlemen. I just like to put my duks in a row, first.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dvd]

This is a piece of powered equipment? Vibrating? My image is that the cement/sand/aggregate pulverizes and your cement/steel coefficient of friction becomes silica dust/polished steel coefficient of friction. Why wouldn't a restraint restrain the skid without friction involved?

 

[dik]

Not vibrating... loading is essentially static... thanks.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[oldrunner]

Should also check the thermal stresses. Might have to let one end slide and the other end be an anchor. The COTE of the concrete is unknown because you probably don't know which quarry the aggregate came from. This is currently a contentious discussion concerning transformers and their anchorage failures during Northridge. The steel manual stated value for concrete cote should actually be a range of values. Don't forget thermal expansion is in all directions.

 

[dik]

Thanks oldrunner... I'd considered thermal issues, but with the concrete and steel being at similar temperatures. Also, the structure is not large.

This did raise an issue, however. I've sent the client a note to see if an insulated 'skirt' is required.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[oldrunner]

Dik: That's the point. What is the maximum variation? The coefficient of expansion of concrete and steel are different and the concrete value is probably not what is in the back of the steel manual. Take the maximum differences in the maximum possible coefficient of expansion of concrete and between the coefficient of steel and use that value in the method of determining the ksi force with the temperature change for the pressure and length values which an example is also shown in the back of the steel manual. That force per psi is then multiplied by the area of the cross section of the skid which will give you the value the forces that the anchor bolts have to resist if they have snug bolt holes. I've got a TVA thermal analysis and recommendations document that you can download but I'm not in my office with the doc number.
This is a problem with anchorage with welding base plates to embeds. Look for broken welds or movement/spalling of the embeds or cracks in the foundation pad.

 

[dik]

often considered for shelf angles attached to grade beams for supporting veneer brickwork... not an issue in this case.

Thermal expansion or contraction is not considered an issue, other than maybe the cold transfer into the interior. Thanks

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[IFRs]

API 650 5.12.2:
Unless otherwise required, tanks that may be subject to sliding due to wind shall use a maximum allowable sliding friction of 0.40 multiplied by the force against the tank bottom

 

[HTURKAK]

My points for sliding resistance of API 650 tanks are ;

- The subject clause is 5.11.4 Sliding Friction
Unless otherwise required, tanks that may be subject to sliding due to wind shall use a maximum allowable sliding
friction of 0.40 multiplied by the force against the tank bottom. And 0.4 is MAXIMUM.

- API 650 tanks has cone down or cone up bottom . The sliding resistance is totally different if the bottom has cone shape.

- E.7.6 Sliding Resistance
The transfer of the total lateral shear force between the tank and the subgrade shall be considered.
For self-anchored flat-bottom steel tanks, the overall horizontal seismic shear force shall be resisted by friction
between the tank bottom and the foundation or subgrade. Self-anchored storage tanks shall be proportioned such
that the calculated seismic base shear, V, does not exceed Vs:
The friction coefficient, μ, shall not exceed 0.4. Lower values of the friction coefficient should be used if the interface
of the bottom to supporting foundation does not justify the friction value above (e.g., leak detection membrane
beneath the bottom with a lower friction factor, smooth bottoms, etc.).

So, friction coefficient, μ, 0.4 should not be applicable for smooth bottoms, or single slope tanks.

- API 650 suggests compacted sand layer under the bottom . The angle of friction conservatively 30 dgr. and TAN 30= 0.577. The use of friction coefficient, μ = 0.4 is conservatively OK for tanks having bottom cone up, cone down tanks, having compacted sand layer.


My opinion..






Don't underestimate a nail. A nail saves a horseshoe, a horseshoe saves a horse, a horse saves a commander, a commander saves an army, an army saves a whole country.. GENGHIS KHAN

 

[dik]

"My opinion.." and valued... thanks.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Zain_117]

Hello,
I am trying to model the interaction between prestressed CFRP strands and concrete in ABAQUS. I have some questions:
1. What would be the friction coefficient between concrete and CFRP strands in tangential behavior?
2. I am using Coeff. friction as 1.4, is it fine for tangential behavior (screenshot attached)?
3. In the case of cohesive behavior, what should be the values of Knn, Kss, and Ktt (default values as 1)for defining traction separation behavior?