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Friction coefficient between concrete and bridge bearing shock pad

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grrams

Civil/Environmental
Jan 25, 2002
3
Railroad Bridge: Fixed, High-Load, Multi-Rotational Disc Bearing

Per AISC - Modern Steel Construction - OCtober 2004 - Steel Quiz - Question #9:

Part or all of the shear may be absorbed by the friction between the base plate and the foundation. In the rail bridge application the friction would be between the Masonry plate and the shock pad or the shock pad and the concrete pier cap.

Does anybody have any data on friction coefficients between these materials?
 
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By "shock pad" I'm assuming you mean something like a 1/8" unreinforced elastomeric or cotton duck pad placed between the masonry plate and concrete pier cap.

At first glance, I'm not sure if the thickness will affect this, but I've heard that the coefficient of friction between concrete or steel and elastomer is about 0.20. I think this is the basis for the Horiz. Load < (1/5)(Vert. Load) anchorage check in AASHTO 14.6.6.4, AASHTO LRFD 14.7.6.4, and AREMA (1999 - only one I have) Vol. 2 Chap. 19, Section 1.6.3.10.
 
The friction will be somewhere in 0.25 - 0.35 range, or even more, dependant on the surface treatment for the steel. For the concrete use upper boundary, so in the load path bearing plate - pad - concrete, the weakest point will be the boundary in between the pad and the steel plate You can increase the friction by roughening of the surface, or application of some kind of glue.
 
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