What is frictional resistance?
Frictional resistance is the resistance an object meets from the material it moves over or along. It depends on how hard the surfaces are pressed together, the roughness of both surfaces, and the slope. The Dutch term is wrijvingsweerstand.
In cone penetration testing
In geotechnics, frictional resistance is the force the soil exerts on the sleeve of the penetrometer. In an electric CPT it is measured with a friction sleeve just above the cone tip (local sleeve friction fs). Divided by the cone resistance it gives the friction ratio, an indicator of soil type.
In pile foundations
A pile carries load through end bearing and shaft friction. If the soil around the pile settles, it drags the pile down: negative skin friction. The structural engineer allows for both.
In everyday building
- Sliding: a retaining wall or ground slab stays put because friction exceeds the horizontal force. A slip membrane deliberately reduces friction so a slab can shrink without cracking.
- Slip resistance: for bathrooms, external steps and ramps, choose a floor finish with a suitable slip rating.
- Connections: preloaded bolts hold parts together by friction between the faces; paint or grease between them reduces it.
Related terms
- Shaft friction
- Friction ratio
- Foundations
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