Anti-skid

The slip resistance (symbol or ) is the physical resistance of a structure against horizontal displacement in the base or a joint . It is one of the criteria for verifying the stability of flat foundations , foundations , (angle) retaining walls , dams , dams , etc. ${\displaystyle \eta }$ ${\displaystyle \gamma }$

The mathematical proof of slip safety is called slip safety or shear strength proof . It must be met with certain safety factors, which vary in height depending on the load case ; Safety factors of 1.2, 1.5 or 2.0 are common. These numerical values ​​must be reached or exceeded, i.e. H. it must z. B. apply. ${\displaystyle \eta }$ ${\displaystyle \eta \geq 1{,}2}$

The sliding safety factor is the quotient of resisting (holding) and attacking (pushing) horizontal forces . The holding forces are added from two parts: one from friction and one from cohesion in the case of cohesive material:

${\displaystyle \eta ={\frac {\mu \cdot N+c\cdot A}{H}}}$

With

${\displaystyle \eta }$ = Sliding safety factor

µ = coefficient of friction (Coulomb friction)

N = sum of normal forces (vertical forces)

c = cohesion (or shear strength )

A = contact area

H = sum of the acting transverse forces (horizontal forces )

Instead of using forces, the verification can also be carried out using stresses :

${\displaystyle \Leftrightarrow \eta ={\frac {\mu \cdot \sigma +c}{\tau }}}$

With

• Normal stress ${\displaystyle \sigma ={\frac {N}{A}}}$
• Shear stress ${\displaystyle \tau ={\frac {H}{A}}}$

The slip safety verification is usually carried out in horizontal joints, in particular in base joints of buildings, or in a deeper layer of low shear strength. Such proof is also possible in inclined joints. Here the sliding safety increases or decreases according to the incline .

See also

Proof of stability

Web links

Shallow foundations (PDF file) Section I.4

Individual evidence

1. ^ Karl-Eugen Kurrer : The History of the Theory of Structures. Searching for Equilibrium , Ernst & Sohn , Berlin 2018, ISBN 978-3-433-03229-9 (here: p. 58)