Basic mechanics - The Mechanics of Soils and Foundations - page 13

Figure 2.1 Stress and strain.

load δ F n are given by

δσ =− δ

F n
δ

(2.1)

A

δε =− δ

l

(2.2)

δ z

(Notice that negative signs have been added so that compressive stresses and strains
are positive quantities.) The changes of shear stress δτ and shear strain δγ due to a

change of load δ F s are given by

δτ =− δ

F s

(2.3)

δ A

δγ =− δ

h

(2.4)

δ z

(Notice that negative signs have been added so that positive shear stresses and shear
strains are associated with increases in the angles in the positive quadrants of the
element as shown.)