Civil Engineering Reference
In-Depth Information
W
L
2
L
2
(a)
W
2
ve
Shear force diagram
ve
W
2
(b)
WL
4
Bending moment diagram
ve
F
IGURE
8.3
Bending test on a
beam, single load
(c)
Load
Shear tool
Test piece
Block
F
IGURE
8.4
Shear test
SHEAR TESTS
Two main types of shear test are used to determine the shear properties of materials.
One type investigates the direct or transverse shear strength of a material and is used
in connection with the shear strength of bolts, rivets and beams. A typical arrangement
is shown diagrammatically in Fig. 8.4 where the test piece is clamped to a block and the
load is applied through the shear tool until failure occurs. In the arrangement shown
the test piece is subjected to double shear, whereas if it is extended only partially across
the gap in the block it would be subjected to single shear. In either case the average
shear strength is taken as the maximum load divided by the shear resisting area.
The other type of shear test is used to evaluate the basic shear properties of a material,
such as the shearmodulus,
G
(Eq. (7.9)), the shear stress at yield and the ultimate shear
stress. In the usual form of test a solid circular-section test piece is placed in a torsion
machine and twisted by controlled increments of torque. The corresponding angles of
twist are recorded and torque-twist diagrams plotted from which the shear properties
of the material are obtained. The method is similar to that used to determine the
