Shearing force in beams
When a beam is loaded the forces cause the beam to bend and to undergo vertical displacement.
These effects are due to vertical component of forces acting perpendicular to the longitudinal axis of the beam.
The vertical displacement tends to shear the beam. Shear means relative movement between two parts of a structural member.
Any beam must be designed in such a way that it can resist shear and bending.
In this experiment we shall analyse the shearing force in a beam.
In this experiment a horizontal beam has been actually cut into two parts (A) and (B) by a vertical cross section, and is then held together with springs (or spring balances) which must produce a system of forces equivalent to those which would exist internally in the beam at that section if it had not been cut. Since the forces in part (A) acting on part (B) must be equal and opposite to those in (B) acting on (A), it follows that the same values will be obtained by working to the right or left of the section plane. Given a horizontal beam with vertical loading the internal forces will be:
* For vertical equilibrium a shearing force in the section plan
* For equilibrium of moments a moment of resistance due to compression in the top half of the beam section and tension in the bottom half.
In the experimental beam the second system of forces is replaced by compression at a hinge in the beam and tension in the underslung spring (or spring balance)
1. To understand the action of shear in a beam.
2. To measure the shearing force at a normal section of a loaded beam and verify its agreement with theory.
1. A beam (2 parts: part (A) being smaller and part (B) larger)
2. Three 10N and three 20N weights
3. A pair of ball bearing rollers
4. Underslung tension spring
5. Spring balance
6. Three load hangers
7. Spirit level
The beam was set up so that the...