SUPPORT REACTIONS

Introduction- When a number of forces are acting on a body, and the body is supported on another body, then the second body exerts a force known as the reaction at the first body at the points of contact so that the first body is in equilibrium. The second body is known as support and the force exerted by the second body on the first body, is known as support reaction.

Types of supports

Though there are many types of supports, yet the following are important for the study of support reaction-

• Simple supports or knife edge supports
• Roller supports
• Pin joint[or hinged] support
• Fixed or built in support

{a} Simple support or knife edge support- A beam supported on the knife edges A and B is shown in fig. 1-a The reaction at A and B in case of knife edge support will be normal to the surface to the surface of the beam. The reactions Ra and Rb with free body diagram of the beam is shown in fig. 1-b

fig. 1-a &1-b

{b}Roller support- A beam supported on the rollers at point A and B is shown in fig.2-a The reactions in case of roller supports will be normal to the surface on which roller are placed as shown in fig. 2-b

fig. 2-a & 2-b

{c}Pin joint or hinged support- A beam which is hinged at point A, is shown in fig. 3-a The reaction at the hinged end may be either vertical or inclined depending upon the type of loading. If the load is vertical, then the reaction will also be vertical. But if the load is inclined, then the reaction at the hinged end will also be inclined.

fig. 3-a

{d}Fixed support- Fig.4-a shows the end A of a beam, which is fixed. Hence the support at A is known as a fixed support. In case of fixed support, the reaction will be inclined. Also the fixed support will provide a couple.

fig. 4-a

TYPES OF LOADING
The following are the important types of loading-
a .Concentrated or point load

Fig. a

b.Uniformly distributed load

Fig. b

c.Uniformly varying load

Fig. c

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