Chapter-4
Bending Moment and Shear Force Diagram
S K Mondal’s
4.7 Load and Bending Moment diagram from Shear Force diagram OR Load and Shear Force diagram from Bending Moment diagram If S.F. Diagram for a beam is given, then (i)
If S.F. diagram consists of rectangle then the load will be point load
(ii)
If S.F diagram consists of inclined line then the load will be UDL on that portion
(iii)
If S.F diagram consists of parabolic curve then the load will be GVL
(iv)
If S.F diagram consists of cubic curve then the load distribute is parabolic. After finding load diagram we can draw B.M diagram easily.
If B.M Diagram for a beam is given, then (i)
If B.M diagram consists of inclined line then the load will be free point load
(ii)
If B.M diagram consists of parabolic curve then the load will be U.D.L.
(iii)
If B.M diagram consists of cubic curve then the load will be G.V.L.
(iv)
If B.M diagram consists of fourth degree polynomial then the load distribution is parabolic.
Let us take an example: Following is the S.F diagram of a beam is given. Find its loading diagram.
Answer: From A-E inclined straight line so load will be UDL and in AB = 2 m length load = 6 kN if UDL is w N/m then w.x = 6 or w u 2 = 6 or w = 3 kN/m after that S.F is constant so no force is there. At last a 6 kN for vertical force complete the diagram then the load diagram will be
As there is no support at left end it must be a cantilever beam. Page 156 of 429