Page 7 - Mechanics of Structures – Chapter 1
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Mechanics of Civil Engineering Structures – Chapter 5



               Solution
                                                      Shear Stress Equation, τ =     .  .  
                                                                                      .  
                                                      Where,

                                                      S = Shear at 0.75 m from diagram is as shown in sketch by similar
                                                      triangular.
                                                                                    5
                                                      SF at 0.75 m = 3.75 kN = 3.75 x 10  N
                     7.5                     7.5       A = Area above the N.A or below N.A = 150*125= 18750 mm

                                                      y = Distance of C.G of Area considered from N.A = 125/2      =62.5 mm

                                                      b = width of c/s at N.A = 150 mm
                     0.75        0.75

                                                                                       3  150 (250) 3
                                                                                                                 4
                                                                                                            6
                        1.5 m                         Ixx = Second moment of area =    =         = 195.31 x 10  mm
                                                                                   12     12

                                                      Substitute,  τ N.A =     .  .  
                                                                              .  
                                                                    (3.75    10 )(18750)(62.50)
                                                                           3
                                                                                                     2
                                                                       =                  = 0.15 N/mm
                                                                                6
                                                                       ((195.31   10 )(150)


               7.3.2 Shear Stress for ‘T’ section of beam


               Example 5

               Draw shear stress distribution diagram for cross section of beam with T section flange, 90 mm x
               10 mm and web 80 mm x 10 mm, span of beam is 4m subjected to uniformly distributed load of
               20 kN/m over entire simply supported beam.

                                                     90 mm


                                                                             10 mm



                                                                            80 mm






                                                       10 mm



               NHO JKA PSAS                                                                             Page 7
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