The three hinged stiffening girder of a suspension bridge of span 120 m is subjected to two point loads of 250 kN and 300 kN at a distance of 25 m and 80 m from the left end. Find the shear force and bending moment for the girder at a distance of 40 m from the left end. The supporting cables has a central dip of 12 m. Find also the maximum tension in the cable and draw the B.M.D. for the girder.

(1)To find $V_A$ & $V_B$:

Considering the stiffening girder asasis beam supporting the given external loud system.

$\sum M_A=0$

$250\times 25+300\times 80-V_B\times 120=0$

$V_B=252kN(\uparrow)$

$\sum F_y=0(\uparrow +ve)$

$V_A-250-300+252=0$

$V_A=298kN(\rightarrow)$

(2) To find: H

B.M at centre of girder

$B.M_C=298\times 60-250\times 35=9130kN.m$

$B.M_D=298\times 25=7450kN.m$

$B.M_E=252\times 40=10080kN.m$

Horizontal sere-action at each end …