The concrete highway bridge show in Figure Q3a is supported on columns at B and E, and abutments at A and F. The bridge has joints at C and D, which can be modelled as pins. Figure Q3b shows an idealised model of the bridge deck. Draw influence lines for: i) the shear force across joint C; ii) the axial force in column E; iii) the bending moment in the beam over column B. I attempted part (i) and got: when x<15m shear force at C=0, when 15m<x<30m shear force at C=(30-x)/15 and finally when x>30m shear force at C=0. I assumed the moments about joints C and D will equal 0 as they are pinned. Can anyone tell me if I'm correct? Parts (ii) and (iii) are puzzling me though. Could anyone give me some advice/tips on how to get an expression for the axial force in column E and bending moment over column B for the influence line?