Influence lines of any functions in a flexural member are always needed to design bridges. When we design a continuous bridge with many spans, we have to solve a lot of simultaneous equations to obtain moments on supports to draw influence lines for a...
Influence lines of any functions in a flexural member are always needed to design bridges. When we design a continuous bridge with many spans, we have to solve a lot of simultaneous equations to obtain moments on supports to draw influence lines for any functions which are very tedious thing. But it can be found that we can obtain support moments without solving many simultaneous equations using particular properties (situations) of unloaded part of continuous beams. We can get support moments simply by multiplying constants which have always the same values by first-support moment. Regardless with lengths of spans only if having the same lengths, these first-supports moment on each sides can be obtained using 3-moment equations.