# Homework Help: Influence lines (concentrated load system)(with the problem this time)

1. Aug 15, 2013

I started by getting the equation for the reaction(which is really simple). I'm a bit confused here, they're asking for the absolute maximum moment, but they're not locating the location of where the maximum moment will occur, should I assume it's happening on the middle of the beam? And another question, how can I find the value of this maximum moment, I'm normally accustomed to a concentrated load, or a uniformally distributed load, but not a system of concentrated forces. Thank you.

https://www.dropbox.com/s/5rngrqme4fv929y/2013-08-15 17.52.30.jpg

2. Aug 15, 2013

### SteamKing

Staff Emeritus
No, the location of the maximum moment probably will not be in the center of the beam. The beam is not loaded symmetrically.

You are forgetting one critically aspect of analyzing beams. Multiple loads can be treated using the principle of superposition, i.e., find the effect of one load at a time on the beam, and then add up the effects of a series of single loads to find the total effect of ALL the loads on the beam.

The superposition principle also works with influence lines.

3. Aug 15, 2013

Could you provide some more information? Because I don't know where I should take the cut on the beam.
Ohh and something else should I find the center of gravity of the load system(Gx)? Is the location where maximum moment occur equal to Gx?

Last edited: Aug 15, 2013
4. Aug 15, 2013

### SteamKing

Staff Emeritus