# Homework Help: Influence line for trusses

1. Jan 23, 2017

### fonseh

1. The problem statement, all variables and given/known data
Pls refer to the second photo , the red line part ....I don't understand the meaning of when 1 unit load move at C , the unit load is inclusive in the right system... I can understand the FBG sin45 + 1 = RE

2. Relevant equations

3. The attempt at a solution
When the in unit load move at b , shouldn't the equation become like this ? FBG sin45 + 1 = RE

Why the author didn't consider the unit load when the unit load is moved to B ?

#### Attached Files:

File size:
31.9 KB
Views:
54
File size:
33 KB
Views:
67
• ###### 553.jpg
File size:
32.4 KB
Views:
60
2. Jan 24, 2017

### fonseh

When 1 unit load moved to B , the equation of vertical forces should be like this , right ? 1-FBGsin45 - FBH = 0.25 , i dont understand why the author used 0.25-FGBsin45 = 0 , by dosing so , he ignored the unit load and also the FBH.... How can it be correct ?

3. Jan 26, 2017

BUMP