vertical reaction

[dgkhan]

Need to find out what will be vertical reaction on this truss, manually

 

[structSU10]

student posts are not allowed. Correct me if this is for work, but it looks like a homework problem.

Review your classnotes.

 

[JoshPlumSE]

And such an easy problem too....

 

[rb1957]

it'd be easier if the vertical distances were 3m (and not 2.5m)

another day in paradise, or is paradise one day closer ?

 

[damorim]

lol JoshPlum

 

[WARose]

I came out with the reactions being 72 kN horizontally at each support (with opposite signs). And 30 kN vertically at the top support & 18 kN (vertically) at the bottom support.

 

[WARose]

student posts are not allowed. Correct me if this is for work, but it looks like a homework problem

I doubt it is. His posting history is just too long (i.e. too many years) to be a student.

 

[MotorCity]

I would like to believe its a homework problem, otherwise I would question the quality of the engineering curriculum these days

 

[JoelTXCive]

As a recent student, I always needed help......

Basic truss solving methodology: Find external reactions first, then dive into truss to find internal forces if needed for a problem.

For this problem you can start by taking a moment down at L5. Taking a moment at this point leaves only 1 unknown item, which is the x-component of the force at U4.

The vertical component of the reaction at U4 goes through L5 so it creates no moment. All that is unknown is the horizontal component at U4, which you can solve for.

Once you have the horizontal component at U4, you can find the axial force in element U3-U4 by using sines/cosines. Or you can use sines/cosines to find the vertical reaction at U4. You know the direction of the force at that point, which is along the line U3-U4 and you also now know the x-component of this force.

Hope that helps.....

 

[Shu Jiang PEng SE]

The picture shows How I get the answer. There are more than one methods to get the solution.

 

[rb1957]

I confirm WARose's solution ... now I see why they use 2.5m and not 3m !

another day in paradise, or is paradise one day closer ?

 

[WARose]

I confirm WARose's solution...

Excellent. In addition, I got:

U2-U3= 78 kN (T)

U1-L3= 15.6 kN (C)

U2-M1= 31.2 kN (C)

 

[Tmoose]

Quote: WARose and structSU10
student posts are not allowed. Correct me if this is for work, but it looks like a homework problem

I doubt it is. His posting history is just too long (i.e. too many years) to be a student.
===============

And dgkhan has received 11 votes on this very forum, to boot. At least 1 as far back as 2007

 

[rb1957]

i just used Xian's idea about the moment arm for U4-U3 ... 5:12:13 triangle, who'd've thunk it !?

previous to that I was working long hand ...
L1-U1 is 12*13/5 = 31.2kN T
L1-L2 is 12*12/5 = 28.8kN C
U1-L2 is 12kN T
L2-L3 is 28.8kN C
U2-U1 is 46.8kN T
U1-L3 is 15.6kN C
... oh god, this is boring ...



another day in paradise, or is paradise one day closer ?