Triangle Cantilever Truss Design

[caseyvoigt]

1. I am an architecture student and the assignment is to design a truss, set up the problem and solve it using graphic statics. I think I did it correctly using the graphical method but I am interested in solving it mathematically. Did I set the problem up correctly in my diagram and if so, where do I go from here? I know that if this was just a simple overhang, I would not need the members AD and BD but the top chord is supporting joists so I thought the chords AD and BD were necessary.




2. \summ=0
\sumFv=0
\sumFh=0
m=moments
v=vertical
h=horizontal


3. I Just used sum or forces in vertical and horizontal I removed chord AD because I realized it did not do anything. The new link Shows my work. I am concerned because I feel like the top chords (a,b and a,c) ahould not be equal for some reason but it does make sense that they are too. Did I do this problem correctly?


MY WORK

http://i1128.photobucket.com/albums/m490/caseyvoigt/TrussBwithwork.jpg"

 

[pongo38]

If you intended the structure to have pinned joints then you have designed a mechanism unless you also join AD with a member. Alternatively, as you are an architect, you can have what you like as long as you have rigid joints and are prepared to pay for the extra costs.

 

[caseyvoigt]

If you intended the structure to have pinned joints then you have designed a mechanism unless you also join AD with a member. Alternatively, as you are an architect, you can have what you like as long as you have rigid joints and are prepared to pay for the extra costs.

I did intend to have pinned joints. So if I use pinned joints, It would be better to have a member at AD? I do not like the idea of rigid joints here because it would transfer moment into the wall corner instead of transferring vertical and horizontal forces into the wall, correct?

 

[caseyvoigt]

This worksheet shows forces transferred into the wall and building structure. So if I add member AD would it decrease the forces applied into the wall from DE and even out the forces?

http://i1128.photobucket.com/albums/m490/caseyvoigt/CaseyandSohailTrussWork.jpg"

 

[pongo38]

You can have pinned supports and rigid joints elsewhere, but the frame would deflect more, and therefore the members would have to be heavier. The economical solution is to put in the extra member, and then you would have to do your analysis again, if you did that. Resubmit if you want it checked, but actually all such analysis can be self-checking, just as the graphical method is also self-checking if the graph closes at the end.