Basic Load paths

[Ozai82]

Hi, this is my first post, currently, I have a 2D model which I need to draw the load path, most of it has been done however I am unsure about this section with this cantilever, I am unsure whether the load path would be going upwards or downwards in this section.

I've drawn an arrow going in both directions but I'm really unsure if its correct, I've been given this by a friend to help solve, the black arrows represent vertical loads and the red arrows the load vectors.

 

[rb1957]

if the load is down (inertia load) then the bottom member is in compression and the upper (inclined) member is in tension.

if the load is up (wind load ?) then opposite reactions.

btw, the inclined member needs to resist bending (if it has transverse loads along it's span). But it is still reasonable to assume pinned connections.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[Ozai82]

the laods are going down but in this case the load vectors need to show the route a load would take to reach the foundations with the least resistance or aka the shortest path, its essentially impossible to observe but I'm trying to figure out if the best path would be up the diagonal section and down through the vertical sections or down the diagonal sections, across the connected horizontal section and then down the vertical sections.

 

[rb1957]

well your picture only shows a tiny portion of the structure, I thought this is what you were interested in.

going into the truss in general it is harder to see the reaction directions. But draw some direction (maybe tension in all members) ... a positive means you had the direction correct, a -ve menas you have compression.


"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[BridgeSmith]

There is no "best", "shortest route", or "least resistance" involved in a load path, there is only the flow of the forces through the members based on statics. For the loads on the cantilever there is no single load path. There are forces following multiple paths to multiple supports. Each connection and member along each path must be evaluated for the loads flowing along and through those members and connections.

 

[BAretired]

The three figures below indicate similar structures. Fig. 1 does not show the support locations, so it is impossible to know what the truss forces are in all of the members. Figs. 2 and 3 indicate two possible support conditions; red arrows represent reactions.

Boundary conditions must be known before you can solve the problem.