Truss Simple Question

I have just completed my bachelors in Civil(Road Transport).A simple questions concerning Truss analysis:
Let us say if we have a statically determinate truss, now supposing the force in a member of the truss is say tensile(thus acting away from the joints),as a result of which joints move closer right?
Now as the joints are moving closer it implies member should become shorter?Then it is in compression.How can we say if the force in a member acts away from the joints is known as tensile force, because if the force is acting away from the joints joints should move closer as a result of deformation hence member should become shorter, is'nt that compression?

 

I think you're confusing the force in the member and the reaction at the joint.

As you know, to remain static there has to be an equal and opposite reaction. Therefore, if a member is in tension it will "pull" on the joints. For the joints to remain stationary they must exert an opposite (in direction) reaction on the member. Hence, the joint "sees" a force TOWARD itself.

Hope that makes sense. I'm sure others can explain is bette then I.

 

[pechetty]

dear keps,
due to the load or exterrnal forces stresses are induced with in the member.these stresses are such as to keep the member in equilibrium.i.e these stresses will be proportinal to the force acting.as ur doubt is concerned . as the stresses is with in the limit the truss will be stable . as this limit exceeds in the member the member fails and hence the truss fails. Pechetty.

 

pouring, pechetty,
This thread was beautifully explained by trilinga in particular.Refer to the threads dated July 28,29(handle:cest)