(Statics) Truss with no vertical members, will it work

[joebobjoe]

Homework Statement

Supposed to support a 50 kN weight at a pin joint at the center of a void as cost effectively as possible using trusses (e.g., trusses and pin joints have costs)

Homework Equations

Basic sum of moments and sum of forces = 0

The Attempt at a Solution

Why can't I just use two horizontal members from the edges of the void to the weight. Since the trusses are ideal and can't expand the weight won't fall. But I'm having a hard time figuring out the equations. Maybe this solution is statically indeterminate? At the center pin joint I get sum of all forces in x direction = tension in truss 1 - tension in truss two. In the y direction I just get -50 kN. But somehow the forces in the y direction have to equal 0. When I look at it I know it will work (I think there would just be a very strong moment in the trusses). But when I do the equations I'm confused. Does the 50 kN translate into a moment? Why can't we have ideal trusses without vertical components?

 

[LawrenceC]

How about providing a diagram of your truss. How is it anchored to the edges of the void? Are you saying the beams do not streach or bend?