How do trusses work?

In the simple triangular roof truss the load of the pitched roof is supported partly by the sustaining walls and partly by the pull of the horizontal element between the two walls. In the fan truss shown, the same priciple of dividing loads into thrusting and pulling elements is used in order to give better distributionof thrust over the supported area Reduction of the weights and forces on individual members, that cause distortion and deformation can permit the use of less expensive or thinner materials reducing costs.