Jointed Roof Truss
The basic roof truss consists of two rafters or struts and a restraining tie. Both rafters are pivoted at their apex.
The other end of one of the rafters is pivoted to a free standing base, whilst the remaining rafter end runs on ball bearings along a track.
When a load is hung from the apex, the free end of the rafter moves sideways, restrained by a spring balance tie.
Both rafters also include spring balances so that all internal loads can be directly measured.
Re-adjustment of the geometry back to its original unloaded configuration is easily made before taking measurements. The length of the tie can be varied to change the angles of the truss.
Evaluation of co-planar forces in the struts and tie of a basic roof truss
Effect of changing tie bar length
The apparatus consists of two rafter struts and a restraining tie mounted on a self contained, bench top base
Both struts and tie incorporate linear, direct reading spring balances to measure forces
Loading at the hinged apex by load hanger
The tie length, and hence angle of truss, variable
Struts and tie re-adjustable to original lengths
An instruction manual for student and lecturer provided
Set of weights