The Vierendeel Truss, or open frame girder, is an indeterminate structure named after the Belgian prof. A. Vierendeel, who first applied the principle of rigid frame construction to bridges, about 40 years ago. Its distinguished feature is that the supporting trusses are composed of a series of rectangles, or trapezoids with no diagonal members. Each member is capable of resisting shearing force, bending moment, and axial load. The original idea in introducing this form of truss was to obviate certain faults of bridge design pertaining to the triangular truss using rivet construction- In a riveted truss, the secondary stresses due to' the rigidity of the connections may run very high, yet they are seldom considered in design, it being customary to calculate the stresses on the assumption that the ends of members are hinged. In reality this is far from the truth. The ends are subjected to moment and there is a point of contra-flexure somewhere in the member. With absolutely rigid end connections, the diagonals are unnecessary. Vierendeel conceived the idea of simplifying the truss plan by eliminating all diagonal members and then strengthening the joints to take the necessary moment