1. THE GEORGE WASHINGTON BRIDGE ( 1931 – New York ) Cables can only support tensile forces. A uniform distributed dead load gives a parabolic shape for the main cable

2. THE VALTSCHIELBACH BRIDGE ( 1925 – Switzerland ) A uniform dead loads gives only compression in the parabolic arch.

3. THE SALGINATOBEL BRIDGE ( 1930 – Switzerland ) Why has the arch a non uniform thickness ? Answer : the design of the arch is well adapted to support live loads.

4. Live loads are represented by point forces. The largest stresses are obtained with two point forces applied at the quarter points Equilibrium of the left part of the arch symmetry  V 2 = 0 equilibrium equation :

5. Bending moment due to horizontal forcesBending moment due to vertical forces Total bending moment