Structural Damping in Suspension Bridges

The collapse of the Tacoma Narrows Bridge in Washington in 1940 focused attention on the importance of a better knowledge of the capacity of suspension bridges to dissipate energy imparted by wind action. This paper reports part of the investigational work undertaken by the Advisory Board on the Investigation of Suspension Bridges. It comprises: (1) A theoretical study of damping capacity of suspension bridges resulting from internal friction and from various sources of dry or Coulomb friction in the structure; (2) an account of an extensive laboratory study of frictional damping in structural members; and (3) a correlation of the theory with experimental data. The paper suggests that a substantial amount of additional damping can be provided without resort to special damping devices if consideration is given in design to the potential sources of friction available in the floor system.