Unusual Design Problems - Second Tacoma Narrows Bridge

The purpose of this paper is to outline the unusual problems that confronted the designing engineers and consulting board in developing a safe, yet economical, design to replace the first Tacoma Narrows Bridge in the State of Washington which had failed under dynamic wind forces on November 7, 1940. Some of these are problems applicable to the specific problem at hand and result from physical conditions of the former structure as they remained after the failure. Although many of the solutions will be of interest to engineers, they will not be useful in future bridge design unless a similar failure should occur to make them so. Other solutions should have important bearing on the design of future suspension bridges, especially those which involve long spans and are situated where traffic is relatively light, requiring extreme economy. The first Tacoma bridge was such a structure. The designer was limited by a relatively low estimated income from tolls and consequently extreme economy. In spite of these limitations, the first structure did meet all the requirements of modern suspension bridge design practice and was amply designed to withstand all possible live loads, dead loads, temperatures, and direct wind forces as they had been applied in other bridges.