Tacoma Narrows Bridge

INTRODUCTION 
 

. . . . the Tacoma Narrows bridge failure has given us invaluable information . . . . It has shown [that] every new structure which projects into new fields of magnitude involves new problems for the solution of which neither theory nor practical experience furnish an adequate guide. It is then that we must rely largely on judgment and if, as a result, errors or failures occur, we must accept them as a price for human progress. 

The Tacoma Narrows Bridge was the first suspension span constructed in the United States after its predecessor's failure in 1940 from wind-induced torsional oscillations. Research of design flaws in the first Tacoma Narrows Bridge led to the use of aerodynamic testing as a standard procedure in suspension span structural analysis.

 

 

The Collapse of the Tacoma Narrows Bridge, Evaluation of Competing Theories of its Demise, and the Effects of the Disaster of Succeeding Bridge Designs

 

       The Tacoma Narrows Bridge gained notoriety in the engineering and scientific communities when it collapsed on November 7, 1940. Even though the odd motions of the bridge were recorded in detail, including film footage that documented the final moments of the structure, technical experts still disagree on the exact nature of the phenomena which led to its destruction. One aspect of the failure remains quite clear, however. The Tacoma Narrows Bridge, despite the embarrassment it caused those involved with its design, has played a significant role in creating more sophisticated analytical tools for engineers to use. This document presents an evaluative review of the major theories presented about the cause of the failure, the accepted results within the engineering community, and the effects of the collapse on structural designs that followed. 

 

 

Conclusions 

       I therefore feel, that with the exception of the unusual narrowness of this bridge with reference to its span length, the super-structure design is technically sound. It is probably technically sound notwithstanding its narrowness, but there are several reasons why it would be of material advantage if the bridge could be widened at a reasonable increase in the cost, and therefore, I recommend that serious consideration be given to the possible increase in the width of this structure, before the contract is let or work begun. This would undoubtedly increase the width of the anchorage blocks and the smaller piers, but it would seem reasonable to assume that the widths of the main piers would not have to be increased. Assuming it is expedient to consider changing the width of the bridge as now designed, I would suggest increasing the width of the roadway from 26 ft. to 30 ft. and making the two sidewalks each 2 ft. 9 in. clear, instead of 4 ft. 9 in. clear.