Experimental and Numerical Evaluation of Braced-Chain Eyebar Bridge

Braced-chain eyebar bridges were common variations on the suspension bridge in the nineteenth century. The particular integration of a suspension system (eyebar chains) with the truss system (single diagonals and fabricated verticals) used at English Center, Pennsylvania, represents an important step in the evolution of the suspension bridge through its developmental stages in the late nineteenth century. The bridge, which spans 91.4 m (300 ft), was constructed in 1891 and was placed on the National Register of Historic Places in 1978 as a rare short-span suspension bridge. Because of the complex, apparently dual structural system of the bridge, identification of the bridge response to loading using analytical techniques was considered inadequate. Results of controlled load testing consisting of strain response measurements in selected suspension and truss components of the bridge are presented, and the interaction of the bridge truss and suspension systems is discussed. Field-measured response and predicted response derived from analytical models are compared and discussed. The Lower English Center Bridge is also evaluated for capacity of current legal loads considering the strength limit states.