Civil Engineering Reference
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many American engineers had lost confidence in even wrought iron girder, truss,
and suspension railway bridge construction.
At this time railway construction was not well advanced in Germany, and these
failures interested Karl Culmann during the construction of some major bridges for
the Royal Bavarian Railroad. He proposed thatAmerican engineers should use lower
allowable stresses to reduce the fatigue failures of iron truss railway bridges and he
recognized the issue of top chord compressive instability. Culmann also proposed
the use of stiffening trusses for railroad suspension bridges after learning of concerns
expressed byAmerican bridge engineers with respect to their flexibility under moving
live loads.
A railroad Howe truss collapsed under a train at Tariffville, Connecticut, in 1867
and a similar event occurred in 1877 at Chattsworth, Illinois. However, the most
significant railway bridge failure, due to the considerable loss of life associated with
the incident, was the collapse of the cast iron Howe deck truss span on the Lake
Shore and Michigan Southern Railroad at Ashtabula, Ohio, in 1876 ( Figures 1.10a
and b). The Ashtabula bridge failure provided further evidence that cast iron was
not appropriate for heavy railway loading conditions and caused American railroad
companies to abandon the use of cast iron elements for bridges. This was, apparently,
a wise decision as modern forensic analysis indicates that the likely cause of the
Ashtabula failure was a combination of fatigue and brittle fracture initiated at a cast
iron flaw.
FIGURE 1.10a The Ashtabula Bridge, Ohio before the 1876 collapse. (Ashtabula Railway
Historical Foundation.)
For example, following the collapse of an iron bridge in 1850, all metal bridges on the Boston andAlbany
Railroad were replaced with timber bridges.
With the exception of cast iron bearing blocks at the ends of truss compression members.
 
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