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post showed maximum unit strains of 42 microinches/inch in tension and 23 microinches/inch in compression. These correspond to stresses of approximately 1300 lbs. per square inch tension and 670 lbs. per square inch compression. These alternating stresses occurred in a member designed to carry a primary compression load at an allowable design stress of 20,000 lbs. per square inch. A fatigue failure is therefore improbable. Secondary stress effects were also measured in gusset plate U7N and in an eyebar head at joint C11S.
d. A supplemental study to determine whether the eyebars did in fact rotate on the pins produced indications that such rotation does occur when large live load tensions are produced in the chain by loadings in the main span, but not when the loadings are within the side span.
e. An additional secondary effect was observed with the live load in one lane only. Such loading produced distortion of the floor beam-truss-vertical rigid frame, inducing lateral motion of the deck with respect to the eyebar chain. This distortion therefore produces not only bending stresses in the hangers but also bending moments at the connections of the floor beams to the trusses.