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Plate Girder Spans

"There are six plate girders in each span beneath the flooring, namely, one girder under each rail and one girder under each sidewalk, which is detachable on the up-stream side.

"This arrangement was chosen to admit of the erection first of the new down-stream street track, which came to lie sideways of, but on a higher grade than, the down-stream track of the old bridge. To this track travel was confined during erection. Plate girders were chosen for this reason that for the limited depth of floor (for a grade 15 feet higher than old bridge, as at first contemplated), it gave a more rigid construction than open girders of low depth. It was also more convenient to work into them, and get rid of a lot of wrought-iron which was on hand, and was left over from orders for the suspension bridge originally intended to be built.

"Could the writer have foreseen that the new grade would be 20 feet higher than the old bridge, the deck spans of the approaches would have been made of two open girders of greater depth, in a manner that would have admitted of finishing both tracks on them at the same time. This would have been also more economical. As it was, the plate-girders were nearly finished when the change in grade was made.

"For all wrought-iron work in the bridge the quality of iron was required to be equal to that of standard bridge iron.

"Steel rivets were used for all wrought-iron bridge-members and girders.

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