TOMORROW'S ROADS TODAY - Maryland State Highway ...

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Appendix B: Bridge Types and National Register of Historic Places Eligibility Justification for
1948-1965 Bridges
Twelve different types of bridges were constructed on the state’s highways from 1948 to
1965: arch through, arch deck (filled), box beams or girders multiple, concrete slab, concrete
encased steel beam, girder and floorbeam system, movable – bascule, movable – swing, rigid
frame, stringer metal beam or girder, Tee beam, deck truss. The terms are defined below and in
the following Highway and Bridge Terms and Definitions below.
Bridge Types found on Maryland’s Highways
Steel Through Arch – The steel through arch generally consists of two fabricated
steel ribs constructed with the crown of the arch above the roadway and the arch foundations
below the roadway. The deck is suspended from the two steel arches by wire rope cables or
other tension members. Traffic loads are transmitted as follows: deck, steel flooring
system, cables, arch ribs, and arch foundations. Drivers pass through the two arches.
Steel Through Arch (SHA Bridge No. 0106600 -- Blue Bridge, Cumberland, MD)
Steel Through Truss - similar to Steel Through Arch except traffic loads are transmitted from
trusses directly to abutments/piers via bearings, in lieu of arch foundations. The Chesapeake Bay
Bridge, Bridge No. 0204000, has several spans of steel through trusses.
Concrete or Steel Deck Arch - The deck arch carries traffic on its deck. There are several types
of arches. The oldest type is a filled concrete arch similar to stone masonry arches built over the
centuries. This type consists of a solid concrete arch barrel with solid concrete sidewalls
(spandrel walls) that contain fill which supports the roadway. Alternately, there are the open
concrete or steel arches that generally consist of two or three concrete/steel ribs that transfer the
loads to the arch foundations. Traffic loads are transmitted as follows: concrete deck,
concrete/steel flooring members, concrete/steel columns, arch ribs, arch foundations. The sides
of the arches are "open" so no fill or embankment is contained. Drivers pass above the arches.