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B. Structural Information

Although fifty-five years old, the main structural components of the northern trusses are still in good physical condition. The tied-arch bridge (main river span) is currently posted to restrict trucks from using the outside lanes of the bridge. The outside stringer supports under the northern span trusses appear to be in better condition than those of the main span and southern approach spans. The probable reason for the better condition of the stringer supports in the northern approach trusses is the better condition of the expansion dams, specifically, the copper water troughs, in this section. The deteriorated troughs of the main span and southern spans have allowed the intrusion of corrosive deicing salts.

Through the years, several repairs have been performed on the entire bridge. In 1948, bridge improvements included a bituminous overlay for the deck, a raised median, repairs to the expansion dams and drainage systems, and repair of the concrete on the abutments and stairs. In 1955, a new concrete deck, reinforced with wire mesh and a raised median barrier, were placed on the existing buckle plates. In 1958, the structure was painted. In April 1977, during an in-depth inspection, temporary stringer repairs were made at 63 locations. The bridge was painted again in 1980.

The bridge deck and sidewalk deck are in bad condition. Severely delaminated and spalled concrete areas are present throughout the bridge. There are several holes in the concrete deck along the roadway gutter line and inside curb of the sidewalk.

The only significant problem with the structure is the section loss of the vertical and diagonal truss members at the intersection of the concrete sidewalk. Span 8 has the most deterioration. All members at the top of the sidewalk deck show 10 percent to 25 percent loss in cross-section. Member U1-L1, span 8, west truss; member U1-L1, span 8, east truss, and members U1-L1, spans 6 and 7, west trusses, show 50 percent section loss in their respective webs. Members U1-L1 in spans 5 and 6, east trusses, have 50 percent loss in web. Members U5-L3 and U4-L4, span 5, east truss, have 40 percent loss in web. Member U4-L4, span 6, east truss, members L3'-U3', spans 6 and 7, east trusses, and members U1-L1, spans 5 and 6, east trusses, all have 50 percent loss in web. Member U1'-L0', span 5, east truss, has 30 percent loss of web section and three rivets with badly deteriorated heads. Most truss members at the intersection of the bottom side of the sidewalk slab show 10 percent to 25 percent section loss.

The west truss of span 8 has four separate areas where flanges were bent due to collision by vehicles. Other areas where members were bent by vehicles are span 8, east truss, U1'-L0', and span 7, west truss, members U2'-L2' and U1'-L0'.

The floor beams and stringers are in fairly good condition. There are about 15 pitted and scaled rivet heads on the bottom flange of about ten floor beams (some exhibit 30 percent loss in the head). The north floor beam over bent 7 at stringers 2 and 3 has 30 rivets with 50 percent head loss each. The floor beam beneath stringer 6 has 20 percent web loss in a one square-foot area. There are about ten rivets on the east end and the west end of the bottom flanges of both floor beams that exhibit 50 percent section loss. At bent 8, there are temporary supports under the outer two stringers (stringers 1 and 8) in each floor beam. The first stringer between both floor beams is paper thin and full of holes. The span 7 end floor beam web has 25 percent loss in a one-foot square area underneath stringer 1. The floor beam from span 7 over bent 8 has 10 percent web loss under stringer 7 and a 50 percent loss under stringer 8, both about one square foot in area.

Bent 7 has four lacing bars on the top chord that have lost a quarter of their sections Bent 8 has about 20 rivets on the top chord that show approximately 50 percent head loss. Also in the top chord intersection, the stay plate is heavily scaled; the lacing bars have 25 percent loss of area at this juncture. The river pier (pier 5) is in good condition. There are two hair-line cracks in the granite on each face of the pier that run three-quarters of the way up from the river and the railroad. The concrete northern abutment is heavily spalled in the upper west corner of the bearing wall and efflorescent stains are evident. A quarter-inch crack and a 1/8-inch crack run vertically along the face of the bearing wall. A 4x2-foot area is heavily spalled along the joint between the back wall and the bearing wall on the west side of the abutment. The 1969 in-depth inspection report showed that the northern abutment had rotated about its base 2 to 2-1/2 inches toward the river (southward). No additional movement of the abutment has been noted. Span 8 is fixed at the northern abutment, so the movement of the abutment was absorbed by the expansion dams and rockers at piers 5 and 8, and by the longitudinal deflection of pier 7, which is fixed. The shoes appear to be in good condition; however, expansion shoes at bents 6 and 8 are overly inclined to the south due to the inclination of the northern abutment.

All visible bearings and anchor bolts at the foundations are in good condition, except at pier 8 where two anchor bolts are scaled and have lost about 5 percent of their cross-sections.

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