The Birmingham Bridge, the subject of an engineering investigation because of an approach span that dislodged and dropped 8 inches, has forever been a misfit.

The huge, six-lane structure was erected next to its predecessor, the two-lane Brady Street Bridge. The earlier bridge was opened in 1896 as the first toll-free Monongahela River bridge into Downtown, well before cars replaced horses.

In 1963, the state Department of Highways awarded a $278,000 contract for the design of a new bridge to be built for no more than $6 million. Money problems and political controversy delayed progress -- sound familiar? -- and the bridge ended up costing $30 million.

Two large river piers were built in 1969 and, for four years, they sat there. Indecision had left Pittsburgh with another "Bridge to Nowhere" immediately after another debacle had left the Fort Duquesne Bridge hanging in mid-air near a North Side riverbank for six years.

Finally, 13 years after engineers started the design, the Birmingham Bridge opened to traffic, linking East Carson Street on the South Side with Forbes and Fifth avenues in Soho, a neighborhood between Downtown and Oakland.

It was the first piece of an inner-city beltway that was to cut across town, connecting a Mon Valley/South Hills Expressway with a Route 28/Allegheny Valley Expressway. No other piece of the proposed beltway was ever built, and the grandiose idea was abandoned.

Three years later, PennDOT's chief construction inspector for the Birmingham Bridge was charged with extorting gifts from the contractor: auto parts, gas, tires, tools and groceries. Wisely, the contractor said no when the inspector sought $4,500 for a relative's funeral costs.

Shortly thereafter, a series of cover-ups and flaws became public, including faulty welds, defects, fraudulent billing and the "wining and dining" of PennDOT supervisors.

PennDOT spent several hundred thousand dollars repairing those old "electro-slag welds" that also were responsible for a highly publicized crack that closed the Interstate 79 bridge over the Ohio River shortly after it had opened.

In 2005, PennDOT spent another $230,000 to repair other cracks in the massive steel superstructure of the Birmingham Bridge.

Dammed up? Several readers, including Ed Brown, a civil engineer, and Joe D'Agostino, of Monroeville, are skeptical about "frozen" rocker bearings being responsible for the 2.1-million-pound Birmingham Bridge southbound approach span breaking loose and dropping onto Pier No. 10.

"Could part of the problem be that the expansion dams are so full of dirt that they did not work properly?" Mr. D'Agostino asked.

"It is highly improbable that the supporting pier moved after years of solid service and had not been noticed during recent inspections," Mr. Brown said. "It seems more logical that the expansion joints locked and transferred this large force to rocker arms not generally designed to accept lateral movement."

While poorly maintained expansion dams are prevalent in this bridge-dominated region, it's unlikely they were a cause of the latest incident. That's because PennDOT replaced and repaired the expansion dams last summer as part of a $3 million preventive maintenance and low-level rehabilitation project.

Why Birmingham? The state Legislature changed the name from the Brady Street Bridge to the Birmingham Bridge in 1977 at the behest of former state Sen. James Romanelli, D-South Side. The site of the original bridge was laid out by a surveyor from Birmingham, England, and the South Side neighborhood where it connected was once called Birmingham.