Problems with the Gusset joints?

Potential Flaw Is Found in Design of Fallen Bridge

Excerpt:

If those who designed the bridge in 1964 miscalculated the loads and used metal parts that were too weak for the job, it would recast the national debate that has emerged since the collapse a week ago, about whether enough attention has been paid to maintenance, and raises the possibility that the bridge was structurally deficient from the day it opened. It does not explain, however, why the bridge stood for 40 years before collapsing.

In an announcement, the safety board said its investigators were “verifying the loads and stresses” on the plates as well as checking what they were made of and how strong they were.

State authorities here said the plates were made of steel, and were, in most such bridges, shaped like squares, 5 feet by 5 feet, and a half-inch thick. Such plates are common in bridge construction as a way to attach several girders together, said Jan Achenbach, an expert in testing metals at the Northwestern University Center for Quality Engineering and Failure Prevention.

Below is a picture of a gusset joint (not from I35W bridge!):