I-90 Mississippi River (Dresbach) Bridge

Deck Width: 67.3 ft
Under Clearance: 62 ft

Deepest section: 21 ft 10 in

The MNDOT web page stated that although the current bridge had no weight restrictions and operated at an acceptable level of service, there were a couple of problems with the bridge and surrounding roadways that motivated its replacement.  Such as:

• Current interchange geometry created difficult and unsafe traffic movements for commuter traffic.

• Bridge structural deficiencies – had no structural redundancy (that could be accounted for by current guidelines); portions were beyond useful life; fatigue cracking had occurred

• Narrow bridge shoulders – did not meet state/federal standards; no emergency vehicle bypassing or stalled vehicle storage

• Traffic buildup during parts of the day

• Traffic safety concerns – I-90 curve had higher crash rate; northbound Hwy 61 to eastbound I-90 had pattern of crashes

• Riverfront access – no access to riverfront from southbound Hwy 61; no access to riverfront from eastbound I-90

• I-90 as regional river crossing – nearest crossings are five miles south and 24 miles north

The bridge specimens donated to S-BRITE showcase simple and effective retrofits that were performed at the intersection of welds on the lateral gusset plate details.  This retrofit was most likely performed following the fracture of a girder on the Lafayette St. Bridge near St. Paul Minnesota in 1975.    

Figure 1. I-90 Mississippi River Bridge before demolition (Source: MNDOT)

Figure 2. Elevation view showing 21'-10" tall haunched section of the main girders (Source: MNDOT)

Figure 3. View showing floor system on the two-girder design (Source: MNDOT)

Historic Documents:

1964 Dresbach Design Drawings