I-35w Mississippi Bridge

The I-35W Mississippi bridge was an eight lane, three span deck truss bridge which carried the interstate highway 35 across the Mississippi river. It was located in the biggest city of Minnesota, Minneapolis. It carried around 140,000 vehicles per day, making it the second busiest bridge in Minnesota. Construction repair and renew work was scheduled to be carried on the bridge again in 2020 or so. However, on August 1st, 2007, it collapsed all of a sudden, thereby killing 13 people and injuring 145. The National Transport Safety Board (NTSB) said that a flaw present in the design of the structures caused this huge catastrophe. The gusset plate turned out to be too thin, and hence it ripped out along a rivet line. The NTSB also stated that excessive …show more content…
Out of those 14 spans, 11 were approach spans to the deck truss portion. The bridge's 14 spans extended to 1907 feet. The bridge consisted of two main trusses. The two main trusses on either side ranged from 60 feet above the pier to 36 feet at the mid span and to 30 feet deep at the outer ends of the adjacent spans. The bridge was approximately 115 above the river water level. The south approach spans were supported by the south abutment. A combination of fixed and expansion bearings were provided at bridge/pier interfaces so that the bridge would be able to withstand thermal expansion. The deck of the bridge consisted of two reinforced concrete deck slabs which were separated by 6 inches. Each deck slab held four 12 foot wide traffic lanes along with 2 foot shoulders. The bridge deck consisted of 11 expansion joints. The deck truss part of the bridge consisted of two Warren type trusses along with verticals. The upper and lower chords of the main truss were connected by vertical and diagonal members, thereby making the entire truss structure. All the members were welded box members, designed mainly to withstand compression. Steel gusset plates which were riveted were present at each of the 112 nodes of the two trusses. All nodes had at least two gusset …show more content…
A lot of construction equipment and material were present on the south side of the bridge, which also was the weaker side of the bridge. It should have been noticed that this construction material and equipment were having an impact on the load bearing capacity of the structure. Eventually, this also added reason to the structure's failure. Although the cracks were noticed, experts did mention that it is most probably no coincidence that the failure of the structure took place while there were additional loads of the construction equipment and materials. The ongoing construction work consisted of resurfacing and maintenance of guardrails, lights and other repairs. This work required material and