Monday, October 8, 2012

Hastings Bridge


The average life span for a highway bridge is 70 years. Hastings, MN has gone through three bridges since 1895; the first two lasting less than 60 years before it was decided to rebuild. The most current bridge is being built right next to the existing one that was built in 1951, crossing the Mississippi River (Hwy 61).

Original Spiral Bridge
The original bridge, built in 1895, had a spiral design, and featured a Parker through truss bridge for the main span, with two wooden and steel trestle approaches. Wisconsin Bridge and Iron Works Company designed and built the bridge with a spiral approach on the south end of the bridge, so the bridge could be high enough to clear the height clearance for ships and barges passing through.

The Main Span of the new bridge
next to the existing Hastings Bridge.
The Spiral Bridge became a historic icon and an icon for other engineers. In 1951, it was blown up and replaced by the bridge that is currently standing, a tied arch bridge. This bridge is the longest bridge in the Western Hemisphere. This standing bridge is also being replaced. The new bridge is being built right next to the tied arch bridge, so there is no major interference with traffic. The reason for the new build, besides the wear and tear that is becoming apparent, is the tied bridge was built by Sverdrup and Parcel (the same company to build the I-35W Bridge in Minneapolis).

Current Hastings Bridge
The bridge in Hastings was built with a similar design, and after the I-35W collapse this bridge became a huge concern. The reason for the I-35W collapse was the gusset plates were too thin and therefore buckled and the bridge collapsed. It is said that the Hastings bridge has the correct thickness of gusset plates, but is still a concern. This is not the only reason the rebuild is being done. Signs of wear and tear from increased traffic and extreme weather have done damage to the bridge. Even the salt used for roads during the winter have eaten away at the structure.

With two past icon bridges, the new Hastings Bridge has a reputation to withhold. In 2008, less than a year after the I-35W collapse, Minnesota legislature passed transportation funding that allowed for the acceleration of construction to begin in 2010. The Minnesota Department of Transportation will pay $2.1 million to ensure it will be open by December 13, 2013. In the spring of 2011, the construction was delayed 12 months due to the Mississippi River flooding and the 20-day state government shutdown in July. The goal is to open the first two lanes of traffic on the new bridge in early to middle 2013, and all four lanes be open by the set date. The total construction cost is $120 million.
Main Span being floated in on the
Mississippi River.

When I was living in Cottage Grove, MN this summer, construction was making way. The amount of work that had been done since construction started was impressive, and the work continues to be hitting deadlines. The Main Span of the bridge was floated and lifted into place through September 22 and 24.

The current bridge has two lanes and carries over 30,000 vehicles daily. Although officials ensure that the current bridge is safe, the width and clearance is not high enough for what the traffic count is. The new bridge will be another one for the history books spanning 545-ft long with free-standing tied arches and an expected life span of 100 years.

This development, as well as the previous bridges that have taken place in Hastings, MN, directly affects the community as well as the thousands of people that travel that path everyday. The design of the new bridge after the I-35W collapse shows that the safety of the people are a key aspect in the field of Civil Engineering. This is one aspect that will not change from now until I become a Professional Engineer. The Hastings Bridge changes shows that there are many aspects a Civil Engineer needs to stay on top of including inspections, safety, design, materials, and environment. The materials of a design are key to a development that will last a long time. Developments like this one are a constant reminder of what changes and advancements are made in the field every day. Throughout the three bridges materials, design, machinery, and processes have improved and have made better, longer-lasting structures. 

These improvements are what makes me excited to learn all I can in school so I can get out there and make advancements and history icons that make a difference in the lives of people that use my designs everyday. Roads, Bridges, and even structures are a part of everyone's every day life and the developments like the Hastings Bridge, shows us how they can be developed without decreasing the quality of life for a community. 

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