‘Bridge’ Tag

Mackinaw Bridge

Photo Credit: Karl Jansen

This photo is of the Mackinaw Bridge, which connects spans between the Upper Peninsula of Michigan and the Lower Peninsula over Lake Michigan/Huron. The Mackinaw Bridge is suspension bridge and was completed in 1957. The length of the bridge is 26,372 feet (4.99 miles) and its longest span is 3,800 feet. Suspension bridges are unique in the way the loads of the bridge are transferred to the ground. The cables of a suspension bridge work in tension, carrying the loads to the two towers which work in compression against the foundations on the earth. The cable ends are then secured in massive blocks of concrete that hold the tension in the cables completing the load path.

Suspended-Cable Pedestrian Bridge

Photo Credit: Timothy Lewis

This 255 ft. long suspended-cable pedestrian bridge is located in Nueva Providencia, Guatemala and was constructed in May 2012 by Marquette University Engineers Without Borders over the course of 15 days. The design uses concrete masonry foundations, steel suspension cables, concrete anchors, and wooden decking. This bridge type was selected because it will be far above the water line and in an extreme rain event, it would be safe from damage incurred by large floating debris in high water. The structure consists of 3 deck cables, 2 handrail cables, and wind guys on either side of the bridge for lateral stability. This bridge services a local community of more than 350 people and restores their year-round access to healthcare, employment, and education.

Mike O’ Callaghan-Pat Tillman Memorial Bridge – Hoover Dam Bypass

Photo Credit: Jessie Benaglio

Mike O’ Callaghan-Pat Tillman Memorial Bridge is built over the Colorado River near the Hoover Dam connecting Nevada and Arizona. It was meant to bypass driving over the Hoover Dam so there is not as much traffic for the pedestrians viewing the Dam. This bridge opened October 18, 2010. It is the first concrete-steel composite arch bridge built in the United States. It is the second highest bridge in the United States, 840 feet above the Colorado River, and also the widest concrete arch in the Western Hemisphere.

The bridge was constructed with seven pairs of columns. The arches were constructed on both sides of the bridge simultaneously while being supported by diagonal cables. When the two halves of the arch was completed, there was only a 3/8 inch gap which was filled with reinforced concrete.

Pin and Hanger Assembly

Photo Credit: Karl Jansen

This is a common type of connection seen on road bridges. Next time you are driving on the highway, look up at a bridge you go under and see if you notice one of these. Pin and hanger assemblies are used to connect two girders together where the bridge span is otherwise too long for one girder. One girder is supported by a column to the earth, and on the cantilevered end of this girder is the connection to the second girder. While these connections are common sights, they have been determined to be too costly to maintain and ineffective at preventive catastrophic failure. For this reason, new bridges aren’t built using this type of connection.

Cable Stay Pedestrian Bridge

Photo Credit: Alex Mead

Seen here is the Bob Kerrey pedestrian bridge in Omaha, Nebraska. This serpentine cable stay bridge crosses the Missouri River and is an impressive 3000 feet long. The bridge connects two parks, one in Nebraska and one in Iowa, to make an interstate-park system that people can enjoy during all seasons of the year. This bridge is certainly one of the most visually beautiful pedestrian bridges in the world.

Viaduto do Corgo Bridge, Portugal

Photo Credit: Cláudio Venceslau Ferreira

Seen here is the Viaduto do Corgo bridge project in the Vila Real region of Portugal. The photo is of over two dozen bridge piers being constructed for a large car and truck bridge. Specifically one can see two slip-form carriages riding up piers and tower cranes built alongside these piers to aid in their construction. Projects like this require many people to work on them, ranging from politicians to get money for the project, to engineers to design the project, to construction works to build the project. In most cases these large scale construction projects employ many thousands of people over the course of years and can stimulate the local economy with the massive influx of works and materials for the bridge.

Mechanical Lift Bridge – Duluth, MN

Photo Credit: Troy Clack

Seen here is a mechanical lift bridge in Duluth, Minnesota. Lift bridges are advantageous because they can use proportionally smaller counterweights than swing-span or bascule bridges, yet still allow for tall vessels to pass when the bridge is in the up position. However, the bridge superstructure is still above the water, so the height of the boats is still somewhat limited. This particular bridge has an interesting story of why it was needed and can be read about here.

Ambassador Bridge – Suspension Bridge

Photo Credit: Alex Mead

Seen above is the Ambassador Bridge connecting Detroit, MI, USA to Windsor, Ontario, Canada. It is a standard suspension bridge with two anchorages, two towers, and two main cables. A unique feature of this bridge is it is privately owned and an international border crossing. It is owned by Michigan billionaire Manuel Moroun and has lead to many controversies as this bridge is the only connection for many miles which commercial truck traffic can cross between the two countries.

Concrete Bridge Substructure

Photo Credit: Karl Jansen

This is the underside of a concrete bridge. Technically, this is known as the substructure, or the part of the whole structure that supports the superstructure, or the roadway in this case. You can see nicely the beams and girders that run laterally and longitudinally under the bridge superstructure, and the massive columns that extends vertically down to the ground to provide the support. The substructure is an important element of every bridge.