The Waddell: A Truss Bridge

In the small town of Waco, Texas who would have thought it was once well known for the structure of a bridge, the Waco Suspension Bridge to be exact. Up until 1870, the Brazos River was just a simple river that had no special meaning to it. The land around it was empty, occasionally you would find cattlemen pushing their cattle across stream, but that was only because you could not find one bridge that spanned the eight hundred miles of river flowing through Central Texas. This caused a serious transportation issue for merchants and travelers. It became clear that a better means of crossing the river was necessary.

Initially, suspension bridges before 1940 were made of piers, towers, wires, anchorages, and roadways. Piers were the main foundation for the suspension bridges. There usually were two of them, which were made out of cement and were entrenched in ground underneath the body of water that the bridge was spanned across. Towers were built on top of the piers to provide a means of connection for the roadways and wires. Wires were connected to the towers, roadways, and anchorages to provide tension support for the weight of the bridge. The anchorages were large cement platforms that were planted into the ground on either side of the land so that the wires could be connected to it. Lastly, the roadways were the main point of the suspension bridge. They usually were wide enough to provide four lanes of traffic and stretched from one side of the bridge to the other. This was the basic design of the suspension bridges

The I-35W Mississippi river bridge also known as Bridge 9340 officially was an eight-lane, steel truss arch bridge which carried the Interstate 35W across the Mississippi river connected the downtown east and Marcy-Holmes. Its construction began in the year 1964, was finally opened in 1967. It connected the northeast of Metrodome on its south end and the University of Minnesota on the North end. The bridge was the boundary of “Mississippi Mile” downtown riverfront parkland. The north foundation of the bridge was near the hydroelectric plant built in 1988. The south abutment was in an area polluted by the coal gas processing plant. There weren’t any mentions of this in the failure investigations. The bridge was a continuous truss bridge that had a total span of 1,907 ft. It was an 8-lane bridge having a width of 113.3ft. and was 115 ft. high. It was designed by Sverdrup & Parcel to 1961 AASHO (American Association Of State Highway Officials) standard specifications. The construction contract worth more than US $5.2 million at the time, went to Hurcon Inc. and Industrial Construction Company, which built the steel trusses and deck. The piers were not built in the navigation channel instead the center span of the bridge consisted of a single 456- foot steel truss over a 390-foot channel being the longest span of the bridge.

There are many differences between our bridge and other bridges. One being location. Another one being that thing that was sacrificed for it. Another one being cost. Also another difference would be weight and capacity, and the size or length.

The Pratt truss bridge was originally founded by Caleb and Thomas Pratt in 1844. It is mainly used to carry trains. The biggest advantage of this bridge was its low costs for construction and the materials to construct a truss bridge are minimal. It also use materials that is cheaper and light in weight. We can easily identify a pratt truss by detecting its diagonal members, which (excluding for the very end ones) all slant down and in toward the center of the span. The pratt truss was designed by applying few laws that related to the mechanics of materials concept. The bridge is mainly built using steel girders to support the construction of the structure. The below part of bridge weight is high so, it need an enough support to prevent from

Although the Tacoma Narrows Bridge is oft considered “the most spectacular failure in bridge engineering history”, it was far from being the first unsuccessful suspension bridge. There were ten prior suspension bridges that failed due to unaccounted wind/oscillating forces. However, the Tacoma Narrows Bridge collapsed 50 years after the last bridge, and it was the most expensive and longest- more than double any previous bridge- that is the reason why its failure is so significant. The remains of this bridge now serve as “one of the world’s largest manmade

The I-35W Bridge, located in Minneapolis, Minnesota, was a bridge that opened in November of 1967 and was designed by Sverdrup & Parcel and Associates, Inc. The bridge had a truss arch design that spanned a total distance across the Mississippi River of 1907 feet. Also, the bridge was a deck truss which means the roadway was located on top of the truss itself. With a total of 4 piers, 2 on either side of the Mississippi River, that supported the bridge, the I-35W Bridge crossed the Mississippi River in 3 main spans; the longest span, which was located directly above the river, was 458 feet long. On August 1, 2007, the I-35W Bridge collapsed and sent the 80+ vehicles on the bridge into the Mississippi River.

Hecox (2011) says that the arch structure of the Tillman Bridge makes the canyon walls hold the weight of both vehicles and the bridge itself. In addition, the arch structure allows a better vision of the canyon for the drivers, which was a request of the population to the engineers of the project. In the other hand, according to Jones (2015), the truss structure of the new St. Anthony Bridge also was requested by the population because they wanted to keep a truss bridge in that place. The author also affirms that the St. Anthony Bridge is a truss, but the project team proposed adding a posttensioned concrete bottom chord to the steel truss in order to reinforce it. The project team made this choice because one bridge in Minnesota has collapsed in 2007, and the engineers wanted to lessen the fracture-critical issues to avoid a new catastrophe. In addition, this posttensioning approach wiil make the structure redundant for both resiliency and long-term durability. In conclusion, both bridge's structures were right chosen in order to provide safety and beauty in both

In 1989, an earthquake caused the top deck of the bridge to collapse. This has raised concern in recent years in the case of a large scale earthquake. During an inspection in September of 2009, a 1.5 inch crack was found in a structural truss called an eyebar. The system of the truss is meant to distribute report will describe the tensile load from the weight of the bridge over 4 eyebars. One of them being broken, this same load was now distributed between only 3 eyebars. Because these eyebars were not designed to carry extra load, it became crucially important to repair the eyebar as soon as possible. However, because the bridge is so old, its mechanisms were more complex than what would be designed now in the current day. The engineering company C.C. Myers was contracted to do the repair. C.C Myers decided to repair the eyebar by welding a crossbar to the saddles which had been placed on each end of the broken eyebar (Alfrey, 2010). Four tie rods were then bolted to distribute the tensile load (Reid, 2010). This repair was completed in only 70 hours (Carlsen,

When the bridge was tested, at 26 pounds of pressure, it began to buckle. The top support near the middle of the bridge on one side caved in, and as the weight increased, more of the top supports collapsed. At 47.3 pounds of pressure, the bridge snapped in half. By the end of the testing, the bridge had lost all of it’s top supports, two sections of diagonal supports on either side, and a small portion of the roadway.

By the early twentieth century the truss bridge reflected many of the qualities of America 's industrial society: mass manufactured, steel-made, practical and unglamorous, sturdy and dependable, cost-competitive, and highly versatile. Such structures were wrote by David Plowden in his splendid Bridges: The Spans of North America, "appropriate icons to our industrialization." For the developing state of Oklahoma, steel trusses held symbolic value too, for they provided tangible proof to a wider world of economic possibilities.

From brainstorming, we have considered numerous bridge designs that will suit the spaghetti bridge experiment that can withstand the load. We have decided to focus on a truss bridge type with suggestions of either Howe, Pratt or Warren truss bridges. Upon research of each type of trusses we have decided to build a Pratt truss bridge based on the simplistic design and the ability of the group members to construct the bridge with spaghetti. The Pratt truss bridge is an ideal bridge for its structural mechanics. The design of the Pratt truss bridges combines the elements of internal web members of diagonal and vertical beams. Thus, it is strong yet fairly light for its structure. The diagonals members are subjected to tension forces, whilst the

It is shaped in a way to transfer weight to the towers and anchors with its tension (O'Connor, 1971, p. 372). Cables are made of high strength wires spirally bound to form a rope (O'Connor, 1971, p. 372). Vertical cable suspenders that are fastened to the main cables hang the actual roadway. Stiffening girders and trusses are along the side of the bridge to distribute concentrated loads and help to keep the motion of the bridge at a minimum (Troitsky, 1994, p115).

The bridge that I build in class was a Warren Truss. It turned out to be a decent little bridge. It weighed 21.4 ounces so that put it on the lighter side of the bridges compared to the rest of the class. It wasn’t the lightest, but it was down with the smaller ones. It ended up holding right around thirty pounds and I’d say that not too bad. I knew my bridge was going to be on the lighter side, but I was okay with that because I knew that would maybe help me out in the long run by having a better overall ratio. I didn’t calculate what the ratio actually was, but I think I did alright considering what my bridge weighed and how much it held. It’s kind of crazy that a tiny bridge like that could hold 30 pounds.

Because of advancements in today’s technology in construction field, many types of bridges are being constructed depending on the requirement and their suitability for the situations.