Smithfield Street Bridge - Research Paper Example

Smith field street bridge In 1818, the first river bridge in Pittsburghs was constructed across the Monongahela River and was named the Smithfield Street. The Street historically speaking was a combination of three successively built bridges. The bridges were built by famous bridge engineers like Lewis Wernwag, Gustav Lindenthal and John A. Roebling. All these engineers were born in Germany, which was the most famous engineering and technology hub of the century. America was swift to identify their unique abilities in the bridge engineering field. The paper will reveal how construction of the bridge revolutionized the engineering and technological fields. Key words: Smithfield Street, bridge engineering, technology hub Introduction Pittsburgh’s huge need for bridges presented a good opportunity for the engineers to showcase their knowledge and talent .The only form of transport within the town and some sections of the river banks in the early 19th century was the use of skiffs or canoes. As the community developed people realized that it was mandatory to build a ferry service and in 1818 the Jone’s Ferry service was established, in order to improve their business oriented culture. The ferry operated between southern bank of Monongahela and the base of Liberty Street. Stock and goods were carried by boats while passengers were carried by skiffs. In 1840, a more advanced horse ferry was developed which used blind horses as motive power. The blind horses were fitted in horizontal wheels when then propelled the boats (Von 77). A few years later a steam ferry was established by Captain Erwin on the southern bank of Ohio near the section where the rivers formed a confluence. Sadly, the ferry project collapsed a few years later together with the Jones ferry project.Leaving just one operational steam ferry which operated from Penn Street to Saw Mill Run.The essay will deal with the three bridges elected at the Smithfield Street and how their construction revolutionized the bridge construction technology in the 19th century when civilization was developing at a remarkable speed The Three Bridges The first bridge among the Pittsburghs highway bridges was known as the Monongahela Bridge. A bill was passed In Pennsylvania by the state legislative council allowing two bridges to be built at Pittsburg. One would be built over the Allegheny and the other one over Monongahela. Judge Findley, a member of the legislative council was given the task of calculating the overall cost of the structures. His calculations indicated that approximately 1200 feet of the river required chains that were 1590 feet long and four other iron chains weighing 64 pounds on the foot all amounting to $8,800 (Henry 77). Work done by Smith’s would cost approximately $3,080. A bridge that was 30 feet wide would need plank worth $900 and three piers each at $15,000. Other expenses would be from buying certain patents rights, incidentals and putting together all adding up to$32,326. The first arch on the piers was laid in 1818. The bridge was promptly built and rested on seven intermediate piers of stone and two abutments. It was constructed using iron and wood and the arches were made of catenaries curves with the contract price being $ 110,000. The weather also seemed to favor the contractor since the weather was excellent during the fall. The awesome bridge as many described it many people hoped it would reach the northern shore before the December of 1818. The second bridge on the Allegheny surprisingly did not fascinate many people like the one on the Monongahela side. This is because it was not very advanced but management was keen to ensure it would be completed on time (Eric 87). What Pittsburg unleashed was very fascinating and unique and had not been exhibited in any American town or city. Pittsburg had developed two marvelous bridges over two enormous rivers which were 400 yards apart from each other. On November 1818, the Monongahela Bridge was completed after the last arch was laid and the whole was floored. To announce the achievement the builders and undertakers of the building discharged cannons in the middle pier and started waving the American flag over the middle arch. The flag had been attached to a beautiful banner with attractive representations. The Washington guards and the city guards each on different sides of the river trooped across the bridges saluting (Von 66). In the evening the laborers sat to take a substantial dinner which was presided by the superintendent or meritorious undertaker of the construction, Mr. Johnston. Llewellyn Edward, another engineer described the Monongahela Bridge as a superstructure made up of eight wooden truss spans and 1500 feet in length. The substructure had 7 piers of masonry stone and two abutments. Lewis Wernwag was the designer of both the Allegheny and Monongahela bridges and perhaps the most famous American bridge engineer. He was born in Germany but came in U.S.A at 17 and decided to settle in Philadelphia and mainly specialized in wood truss spans. His skills and knowledge were first exhibited when he constructed the single–span bridge in 1812 across the Schuylkill River in Philadelphia. He later on constructed many railroads and highway bridges. A letter written to Samuel Smedley by John the son of Lewis was published in the “Engineering News” in 1885 (Henry 37). The letter had a list of 29 bridges built by Lewis during his 27 year old active career. Out of the many bridges the Monongahela Bridge was listed among the most legendary. The Monongahela Bridge, for many years, was used to give service to the Pittsburgh community but unfortunately it was destroyed in just ten minutes in the “Great Fire” in 1845. The bridge disappeared in a trailing line of flame and smoke on April 10. It was a huge conflagration that devastated USA cities in the 19th century. Unfortunately, during the period of its destruction it was the only the bridge across Monongahela in Pittsburgh. After the disaster abutments and old piers were repaired. John Roebling oversaw the reconstruction of a new suspension bridge at a price off $55,000. In June 1845, construction of the new structure began what many people considered to be a short period after the fire incident (Eric 91). The abutments and piers of the wooden structures were damaged by the great fire and needed extensive repairs in order to fit in the newly built superstructure. Reconstruction had to be done again using new measurements. The length between the abutments had to be precisely 1,500 feet and also had to be divided into 8 spans with its average distance from one to Centre to the other being 188 feet. The piers were to be 50 feet long and 36 feet high with their top being 11 feet wide. Two masonry substantial cut stones measuring 3 feet high and 9 feet square inches were to be erected on every pier which were 18 feet apart from each other. The bed plates were laid down on the piers so that they could support iron towers that also held wire cables through the method of pendulums. Each span had to be separated by two different cables meaning that 18 cables suspended 18 towers. The towers were made up of 4 columns made in the form of a double cornered or sided pilaster. The pilasters were linked together by 4 lattice panels held firmly by screw bolts (Von 44). The panels of the upward and downward stream would close the entire section of the tower but those located in the bridge’s side would just act as an open entry way for the extension of sidewalks. The columns and pilasters had huge casting rests which supported the pendulum that held the cables. The top most pin of the pendulum lied within a seat made up of ribs and seats of a square box that filed the middle of the casting. In order to exact the whole pressure on the four columns underneath twelve fragments of arches butt were placed on the center box and the rest on ends of the fourth corners. The pendulums were made up of 4 solid bars each measuring 6 inches 2 feet long, from every midpoint of the pin. The pins had a diameter of three inches (Eric 60).In order to lower the pin the cable of single span was straightly attached and the connection made had 4 links measuring 6 inches 3 feet long and 1.4 inches by 4 inches. The pendulums and the opposite cables were all placed in an inclined position. The two outer sidewalks were five feet wide. The roadway was exactly 20 feet and the fender rails separated it from the sidewalk. Fender rails built were raised from the ground by using blocks that were six inches high and eight feet apart this made the total width between the railings of the bridge to be 32 feet. The anchor chains supporting the cables of the last and first spans used the same method used in the Pennsylvanian canal to support it below the ground. The method was known as aqueduct which was used to protect the oxidization of the anchor chains. The cables had a diameter of 4.5 inches and a solid wrapper was used to protect them. Stays of charcoal iron were also used which were exactly 1.4 inches round (Henry 29). The suspenders of the charcoal iron on the other hand were also made of the same material and had a diameter of 1.5 inches and were four feet apart. The first construction design of the Monongahela Bridge had aimed at acquiring a high level of stiffness. In most cases stiffness was the most crucial aspect of suspension bridges. According to John its engineer, the wind and did not affect the structure and the vibrations made by the two heavy coal locomotives each weighing seven tons could not match the power of the truss bridge supported by powerful wooden arches. The bridge had been built to allow large and heavy locomotives to pass through safely. Most of the coal used in Pittsburgh was carried by four to six locomotives every day. In the old structure the pressure exacted by arch timbers had destroyed two piers as a result of the pressure and shaking (Eric 59). The new bridge according to its engineers would not be prone to such an accident as it was only under pressure from the vertical towers unlike the previous bridge. The bridge during its period of service under went through a lot of trials. It had to endure huge crowds viewing steamboat races who would make sudden rushes on both sides of the bridge. Such conditions were major tests on the designer’s foresights on various stability oversights. For 35 years, the bridge continued to serve the people by carrying the heaviest steam rollers,horse cars, horse teams puling truck loaded with heavy machinery and iron. Defaults in the span arrangement started being evident as the suspension bridge seemed to be under a lot pressure constantly due to the load they were carrying each and every day (Von 80). Despite Roebling installing the inclined stays, at times a loaded span would at times deflect a distance of about two feet. The same deflection was also noted in the adjoining spans. The experience did not only enlighten the designer but also the whole profession of engineering. As a result of the large and busy traffic the bridge began to display signs of strain. The managers of the bridge company decide to review the possibilities of building a new bridge. In 1871, bids were ready to open up but, later on the Pittsburgh city tried to acquire the franchise. In 1880, the board of managers finally decided to take down the Roebling Bridge and build a new one. To do so the board of managers began by selecting a local engineer for the project, Charles Davis. The engineer made a design of another fascinating suspension bridge, his unique design drawing skills were linked with his abilities in railway surveying. He was elected as the top government engineer of Allegheny County. Work on his design began in mid-summer of 1880. Davis planned to build a suspension bridge that would have 2 channel spans each measuring 360 feet each and 2 other shore spans each measuring 180 feet (Henry 92). The base of the channel piers was first laid and later on the piers were built with each pier having a height of 10 feet. However, his project, design and prior contracts were cancelled and stopped. David Hostettler, an influential businessman wanted the bridge to be me accommodative and more advanced and urged that Davis’s design was below average. He wanted a bridge that could allow cars to pass over it over the southern banks of Ohio and Baltimore. The bridge managers had to call another engineer by the name Gustav Lindenthal to a developed a more advanced design of the truss bridge. David unlike his fellow counterparts was very bold and original in his complex structural designs. David was invited by the board of managers to help them improve the newly revised bridge design. He suggested that there was need to widen the bridge by constructing another track or roadway. The proposed plan would utilize the piers and foundations which had been used earlier by Davis. The new plan would ensure that the superstructure reached 64 feet upwards or was 8 feet wider than the already constructed piers (Von 31). The width of the new channel span would be 48 feet. The channel spans would be made up of Pauli trusses which would be 8 inches and 25 feet apart. The sidewalk on the upper part would also be detachable. Materials and methods used in the construction This consisted of hard, durable and grey sandstone that was not mixed with iron oxide or clay particles. It was mined at Homewood, near Lake Erie Railroad in Pittsburgh. In the mines it was in huge blocks of a hundred to five hundred cubic yards without being stripped. The masonry was rock faced with one inch wide drafts round the surface of the stones that were in courses of alternate stretchers and headers. The stones had a dimensional thickness of between 24 to 16 inches, 3 to 11 feet in width, 7 to 4 feet in length and with regularly dressed joints and beds. The wing walls and abutments were made using regularly shaped stones that had dressed beds as the core of the pier’s concrete filling had already been used up. The layers applied were 12 inches thick and were undoubtedly the most superior form of stone backing. Using of spalls was prohibited in the masonry (Eric 63). The spaces in between the stones had concrete which was also bumped with iron rammers automatically making the course water tight. The bond was given a lot of attention. The blocks of stones were placed in alternate stretcher courses and headers which made the possibility of finding joints in the cores of the piers impossible. This method ensured each stone was bonded in all directions. After setting occurred the concrete backing became very tough and hard and actually made the piers to be monolithic as a result of the great tenacity and adherence the concrete backing had on the stones. Every stone was keenly laid using heavy wooden rams and if any stone broke in the operation it was immediately removed. The surface joints of the completed masonry we curved out to a depth of exactly 1 inch and carefully moistened and caulked using sand mortar and Portland cement mixed in the ratio of one is to one. American Portland cement provided the mortar for making foundations and concrete backing while Rosendale was used ordinarily. The cement had to have certain standards for it to be used. All the cement had to be grounded finely such that 90% of the cement could pass sieves of about 50 meshes down to the lineal inch (Von 33). The cement was also tested using a Fairbanks testing machine to test its tensile strength with other molded briquettes of cement. The third design of the bridge was the most thoroughly scrutinized design plan among the bridges ever built in Pittsburgh. The cement, cables and spans were keenly measured and tested to ensure the bridge was constructed to perfection. Many people agree that due to the strict and keen supervision of the methods and materials used, the bridge was listed among the marvelous technological monuments. If a structure was to be built currently combining modern technological advancements with the olden details, scrutiny and team work witnessed in construction of the Smithfield Street Bridge then we would build a magical, splendid and fault free structure. The Monongahela Bridge due to combined efforts and ability to learn from catastrophes became the largest bridge in the 19th century (Eric 59). The graceful structure proved that modern advanced engineering practices could build a useful and at the same time along lasting splendid land mark. Modern engineers should adopt the strategies used by the ancient bridge constructors of learning from their mistakes. Their ability to identify and correct their mistakes assisted them to build the strongest steel truss bridge in USA. If earlier engineers with their limited technological exposure could make the only bridge using the Pauli system or lenticular truss design in Pittsburgh, then modern engineers with their advanced technology can definitely build more stunning structures. Smithfield Street Bridge is perhaps the most graceful bridge in Pittsburgh this is supported by the fact that it was included in the Civic engineering landmark by the national historic council of civic engineering (Von 70). Modern engineers have a lot to learn from the marvelous innovative design built at a time when technology was not very advanced. If a group of innovators can sit down and adopt some of the methods used in building the bridge then an outstanding structure with numerous purposes can be established. Scholars insist that necessity is the mother of invention. The city of Pittsburgh’s need to have bridges made them construct a bridge that can be listed among the renowned historic landmarks due to its usefulness and general outlook. If a bridge can get the honor of being listed as a historic landmark then this means that the structure is very stunning and the honor is among the rarest and highest America can bestow on a bridge. Our modern engineers should embrace this type of innovation and build a bridge that can withstand numerous catastrophes such as earthquakes, fire and tornadoes. As time goes by new forms of catastrophes are emerging and as technology grows there is need to be more innovative to more significant impacts in the technological field. Conclusion Smithfield Street Bridge in Pittsburgh was built around 1883 and is still standing strong up to date. It is also the oldest remaining river bridge in Pittsburgh. In 2014, the bridge marked 132 years in service. Its stunning longevity and unique design made it a Pittsburgh monument as well as a national treasure. Regardless of its age, Smithfield Street Bridge is still among the city’s major links that connects the southern and the northern shores of Monongahela River. Apart from the high transit use and the auto mobility it provides, the pedestrian walkway forms a crucial link between the famous Golden Triangle and the various attractions on the waterway especially around the Station Square. In 1994, the bridge was shut down again for another major reconstruction to strengthen the structural supports. This improved the bridge’s weight limit from 3 to 23 tons making it the ultimate bridge in Pittsburgh. Works cited Eric, Mare."Aluminum Floor for an Old Bridge, "London: Belleville, Pittsburgh Press, 2011, Print. Von,Powel. Pittsburg and the Vicinity. Boston: Pennsylvania, Madison and Wise press, 2009, Print. Henry, Joseph. The Bridges of Pittsburgh. New York: Maryland, Yale, 2012, Print. Read More