The renowned Steel Bridge is a double deck structure that has a vertical-lift and is also known as through-truss. It goes across the Willamette River in the city of Portland in the United States and was opened in 1912, so it recently celebrated its 100th anniversary. The bridge has the dual function of carrying rail and bicycle traffic on its lower deck whilst the upper deck is dedicated to road traffic. This innovative arrangement makes the bridge extremely innovative and the fact that it has an independent lift continues to emphasise its prominence as the second oldest vertical lift bridge in the United States. The bridge is an important link between the Lloyd District, the Rose Quarter and the Old Chinatown area in the western part of the city.
A note about bridges in general
The primary sorts of scaffolds are curves, bar extensions, link stayed scaffolds, cantilever extensions and suspension spans. You will have perceived that this schedule does not incorporate truss spans. These are typically curves, shafts or braces, or cantilevers, or they may be parts of extensions, for instance the suspended compass of a cantilever scaffold, or the deck of a link stayed extension or a suspension span. The expression "truss span", in any case, is frequently saved for those which demonstration principally as shafts, while the others are talked about under the heading of the extensions of which they structure a part. You could say that a truss, in the same way as a container support or a prestressed compass, is more a kind of development than a sort of structure.
At different places in this site there are segments which clarify that the limits between the different sorts of scaffolds are not totally impenetrable, and that on a fundamental level at any rate, extensions might be constructed that are not clearly in a straightforward classification. The reason that the sorts of most extensions are evident is that these sorts have gotten prominent on the grounds that they are fruitful, and victory is best in the expansive focal areas of the accessible variable-space. Case in point, in the event that you make an amazingly level suspension span, you could put the wires in a solid lattice, and you might have a pre-stressed shaft obliging no harbors. The same is valid for curves - a greatly even curve might produce colossal push, and a bar might be a superior result.
The same trouble applies to numerous other human exercises, and in fact of numerous regular assemblies of species: despite the fact that there are numerous genera and species which charge the forces of scholars to order them, the larger part fall all the more effortlessly into aggregations. Then again, where there are a lot of nearly related species, there may be sporadic debate between "lumpers" and "splitters".
Construction of the bridge
The bridge was finished in 1912 and replaced an earlier Steel Bridge that was constructed in 1988 as a double-decker bridge. The structure was an ambitious one for its time and was the first bridge to span the Willamette River in Portland, Oregon. The name was coined due to the fact that the bridge was made out of steel and constructed from the usual wrought iron – this was an extremely innovative technique for its time. The Steel Bridge that followed in 1912 was simply named after the one preceding it.
The bridge’s design was entrusted to the engineering company of Waddel and Harrington who were based in the central city of Kansas City, Missouri, although the firm also had offices in Portland, Oregon. The building of the bridge was a joint venture between the Oregon-Washington Railroad and Navigation Company and the Union Pacific Railroad for a total cost of USD 1.7 million. This amount is calculated to be about USD 42 million in today’s money. The bridge opened in July 1912 for rail traffic whilst it opened for cars the following August.
The steel bridge that preceded the present one in 1888 had usually been crossed by horse-drawn streetcars with the city’s first electric street car following suit in November 1989. Being quite an advanced city for its time, all the electric streetcar lines were eventually moved to the new bridge beginning from September 1912. This service continued until August 1948 when the last company using the lines on the bridge which was the Alberta and Broadway Line went out of business and abandoned the bridge. There was also a single line of Portland’s trolley bus service that used the bridge for a little more than a decade – February 1937 till October 1949. Ironically, a similar electric car service returned to the Steel Bridge in 1986 when the Max Light Rail and the Portland Vintage Trolley were introduced in 1986.
The Steel Bridge became an important link in the new US 99W highway system between Harbor Drive and the busy Interstate Avenue. After almost a quarter of a century, Harbor Drive ceased to exist and the area became known as the Tom McCall Waterfront Park which now links the bridge to the city centre. There are currently four Max Light Rail lines across the bridge with over 600 trips being made on a daily basis.
Reconstruction and adaptation to today’s world
The Steel Bridge underwent a considerable rehabilitation and reconstruction in the middle of the 1980’s that cost around ten million dollars. The reconstruction included the building of a light rail line for the Trimet Company that serves the MAX light rail cars. The bridge was effectively closed for traffic from June 1984 and opened again in September 1986. The features of the bridge include a single-lane viaduct that connected the east approach of the bridge to another old viaduct that was still being used until 1988. Traffic passed from the southbound Interstate 5, eventually moving to Interstate 84, with the route eventually closed in 1989 as part of the changes that were intended to greatly facilitate traffic flow in the area of the Oregon Convention Centre. The Centre was still being built at the time but it eventually opened in 1990. Although there were several floods in the area in 1948, 1964 and 1996, the bridge did not suffer any significant damage largely due to its extremely sturdy construction.
Further improvements to the bridge were made in 2001. A 220 foot and 8 foot wide walkway with cantilevers was eventually installed across the south side of the lower deck of the bridge that was part of the Eastbank Esplanade. This brought the number of walkways accessible by foot to three, since there are also two very narrow sidewalks on the upper deck of the bridge. The Steel Bridge is still owned by the Union Pacific company with its upper deck leased to the Transportation Department of the state – this is eventually sub leased to the electric rail company Trimet. The City of Portland retains responsibility for the bridge’s approaches.
Statistics for the bridge’s usage include some figures released in the year 2000 indicating the busy nature of the viaduct. Daily traffic was around 23,000 vehicles that included a number of Trimet buses, 200 electric MAX trains as well as forty Amtrak trains. 500 bicycles also crossed the bridge – this was coincidental with the construction of the lower deck walkway. No less than 2100 bicycles crossed the bridge on a daily basis in 2005, this represented an increase of over 500 per cent over a five year period. MAX railway traffic has also increased considerably since the year 2000 when only one line was in operation (the Gresham-Hillsboro line or the ‘Blue Line’) with no less than 605 crossings on a daily basis in 2012. This vast increase in traffic resulted from the addition of three new lines over a twelve year period that were called Red, Yellow and Green, bringing the total of lines up to four.
Other construction work on the bridge took place in 2008 when the bridge’s upper deck was closed to traffic for a three week period to allow the building of a junction at the west end that was intended for the MAX Green Line. The main change was that the two inner lanes were restricted to MAX trains whilst the other vehicles, as well as all other motorized traffic were made to use the outer two lanes.
The Steel Bridge celebrated its 100th anniversary in 2012 with several celebrations across the city. The bridge was lauded as one of the best constructed structures in the state, but also across all of the United States with its wide variety of rails and tracks that carry all sorts of vehicles; cars, freight trains, trucks, Amtrak trains, MAX rails, bicycles, buses and last but not least, pedestrians.
Bridge structure and lift operation
The Steel Bridge has a lift span of around 211 feet or 64 metres. At the lower levels of the river the bridge’s lower deck is about 26 feet above the water with around 163 feet of vertical clearance when both decks are in a raised position. Additionally, the option of an independent lift allows the lower deck to be raised to no less than 72 feet – this means that the deck actually conflicts with the upper deck but the ingenious engineering does not allow it disturbance. Each deck is equipped with a system of complex counterweights, with two for the upper deck and eight for the lower deck for a total weight of no less than 4,100 metric tonnes.
The bridge’s machinery house is strategically placed on top of the upper deck lift truss with the operator’s room suspended from the top of the lift span’s truss. This is situated right below the machinery housing, enabling the operator to observe the river traffic as well as being able to keep an eye on the upper deck. The addition of the pedestrian walkway in 2001 resulted in the installation of a number of cameras as well as closed-circuit television monitors – these facilities greatly improved the operator’s capabilities to view the walkway across the lower deck.
The bridge’s renovation in the 1980’s allowed for several changes being made to the operation of the decks. The crossing gates that blocked the roadway and the raising of the sidewalks had been manually operated by two gate operators positioned at each side of the lift span. There were also small shacks for these gatekeepers that were strategically placed on the roadway deck right between the outer and inside traffic lanes – these were eventually removed to make way for the new design of the bridge’s decks. The bridge’s new gate house was eventually constructed above the roadway to allow for automated gate control. The bridge operator still accesses the gates, but these are now automated and not manually opened or closed.
Comments on the bridge
The Steel Bridge is a tribute to the engineering genius of one John Lyle Harrington who came up with the mechanism that managed to transform J.A.L. Waddell’s vertical lift bridges into structures that were both very solid, and extremely reliable. The bridge’s two moveable decks are masterpieces of engineering and when one view them simultaneously, the sheer originality and technical ability of Wadell and Harrington’s designs strikes you to the core. The bridge has survived in no small part to the modifications of the small components such as equalizers that are used to distribute the weight amongst the ropes and guides that eventually keep the bridge spans in alignment as these move. Other innovative features that are larger, include the vertical member that is telescopic as well as a complex system of ropes, counterweights and sheaves. The bridge has consistently won plaudits for its design and over one hundred years after its completion, it is still seen as ground breaking today and has also been described as being exemplary.
The bridge’s original components also have their own story to tell with several lifts and lowers. There are the Band brakes with old oak blocks that have a particular smell, this has been described as a sort of barbecue. The operation of new trains means that there is considerable skill on the part of the original builders that is revealed in the manner when the motor cuts off at just the right moment – this allows the bridge to coast to a stop in a remarkably smooth manner. Since the bridge operates through the friction of two separate sides of metal, the right moment varies from one day to the next and even at different hours. The innovative engineering allows the bridge to adapt to the natural circumstances. The application of grease to the sides of the bridge’s metal plates is crucial to its smooth and continues operation, and it has been described as ‘running on grease’ by some commentators.
Another intriguing aspect of the bridge is the amount of grease that is required to operate it properly. The machine room inside the bridge contains a hugely detailed map of the bridge that shows the right amount of grease that has to be applied to the many thousands of its joints to allow it to operate correctly. There is a whole army of workers who are specifically trained in applying and wiping off the excess grease who know perfectly well what amounts are required. Intriguingly, the colourful paintwork of the bridge is also used as an indicator to demonstrate how much excess grease is visible and how this can eventually be wiped off to ensure operation at the best of levels. Although this is a modern bridge, the systems it uses can be applied to today’s bridges and large structures since such mechanisms are timeless.
The Portland Steel Bridge is also a reminder of the sturdiness that the people of this great port city wanted out of their bridges. The bridge has nearly four and a half million kilos of counterweights and liftspans all held together in what can only be termed as highly innovative engineering styles. The posts of the bridge are incredibly massive, they are also very deeply embedded into the river bed thus enabling the bridge to carry all the latest passenger as well as freight trains, heavy trucks, buses and all sorts of other automobiles that traverse its upper span with absolute ease. Of course, the bridge does require the periodic renewal through occasional paint jobs and lubrication that has to take place more or less on a daily basis. Harrington was no idle boaster when he declared that if properly maintained, his bridges would remain forever.
If the Steel Bridge in Portland were built today, it would not be far different from the original structure. Fabricated together by the Oregon Railway and Navigation Company and the Union Pacific Railroad, the Steel Bridge was the biggest extendable extension on the planet at the time of its opening. The extendable capacity of the focal compass, a 211-foot steel through Pratt truss, twofold vertical lift compass, makes the Steel Bridge a paramount illustration of an uncommon designing configuration. The easier line deck could be raised for the section of little vessels without exasperating vehicles movement on the upper deck. For bigger vessels, both compasses could be raised. It is accepted to be the world's just twofold lift compass that can raise its lower deck freely of the upper deck. Opening both decks considers 163 feet downright leeway. The scaffold was outlined by Waddell and Harrington, counseling designers from Kansas City, and the railroad engineers. The extension was constructed over a two-year period at an expense of $1.7 million. There are two auxiliary steel through Pratt truss compasses, every 290 feet long. The structure has minimal beautifying frivolity, other than a fashioned iron woven grid railing. This structure is found close to the site of the first Steel Bridge (1888). The 1912 structure was resolved qualified for the National Register in April 1980. The City of Portland has created an extremely pleasant site highlighting the new pedestrian/bicycle pathway over the Steel Bridge (click here), and incorporates short history and a determination of photos from the Historic American Engineering Record.
The Steel Bridge can also be compared to other bridges that span several great rivers in the United States. The first one that springs to mind is the Golden Gate Bridge that is surely another masterpiece of engineering and demonstrates the skill of the engineers and designers. Although there are some similarities with the Oregon Steel Bridge, the Golden Gate is much longer and wider and spans a far greater arc of river. However, the main facets of this bridge are very much in keeping with the Portland bridge, since it is also used for trains and freight as well as normal automobiles. This is a suspension bridge that was built much later than the original Oregon Steel Bridge and uses over 1.2 million rivets to hold the bridge together. It is a masterpiece of civil engineering and includes some original art deco features that are not found in the Portland Bridge although the latter appears to be slightly more sturdy and reliable. These features add to the sense of mystique and beauty of the bridge.
The Verrazano- Narrows bridge is another wonderful suspension bridge that could be compared to the Portland Steel Bridge. This has now superseded the Golden Gate Bridge as the longest suspension bridge in the United States but has had to cede that accolade to the Humber Bridge that was constructed over the Humber River in England in 1981. The bridge is a marvel of suspension engineering and is comparable to the Oregon Steel Bridge although the latter continues to thrill due to its construction that dates back over a century. Like the Portland Bridge, the Verrazano-Narrows Bridge is an important highway link and is one of the crucial highways through the clogged traffic of New York City. The bridge is also an important landmark in Hudson Bay since all the container traffic passes from right underneath it.
The Portland Steel Bridge can be considered as one of the modern wonders of the engineering world since it has an incredible sense of momentum in its design. There is a great sense of achievement in the bridge especially with its excellent workmanship and design. The complex system of counterweights is also an engineering marvel and demonstrates how the greatest engineers of the time solved problems that appeared to be insurmountable. If the bridge were to be built today, construction methods would undoubtedly be far more modern, but the essential engineering style would be very much the same.
The Portland Steel Bridge is truly a marvel of engineering and although it is over a century old, it could have easily been built today. It continues to provide essential service to the city of Oregon and with its incredibly complex mechanisms; it is surely one of the landmarks of civil engineering in the United States. The innovative double decker structure makes it ideal for various transport services with bicycles having increased substantially over the bridge in the past decade – the Steel Bridge is one of the very few all over the world that has dedicated bicycle lanes. It is an incredible feat of engineering and will continue to be considered so for many decades to come.
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