Harvard Bridge
42.35457 - 71.09132Koordinaten: 42 ° 21 ' 16.5 "N, 71 ° 5' 28.8 " W
F1
MA 2A ( Massachusetts Avenue )
The Harvard Bridge (also MIT Bridge, Massachusetts Avenue Bridge, Mass.. Ave. Xylophone Bridge or Bridge ) is a concrete -clad, steel girder bridge in the state of Massachusetts in the United States. It connects the Boston's Back Bay with the city of Cambridge by ( Massachusetts Avenue at the same time there ), the Massachusetts Route 2A on the Charles River. It is with a length of 2165.1 ft ( 659.9 m), the longest bridge over the Charles River, with their length in the idiosyncratic unit Smoot is measured (as a result " 364.4 Smoots plus / minus an ear " ).
Only after several attempts, succeeded in the municipalities of Boston and Cambridge to build the bridge from 1887 to 1891 as a swing bridge, despite the frequently expressed antipathy of the population. In the following decades, the building was repeatedly overtaken and eventually completely renewed in the late 1980s, as the vibrations had not adopted acceptable dimensions and an identical bridge had collapsed for this reason.
The bridge was named after the Puritan theologian John Harvard.
Conception
The legislature of Massachusetts already adopted within the Acts of 1874, Chapter 175 and Chapter 314 of the necessary enabling provisions to build a bridge between Boston and Cambridge. Actually happened until 1882, however, nothing more, until the Act of Succession Chapter 155 of the Acts of 1882 more details for the construction of the proposed bridge stipulated, including the exact location:
"Acts of 1882, Chapter 155, Section 1: The cities of Boston and Cambridge are authorized to construct a bridge and avenue across Charles river, from a point on Beacon street in Boston, to a point in Cambridge, west of the westerly line of the Boston and Albany railroad. To the limitation ... did the line thereof Shall not be north-east of a line drawn from the junction of Beacon street and Westchester park, in Boston, to the junction of the harbor line with Front Street, extended, in Cambridge, normal south-west of a line drawn from the junction of Beacon street, Brookline avenue and Brighton avenue, in Boston, to the junction of the Boston and Albany railroad with Putnam avenue, extended, in Cambridge. "
The bridge should it be construed as a swing bridge and a passage width of at least 38 ft ( 11.6 m ) have. The city of Boston did not like these plans primarily because they offered no opportunity to lead the route of the Boston and Albany Railroad across the bridge. So happened again three years nothing until the Chapter 129 of the Acts of 1885, the required opening width to a maximum of 36 ft (11 m) was limited. This should apply until the other bridges would have a larger opening below the engaged position.
It was then still nothing until the city of Cambridge turned in 1887 with a petition to the federal legislation to move Boston to start of construction. This led to the adoption of Chapter 282 in the Acts of 1887, which was valid for both cities and they contributed equally to the construction costs. To this end, the city of Boston was allowed to exceed their credit limit and additional U.S. $ 250,000 (equivalent to approximately $ 6,570,000 today ) take. The estimated construction cost of the bridge amounted to order half a million U.S. dollars (equivalent to about $ 13,130,000 today ).
The law authorized a commission to build the bridge that a third, should be composed of the mayors to be determined person from the mayors of the cities involved and. If no agreement could be reached on this third person, the Governor of the State should take over this task. So far it did not come, as Hugh O'Brien and Willam Russell were able to agree on a native of Cambridge Leander Greeley. Over time changed with the political offices and the composition of the committee, as the following table shows.
From the construction of the bridge to its builders promised many advantages. The formerly as good as worthless land on the side of Cambridge were filled and been upgraded to valuable land, so the city was connected via the new bridge with the most valuable areas of Boston. In particular, for the residents of the neighborhoods Back Bay, South End and Roxbury was hoped by the new direct access to Cambridge extensive improvements, since in this way also Belmont and Arlington could be reached more quickly than before. It was expected that the road leading over the bridge will evolve over time to the central thoroughfare in both cities.
Construction
With the Acts of 1887 established that the bridge should be resting on wooden pillars, the ft on the first 200 (61 m) should be secured with stone foundations, since it was expected that the expansion of bank stabilization needed this place. This provision was, however, amended that the entire bridge of steel beams should insist on stone foundations, and approved July 14, 1887. As executive engineers William Jackson, John were. E. Cheney, Samuel E. Tinkham and Nathan S. Brock commissioned.
The requirements on the construction of the bridge were enormous, as the ground on which the building was to be built, has inherently some difficulties. Below a large part of Boston's soil is a layer of clay, and along the Charles River runs a geological fault line. At a depth of 200 ft (61 m) to 300 ft (91.4 m), the soil consists of a highly compacted mixture of gravel, boulders, silt and clay. It is located to about 30 ft ( 9.1 m ) below the surface of a pure layer of clay, the Boston Blue Clay ( BBC ), and, over that extend thinner layers of sand, gravel and other fill material. The BBC - layer to a depth of approximately 70 ft ( 21.3 m) consolidated high.
The substructure of the bridge originally consisted of two masonry abutments, 23 brick piers and a pile foundation, which was wearing a protective pillar of the rotating element. The upper structure consisted of 23 Gerber steel beams and the rotational member. The abutment on the Boston side resting on vertical piles sunk in the ground, while it is directly on the river bed on the side of Cambridge.
Originally connected the bridge to Boston Westchester Park with Front Street in Cambridge; Today, the entire route is known on both sides of the river as Massachusetts Avenue. The total length - measured from the respective center of the two abutment - amounted to 2,164 ft ( 659.6 m), the width was 69.3 ft ( 21.1 m) specified. The centers of the pillars were each 90 ft ( 27.4 m) apart, and the span of each item was alternately 75 ft ( 22.9 m) and 105 ft (32 m), with the longer carrier were self-supporting and the shorter were suspended between them.
The bridge leading over the road had two lanes for horse-drawn carriages and two rail tracks for trams on a total width of 51 ft ( 15.5 m). In addition, ran two 9.2 ft (2.8 m) wide sidewalks. Both the roadway and the side rail of the pedestrian walkways were made of wood, where the sidewalks were covered with an approximately 1.25 in ( 31.8 mm) thick asphalt layer. The rotating element, however, was only 48 ft ( 14.6 m) wide, about 149 ft ( 45.4 m ) long and was mounted on a wooden pillar. It had an electric drive and a small house for the bridge operator.
The bridge was opened on 1 September 1891. The announced on March 1, 1892 construction costs amounted to $ 510,642.86 (equivalent to approximately $ 14 million today ).
Naming
After the particular name Blaxton, Chester, Shawmut and Longfellow were discarded, the bridge was named after the Puritan theologian John Harvard, whose name bears the Harvard University. Today's Longfellow Bridge was opened 15 years later. Harvard was an early patron and financier of the University, but not - as is often assumed - its founder.
Possibly because of the proximity to the building, there are a lot of rumors at MIT with regard to the naming of the bridge, but all must be strongly doubted. This stems mainly from the fact that the bridge was built in 1891, during the MIT in 1916 moved to its current location, and thus in their direct neighborhood.
Maintenance and Events
In 1898, in addition to the curbs cycle paths have been installed. It was only in 2011, ie 113 years later, the city of Boston joined their own network of cycle paths with the driveways on the bridge.
Near the southeastern end of the bridge there is a memorial stone, reminiscent of a leap of Harry Houdini from the Harvard Bridge on 1 May 1908. Other sources date the leap already on 30 April of the same year.
In 1909, the bridge was declared and demanded to replace all iron and steel elements unsafe. In this context, at the same time the level of the bridge were increased slightly and replaced the tram tracks.
When the Metropolitan District Commission ( MDC) gained jurisdiction over the Harvard Bridge in 1924, the authority renovated a large part of the superstructure. In particular, the wooden beams were replaced with double T -beam, steel and wood elements of the deck with concrete and bricks. The tram tracks were also replaced again. The rotating element was removed and replaced with two fixed segments each with a length of 75 ft ( 22.9 m) replaced. The wooden pier was heavily modified by the use of concrete and stones to visually match the other pillars. The number of stone pillars rose from 23 to 24
In 1931 a tunnel under was built due to the ever increasing traffic at the intersection of Massachusetts Avenue and Memorial Drive, which replaced the level crossing.
The building has long been known as a Xylophone Bridge, which dated back to the special sounds, which produced the vehicles when crossing the bridge. The road, however, was in 1949 replaced by a new surface made of concrete and bitumen, and in the same part of the street car tracks have been removed and replaced by street lights. In addition ramps were added by outstanding at that time still under construction Storrow Drive. 1962, covering the sidewalks was replaced.
Investigation 1971-1972
The former Metropolitan District Commission ( later merged Department of Conservation and Recreation in ) commissioned a study on the technical examination of the Harvard Bridge to go to the cause of excessive vibration to the bottom due to numerous complaints from users of the bridge in the years 1971/72. As a result, it was found that the stability of the bridge for the loads occurring was not sufficient. Even before the completion of the study, the recommendation was made to introduce a limit of 7.3 tonnes per axle and 14 tons per vehicle. Alternatively truck should only be allowed to use the inner lanes where the bridge was stable. Despite these recommendations a weight limit of 23 tons per vehicle was imported.
The study's recommendations included, among other things, a strengthening of the existing structure by adding additional components to make them more stable in the longitudinal direction, as well as a complete replacement of the superstructure by either steel or concrete elements according to the current standards. Here, the new building should not weigh more than the old one, so that the pillars which were still in good condition, could be used as possible.
The advantage of a new building lay in the fact that the cost could be this much better calculated as a repair and reinforcement. A new bridge would consist of materials already known in advance ( for example, stretchable profile steel instead of brittle wrought iron) and be certified according to the AASHO standard HS -20. A repair would not, however, replace the old components from wrought iron with unknown quality and unknown condition and do not meet the requirements of the then current standards. The study provided we can already extensive calculations. The costs were estimated to be 2.5 to 3 million U.S. dollars (equivalent to about $ 17 million today ).
After completion of the study the weight limit to 14 tons to 23 tons on the outer and the inner lanes was adjusted. In 1979, this limit was extended to 14 tons on all lanes.
Replacement of the superstructures in the 1980s
After the collapse of the Mianus River Bridge in Greenwich, Connecticut in 1983, the Harvard Bridge was closed immediately and undergo an intensive inspection, as it was partially identical to the collapsed bridge. The investigation revealed that already two suspensions were broken, and then the traffic was limited to the inner two lanes. A few days later the bridge for all trucks and buses has been banned.
In 1986 published plans to replace the superstructure of the bridge while maintaining the abutment. The alternatives were very similar to those in the 1972 study conducted and were decided on the same basis. The structural modifications of the expansion from four to six longitudinal beams, removing the ramp "B" and the replacement of a staircase counted by a suitable also for disabled ramp at both ends of the bridge.
The historical value of the bridge was classified as very high, so that the plan provided to design the look of the bridge as similar as possible to the original building. In particular, the railings and lighting should be adopted. In order to develop precise definitions of the characteristics, the creation of a Historic American Engineering Record ( HAER ) was commissioned.
The work should be completed in two phases. In the first, for a period of 5 months scheduled phase, the downstream facing side of the bridge should be strengthened in order to allow the MBTA bus again. This only had to be done to the substructure work, so the car traffic was not affected. The prepared with a period of three Bausaisons phase 2 should then be used to replace the entire structure of the bridge. The cost of these measures have been estimated at 20 million U.S. dollars (equivalent to about $ 44 million today ). Phase 1 and Phase 2 in 1987 was finally completed in 1990.
- Comparison views before and after
In about the same view in 2009.
The underside of the bridge in 1985.
The same picture in 2009. Possible to see in particular the added side rails.
Measuring the length of the bridge
The length of the Harvard Bridge is also measured in the idiosyncratic unit Smoot. This goes back to the year 1958, where some members of the MIT fraternity Lambda Chi Alpha measured the length of the eastern sidewalk of the bridge by or the smallest new addition this year, a certain Oliver R. Smoot, carried from one end to the other attracted. 1 Smoot corresponds to its body size of 67 in ( 1.7 m). Oliver Smoot was later ironically, President of the International Organization for Standardization (ISO).
Since pedestrians are informed about applied at intervals of 10 Smoot marks the fact that the length of the bridge 364.4 Smoot ( plus / minus one ear) is. Scientifically correct to be expressed by a certain measurement error. Over the years, however, disappeared the negative deviation from the quotations as well as most markers on the bridge. Today, the markers are traced twice a year by members of the fraternity.
During the renovation of the structures in the 1980s, the markings were transferred to the new look of the eastern sidewalk with the express permission of the authorities. Likewise, the length of the plates for the walkways, instead of the usual 6 ft (1.8 m) in set Smoot. Today the police in Cambridge used these marks as positions in accident reports on the bridge.
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