Harvard Bridge
Template:Short description Template:Use American English Template:Use mdy dates Template:Main other{{#invoke:Infobox|infobox}}Template:Template other{{#invoke:Check for unknown parameters|check|unknown=Template:Main other|preview=Page using Template:Infobox bridge with unknown parameter "_VALUE_"|ignoreblank = 1| also_known_as | alt | aqueduct_name | architect | begin | below | bridge_name | builder | built | capacity | caption | carries | child | clearance | clearance_above | clearance_below | closed | collapsed | demolished | complete | contracted_designer | coord_format | coordinates | cost | crosses | dedicated | depth | design | designer | destroyed | diameter | downstream | electrification | embed | embedded | ends | engineering | extra | fabricator | fetchwikidata |first_length | first_diameter | followed | gauge | height | heritage | id | id_type | image | image_caption | image_size | image_upright | inaugurated | lanes | length | life | load | locale | location | mainspan | maint | maintained | mapframe | mapframe-caption | mapframe-custom | mapframe-id | mapframe-coord | mapframe-wikidata | mapframe-point | mapframe-shape | mapframe-frame-width | mapframe-frame-height | mapframe-shape-fill | mapframe-shape-fill-opacity | mapframe-stroke-color | mapframe-stroke-colour | mapframe-stroke-width | mapframe-marker | mapframe-marker-color | mapframe-marker-colour | mapframe-geomask | mapframe-geomask-stroke-color | mapframe-geomask-stroke-colour | mapframe-geomask-stroke-width | mapframe-geomask-fill | mapframe-geomask-fill-opacity | mapframe-zoom | mapframe-length_km | mapframe-length_mi | mapframe-area_km2 | mapframe-area_mi2 | mapframe-frame-coordinates | mapframe-frame-coord | mapframe-switcher | material | material1 | material2 | name | named_for | native_name | native_name_lang | notrack | num_track | number_spans | official_name | onlysourced | open | opened | opening | os_grid_reference | other_name | owner | passable | piers_in_water | pierswater | preceded | qid | rebuilt | references | refs | replaced_by | replaces | second_length | second_diameter | spans | starts | structure_gauge | third_length | third_diameter | toll | towpath | track_gauge | traffic | traversable | upstream | website | width | winner }}Template:Main other
The Harvard Bridge (also known locally as the MIT Bridge, the Massachusetts Avenue Bridge, and the "Mass. Ave." Bridge) is a steel haunched girder bridge carrying Massachusetts Avenue (Route 2A) over the Charles River and connecting Back Bay, Boston with Cambridge, Massachusetts. It is the longest bridge over the Charles River at Template:Convert.<ref name=structurae />
After years of disagreement between the cities of Boston and Cambridge, the bridge was built jointly by the two cities between 1887 and 1891.<ref name=haer3 /> It was named for Harvard University founder John Harvard.Template:Sfn Originally equipped with a central swing span, it was revised several times over the years until its superstructure was completely replaced in the late 1980s due to unacceptable vibration and the collapse of a similar bridge in Connecticut.
The bridge is known locally for being marked off in the idiosyncratic unit of length called the smoot.<ref name=haer5 /><ref name=mithistory49 />
ConceptionEdit
In 1874 the Massachusetts Legislature authorized construction of a bridge between Boston and Cambridge,Template:Sfn and in 1882 follow-up legislation set out its location.Template:Sfn
The bridge was to have a draw with an opening of at least Template:Convert.Template:Sfn Boston interests opposed the bridge, mainly because it did not provide for an overhead crossing of the Grand Junction Branch of the Boston and Albany Railroad. Further legislation in 1885 changed the draw to a clear opening of at least Template:Convert and no more, until the other bridges below the proposed location were required to have a larger opening.Template:Sfn There was still no substantive progress until 1887, when Cambridge petitioned the Legislature to compel Boston to proceed; the resulting act required each city pay half the cost, and allowed Boston to raise up to $250,000 (US$Template:Inflation with inflationTemplate:Inflation-fn) for this purpose, in excess of its debt limit. This implied an estimated cost of US$500,000 (US$Template:Inflation with inflation<ref name=inflation-US />) for the bridge.
The Legislature provided for a bridge commission, to consist of the mayors of Boston and Cambridge plus a third commissioner to be appointed by the mayors.Template:Sfn The mayors of Boston and Cambridge, Hugh O'Brien and William E. Russell, appointed Leander Greeley of Cambridge as the third commissioner,Template:Sfn though this appointment changed over time.Template:Sfn
| Year(s) | Mayor of Boston | Mayor of Cambridge | Third Commissioner | |
|---|---|---|---|---|
| 1887–1888 | Hugh O'Brien | William E. Russell | Leander Greeley | |
| 1889–1890 | Thomas N. Hart | Henry H. Gilmore | ||
| 1891 | Nathan Matthews, Jr. | Alpheus B. Alger | Leander Greeley (died February 15, 1891Template:Sfn or February 16, 1891<ref>{{#invoke:citation/CS1|citation | CitationClass=web
}}</ref>) |
The commission's 1892 report claimed:Template:Sfn
<templatestyles src="Template:Blockquote/styles.css" />
The effect that the bridge will have upon both cities is obvious. The low land and marshes on the Cambridge side, formerly almost valueless, have been filled in and have become valuable; and Cambridge is now connected with the choicest residential portions of Boston. The residents of the Back Bay, South End, Roxbury, and other southern sections of Boston are now connected directly, by way of West Chester park and the bridge, with Cambridge, Belmont, Arlington, and adjacent towns; and this thoroughfare in Boston, it is believed, will ultimately be the central one of the city.{{#if:|{{#if:|}}
— {{#if:|, in }}Template:Comma separated entries}}
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NameEdit
The bridge is named for the Reverend John Harvard, for whom Harvard University is also named, rather than for the university itself. Other names suggested included Blaxton, Chester, Shawmut, and Longfellow.Template:SfnTemplate:Efn
EngineeringEdit
Originally projected as a wooden pile structure with stone pavement for the first Template:Convert (because the Charles River Embankment extension was expected to take that space) the design was changed to be entirely iron spans on stone piers. The general plans were approved on July 14, 1887.Template:Sfn The engineers were William Jackson (Boston City Engineer), John E. Cheney (assistant Boston City Engineer), Samuel E. Tinkham (assistant engineer), and Nathan S. Brock (assistant engineer at bridge).Template:Sfn
The subsurface conditions at the bridge location are extreme. Much of Boston is underlain with clay, but the situation at the bridge is exacerbated by a fault which roughly follows the path of the Charles River itself. From a depth of approximately Template:Convert below existing ground, is a very dense till composed of gravel and boulders with a silt-clay matrix. Above that to approximately Template:Convert below the surface is Boston blue clay (BBC). Over this are thin layers of sand, gravel, and fill. The BBC is overconsolidated up to a depth of approximately Template:Convert.<ref name=haer4 />
The substructure originally consisted of two masonry abutments and twenty-three masonry piers, as well as one pile foundation with a fender pier for the draw span. The superstructure was originally twenty-three cantilevered fixed spans and suspended spans, of plate girders with one swing span.Template:Sfn The Boston abutment rests on vertical piles, while the Cambridge end is directly on gravel.<ref name=haer4 />
Originally, the bridge was built across the Charles River connecting West Chester Park, in Boston, with Front Street, in Cambridge. This is now called Massachusetts Avenue on both sides of the river. As originally built, the total length between centers of bearings on abutments was Template:Convert with a draw Template:Convert wide between centers. The width of the bridge was Template:Convert except near and on the draw.Template:Sfn
The bridge as built was composed of fixed and suspended spans roughly Template:Convert long and piers Template:Convert apart, center to center.Template:Sfn The span lengths alternated between Template:Convert. The longer spans were cantilevered, while the shorter spans were suspended between the cantilevers.<ref name=haer4 />
The original roadway contained two lanes for horse-drawn vehicles and two street car tracks, for a total width of Template:Convert. There were also two Template:Convert sidewalks.<ref name=haer3>HAER, p. 3</ref> The original roadway and sidewalk stringers were of wood, with an approximately Template:Convert thick covering of asphalt on the sidewalk and a Template:Convert spruce wearing surface on the roadway.<ref name=haer3 />
The exception was at the swing span, which was Template:Convert wide. This span was approximately Template:Convert long, and sat on a wooden pier. It was a double-cantilevered, electrically-driven structure also carrying a bridge caretaker's house.<ref name=haer3 />
The bridge opened on September 1, 1891.Template:Sfn The original cost of construction was $511,000,Template:Sfn $Template:Inflation in current dollars.<ref name=inflation-US />
Maintenance and eventsEdit
In 1898, Template:Convert bicycle lanes were installed next to each curb.<ref name=haer3 /> In 2011 (113 years later), the City of Boston finally connected these lanes to its own bike lanes.<ref name=bglanes>Template:Cite news</ref>
A marker near the southeast end of the bridge memorializes one of Harry Houdini's "well known escapes", during which he jumped from the bridge on May 1, 1908. (Other sources give the date as April 30, 1908.)<ref name=clinger>Template:Cite book </ref>
The bridge was declared unsafe in 1909, requiring all of the iron and steel to be replaced. The draw was elevated slightly and the trolley rails were replaced as well.<ref name=nyt1906>Template:Cite news</ref>
When the Metropolitan District Commission (MDC) took control of the bridge in 1924, they rebuilt much of the bridge superstructure. They replaced the wooden stringers with steel "I" beams, topped wooden deck elements with concrete and brick, and replaced the street car rails.<ref name=haer3 /> Structural steel hangers replaced wrought iron. The swing span was converted into two Template:Convert fixed spans the same width as the rest of the bridge. The wooden pier was heavily modified with concrete and stone to make it resemble the other piers, increasing the number of stone piers from 23 to 24.<ref name=haer4>HAER, p.4</ref><ref name=tech044>Template:Cite news</ref>
Heavy traffic at the Mass Ave and Memorial Drive intersection on the Cambridge end of the bridge led to the construction of an underpass in 1931.<ref name=haer5>HAER, p. 5</ref>
The bridge was formerly referred to as the "Xylophone Bridge" because of the sound its wooden decking made when traffic traveled over it. This decking was replaced in 1949 with Template:Convert concrete-filled "I-beam lok" grating topped with a Template:Convert thick bituminous wearing surface. At this time, all bearings were replaced, and the trolley car tracks were removed, as were granite blocks. The trolley car poles were reused for street lights. Ramps between the bridge and the under-construction Storrow Drive were added.<ref name=haer5 />
The 1924 sidewalk slabs were replaced by precast, prestressed slabs in 1962.<ref name=haer5 /> The fifteen expansion dams were replaced or repaired in 1969.<ref name=haer6>HAER, p.6</ref>
Engineering study, 1971–1972Edit
An engineering study was performed by the Metropolitan District Commission (later merged into the Department of Conservation and Recreation) in 1971–1972 due to complaints by bridge users of excessive vibration.<ref name=haer5 /><ref name=leet2>Leet, phase 2</ref> The bridge was found to be understrength for its load. Before the final study was complete, the recommendation was to place a load limit of Template:Convert per axle and a total of Template:Convert per vehicle, or to restrict trucks to the interior lanes, where the bridge was stronger. A Template:Convert limit was imposed.<ref name=leet3>Leet, phase 3</ref>
Suggestions made included strengthening the existing structure by adding either struts or plates to make the existing four beams along the length of the bridge into a stiffening truss, or to replace the superstructure with a new one, made of either steel or concrete, which would be up to current standards.<ref name=leet2 /> The recommendation was to replace the superstructure with one weighing approximately the same in order to reuse the piers, which were in good condition.<ref name=leet3 />
The reasoning was that the cost of a new structure could be predicted much more easily than the cost of repairing and reinforcing the existing bridge. The resulting new bridge would be of known materials and quality, such as ductile structural steel rather than brittle wrought iron, and rated at AASHO HS-20. Repairing the existing structure would leave old wrought iron of uncertain quality and condition standing, and would not bring the design up to (then) current standards.<ref name=leet3 /> Detailed engineering calculations were included.<ref name=leet32>Leet, phase 3, appendices</ref> The price was estimated at US$2.5 million to US$3 million<ref name=leet3 /> (US$Template:Inflation to US$Template:Inflation with inflation<ref name=inflation-US />).
The action taken based on this study was to establish load restrictions on the bridge, Template:Convert in the outer lanes, Template:Convert on the inner lanes. This was expanded in 1979 to a flat limit of Template:Convert on the whole bridge.<ref name=haer8>HAER, p.8</ref>
Superstructure replacement, 1980sEdit
After the failure of the Mianus River Bridge at Greenwich, Connecticut in 1983, the Harvard Bridge was shut down and inspected because it contained similar elements, specifically the suspended spans.<ref>Template:Cite news</ref><ref>Template:Cite news</ref> Traffic was restricted to the inner two lanes due to the discovery of two failed hangers on span 14. A few days later, all trucks and buses were banned from the bridge.<ref name=haer8 />
In 1986, a report was published containing the plan to replace the superstructure on the existing supports. Alternatives considered were very similar to the 1972 report, and were similarly decided.<ref name=replacement7>Replacement, p.7</ref> Structural modifications included an upgrade from four longitudinal girders to six of the same shape and replacement of a stairway with a handicapped pedestrian ramp on the Boston end of the bridge.<ref name=replacement>Replacement, p.4</ref>
Ramp "B", from southbound (Boston bound) bridge lanes to eastbound Storrow Drive, caused traffic to merge onto Storrow Drive from the left (high speed) lanes using a short acceleration lane, causing safety issues. The MDC requested elimination of this ramp. Compared to overall bridge traffic of 30,000 vehicles per day, traffic on ramp B was found to be low, approximately 1,500 vehicles per day with a peak of 120 vehicles per hour.<ref name=replacement910>Replacement, page 4-6</ref>
The historic value of the bridge was considered significant, so the plan was to make the replacement superstructure appear similar, with similar railing and lighting. In order to document the pre-existing structure, a Historic American Engineering Record (HAER) would be prepared.<ref name=replacment11>Replacement, p.11. Note the use of the HAER document throughout this article.</ref>
Pier 12 was exhibiting inappropriate movement and was scheduled for reinforcement.<ref name=replacement5>Replacement, page 5</ref>
The work would be done in two phases. Phase 1 would reinforce the downstream side of the bridge to allow MBTA bus traffic, and was expected to take 5 months. Most of this effort would be spent on the underside of the bridge and would not affect existing traffic. Phase 2 would replace the entire superstructure and was expected to take three construction seasons to implement. Cost was estimated to be Template:USD<ref name=replacement5 /> (US$Template:Inflation with inflation<ref name=inflation-US />). Phase 1 finished in 1987, and Phase 2 in 1990.<ref name=globe1990>Template:Cite news</ref>
- Before-and-after images
- Harvard Bridge, Spanning Charles River at Massachusetts Avenue, Boston ( Suffolk County, Massachusetts).jpg
Bridge viewed from the upstream Cambridge side in 1985. Construction barrels restricting traffic from the outside lanes, and general wear and tear are visible (click on image to enlarge)
- Harvard Bridge from Cambridge, 2009.jpg
Roughly the same view, in 2009. Superstructure is in much better shape only 20 years after completion, than the 1985 superstructure was roughly 40 years after its most recent major work.
- Underside, centerline, 1985.jpg
Underside of the bridge in 1985. Image shows how the bridge was originally built, and later modified, but before the superstructure was replaced.
- Harvard Bridge, centerline, looking north, 2009.jpg
Underside of the bridge in 2009. Image shows how the replacement superstructure was built, with six longitudinal girders, different bracing, etc.
Subsequent eventsEdit
In the fall of 2014, the Charles River Conservancy announced that an anonymous donor would fund an upgrade of the street lights for both the roadway and both sidewalks on the bridge.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The new roadway and aesthetic lighting was installed in 2015, highlighting the smoot marks along the sidewalk. The design was selected after a competition won by Miguel Rosales of Rosales + Partners.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite news</ref><ref>Template:Cite news</ref> The light posts were located Template:Convert apart.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> "It will provide safe lighting for pedestrians and drivers, and the elements of design on the bridge will be pulled out and emphasized. It will become a really beautiful bridge," said Renata von Tscharner, founder and president of the Charles River Conservancy.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Separated bicycle lanesEdit
In November 2021, to improve bicycle safety, MassDOT initiated a separated bicycle lane pilot on the Harvard by placing cones to create two wide bicycle lanes. This reduced general purpose lanes from four to two over the bridge. Despite some hiccups involving vandalism, the pilot was deemed a success in the Fall 2022. MassDOT went on to hire Toole Design Group to engineer flex-post separated bicycle lanes, bus priority lanes, and new traffic signal phasing for the corridor. These changes were implemented just before 2023, and have been in place since. To this date, the Harvard Bridge remains one of the most popular cycling routes in New England, with an average of over 1,000 bicyclists in each direction per day.
SmootsEdit
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The Harvard Bridge is marked off in an idiosyncratic unit of measure, the smoot.
In 1958, members of the Lambda Chi Alpha fraternity at MIT measured the bridge's eastern sidewalk by using that year's shortest pledge, Oliver SmootTemplate:Mdashbnominally, Template:Convert tallTemplate:Mdashbas a measuring stick.<ref name=haer5 /><ref name=mithistory49>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Years after this stunt, Smoot became president of the American National Standards Institute (ANSI), and later president of the International Organization for Standardization (ISO).<ref name=ANSI>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Markers painted at Template:Convert intervals give the bridge's length 364.4 smoots long, "plus one ear". Originally this read "plus or minus one ear"Template:Mdashbrepresenting measurement uncertainty<ref>Tavernor, Robert, Smoot's Ear: the Measure of Humanity (Yale University Press, 2007; paperback edition 2008), Template:ISBN, Preface</ref>Template:Mdashbbut over the years the words "or minus" disappeared.<ref name="stone">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The marks are repainted periodically by members of the fraternity<ref name=haer5 /><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>Template:Failed verificationTemplate:Mdashboriginally surreptitiously and later openly.<ref name=topfive />
During the major reconstruction in the 1980s, the new sidewalks were divided into smoot-length slabs rather than the standard six feet, and the smoot markings were painted on the new deck.<ref>Template:Cite news</ref> Officials' original determination to omit the smoot markings from the reconstructed bridge, and to scrupulously prevent the fraternity from repainting them, evaporated when it was realized that police routinely used the smoot marks as reference points in accident reports.<ref name=topfive>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The nominal length of 364.4 smoots (from two designated points at the bridge's ends) corresponds to about 2030 feet or 620 m, somewhat less than the bridge's published length of Template:Convert.<ref name=structurae />Template:Sfn A possible cause is that in 1958, there were ramps to Storrow Drive on both sides of the bridge, which interrupted the sidewalk earlier than it extends today. A bridge of Template:Convert<ref name=structurae /><ref name=AM17>Alger and Matthews, p. 17</ref> corresponds to 387.7 smoots ± one ear.
See alsoEdit
- List of bridges documented by the Historic American Engineering Record in Massachusetts
- List of crossings of the Charles River
ReferencesEdit
Informational notes Template:Notelist
Citations Template:Reflist
Bibliography
- (Nationalbridges.com): {{#invoke:citation/CS1|citation
|CitationClass=web }} Note: this is a formatted scrape of the 2009 official website, which can be found here for Massachusetts: {{#invoke:citation/CS1|citation |CitationClass=web }}
- Template:Citation
- Template:HAER
- (Replacement): Template:Cite book Submitted pursuant to 42 U.S.C. 4332 (2) (c), and 23 U.S.C. 128 (a).
- Template:Cite book
- Template:Cite book