Harvard Bridge

Harvard Bridge, also known locally as the Massachusetts Avenue Bridge and "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. At , it is the longest bridge over the Charles River.)<br>George W. Gale

The commission's 1892 report claimed:

Name

The bridge is named in honor of John Harvard, whose philanthropic gift was used to establish Harvard University. Other names suggested included Blaxton, Chester, Shawmut, and Longfellow.

Engineering

thumb|A postcard of Harvard Bridge looking toward [[Boston in 1910, from the roof of the Riverbank Court Hotel, which is now Maseeh Hall, a dormitory at the Massachusetts Institute of Technology]]

thumb|An early 20th century postcard of Harvard Bridge looking toward [[Cambridge, Massachusetts|Cambridge and MIT]]

Originally projected as a wooden pile structure with stone pavement for the first (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. 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).

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 below existing ground, is a very dense till composed of gravel and boulders with a silt-clay matrix. Above that to approximately 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 . The original roadway and sidewalk stringers were of wood, with an approximately thick covering of asphalt on the sidewalk and a spruce wearing surface on the roadway.

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.)

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.

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.

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.

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 concrete-filled "I-beam lok" grating topped with a 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.

Engineering study, 1971–1972

thumb|Harvard Bridge is decorated with both serious and whimsical works of art.

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. 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 per axle and a total of per vehicle, or to restrict trucks to the interior lanes, where the bridge was stronger. A limit was imposed.

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. The price was estimated at US$2.5 million to US$3 million

Superstructure replacement, 1980s

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. 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. 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.

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.

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.

Pier 12 was exhibiting inappropriate movement and was scheduled for reinforcement.

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

File: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)

File: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.

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File: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.

File: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.

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Subsequent events

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. 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. The light posts were located apart.

"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.

Separated bicycle lanes

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, when multiple persons were captured on surveillance damaging bike lane infrastructure and throwing it into the river below; 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.

Smoots

275px|thumb|Smoot mark 210 on the eastside of the bridge

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 Smootnominally, tallas a measuring stick. Years after this stunt, Smoot became president of the American National Standards Institute (ANSI), and later president of the International Organization for Standardization (ISO).

Markers painted at intervals give the bridge's length 364.4 smoots long, "plus one ear". Originally this read "plus or minus one ear"representing measurement uncertaintybut over the years the words "or minus" disappeared. The marks are repainted periodically by members of the fraternityoriginally surreptitiously and later openly. 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.

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 . corresponds to 387.7 smoots ± one ear.

References

Informational notes

Citations

Bibliography

(Nationalbridges.com): Note: this is a formatted scrape of the 2009 official website, which can be found here for Massachusetts:
(Replacement): Submitted pursuant to 42 U.S.C. 4332 (2) (c), and 23 U.S.C. 128 (a).

External links

1895 photo