A short-ton 23 t 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 recommendation was to replace the superstructure with one weighing approximately the same in order to reuse the piers, which were in good condition.
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 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.
Detailed engineering calculations were included. The action taken based on this study was to establish load restrictions on the bridge, 15 short tons 14 t in the outer lanes, 25 short tons 23 t on the inner lanes. This was expanded in to a flat limit of 15 short tons 14 t on the whole bridge. After the failure of the Mianus River Bridge at Greenwich, Connecticut in , 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 A few days later, all trucks and buses were banned from the bridge.
In , a report was published containing the plan to replace the superstructure on the existing supports. Alternatives considered were very similar to the report , and were similarly decided. 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, vehicles per day, traffic on ramp B was found to be low, approximately 1, vehicles per day with a peak of 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. 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.
Phase 1 finished in , and Phase 2 in Bridge viewed from the upstream Cambridge side in Construction barrels restricting traffic from the outside lanes, and general wear and tear are visible click on image to enlarge. Roughly the same view, in Superstructure is in much better shape only 20 years after completion, than the superstructure was roughly 40 years after its most recent major work.
Add your comment in english. Your comment: Post comment. Similar places Nearby places Nearby cities. Maurice J. Tobin Memorial Bridge 5. MIT Neighbourhood 0. What on earth is a smoot? The smoot marks are repainted every year by students. Just go to google. However, as of March , you can now access in more browsers like Firefox, Opera, and Edge.
Check if your browser is up to date, but this should happen automatically. We know that bridge heights are measured in feet above Mean High Water.
The MIT students have clearly claimed the bridge as their own. The bridge length is famously measured in "smoots," with painted markers on the sidewalk every 10 smoot-lengths, thanks to the efforts of a fraternity in As the story goes, and this story was confirmed to my satisfaction by a relative who graduated from there, the frat took one of its pledges, Oliver Smoot, and rolled him head over heels across the bridge, keeping measure of how many body lengths they had covered.
The bridge is marked at Using standard measurements, the bridge is about 0.
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