Continuous Prestressed Post-tensioned Segmental Concrete Box Girders

Last week we inspected four ramps in Boston and Cambridge Mass near Leverett Circle and the Boston Sand and Gravel.

The ramps take traffic from the Tobin Bridge to I-93, Zakim BridgeLeonard P. Zakim Bunker Hill Memorial Bridge, Leverett Circle or Storrow Drive. The ramps consist of continuous prestressed post-tensioned segmental concrete box girders.

To inspect the exterior of the box girders an 80' man lift was used since most of the structures were no accessible with smaller lifts due to on going construction and a park. The exterior inspection consisted of visually inspecting the box girders, piers and measuring the bearings for movement.

The interior of the box girders were inspected with three man teams since they are considered a confined space. When inside the box girder the inspection team needs an air meter, rescue air tank and radio, luckily we have only had to carry these once down the interior since there is a hatch at both ends. The interior inspection consisted of visually inspecting (even though we were always within an arms reach)the box girders even though we were always within an arms reach, utilities and measuring the pintle slots for movement. 

Transit Steel Trapezoidal Box Girder

A few weeks ago I inspected a two span continuous steel trapezoidal box girder which carries the subway over Leveret Circle in Boston. The bridge consists of curved two box girders, a composite deck and reinforced concrete substructure. The viaduct was constructed as part of the Green Line Relocation Project from Haymarket Station to Science Park Station with an original design loading of Green Line Passenger Car.

Constructed in May 2005, The bridge spans 135 feet over gravel and 162.75 feet over Leveret Circle. The bridge has a maximum width of 30 feet out to out. 

The concrete composite deck has hairline cracks in the negative moment region.

A 45' lift truck was used to inspect the span over Leveret Circle and the span over gravel was inspected by ladder. Each girder's interior was accessed by hatches near ground level over the gravel.

When we tried to access the girders we had to cut the locks off with a grinder but one lock was already removed. When then heard and saw movement inside the girder. A homeless man had been living inside the girder. We notified our police details and they helped escort the tenant who left without incident. Inside the girders were filled with an accumulation of homeless peoples debris making for a difficult and unpleasant inspection.

Rules of the hole.....