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. 

P.T. Segmental Concrete Box Girder Inspection

This past week I started inspecting the Central Artery ramps in South Boston. The ramps we are inspecting consist of concrete Type IV precast box girders and span over 150 feet. The ramps carry I-93 Northbound and Southbound as well as the Southbound HOV lanes.

The past two weeks we have inspected seven ramps, which has made me very familiar with South Boston (one of the few areas I wasn't familiar with before).

To gain access to the interiors we used a 40' bucket truck and on the last day we used a 70' elliot with a HUGE basket. 

Each span has access hatches but one near the ground level was locked. After calling MassDOT to unlock it we found out that the lock was not theirs. Once inside we discovered the typical debris left by the homeless. All the other boxes were fairly clean in comparison though.

The previous inspections had sketches with deficiencies which made the inspections move a efficiently with the majority of the efficiencies still in the same condition as it was two years ago.

What a concrete box girder motel looks like.