Memorial Boulevard Rigid Frame

Back in July of 2009 I rated a rigid frame in Providence RI which carries Memorial Boulevard over a pedestrian underpass. The frame spans 40 feet allow foot traffic to the Providence and Woonsaquatucket River where each year the Waterfire festival is held. The frame was constructed in 1994 and has several unique features.

The reason I remembered this bridge is from reading tallbridgeguy's post on Green Bridge and Landscaping, where he mentions the positives of adding flower plants and trees along with negatives freeze/thaw (a big problem in New England), drainage, extra load and maintenance.

Along with planters the bridge also has a glass atrium which allows light to the underside of the frame and decorative tiling along the legs of the frame.

These decorative accents help create an aesthetically pleasing bridge which is the goal for both a consultants and a necessity for clients when it comes to pedestrian traffic. When it comes to this bridge tho these accents can cause problems down the road. As most would suspect the glass atrium now has several broken panes, the tiles do not allow for inspection of the legs and the underside of the roof below the plants have cracking with efflorescence, incrustation and stalactites. 

The rating of the concrete rigid frame was performed using influence lines to determine the maximum live load effects and we treated the rigid frame's support conditions as pinned-pinned.

The architectural “waffling” on the underside of the rigid frames was not considered as a structural component and was not taken into account as part of the section properties. 

  

Prestressed Concrete I-Beam Rating

Last February I worked on a rating for MassDOT on two simple span prestressed concrete I-beam bridge with an 8" composite deck. The bridges were built in 1982 and carries route 146 through Sutton MA. The bridges span 78'-4" with a 8°-22'-09" skew.

I used Virtis to perform the rating of the prestressed concrete I-beams.  The rating of the reinforced concrete deck was computed by hand in accordance with the AASHTO Standard Specifications and MassHighway Bridge Manual.

The prestressed concrete I-beams have a set of 16 straight low relaxation strands and 7 harped or draped relaxation strands. At first I had trouble modeling the beams in Virtis and would come up with rating factors lower than 0.05. At first I thought the strand pattern may have been incorrect or a material was entered wrong. After exhausting all the typical mind fart errors, we were able to figure out a problem with the live load modeling.

When we inspected the bridge to confirm measurements and gather other information we noticed that the majority of the prestressed beam ends had areas of rust staining with minor cracking throughout but nothing serious enough to effect the rating.