J.F. White on Schedule at I93 Fast14
 This unprecedented fast-track, design- build project replaced 14 deteriorated bridge superstructures on I-93 in Medford, MA under the Accelerated Bridge Program during 10 weekends between June and mid-August 2011. The extremely compressed time frame was “every day critical” from Contract Award in early February 2011 through completion and opening to traffic of the 14 bridges on August 15, 2011. The expedited design process as well as the integrated quality control and assurance system was managed by the project team in conjunction with MassDOT and the Federal Highway Administration during multiple weekly focus meetings over the course of 4 months. Extensive traffic planning efforts through weekly working sessions with the Massachusetts State Police along with a comprehensive public awareness and outreach program resulted in minimal traffic congestion during the 10 weekend diversions.
Key elements included the fabrication of 504 steel plate girders released at the 60% Design level and later incorporated into 252 precast structural deck modules; installation of two 1,800 LF traffic “crossovers” used to divert traffic during weekend bridge replacement utilizing 22,000 LF of movable “zipper” barrier. An Ultra-High Performance concrete achieving 2,000 PSI within 4 hours of final set (~10,000 psi in 28 days) was developed on the project for use in the “closure pour” joining the precast deck modules and completing the deck prior to opening to traffic on Monday mornings. The existing substructures were structurally evaluated and upgraded to receive the new superstructure and extend the service life of the bridges another 75 years. Preparations for the 1,008 bearing locations began in late April and completed to allow sufficient cure time and strength gain to support the aggressive schedule. Existing bridge stringers were temporarily supported utilizing 200K shoring posts at 628 locations to permit coping and bearing pedestal placement in advance of the bridge replacement.
The typical 55 HR weekend schedule involved 7 major activities, varying in duration from 4 to 12 HR: traffic diversion, demolition, precast erection, formwork/rebar, concrete placement & cure, pavement milling/shimming, and traffic restoration. Traffic diversion utilized 2 “crossovers” at the northern and southern extremities of the site into which movable barriers were deployed to permit 2 lanes normal direction flow and 2 lanes of “contraflow” traffic. Demolition operations commenced once the traffic was diverted at 10PM and utilized up to 40 pieces of equipment concurrently. Precast erection of the 18 to 24 pieces per bridge up to 94 TN loads each used multiple 500 and 600 TN mobile hydraulic cranes. Conventional wood formwork was supported via inserts placed into the precast elements. Over 110,000 Dowel Bar Substitutes were used on the project to join the precast elements together. Two mobile concrete testing laboratories were set up on site to test key parameters as well as confirm compressive strength was achieved prior to opening to traffic. Bridge approaches and departures were surveyed and milled or shimmed to suit existing conditions. Finally, the traffic was restored to the normal Northbound and Southbound flows in time for the Monday AM rush hour.
During the weekend of July 16 to 17 the Fast 14 project was “showcased” by MassDOT to highway officials from the FHWA and representatives from 40 of the 50 states highlighting the innovative construction methods and the using the project as real-life illustration of the FHWA’s “Every Day Counts” initiative where years of work using conventional methods are performed in a fraction of the time and cost without sacrificing safety or quality.
Read more about J.F. White's work on the Fast 14 Segment of the Massachusetts' Accelerated Bridge Program in the news:
- -Engineering News Record - Test Program Success - -
- - Commonwealth Magazine - Speedy Repairs - -
- - Boston.com - Quick fix for I-93 Bridges - -
For videos of the project check out MassDot's youtube channel and the MassDot Fast 14 home page.
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