Vermont Demonstration Project: Route 2 – East Montpelier Bridge Reconstruction
Project Overview and Lessons Learned
project includes the replacement of a narrow bridge structure with a new wider structure
with minimal approach work on each end of the structure. Key innovations
employed on this project include:
- Use of solid stainless steel deck reinforcing steel for increased deck durability.
- Use of high performance concrete bare deck.
- Use of weathering
steel to eliminate need for repainting.
- Use of integral
abutments to eliminate the need for deck movement joints and bearings at
of membrane and pavement over the deck to eliminate maintenance need to address
ruts and potholes
of curbs that retain salt-laden run-off to minimize deck maintenance due to
- Use of a
two-way temporary bridge and design features that reduce impacts and
disruptions to the traveling public during construction and future maintenance.
- Reduction of
life cycle costs through design of a structure with 100-year design life
incorporating high-quality materials and design details that minimize the need
HfL Performance Goals
Safety, construction congestion, quality, and user satisfaction data were collected before, during, and after construction to demonstrate that innovations can be an integral part of a project while simultaneously meeting the HfL performance goals in these areas.
- Work zone safety during construction—As expected, no incidents occurred during the entire construction period including the full closure period, which meets the HfL goal of achieving a work zone crash rate equal to or less than the preconstruction rate.
- Worker safety during construction—No workers were injured on the project, so the contractor achieved a score of 0.0 on the OSHA Form 300, meeting the HfL goal of less than 4.0.
- Facility safety after construction—The additional bridge width and updated side barriers and beam guards are improvements over the existing bridge. The net effect that these safety improvements will have on the HfL goal of 20 percent reduction in fatalities and injuries in 3-year crash rates after construction is yet to be determined.
- Construction Congestion
- Faster construction—Compressing the time it took to replace the bridge from an estimated 6 months to only 16 days under the ABC approach drastically reduced the impact to motorists and went beyond the HfL goal of a 50 percent reduction in the time traffic is impacted compared to traditional construction methods.
- Trip time— Considering the cumulative trip time over the 16-day detour compared to 6 months of detour estimated for traditional construction, motorists experienced a reduction in trip time, meeting the HfL goal of no more than a 10 percent increase in trip time compared to the average preconstruction conditions.
- Queue length during construction—The project met the HfL goal of less than a 0.5-mile queue length in a rural area, as there were no traffic backups along the detour route.
- Smoothness —Smoothness increased across the bridges. IRI decreased from 221 in/mi before construction to 179 in/mi after construction. Motorists will notice a smoother ride, although the HfL goal for IRI of 48 in/mi—typically expected to be attainable on long, open stretches of pavement—was not met on this project.
- Noise—The sound intensity (SI) data showed a noticeable 3.2 dB(A) increase in noise from a preconstruction value of 98 dB(A) to 101.2 dB(A) after construction which does not meet the HfL requirement of 96.0 dB(A) or less. The new texture of the bridge surface—while aiding traction and increasing safety—is prone to increasing noise.
- User satisfaction—Most motorists surveyed were satisfied with the finished highway and the way the project was carried out, which met the performance goal of 4 or more points on a 7-point Likert scale.
It is estimated that, with the reduced need for
maintenance, the innovative HfL project delivery approach will realize a cost
savings of $1,030,450 in current dollars over the 100-year design life of the
project. The savings represent more than 40 percent of the contract bid amount
of $2,001,500 for traditional construction and exceed the construction cost
estimate of the as-built bridge portion of the project of $918,700.
Some of the lessons learned from this demonstration project are:
- It demonstrates that the HfL program concepts of realizing the benefits of accelerated bridge construction do not apply only to large, complex bridges or other horizontal infrastructure projects in urban settings but also to smaller rural bridges.
- HfL program concept implementation can result in significant cost savings over the life of the project.
- Tolerances for straightness of stainless steel rebar along with what is acceptable in terms of rebar contamination or rust must be well understood by the rebar manufacturer, fabricator, and contractor.
- Early and frequent interaction with the public on the project resulted in users highly satisfied with the end product.
The Iowa DOT gained valuable insights into the use of several innovative ABC techniques and materials, such as prefabricated superstructure and substructure systems, HPC and UHPC, SCC, and fully contained flooded backfill. These innovations were key to successfully achieving the HfL performance goals of increasing safety, reducing congestion, and increasing quality.