State Road 7A over Housatonic Railroad Massachusetts

<figure id='attachment_8126' style='max-width:1394px' class='caption aligncenter'><img class="size-full wp-image-8126" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the Completed State Road 7A over Housatonic Railroad Bridge." width="1394" height="1046" /><figcaption class='caption-text'> Figure 1. Completed State Road 7A over Housatonic Railroad Bridge.Source: MassDOT.</figcaption></figure>Location: Sheffield, Massachusetts Owner: Massachusetts Department of Transportation Year Constructed: 2014 National Bridge Inventory (NBI) Number: S10023BDDDOTDES Crossing Type: Roadway bridge over railroad Superstructure Type: Steel Girders Span: 105 feet Maximum Wall Height: 26 feet Maximum Wall Face Width (edge to edge): 69 feet Skew: 30 degrees Facing Type: Concrete Masonry Unit (CMU) Average Daily Traffic (ADT) (2014): 400 Contract Type: Design-Bid-Build Unique Project Feature: Maximum skew for GRS-IBS bridge at the time of construction; used the piers from the existing bridge as crash walls for railroadBackground: State Road 7A over the Housatonic Railroad bridge (SR 7A Bridge) is located in Sheffield, Berkshire County, Massachusetts (see figures 2a and 2b). Prior to replacement, the SR 7A Bridge featured three spans supported on concrete piers and abutments (see figure 3); the bridge was structurally deficient.<figure id='attachment_8127' style='max-width:1049px' class='caption aligncenter'><img class="wp-image-8127 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Sketches of the project location. To the left, location of Sheffield, Massachusetts. To the right, location of SR 7A Bridge." width="1049" height="530" /><figcaption class='caption-text'> Figure 2. (a) Location of Sheffield, Massachusetts and (b) SR 7A Bridge. Source: Open Street Map, ESRI, FHWA.</figcaption></figure>The SR 7A Bridge is a valuable asset as it provides a grade separation between the Housatonic Railroad and the roadway. The Housatonic Railroad has a long history of serving passenger and freight trains in southwestern New England. Due to poor track conditions, the railroad has been limited to freight train use in recent years.In 2014, the Massachusetts Department of Transportation (MassDOT) purchased a portion of the Housatonic Railroad with the intent to improve its tracks, bring back passenger rail service, and extend service to New York City. To meet this goal, the deteriorating SR 7A Bridge needed to first be replaced to increase the safety of railroad users and motorists crossing the bridge.Deployment: MassDOT was heavily involved in the project to replace the SR 7A Bridge and wanted to be more innovative with their bridge construction practice. Seeing the potential of the Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) technology to reduce costs and construction time, MassDOT engineers decided to use this method to replace the SR 7A Bridge.<figure id='attachment_8128' style='max-width:1022px' class='caption aligncenter'><img class="size-full wp-image-8128" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the SR 7A Bridge over the Housatonic Railroad prior to replacement." width="1022" height="766" /><figcaption class='caption-text'> Figure 3. SR 7A Bridge over the Housatonic Railroad prior to replacement. Source: MassDOT.</figcaption></figure>The first bridge in the state of Massachusetts to be built using GRS-IBS, the new SR 7A Bridge featured a wider roadway and sidewalk. In addition to the bridge replacement, all approaches were modified to reduce skew and raise the road profile. Raising the road profile was necessary to accommodate the new bridge’s longer span of 105 feet and its deep girders. The span had to be increased because of limitations imposed by constructing the bridge next to railroad tracks. The bridge’s superstructure was composed of steel girders on concrete footings with back walls and a cast-in-place (CIP) deck. The abutments provided clearance of up to 19 feet in height to accommodate passing trains.Project Challenges and Solutions: The SR 7A Bridge is an example of a successful project made possible by an efficient and resourceful project team. The challenges described below were addressed quickly and did not significantly impact the project. Some of the challenges are related to constructing the bridge above a railroad, while others are representative of the general challenges encountered by other GRS-IBS projects. The lessons learned from these challenges are important and can be used to further advance the use of GRS-IBS technology.Construction next to railroad tracks Using GRS-IBS technology to replace the SR 7A Bridge resulted in an estimated 49 percent savings when compared with the alternative design. The alternative design called for abutments supported on micropiles deemed necessary because the proposed abutments were to be constructed in proximity to railroad tracks. In cases where construction next to tracks is necessary, excavation is strictly limited to prevent the settlement of the adjacent active railroad and any subsequent damage to the tracks. If the excavation cannot be avoided, it must be done with track supports that significantly increase project costs. While the micropiles included in the alternative design provided the necessary bearing for the abutments without the need of significant excavation by extending into the competent strata, they were very costly. The final design, which featured a longer span and used GRS-IBS, eliminated the micropiles and resolved the excavation challenges by constructing the abutments at a greater and safer distance for the tracks. Elimination of the micropiles in the final design significantly contributed to project cost savings. Conventional spread footings on concrete abutments were also considered for this project. However, MassDOT engineers wanted to try the innovative GRS-IBS and explore its benefits including its cost saving potential.Crash walls Because of the proximity of the abutments to the railroad tracks, the SR 7A Bridge required the use of crash walls. Crash walls protect the structures adjacent to the tracks by absorbing the impacts of derailed trains before they crash into the GRS abutments. To construct crash walls, the project team repurposed existing concrete piers and constructed the new GRS abutments behind the crash walls. The existing concrete piers were demolished to the desired height and remained in place to protect the new GRS-IBS abutments (see figure 4). This ingenious decision reduced project construction time and minimized the costs associated with building new crash walls.<figure id='attachment_8129' style='max-width:990px' class='caption aligncenter'><img class="size-full wp-image-8129" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the old piers repurposed as crash walls along the tracks. Source: MassDOT." width="990" height="742" /><figcaption class='caption-text'> Figure 4. Old piers repurposed as crash walls along the tracks. Source: MassDOT.</figcaption></figure>Concrete Masonry Unit (CMU) block imperfections The CMU blocks used for this project had slight imperfections resulting from small amounts of concrete that got stuck on block surfaces during the molding process. When they occurred at the bottom or the top of the block, these minor amounts of material created uneven joint lines and would have added extra height to the facing wall. The detail-oriented contractor knew about this issue and resolved it by removing the imperfections with a chisel and making sure the top and bottom surfaces of the blocks were perfectly flat.<figure id='attachment_8130' style='max-width:758px' class='caption aligncenter'><img class="size-full wp-image-8130" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Schematic representation of the Abutment corner detail for obtuse corner." width="758" height="393" /><figcaption class='caption-text'> Figure 5. Abutment corner detail for obtuse corner. Source: MassDOT.</figcaption></figure>Abutment corner details Due to the 30-degree skew of the bridge, the GRS-IBS abutments had to be constructed with two sets of two different corners. The GRS-IBS abutments had to fit obtuse and acute corners. The obtuse angles were difficult to construct and required cutting a lot of blocks. A creative solution was found to the problem that involved turning the obtuse corners into two closely spaced corners. The corner details for the west abutment are shown in figure 5. The photo of the abutment with the obtuse corner is shown in figure 6. Splitting the acute abutment corner into two vertices minimized block-cutting efforts and facilitated construction.Conclusion: The SR 7A Bridge project was the first GRS-IBS bridge with a 30-degree skew. When the project began, the effects of such a large skew on GRS-IBS abutments were unknown and had to be further investigated. To investigate this, the FHWA decided to instrument the bridge and monitor its performance for 36 months. The results to date show that the bridge is performing as intended. The success of the SR 7A Bridge project is also measured by cost savings; the project had an estimated savings of nearly 50 percent over the alternative design.Since completion, the SR 7A Bridge has received much recognition. The hard work and ingenuity of the SR 7A Bridge project team earned two awards: the SR 7A Bridge contractor received an “Award of Merit” from Engineering News Record of New England (ENR New England) in 2015 and the engineer received the “Engineering Excellence Award” from the American Council of Engineering Companies (ACEC) of Massachusetts. The SR 7A Bridge was also featured in a number of presentations and at a showcase organized by FHWA and MassDOT. The showcase involved a site visit to the SR 7A Bridge construction site and technical presentations by the project team. The 60 showcase participants represented MassDOT districts, DOT representatives from the northeast region, FHWA representatives, and others.Inspired by the success of the SR 7A Bridge, MassDOT has since constructed five more bridges using GRS-IBS, including bridge D-08-006 in Dighton that was designed in-house, and is looking forward to constructing additional GRS-IBS structures. MassDOT is currently in the process of developing design guidance documents for GRS-IBS to encourage more transportation professionals in the state to build bridges using this technology.Project Contact: Peter Connors Geotechnical Engineer Massachusetts Department of Transportation <a href="mailto:Peter.Connors@state.ma.us">Peter.Connors@state.ma.us</a>(857) 368-9191Project Technical Paper: A technical paper has not been published for this project.REFERENCES“Ashley Falls Road Bridge Design Using GRS-IBS Technology”, Collins Engineers. Retrieved from: <a href="https://www.collinsengr.com/project/ashley-falls-road-bridge-design-grs…;. Accessed April 18, 2017.“Engineering Excellence and Awards - Ashley Falls Road Bridge Design Using GRS-IBS”, American Council of Engineering Companies of Massachusetts, 2016. Retrieved from: <a href="http://www.acecma.org/index.cfm/cd/NAA/cdid/12138/pid/10243">http://www…;. Accessed April 12, 2017.“Instrumentation and Monitoring Program” (presentation, Massachusetts Every Day Counts Showcase on GRS-IBS, 2013).“Small Projects (Under $10 Million) Award of Merit: GRS-IBS Bridge Replacement over the Housatonic RR (2015)”, Engineering News-Record (ENR). Retrieved from: <a href="http://www.enr.com/articles/38470-small-projects-under---million-award-…;. Accessed April 12, 2017.Daniel Alzamora, phone conversation with the author of this document, May 16, 2017Nicks, J., Meehan, C., Dasenbrock, D., Connors, P., and Alzamora, D., “Performance of Geosynthetic Reinforced Soil Integrated Bridge System (GRS IBS)” (presentation, Transportation Research Board Webinar (TRB), 2016).Peter Connors, phone conversation with the author of this document, June 6, 2017.Thomas Pechillo, “GRS-IBS Showcase: Background and Bridge Design” (presentation Massachusetts Department of Transportation, 2014).

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Mechanically Stabilized Earth Wall System