Four GRS-IBS Bridges in Hamilton County Indiana

<figure id='attachment_8121' style='max-width:1424px' class='caption aligncenter'><img class="size-full wp-image-8121" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the completed GRS-IBS bridge at Six Points Road over Jay Ditch, just north of 226th Street (Bridge 302)." width="1424" height="807" /><figcaption class='caption-text'> Figure 1. Completed GRS-IBS bridge at Six Points Road over Jay Ditch, just north of 226th Street (Bridge 302). Source: Hamilton County Highway Department.</figcaption></figure>Location: Hamilton County, Indiana Owner: Hamilton County, Indiana Year Constructed: 2015-2016 National Bridge Inventory (NBI) Numbers: See table 1 Crossing Type: Roadway bridge over stream Superstructure Type: See table 1 Span: 28 to 31 feet (see table 1) Maximum Wall Height: 10 to 14 feet (see table 1) Maximum Wall Face Width (edge to edge): 34 to 50 feet (see table 1) Skew: 0 to 40 degrees (see table 1) Facing Type: Segmental Retaining Wall (SRW) Average Daily Traffic (ADT) (when constructed): 141 to 1243 (see table 1) Contract Type: Design-Bid-Build Unique Project Feature: Rounded abutment wall corners at Bridges 300 and 301; use of timber piles as temporary support for cast-in-place superstructure; 40-degree skewBackground: Hamilton County is located in the centeral part of the state of Indiana, north of Indianapolis. Due to its proximity to Indianapolis, rich social life, and affordable costs of living, Hamilton County county is considered as one of the fastest growing counties in the nation. Four bridges, located in the northern and more rural portion of Hamilton County, will be the focus of this case history. The locations of the four bridges are presented in figures 2a and 2b and described in table 1.<figure id='attachment_8116' style='max-width:989px' class='caption aligncenter'><img class="wp-image-8116 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Sketches of the project location. To the left, location of Hamilton County, Indiana and to the right, GRS-IBS bridges." width="989" height="496" /><figcaption class='caption-text'> Figure 2. (a) Location of Hamilton County, Indiana and (b) GRS-IBS bridges. Source: Open Street Map, ESRI, FHWA.</figcaption></figure><h3>Table 1. Hamilton County GRS-IBS bridge information (2015-2016).</h3><table class='tablepress' id='tablepress-2090'><thead><th><center>Project Name (Route / Over What it Crosses)</th><th><center>National Bridge Inventory (NBI) Number</th><th><center>Local Bridge Number</th><th><center>Superstructure Type </th><th><center>Span (ft)</th><th><center>Maximum Wall Dimensions (ft)</th><th>#colspan#</th><th><center>Skew (°)</th><th><center>ADT</th></thead><tbody><tr><td ><center>Height</td><td ><center>Face Width</td></tr><tr><td >221st Street over Jay Ditch</td><td ><center>2900480</td><td ><center>299</td><td ><center>Adjacent Precast Concrete Boxes</td><td ><center>31.0</td><td ><center>10</td><td ><center>50</td><td ><center>40</td><td ><center>141</td></tr><tr><td > Six Points Road over Jay Ditch (S. of 226th Street)</td><td ><center>2900483</td><td ><center>302</td><td ><center>Cast-in-Place Structure</td><td ><center>28.2</td><td ><center>14.2</td><td ><center>47</td><td ><center>5</td><td ><center>1165</td></tr><tr><td >226th Street over Jay Ditch</td><td ><center>2900482</td><td ><center>301</td><td ><center>Cast-in-Place Structure</td><td ><center>23.5</td><td ><center>13.3</td><td ><center>45</td><td ><center>3</td><td ><center>265</td></tr><tr><td >Six Points Road over Jay Ditch (N. of 226th Street)</td><td ><center>2900481</td><td ><center>300</td><td ><center>Adjacent Precast Concrete Boxes</td><td ><center>28.0</td><td ><center>10.7</td><td ><center>34</td><td ><center>0</td><td ><center>1243</td></tr></tbody></table>The existing four bridges in Hamilton County, previously constructed with concrete box culverts were in poor structural condition and had exposed reinforcement (see figure 3). The box culverts were failing to meet the hydraulic design criteria and would often overflow during 100-year flood events. To upgrade each of the four bridges, the Hamilton County Highway Department decided to use Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS).Hamilton County first found out about GRS-IBS from a bridge conference hosted by Purdue University, where an engineer from Defiance County, Ohio was presenting on the technology. Defiance County pioneered the use of GRS-IBS and continues to build using this method. The success of GRS-IBS in Defiance County sparked interest among Hamilton County engineers and, after obtaining further information from Defiance County and FHWA, engineers from Hamilton County decided to implement the technology. Both FHWA and Defiance County have a lot of experience deploying GRS-IBS, and were very helpful in guiding Hamilton County’s engineers throughout the process.Deployment: GRS-IBS was selected by Hamilton County with the goal of reducing construction and future maintenance costs. In appropriate site conditions, GRS-IBS can save such costs while delivering superior performance. For this project, Hamilton County used local funds to improve their bridges and saved approximately $55,000 to $75,000 per bridge. These savings were possible because GRS-IBS technology utilizes simpler construction methods and only requires readily available materials and equipment. Savings were estimated against traditional concrete box culverts and single span bridges with spill-through abutments. Hamilton County also boasted a location close to quarries and the large number of contractors in the area, which helped keep costs low in competitive bidding.All of the costs saved on each bridge through GRS-IBS were applied to the replacement of the next structurally deficient bridge. In addition to other features, the new bridges featured wider traffic lanes and improved hydraulic performance to prevent overflow during 100-year flood events. See table 1 for further details on the new bridges.Project Challenges and Solutions: The four bridges described in this case history were the first GRS-IBS bridges in Hamilton County, Indiana. Despite little experience with GRS-IBS technology, careful research performed by Hamilton County engineers on GRS-IBS made the projects a success. Some minor challenges, a few of which were general issues faced by every construction project, were encountered during the process and are listed below.Segmental Retaining Wall (SRW) units Bridges 299 and 302 were built using GRS abutment walls with 90-degree corners (video of east abutment construction at Bridge 302 is available <a href="https://www.youtube.com/watch?v=H8sK5jGERkI">here</a>). The SRW split face units used for all four bridges had generic corner blocks that needed to be cut to construct 90-degree abutment walls. Cutting blocks is time consuming and results in wasted block material. To avoid cutting the blocks at Bridges 300 and 301, the abutment walls were constructed with rounded corners (see figure 4). Using rounded corners meant that the blocks did not have to be cut, which significantly minimized construction time. Another minor challenge related to SRW units involved slight variations in the sizes, approximately 0.25 inches, of the corner and straight blocks. This variation in size would create slightly uneven joint lines that would compromise the visual appeal of the facing wall. To solve this challenge, blocks with a textured split face were used; the blocks added texture to the facing wall and helped mask the uneven joint lines.<figure id='attachment_8118' style='max-width:682px' class='caption aligncenter'><img class=" wp-image-8118" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of GRS abutments with rounded corners at Bridge 300." width="682" height="217" /><figcaption class='caption-text'> Figure 4. GRS abutments with rounded corners at Bridge 300. Source: Hamilton County Highway Department.</figcaption></figure>Maintaining straight facing wall during construction One of the construction challenges experienced by some contractors is keeping the wall units in place while compacting the reinforced soil layer. In Hamilton County, an 80-pound SRW block was selected for the bridge replacement program to help keep the wall units straight during compaction of the reinforced soil layers with plate compactor. The heavier block also featured a lip at the bottom that further helped keep the wall units in place during reinforced soil layer compaction. The blocks used in Hamilton County were locally produced proprietary blocks but were bid competitively. The advantage of these blocks and other proprietary SRW blocks currently available in local markets around the country is that they are produced to meet FHWA requirements for durability; especially when they have already been included in a state DOT's pre-approved list. The heavier block proved successful in keeping the wall units in place and its success led FHWA to update the GRS-IBS design guidance documents to make the use of SRW blocks acceptable in addition to the conventionally used concrete masonry units (CMU).Disposal of excavated material Any material excavated from around the existing structures had to be disposed off-site. As disposing of the materials was to increase the cost of the project,Hamilton County engineers chose to instead store the excavated soil locally so that it could be repurposed for the other upcoming local GRS-IBS bridge project. This stored fill material, which otherwise would have been purchased at additional cost, will be used for raising bridge approaches. Additionally, because the materials were stored nearby, material transportation costs will be reduced for the upcoming project.False work for cast-in-place concrete superstructure In order to construct the cast-in-place bridge, falsework had to be constructed to support the concrete bridge until the concrete gained sufficient strength. The contractor elected to support the falsework on temporary timber piles (see figures 5a and 5b). This approach increased the time and cost of building Bridges 301 and 302. Bridge 299 and 300 were built using adjacent precast concrete box beams (see figure 4). This approach significantly reduced the time and cost to construct the superstructure because it eliminated the need to construct the falsework and eliminated the time required to allow the concrete to set and gain strength. Hamilton County wanted to experiment with the two types of structures to evaluate the cost, time, and performance of these approaches.<figure id='attachment_8119' style='max-width:986px' class='caption aligncenter'><img class="size-full wp-image-8119" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Two photographs, at the top, timber piles for falsework support. At the bottom, Steel girders on top of timber piles as part of falsework." width="986" height="531" /><figcaption class='caption-text'> Figure 5. Construction of falsework at Bridge 302 to provide temporary support for cast-in-place superstructure. Source: Hamilton County Highway Department.</figcaption></figure>Conclusion: The Hamilton County GRS-IBS project is a great example of how cost-efficient GRS-IBS technology can allow a county to replace its bridges using local funds. The creative solutions employed by Hamilton County engineers reduced the cost of the bridge replacements even further. One solution that had a particularly large role in reducing costs was the use of locally available SRW blocks. After this successful advance, FHWA has updated the guidance to include multiple options for facing blocks as part of GRS-IBS design guidance documents. The success of Hamilton County is also related to their savvy in choosing contractors. Hamilton County often uses local, small, family-owned contractors that have been in business for several generations and have a record of delivering high quality work. The success of the Hamilton County bridge project is related to their relationship built over time with various small family owned bridge contractors, who typically bid on the local projects. Their attention to detail, ingenuity in construction, and pride in their quality of workmanship provides Hamilton County with a highly skilled labor force. The county’s continual support of these contractors was proven important for the county’s infrastructure and economy. Finally, FHWA and Defiance County have also played a significant role in the bridge replacement program in Hamilton County and their experience was an invaluable resource throughout the process.Project Contact: Faraz Khan Staff Engineer - Bridge Hamilton County, Indiana Highway Department <a href="mailto:faraz.khan@hamiltoncounty.in.gov">faraz.khan@hamiltoncounty.in.g…;(317) 773-7770Project Technical Paper: A technical paper has not been published for this project.REFERENCES“Bridging between problems and solutions”, Allan Block® Technical Newsletter, 2016. Retrieved from: <a href="%20http:/www.allanblock.com/newsletter/PDF/technical-newsletter-issue32.pdf"> http://www.allanblock.com/newsletter/PDF/technical-newsletter-issue32.p…;. Accessed April 18, 2017.“GRS-IBS Hamilton County Bridge 302 East Abutment Construction Time-lapse”, YouTube, January 20, 2016. Retrieved from: <a href="https://www.youtube.com/watch?v=H8sK5jGERkI">https://www.youtube.com/wa…;. Accessed April 12, 2017.“Hamilton County New Bridges #301 & #302 (Small Structure #31069 & #31008 Replacements)”, USI consultants. Retrieved from: <a href="http://usiconsultants.com/featured-projects-awards/hamilton-county-brid…;. Accessed April 18, 2017.“Overcome Challenges With Reading Rock Solutions. GRS-IBS project in Hamilton County, Indiana” (promotional pamphlet). Retrieved from: <a href="http://www.readingrock.com/resources/blog/grs-bridge-abutment">http://w… April 18, 2017.“Visit Hamilton County Indiana” (website article). Retrieved from <a href="https://www.visithamiltoncounty.com/plan/hamilton-county/">https://www…;. Accessed June17, 2017.Daniel Alzamora, phone conversation with the author of this document, May 16, 2017.Faraz Khan, “Geosynthetic Reinforced Soil – Integrated Bridge System. Small Structure #31008 (Bridge #301). 226th St. over Jay Ditch. Adams Township, Hamilton County, Indiana” (presentation, Hamilton County Highway Department, 2016).Faraz Khan, phone conversation with the author of this document, June 6, 2017.Hamilton County, Indiana - Web Page. Retrieved from: <a href="http://www.hamiltoncounty.in.gov">http://www.hamiltoncounty.in.gov</a>. Accessed April 18, 2017.Mike Wigger, “GRS Abutments – Geotechnical Considerations” (presentation, 2016).

Title

Technology

Mechanically Stabilized Earth Wall System