PROJECT REHABILITATING ROUTE 195 (CARROLL AVENUE) BRIDGE OVER

by Fred Braerman, Johnson, Mirmiran & Thompson, and Maurice Agostino, Maryland Department of Transportation, State Highway Administration

The Maryland Route 195 (Carroll Avenue) Sligo Creek, and a county-owned trail access to all four approaches to the Bridge over Sligo Creek, located in the for hiking and biking. In 2011, the bridge. Washington, D.C., suburb of Takoma MDOT State Highway Administration Park, Md., is a nonredundant, open- (SHA) Office of Structures contracted During the planning stage, several spandrel, reinforced concrete arch bridge the bridge design engineer to project-specific challenges were noted. that carries one lane of traffic in each perform an in-depth field inspection, The bridge’s location, 50 ft over a ravine direction, with sidewalks on both sides. structural analysis, and assessment of within the floodplain of Sligo Creek, Nearly 80 years after being constructed the bridge. Because the bridge was constrained the project site. Existing in 1932, the bridge became rated eligible for inclusion on the Historic utilities on the bridge and adjacent structurally deficient in 2011, when Register and on MDOT SHA’s Priority 1 overhead utilities on the west side of routine inspections found extensive and list for preservation, the bridge design bridge would have to be temporarily worsening deterioration of the bridge engineer focused on rehabilitation relocated to allow for construction. deck. While evaluating options for this strategies. Sligo Creek Parkway, located beneath aging structure, Maryland Department of the southernmost span, was a major Transportation (MDOT) officials recognized The bridge design engineer’s findings commuter route within this congested the functional and historic significance of indicated that replacement of all suburb, and a heavily used hiker-biker the bridge and concluded that replacing it portions of the bridge above the arch trail located beneath the northernmost with a girder-type structure would not be ribs would be required to address the span would need to remain open the right solution. Instead, MDOT decided extensive deterioration of the deck, floor during rehabilitation. that rehabilitation was the appropriate beams, columns, and spandrel arches. strategy, a decision that was well received The plan was to repair and preserve the Project leaders conducted extensive by the community. A construction existing substructure units and arches public outreach to gain input and contract was awarded to the prime while reconstructing the remainder of support from the community. For contractor for $9.3 million in October the bridge from the arch ribs up. The example, they held multiple public 2015, and the project was completed less complete reconstruction of the bridge meetings and coordinated plans with than one year after the bridge was closed above the arch ribs would allow for the Washington Adventist Hospital on the to traffic. The bridge was reopened ahead structure to be widened curb-to-curb by north side of the bridge, the Takoma of schedule in June 2017. 2 ft, creating 11-ft-wide travel lanes. The Park City Council, the Montgomery community wanted wide shoulders to County Transit bus system, Montgomery Planning and the make biking safer in this residential area. County Parks, and local emergency Decision Process responders. Originally built with non-air-entrained Additionally, the rehabilitation would concrete and black reinforcing steel, include new sidewalks on both sides Design Challenges the 220-ft-long Carroll Avenue Bridge of the bridge, with new sections of When a bridge is rehabilitated, its has span lengths of 65, 90, and 65 sidewalk extending past the ends of the geometry must be maintained. The ft and traverses Sligo Creek Parkway, bridge to provide improved pedestrian existing Carroll Avenue Bridge was

MARYLAND ROUTE 195 (CARROLL AVENUE) BRIDGE OVER SLIGO CREEK / profile TAKOMA PARK, MARYLAND BRIDGE DESIGN ENGINEER FOR REHABILITATION: Johnson, Mirmiran & Thompson, Hunt Valley, Md. PRIME CONTRACTOR: Kiewit Infrastructure South, Omaha, Neb. REINFORCING STEEL SUPPLIER: Gerdau, York, Pa. OTHER CONSULTANTS (ROADWAY AND TRAFFIC DESIGN): Mercado Consultants Inc., Ashton, Md.; Sabra and Associates Inc., Columbia, Md.

12 | ASPIRE Spring 2019 Debris accumulation on the demolition SHA required the contractor to provide identically. However, details could not shield /work platform. Polystyrene a 295-ft-long temporary pedestrian be exactly matched for the existing protects the arches from debris. All bridge along the east side of Carroll open-balustrade railings, which were Photos: Johnson, Mirmiran & Thompson. Avenue. significant to the Maryland Historical Trust. Fortunately, the Texas Department A major structural concern involved of Transportation Traffic Railing Type maintaining a balanced-loading C411, which was crash tested and met condition during the sequence of the test requirements for the design demolition and build back to avoid speed and classification of Carroll overstressing the existing arches that Avenue, closely resembled the existing were to remain. The project leaders railings. This barrier received approval were especially mindful of this issue without comment. because three workers had died on this site in 1932, when a previous Construction reinforced concrete bridge built in The primary construction challenge for 1904 collapsed during demolition prior the project was access. Steep side slopes to construction of the arch bridge.1,2 at each end of the bridge precluded In the rehabilitation project, every the provision of construction entrances on the crest of a vertical curve, which precaution was taken to ensure safe from Carroll Avenue. The solution resulted in a sump at each abutment conditions. The contract plans included was to provide an entrance off Sligo just past the end of the bridge. The City requirements for a 22-stage systematic Creek Parkway; however, this location of Takoma Park requested that drainage construction sequence working from complicated matters because the improvements be made to alleviate the center of each arch outward in a parkway also served as the temporary flooding from these sumps. During concentric fashion about the crown detour route. Flaggers were employed design, the bridge design engineer of the arch. A structural analysis was daily to facilitate traffic flow while found that the existing sump inlets performed using software under each construction vehicles entered and exited were severely undersized as the result of condition of demolition and build the site. increased development over the years. back to verify that the arches were not The inlets were therefore replaced with overstressed during any of the stages. One of the construction innovations larger, more efficient curb-opening-at- that made the project such a success grade inlets to minimize the potential The reconstruction plans were was the prime contractor’s use of a for flooding in the future. painstaking in recreating and replicating work platform at the elevation of the the details of the existing bridge, arch supports. This work/demolition Maintenance of traffic during which included extensive architectural platform consisted of steel beams and reconstruction of the cast-in-place features for the spandrel arches, floor timber flooring supported by shoring reinforced concrete bridge was a beam overhangs, and columns. These towers 15 to 20 ft above the floodplain significant challenge. Unlike a typical architectural details were matched of Sligo Creek. This platform solved redundant, multi-girder bridge arrangement, removing one of the two Concrete being placed for new floor beams at the top of one of the arches. arches during a staged construction scheme would render the bridge unstable. After this inherent problem with the structure configuration was explained to the stakeholders, all parties agreed that closing the bridge during construction and detouring traffic was the only feasible construction solution. However, this decision presented a problem for pedestrians because there was no alternative way to safely cross the ravine on foot. Therefore, MDOT

MARYLAND DEPARTMENT OF TRANSPORTATION STATE HIGHWAY ADMINISTRATION, OWNER BRIDGE DESCRIPTION: Three-span, 220-ft-long, open-spandrel concrete arch STRUCTURAL COMPONENTS: Repair of substructure units and arch ribs and replacement of columns, floor beams, and deck using 712 yd3 of concrete MDOT SHA Mix No. 6 (28-day compressive strength of 4500 psi); 64 yd3 of concrete MDOT SHA Mix No. 3 (28-day compressive strength of 3500 psi); 172,000 lb of epoxy-coated reinforcing steel; and 15,000 lb of black reinforcing steel BRIDGE CONSTRUCTION COST: $9.3 million AWARDS: American Council of Engineering Companies Maryland 2018 Outstanding Project Award; Portland Cement Association 16th Concrete Bridge Awards (2018) Award of Excellence

ASPIRE Spring 2019 | 13 All superstructure concrete consisted of MDOT SHA Mix No. 6 (which has a 28-day concrete compressive strength of 4500 psi). All reinforcing steel in the deck slab, floor beams, bridge barrier, and sidewalks on the bridge was epoxy coated. To extend the life of the new bridge deck slab, an epoxy-polymer concrete overlay was applied after the bridge deck slab was fully cured.

Pervious concrete was used on the sidewalk approaches to the bridge. This porous concrete feature allowed for stormwater infiltration and minimized Rendering of proposed bridge section shows roadway with space for bicycles and runoff, providing additional stormwater sidewalks for pedestrians. Figure: Maryland Department of Transportation, State management, which was considered a Highway Administration. value-added improvement for the project because the project was exempt from the problem of trying to work on the the abutments of the bridge. However, stormwater management improvements uneven terrain beneath the bridge bringing in a concrete pump truck was per state requirements. and greatly facilitated construction not economical for placing the small demolition and build back. It also volume of concrete needed for the References minimized the project’s environmental short columns. Instead, the concrete 1. “Three Men Killed As Bridge impact. As concrete was demolished placements were made in a fashion Crashes at Takoma Park.” and dropped to the platform, small similar to the original construction in Montgomery News-Advocate, excavators transferred the material to 1932, with workers lifting buckets and January 13, 1932. the staging area, where the reinforcing placing concrete by hand. 2. Hendrix, Steve. 2016. “Three steel was separated and loaded onto Workers Once Died Rebuilding trucks for hauling. Design Criteria and This Historic Md. Bridge. Now Materials a New Makeover Is Under Way.” The contractor made extensive use of All new elements of the bridge were Washington Post, May 13, 2016. polystyrene during demolition of the designed in accordance with American existing superstructure to protect the Association of State Highway and ______existing arches during construction Transportation Officials’ AASHTO LRFD Fred Braerman is vice president, and provide fillers in the formwork for Bridge Design Specifications, sixth edition. structures transportation, for Johnson, creating the architectural details on the The existing arches and substructure Mirmiran & Thompson in Hunt Valley, floor-beam overhangs, spandrel arches, units were analyzed and load-rated Md., and Maurice Agostino is deputy and openings in the bridge railing. Most in accordance with allowable stress director, Maryland Department of the new concrete for the floor beams design methods, which more accurately of Transportation, State Highway and deck slab was pumped from behind correlated to the original design. Administration, in Baltimore, Md.

View of completed Carroll Avenue Bridge from .