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Virginia Demonstration Project: Rapid Removal and Replacement of U.S. 15/29 Bridge Over Broad Run Near Gainesville, VA
The VDOT HfL demonstration project consists of a bridge superstructure replacement and widening with prefabricated segments using high-performance materials and rapid placement methods. The project is located on U.S. 15/29 over Broad Run near Gainesville, VA, 0.55 miles (mi) (0.88 kilometers (km)) north of State Route 215 (Vint Hill Road), as shown in figure 1 below. U.S. 15/29 is a four-lane divided highway at the project site. Because of the traffic volume on this route, detailed construction schemes were developed to minimize the length of the required lane closures and restrict them to offpeak nighttime hours. While HfL program concepts do apply to large, complex bridge projects, the same concepts also need to apply to smaller bridges because the majority of the bridges on the national inventory are short–span rural bridges similar to this urban bridge.
The U.S. 15/29 bridge over Broad Run (VDOT Project No. 0015–076–115, M600) carries southbound Lee Highway over Broad Run in the Buckland Historic District in Prince William County, VA. The district initiated a project review to fulfill the provisions of Section 106 of the National Historic Preservation Act. The Section 106 consulting parties included the Buckland Preservation Society, consisting primarily of directly affected local residents. The society's interests were considered and incorporated into this project.
The existing 56–year–old, two–lane structure carries about 25,000 vehicles per day (figure 2). The deteriorated superstructure is about 130 ft (39.6 m) long and comprised of three equal spans of reinforced concrete T–beams on concrete piers. Total width of the existing bridge is 33 ft (10 m). In addition to the deteriorated superstructure, the bridge has substandard shoulder widths, resulting in the need to widen the bridge. The new total superstructure width is 38.5 ft (11.7 m), consisting of a 4–ft (1.2–m) median shoulder, two 12–ft (3.6–m) lanes, and an 8–ft (2.4–m) outside shoulder. Because the bridge is next to the Buckland Historic District, widening to the median side was required. Similarly, a temporary structure could not be used, which led to the development of a detailed construction sequence dovetailed with a detailed traffic maintenance scheme.
The project was advertised in September 2007 and awarded to Flippo Construction Company, Inc. in December 2007. The prime contractor selected Coastal Precast Systems, LLC to prefabricate the superstructure elements.
The replacement scheme used four prefabricated segments per span, for a total of 12 segments, consisting of two rolled steel beams made composite with the 7.5–inch (in) (190.5–millimeter (mm)) high–performance lightweight concrete deck (figures 3, 4, and 5). A waterproofing membrane and a 3–in (76.2–mm) hot–mix asphalt overlay were placed over the concrete deck for the finished riding surface. The original as–designed scheme for replacing these segments consisted of 12 night closures, one per segment. During these night closures (9 p.m. to 5 a.m.), one lane would remain open for traffic to cross the bridge. Two lanes of traffic would be open during the day.
During construction, however, concerns about the schedule as well as how the segments would fit together led the contractor to propose a revised scheme. The revised scheme resulted in a defined detour route (see figure 6). The segments were replaced during three weekend full closures of the southbound lanes. As a result, rather than 12 separate single–lane closures on 12 nights, complete road closures on three weekends were used to replace the 12 superstructure segments, one span per weekend. VDOT's Public Affairs Office notified the public about the project and the traffic pattern during construction through news releases to the local media. Variable message system (VMS) boards were placed along the highway before construction to inform road users about the closure. The three full closures resulted in reduced risk because all four prefabricated segments were fitted together one span at a time. This change in the construction scheme also allowed the project to get back on schedule and be completed by the original completion date. A detailed discussion of the full closure traffic impacts is presented later in this report. Figure 7 shows the removal of one of the superstructure sections. Figure 8 shows the bridge superstructure partially replaced.
The existing foundations were found to have adequate capacity to carry the additional superstructure dead and live loads, which simplified the construction of the substructure piers and abutments. The abutments and pier stems as well as the wingwalls were reworked and widened to accommodate the increased width. See figure 9 for reconstruction of one wingwall. The pier stem extension is shown in figure 10. The corbel bracket shown in figure 10 was accomplished using grouted dowels and external post–tensioning that extended from one end of the pier cap to the other. Ducts were placed outside the existing concrete along with the necessary reinforcing steel and steel anchor plates. New concrete was formed and poured for the larger pier cap. Once the concrete strength reached the required strength, the strands were placed and stressed to complete the cap.
Other features of the bridge replacement and widening include corrosion–resistant reinforcing steel in the reinforced concrete members, high–performance grout in the transverse post–tensioning tendons for the pier widening, self–consolidating concrete in the beam seats, and a deck extension at the abutments to eliminate the expansion joints at the abutments.
As shown in figure 11, some road work widening was required to provide the necessary shoulder widths on the roadway approaches to the bridge. The complete structure and roadway are shown in figure 12.
Prefabricated Bridge Components and Materials
Traditional construction for a bridge of this type would have been done with composite rolled steel beams with a cast–in–place concrete deck. Construction would have required several stages and many lane closures with significant traffic maintenance effort. Because of the traffic volume on this bridge, modular prefabricated elements were chosen for the superstructure replacement. Each of the 12 segments consists of two rolled steel beams made composite with a concrete deck slab (figures 3, 4, and 5). These segments were fabricated by Coastal Precast Systems, LLC in Chesapeake, VA, and were shipped by truck to the bridge site.
For this bridge superstructure replacement, VDOT selected prefabricated bridge elements and high–performance materials for their superior quality and durability over traditional construction materials and elements. The prefabricated high–performance, lightweight concrete deck and rolled structural steel beam system, waterproofing membrane, and hot–mix asphalt overlay resulted in a bridge that will last longer and perform better than the previous bridge.
This page last modified on 04/04/11