Category 3

Structural Systems

OUTSTANDING PROJECT

Wisconsin Avenue Bridge Strengthening and Rehabilitation

A national treasure is stronger and safer thanks to the strengthening and restoration
of the Wisconsin Avenue Bridge, one of five original stone arch bridges to cross the C&O Canal and its adjacent tow path near Georgetown. Built in 1831, the single-span, 54-foot-long masonry arch bridge is the oldest existing highway structure in Washington, D.C. Since this bridge is listed on the National Register of Historic Places and is a contributing element to the Georgetown National Historic Landmark District, maintaining the visual historic integrity of the structure was a key concern. The rehabilitation was further complicated by the coordination and consensus required
between multiple federal and district agencies, the need to maintain traffic across the bridge, and the extensive public coordination required. FHWA and the District of Columbia called on KCI Associates of D.C. to inspect, analyze and develop plans for the rehabilitation. Once engineers determined that traditional methods of strengthening were not viable due to physical constraints and historic concerns, the team chose to strengthen the bridge using the Archtec™ system—a proprietary masonry strengthening system developed by Cintec. The KCI team worked with Cintec and their engineer Gifford to analyze and design the innovative strengthening system, which called for embedding stainless steel reinforcing rods within the structure to strengthen the bridge without altering its facade. The strengthening was completed in under three weeks with minimal impact to traffic. The Wisconsin Avenue Bridge is again completely open to both pedestrian and vehicular traffic following restoration and strengthening of the wrought iron railings, repairs to the surrounding stone masonry retaining walls, utility relocations, roadway reconstruction and resurfacing, and completion of the brick sidewalks. It is now strong enough to stand the test of time, and the weight of 45-ton trucks, for the foreseeable future.

HONOR AWARD

Hollins Road Bridge over Tinker Creek (VA)

Firm: Alvi Associates, Inc.

Alvi Associates designed a replacement bridge to cross a river in karst terrain, with the depth to rock varying from as little as 5 feet to more than 60 feet. The solution is an innovative bridge consisting of a three-span concrete rigid frame which provides a wide variety of benefits.

Original or Innovative Application of New or Existing Techniques. This bridge is innovative in reviving use of the efficient framed construction which was more common about a century ago. Such construction became less common as designers sought to make design easier, but modern software enables a return to this type of efficient design.
Complexity. While the framed design simplifies construction, it also makes the bridge structural analysis considerably more complex. Moreover, a framed structure can develop significant thermal and concrete shrinkage forces, therefore a special construction sequence was developed to successfully minimize them. Additional complications encountered were the need to stage construction and accommodating the karst terrain.
Social, Economic, and Sustainable Design Considerations. The framed design provides substantial benefits with respect to all key design criteria:
• The use of a thin deck, without beams, maximizes the waterway opening, allowing
floods to pass more easily, in turn shortening the bridge and providing major cost
savings.
• The efficiency of the framed construction reduces material needs and construction
cost, and also provides a structurally redundant and safer design.
• The all-concrete construction, and the elimination of all deck joints, bearings, and
beams, accelerates construction and greatly reduces maintenance costs.
• The visual cleanliness and simplicity of the bridge offers an elegant appearance.
Exceeding Client/Owner Needs. The client originally developed a conventional
design based on hydraulic studies. On the firm’s initiative, they reviewed these studies and proposed the alternate “value engineered” design described herein, which was readily accepted by the client because of its benefits.
Future Value to the Engineering Profession. This bridge serves as an example of how thinking outside of the box, and applying modern computing power, can enable revival of an efficient bridge type from a past era. Hopefully, the example provided by this bridge will gradually result in broad adoption of this bridge type for the many projects where it makes sense, thereby providing considerable value to both the profession and society.