Washington, D.C., is home to a large number of high-profile government offices, landmarks, and other buildings. These vulnerable structures require protection from the potential effects of terrorist attacks, so that the U.S. government and the people working for it can continue their important work safely.
Structural Preservation Systems Inc., Baltimore, was charged with safeguarding one such building, which, for security reasons, PUBLIC WORKS cannot name. The contractor, looking for an effective, durable, and economical way to provide the building with enhanced strength and blast resistance, turned to Hardwire LLC, Pocomoke City, Md., and its family of unique steel reinforcement products to do the job.
The proprietary high-tensile strength steel reinforcement products—based on the same steel-belted technology found in tires—are made from ultra-high-strength twisted steel wire cords that are 11 times stronger than typical steel plates. They can be used on the sides of beams and girders to provide additional shear strength, or wrapped around columns and beam/column joints to provide confinement and additional ductility, resulting in increased flexural strength. In building applications, the products provide high strength (up to 8 kips/inch) and high modulus (up to 30 million psi) in a very thin, ductile envelope. The product can be molded into or onto virtually any structure or part. Structural Preservation Systems selected Hardwire for its durability, economy, and ease of use; on this project, it is being used in conjunction with carbon fiber.
“With all the challenges we are facing today in obtaining carbon-based reinforcement systems, the system offered a timely solution to this project,” said Jay Thomas, vice president of the contractor's strengthening division. “The Hardwire materials were readily available, and the design and installation process was simple and efficient.”
The reinforcement also can be used to strengthen bridges, tunnels, and other infrastructure. Users can apply this material to exterior walls with urethane, epoxy, polyurea, vinylester, or cement-based adhesives and coatings without affecting the appearance of the structure. Hardwire can be applied with cementitious-based adhesives, enabling contractors to upgrade structures to offer the necessary fire rating, often a challenge with carbon-, glass-, or aramid-fiber reinforced structures that require flammable epoxy-based formulations. Pipelines in corrosive service that require composite construction also could be externally strengthened with retrofit layers to guard against natural and manmade stresses.
The product has garnered the interest of the U.S. military, which see its potential reaching beyond civilian use. “The ability of combat engineers to increase the strength of weakened or battle-damaged bridge beams, floors, and support columns to support combat vehicle loads in a matter of minutes or hours, as opposed to days, provides the tactical commander a heretofore unavailable advantage,” said retired U.S. Army Major General Norman Delbridge.
Roger Crane, composite materials section head for the Carderock Division of the Naval Surface Warfare Center, West Bethesda, Md., commented that the reinforcement could provide ships with performance enhancements, because the low-cost, high-stiffness material could reduce the weight and increase the internal working volume of structures, as well as protect sailors.
— Kimberly Kavler is a business writer.