High-Performance Composites

NOV 2014

High-Performance Composites is read by qualified composites industry professionals in the fields of continuous carbon fiber and other high-performance composites as well as the associated end-markets of aerospace, military, and automotive.

Issue link: https://hpc.epubxp.com/i/405736

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Page 63 of 67

FOCUS ON DESIGN 6 2 | H I G H - P E R F O R M A N C E C O M P O S I T E S S STRUCTURAL's V-WRAP CARBON/ EPOXY REINFORCEMENTS teel-reinforced concrete is among the most widely used building materials in the world, but it faces potential threats, including damage from seismic events, and cracking due to temperature-related expan- sion and contraction. The latter is common, and permits moisture inva- sion, and the resulting corrosion and expansion of steel rebar deteriorates the concrete, resulting eventually in loss of structural capacity. In many cases, distressed structures can be repaired. They also can be strength- ened to comply with changes in load demands or code revisions. Further, design or construction defciencies can be corrected to improve load-bearing capabilities. Carbon fber composites play a major role in such repairs and upgrades, and do so at signifcantly less cost than new construction. According to Jay Thomas, VP of strengthening solutions at Struc- tural (Hanover, Md., a Structural Group company), more than 20 million ft 2 (1.85 million m 2 ) of carbon fber already have been installed in reinforced concrete buildings in the U.S. alone. Structural, in the business for nearly 40 years, comes well-prepared. "We take a lot of factors into account, including constructability, aesthetics and cost, and essentially, re- verse engineer the building's structure to improve performance," he asserts. Percentage of ultimate capacity "Both structural repair and structural strengthening require knowledge of the global behavior of the entire building," Thomas explains, noting that the task is sometimes complicated by the fact that the engineer has no frsthand knowl- edge of how the structure was originally designed or built. "A design must be tai- lored for each specifc situation and its load conditions." To that end, Structural's engineers frst conduct a comprehensive inspection. The structure's elements are catalogued as to type (e.g., round vs. rect- • Uni carbon fber, placed in accordance with a structural design, enhances strength of reinforced concrete. • Careful surface preparation ensures that wet-out carbon fabric adheres to the concrete to provide "composite" action. • Carbon composites used in concert with other construction methods is a cost-effective strengthening solution. Carbon fber sheets placed beneath a concrete slab increases tension strength and bending resistance Carbon fber on top of slab over columns counteracts negative bending moment Rebar Cracks U-Shaped carbon fber strips improve shear strength, mimicking rebar stirrups TOP VIEW V-Wrap can be combined with steel plates and enlarged concrete members Column wraps increase column confnement and ductility and act as additional reinforcement ties CARBON FIBER: KEY TO Carbon composites are ef fective solutions for repairs DESIGN RESULTS

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