Reinforced concrete, which is widely used in the construction industry, tends to crack, chip, and be damaged as a result of inadvertent loads or overloads that may not have been accounted for in the initial design. The damage may be extensive enough that the safety of a structure becomes a major concern. Recently, a considerable effort was expended on using fiber-reinforced composites to repair or upgrade concrete structures, and several sessions were devoted to this subject at a recent International SAMPE Symposium and Exhibition in Long Beach, California. It is natural to use composites for repair since the repairing composites tend to be thin laminates. These materials are easily bonded to damaged concrete structures, which usually have cylindrical or flat surfaces.
Different methods for designing and analyzing thin laminates have been developed and are available in many computer codes. Recent research demonstrates that damaged concrete structures and the composites used to repair them can be simulated simultaneously by the composite mechanics included in some computer codes. With composite mechanics, we can represent any concrete structural section by assuming that it consists of several layers through its thickness. In so doing, we take advantage of all the composite mechanics features available in such computer codes as the Integrated Composite Analyzer (ICAN). This demonstrates that computer codes developed at the NASA Glenn Research Center for aeronautics research are applicable to civil engineering problems.
An approach developed at Glenn, and applied to selected reinforced-concrete structural sections and structures, takes advantage of those features and attendant computer codes. It represents a new and effective method for designing composites to repair or improve the overload strength of a concrete structure. The method uses the composite mechanics in ICAN to simulate reinforced-concrete sections that have a typical infrastructure as well as selected reinforced-concrete structures.
Structural sections were modeled by a number of layers through the thickness, where some layers represented concrete and others represented the composite. The reinforced-concrete structures were represented with finite elements, where the element stiffness parameters were from structural sections represented by composite mechanics. The load-carrying capability of the structure was determined by progressive structural fracture embedded in Composite Durability Structural Analysis (CODSTRAN). Results show that the addition of a relatively small composite laminate thickness resulted in up to 40 percent improvement in the damage and overload resistance of structural sections and up to 3 times improvement of the selected composite-enhanced structures (i.e., arches and domes).
CODSTRAN simulation cycle.
Long description of figure 1.
Researchers at Glenn illustrated the new method by using composites to improve the damage resistance of a reinforced-concrete dome section, as shown in the preceding diagram. The section configuration is illustrated in the following diagram. The results obtained for different composite enhancements are shown in the graph: placement of the composite enhancement at the top of the dome improved the dome’s damage resistance about 2½ times. Reference 1 describes this work in greater detail.
Reinforced-concrete dome geometry and structural sections.
Long description of figure 2.
Effect of applied concentrated load on the damage to a reinforced-concrete dome.
Last updated: December 14, 2007
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