Abstract
Externally bonded steel plates, steel or reinforced concrete jackets, and
external prestressingwere the traditional techniques used to strengthen or retrofit existing concrete structures to provide additional strength, compensate
for construction design errors, correct deterioration problems, or improve
the performance as required by code changes. These techniques were expensive because of the heavy equipment needed and, in most instances, did not
provide a long service life. Corrosion of reinforcement, which is the common deterioration mechanism, affects the life cycle of steel plate in a similar
manner. In addition, in certain cases such as strengthening of unreinforced
masonry and concrete walls, the traditional techniques cannot be used. Highstrength composite materials, used by the aerospace industry for more than
40 years, are becoming the preferred materials for the repairs. Since composite materials are extremely light, the process of installing the composite onto a
structure is simplified considerably and, inmost cases, heavy equipment is not
needed for the repairs. The composites also have very high corrosion resistance. Although the materials are expensive, the final cost of repair becomes
competitive because of the ease of construction and the time savings. The
most popular uses include:
• strengthening of reinforced and prestressed concrete beams for flexure;
• shear strengthening of reinforced and prestressed concrete beams;
• column wrapping to improve the ductility for earthquake-type loading;
• strengthening of unreinforced masonry walls for in-plane and out-
of-plane loading;
• strengthening for improved blast resistance.