Composites for Structural Strengthening

Fiber-reinforced polymer (FRP) composites have been used in aerospace and marine applications for more than 50 years and are now increasingly being used in the construction industry especially in the field of repair and retrofit of damaged or deteriorating existing structures. The interest of the research community in the field of structural maintenance and protection as well as of structural safety against environmental actions such as seismic ones has strongly grown owing to high losses related to recent catastrophic natural events. Therefore, more resources have been employed for repairing, retrofitting, and strengthening existing concrete, masonry, steel, and timber structures. In this field, the use of composite materials involving new types of fibers and matrices is becoming an attractive alternative to traditional systems. The primary reasons for which civil engineers select them are related to FRPs high values of specific stiffness and strength as well as their high durability, versatility, and ease of installation. In addition, composite materials may be employed to guarantee the safety and preservation of structures damaged by seismic or catastrophic events even in nonstandard situations (e.g., emergency), such as to retrofit buildings of significant historical and artistic interest for which priority must be given to the requirements of “reversibility” and “transparency” of the strengthening solution. For the mentioned fields of civil engineering, in the following sections, a review of common applications of composite materials on existing buildings is presented; the structural capacity increase achieved by their use as well as the strategies and benefits provided by composites with respect to traditional systems are also illustrated.