By Miss Shirley LEUNG 
Beware! Pieces of concrete fell from old residential buildings in Tsimshatsui and Wanchai four times within a week and even hit the head of a police in an incident! These incidents have raised public concern and the maintenance of buildings becomes a hot topic again. Coincidentally, a technical meeting, which was held by the CV Division on 3 March 2005, introduced FRP and its applications in upgrading and retrofitting works.

FRP is composite material formed by embedding continuous fibers in a resin matrix that binds the fibers together. Common fibers are glass, carbon and aramid fibers. The two main advantages of FRP composite are its high strength to weight ratio and high corrosion resistance. FRP's tensile strength, which can be up to two to ten times of that of steel, minimises the amount of materials to be used. Its low density, which is one-fifth of that of steel, leads to great ease in site handling and reduces labour cost. Its long-term performance under acid, alkali, sunlight and moisture is promising. That explains why FRP has gained popularity in strengthening reinforced-concrete structures among concrete jacketing, steel plate bonding and spraying concrete.

FRP can be applied in a variety of strengthening works, such as flexural strengthening of beams and slabs, shear strengthening of beams and compressive load strengthening of columns. It can be fixed on the structural members by insitu application of epoxy resin to fabrics which is wet-lay method or by bolting fabricated plates onto members which is prefabrication. It can even be applied underwater to reinforce marine structures. 

Indeed, FRP has been applied in Asian countries, such as the restoration of an old structure and strengthening for conversion from a commercial building into a hospital in Singapore, bridge strengthening due to deterioration and increase in traffic load in the PRC, and retrofitting of an earthquake-damaged column in Taiwan. It was also applied as a trial in beam-strengthening works at Central-Macau Ferry Pier. Its application in retrofitting of canopy structures is now being studied by the Hong Kong Polytechnic University. 

Thanks to Ir Dr Wang Jinsong and Mr Giam Sianghai of Fyfe (Hong Kong) Limited who introduced this advanced retrofit technique by warping deficient structural members with the application of FRP. Premises owners, do not ignore your maintenance responsibility. Try to "warp" the problem before the recurrence of similar incidents!