Retrofitting of Structural connections
As compared to other techniques, the use of polymer CTech-LLC® composites repair and retrofit systems provide several unique advantages. The key advantage of composites in these applications is its tailorability, which enables the engineer to decouple stiffness and strength (stiffer columns would attract more forces during the earthquake which are not included in the original design). In the last decade or so, the use of fiber reinforced polymer (FRP) in repair and rehabilitation of different reinforced concrete members has been widely accepted by the structural engineering community. Some of the early successful application of FRP composites was in the repair and retrofit of reinforced concrete highway bridge columns that started in California and now is considered to be standard accepted procedures by different departments of transportation in USA and other countries. This application was extended to buildings and other constructed facilities where hundreds or may be thousands of repair and rehabilitation projects have been successfully executed. The use of these materials was shown to be also effective in repair and rehabilitation of reinforced concrete girders, slabs, shear walls as well as masonry wall structures.
One of the recent applications of composites is repair and rehabilitations of different types of reinforced concrete joints including shear capacity upgrade of beam-column joints, moment frame connections and column-tie connections. The major influence of connections details on the structural integrity and seismic performance of reinforced concrete structures has more evident after the 1989 Loma Prieta, the 1994 Northridge and 1999 Kocaeli (Turkey) earthquakes. Post-earthquake reports of the Loma Prieta indicated that one of the main reasons behind the collapse of the Cypress Viaduct, and the damage of the China Basin and the I-80 Freeway is the failure of connections. As the result of 1994 Northridge earthquake, several parking structures collapsed mainly due to severe damage of beam-column and column-base connections. During more recent events such as the 1999 Kocaeli (Turkey) earthquake, it was observed that beam-column joint failures contributed to the severe damage and collapse of many reinforced concrete buildings. CTech-LLC® composite systems can be used to enhance the strength of structural connections and perform:
- Shear transfer
- Joint shear strengthening
- Correction of an existing construction and/or design error
- Force transfer / progressive collapse prevention