Experimental Studies On Long-Term Behavior Of FRP Retrofitted RC Columns With Earthquake Loading Damage

Fiber reinforced plastics (FRP) has been recently widely studies and found growing applications in civil engineering field, due to the expectation of its high-strength, light-weight, quick and easy installation on site, high resistance against corrosion and easy fabrication. Many researchers found that the strength and ductility of bridge concrete columns could be significantly increased by wrapping FRP around the columns. For significant amounts of existing structures, the retrofit design is based the philosophy to enable the structures to survive essentially one extreme seismic event. Proved by numerous tests, a retrofitted column is reasonably guaranteed to develop a ductile response to a severe earthquake attack. However, several questions related to the post-earthquake health, in other words, the residual behavior of the retrofitted bridge columns remained unanswered. Such question includes of what levels of the stress can be induced by different levels of shaking. Failure criteria and the duration of time without failure of damaged column under the long-term loading are not confirmed. Performance of damaged columns after repair will respond to a second or more earthquake attacks. These issues are of significant importance. This thesis presents the results of a research project designed to address some of the issues presented above. The primary focus is on the sustained long-term axial loading behavior of FRP retrofitted columns after being subjected to limited damage by simulated earthquake loading. The testing contents are as follows:1. Eight RC columns were tested first under cyclic lateral force and a constant load equal to 20% of the column axial load capacity. The main parameters considered were the type of FRP jacket and peak drift ratio where the lateral loading was interrupted. Glass-fiber-reinforced plastic (GFRP) and Carbon-fiber-reinforced plastic (CFRP) were both used for retrofitting.2. Five model columns were applied long-term axial loading after being subjected to different level of lateral cyclic loading. Five sets of long-term axial loading equipment were designed and manufactured. The component of long-term loading test comprised axial creep and creep recovery at two different level of sustained load. The creep data of FRP jacket were obtained in the test.3. The analytical studies were carried out using the age-adjusted effective modulus method for creep of concrete, combined with the Findley's power law...