DURABILITY OF CONCRETE STRUCTURES STRENGTHENED EXTERNALLY USING FIBER REINFORCED POLYMER (FRP) AND IT???S PERFORMANCE DUE TO SEA ENVIRONTMENT

摘要

Overall objective of the research is to establish a strengthening method for damaged concrete structures using Fiber Reinforced Plastics (FRP) as well as to have an understanding of the effect of the tropic and sub-tropic sea environment to its durability and performance. Due to the change of the life demands, the structures may be experiencing changes in the function and an increase in service load so that the structures is no longer safe for use and it may cause a damage on the structural elements or it may be demolished. As an important structural element, beams performance may decrease due to age and or increasing of the service loads as well as due to natural disasters. At certain level of load, a reinforced concrete beams may damage under yielding of the tensile steel reinforcement. The need for strengthening of reinforced concrete structures is become more apparent, particularly when there is an increase in load requirement, a change in use, a degradation problem, or some design/construction defects. The repair of damaged reinforced concrete members by external bonding of fiber reinforced polymer (FRP) is becoming increasingly popular in the construction industry. FRP is a composite made of high strength fibers and a matrix for binding these fibers. FRP system have significant advantages over classical structural material such as steel, including low weight, corrosion resistance, and ease of application. FRP has been successfully used to retrofit all basic structural component, namely, beams, columns, slabs and walls. Flexure strengthening of concrete beams accomplished by epoxy bonding the FRP material are bonded to the beam on the web or the tension face, for shear strengthening the FRP are bonded to the web. The study on the durability of the structures strengthened with FRP materials especially due to tropical severe sea environment has not been sufficiently explored to provide a rational application into worldwide. Aggressive environmental impact of tropical countries may accelerate the delaminating of the FRP. The delaminating of the FRP should be prevented since it causes a catastrophic failure. In application, the failure of the FRP strengthened structures may occur by FRP rupture as well as debonding due to peeling off of the FRP plate, resulting in a sudden drop in loads and brittle failure. The structures on the severe environment may accelerate the peeling off of the FRP plate, decreasing in the entire structure performance. This research is aimed to fulfill the comprehensive study on durability of the strengthening of the reinforced concrete beams and its performance due to tropic sea environment. In order to achieve the objective of this research, a series of experimental study as well as a numerical study has been conducted. A series specimen has been prepared to simulate the effect of sea water to the strengthening effectiveness of GFRP sheet in reinforced concrete beams. Results indicated that sea water effects to the decreasing of the ultimate load. A mathematical model has been achieved to model the effect of sea water to the ultimate capacity of the concrete beams strengthened using GFRPs. However, the model are still needed to be clarified by long term data that will be continued on the second year of research program.