Research On Bond Behavior And Mechanism Of GFRP Bars

As a common supporting technology in deep foundation pit engineering, soil nailing isapplied widely in the world. In the engineering, due to the low corrosion resistance andpoor durability, reinforcement has always been a hidden trouble in anchoring engineering.Glass Fiber Reinforced Polymer (GFRP) as a new composite material, has manyadvantages such as high strength, light weight, corrosion resistance and so on. When GFRPbar replace the reinforcement, many problems of the reinforcement soil nailing will besolved easily. Cohension is the premise of soil nailing under loading, so take studying onthe bond properties of GFRP bars is of great significance in both theory and engineeringpractice. In this paper, the experimental studying on the tensile mechanicalproperties, bonding properties and bond stress distribution are carried out under Project51278391supported by National Natural Science Foundation of China and ProjectQ20121111supported by Hubei Provincial Education Administration of China.In determination of the content and tensile tests, the relationship betweencomposition and tensile properties; GFRP bar will crack when it is under certain load, thecrack will move to the middle as the load increase, it will disappear and close as the loaddecrease before failure; GFRP bar’s elastic modulus is40-45GPa, and the ratio of Poissonis0.28-0.30.In single and cyclic pull-out tests, we use20cm,22cm, and25cm GFRP bars at thebond depth of5d and8d, the failure modes are mainly divided into two kinds: pull-outfailure and the mortar splitting; GFRP bar’s diameter, bond depth and the failure modedifferent will causes in the bearing capacity, bonding strength and bonding stiffnessdifferent; As GFRP bar squeeze the tiny gaps in the mortar, the residual deformationappeared. It lead to the bond slip curves’ slope change in cyclic pull-out test.In the25cm GFRP bar and1meter bond depth pull-out test, researching on the bond stress distribution. When damaged, the bearing capacity is about100kN, and thebonding strength of GFRP bar in anchorage segment is mainly distributed in the range form0to50cm; With the depth increase, the bond strength of GFRP bar increases quickly at thebeginning and then decreases, finally tends to0; When the stress state changes, thedistribution of GFRP bar’s bonding stress change. It mainly reflect in the the position of themaximum bonding stress value changes with the pull-out force increased.