Research On Compressive Behavior Of GFRP-latticed Steel Tube Composite Confined Concrete

It is a very effective method to improve the performance of concrete by imposingconstraint on concrete which forms confined concrete. Compared to ordinary concrete,confined concrete can improve the ductility of components and the seismicperpormance of structures with higher compressive strength and better deformationcapacity. The common forms of constraint are the stirrup constraint, the steel tubeconstraint, the FRP constraint, the steel and FRP composite constraint. Differentforms of constraint show large difference on the performance and mechanicalcharacteristic of concrete, there are also advantages and disadvantages of each whenapplied to engineering practice. Therefore, it is of great significance to analyz theproperties of different confined concrete and explore better forms of constraint.The performance characteristics and research development of steel tubeconcrete, FRP confined concrete, steel and FRP composite confined concrete weresummarized firstly in the paper, on the basis of this, a novel form of GFRP-latticedsteel tube composite confined concrete was proposed, this novel form of confinedconcrete intended to utilize advantages and characteristics of GFRP and latticed steeltube in the confinement to improve the performance of ordinary concrete.1. Ten groups of total thirty cylinder specimens were designed in the paper,including one group of plain concrete, one group of latticed steel tube concrete, onegroup of GFRP confined concrete, seven groups of GFRP-latticed steel tubecomposite confined concrete. And the uniaxial compression experiment was carriedout for comparative study. The fabrication of specimens, the loading system and testdata measurement methods were described.2. The destruction process and morphology of specimens in each group wereexpouded. The characteristics of load–displacement curves under axial load weresummarized. The deformation properties of specimens were evaluated by thecompression toughness index. The constraint mechanism of GFRP-latticed steel tubecomposite confined concrete was illuminated. The effects of GFRP layer number,mesh diameter and mesh form of latticed steel tube on the uniaxial compressionperformanc were studied.3. Based on the experimental stress-strain curves characteristices and the Lamand Teng model, the design-oriented stress-strain model suitable for GFRP-latticed steel tube composite confined concrete was proposed through regression analysis.Results of the study showed that, GFRP-latticed steel tube composite confinedconcrete could give full play to the advantages and features of GFRP and latticed steeltube. High tensile strength of GFRP increased the bearing capacity and ductility in thehardening stage, and good elastic-plastic deformation performance of latticed steeltube improved the attenuation process of bearing capacity and ductility in the declinestage. It indicated that GFRP-latticed steel tube composite confined concrete was aneffective novel form of confined concrete.