An Experimental Study On The Axial Compression Performance Of Concrete Square Columns Reinforeed By Bybrid Fiber Composites

With the increasing of the buildings nowadays, the sustaining and reinforcing for existed structures is gradually playing an widely importance in the engineering field.For the limitation of the traditional reinforcing approaches, with the superior features of high strength, light mass and convenience for construction et al., fiber reinforced polymer composites (FRP) establishes a huge advantageous position in the application of strengthening for the building concrete structures. According to the obviously disadvantage of single fiber material, a relatively low efficiency of concrete structure reinforcing was induced, while the widespread utilizes of FRP in structure strengthening was limited. For the purpose of overcoming the shortages of single fiber material, improving the features of single material and raising the reinforcing efficiency, the application and research of hybrid fiber reinforced polymer (HFRP) material were becoming a new hot spot in the concrete structure reinforcing area.On the basis of systematically summarizing the latest art of techniques of FRP reinforced concrete structure, a research project of uniaxial compressive characteristic of reinforced concrete columns with hybrid fiber composite material was proposed.15steel reinforced concrete columns were desired including the corresponding columns, in the index of bringing to use of CFRP with high strength, high elastic modulo and GFRP with high stretch ratio, for the main destination of enhancing the load capacity and ductility. Through the changes of ratio and methods of hybrid, and distance between reinforcing parts to strengthening the specimens, the experiment research for the comparison of retrofitted columns with HFRP, CFRP and GFRP was conducted. The test results revealed that HFRP was sufficiently taking the advantages of the two single fiber materials, and conquering the shortage of the single fiber, simultaneously improving the axial compressive capacity and the limited strain of the columns hybrid strengthened apparently, while the ductility was also bettered obviously. From the comparison of the experiment research of several types of hybrid reinforcing, it turned out that the hybrid effort of hybrid fibers was significantly affected by the hybrid methods and the volume ratio of hybrid, in fact the layers interior and exterior hybrid as same as the1CF/2GF hybrid methods exhibited a better performance; the axial compressive load capacity of the strengthened column specimens was promoted while the reinforcing distance decreasing.In the analysis of mechanism of fiber constrain, the effective tensile stress of hybrid sheet was under consideration with the hybrid effect affection to the HFRP constrained specimens, including the constraint effect coefficient. The calculation models of compressive strength and limit strain of strip constrained concrete columns were resulted from a regression analysis due to the experiment data, meanwhile combining the test features under pressure, a stress-strain relationship model of FRP constrained concrete column was established. Through the limit compressive strength formula obtained from regression, a calculation method for load bearing capability of FRP constrained concrete column was suggested, moreover the coming results of the theory made a good match with the test outcomes. The study results may provide a theory guideline for the utility of hybrid fiber composite material to the real engineering strengthening and a reference for the fore more relative work.