Impact Behavior Of Concrete Confined With GFRP Tubes And Steel Spirals

In recent years, Fiber Reinforced Plastics/Polymers(FRP) became hot in the field of Civil Engineering because of the advantages of corrosion resistance and its high strength to mass ratio. Because of its convenience in construction, strengthen and repair, FRP is widely used in recent years in the city infrastructure, bridges and other structures, and it's expected to applied in earthquake-resistant structure,blast-resistant structure and impact-resistant area. However, researches on FRP-confined concrete under impact or explosion loading is still in the primary stage. In the face of more and more structural failures because of explosion and impact events, researches on impact performance of FRP confined concrete are still necessary.FRP is a linear elastic material with a brittle failure mode, which is very negative for the structural seismic-resistance. GFRP-Spiral reinforcement(SR)-confined concrete is a kind of composite materals which consists of SR-confined concrete and external GFRP tube. This is a promising structure, its advantages include: increase the plastic performance of GFRP tube as well as improve the corrosion resistance of SR. Moreover, GFRP tube can provide confinement of core concrete as well as permanent formwork, while also protecting the internal structure from external adverse environment.Based on previous works on performance of FRP-transverse steel reinforced(TSR) confined concrete under static load or impact load and mechanical performance study of FRP confined concrete and reinforced concrete, this paper presents test and analytic results of GFRP-SR confined concrete under static and impact load with using high performance drop hammer test machine in Hunan university. Moreover, by using the existing model, simulation of the impact test was also presented. In this paper, the main research works include the following parts:(1) Experimental study on compressive behavior of concrete confined by both GFRP tubes and steel spirals. Compressive behavior of 12 GFRP-SR confined concrete cylinder specimens were investigated using a 10,000 KN compressive machine. The GFRP layers and the volumetric ratio of SR were the test variebles. The axial stress-axial/transverse strain curves were obtained. The combined work efficience of these three materials was discussed and the influences of test variebles on the behavior of GFRP-SR confined concrete were also investigated.(2) A new model based on 30 GFRP-SR confined concrete specimens' test results was proposed to describe the stress-strain behavior of GFRP-SR confined concrete and the predictions were further compared with the test results of other 12 specimens' test results.(3) By using drop hammer test machine, the impact behavior of 24 concrete specimens confined by different categories of GFRP layers and SR volumetric ratio and impacted under four kinds of impact height and two kinds of hammer mass were investigated. The impact stress-time history curves, strain-time histories of front, middle and bottom portion of GFRP tube and SR were obtained. The combined work efficience of these three materials was discussed and the influences of test variebles on the behavior of GFRP-SR confined concrete were also investigated.(4) A comparative analysis of GFRP-SR confined concrete under static load and impact load was presented and strength enhancement coefficients of all specimens were obtained, moreover, the influences of test variebles on strength enhancement coefficient were also investigated. By using theological model, simulation of 12 specimens was conducted and the simulated stress-strain curves and impact stress were compared with the test results.