Testing Research And Numerical Analysis On Flexural Behaviors Of CFRP Strengthend Reinforced Concrete Beams Under Secondary Load

Carbon Fiber Reinforced Polymer(CFRP) is a high-performance composite material,with many good performance,such as low weight,high strength,well corrosion resistance and so on.Compare to traditional strengthening technique,the technique of strengthening concrete structures with CFRP has the characteristic of the short work time and good structure quality.Recently years,it is known to us and used by civil construction engineering.However the theoretic research and application is still insufficient in some aspects. The flexural behavior of reinforced concrete(RC) beams reinforced by CFRP under secondary load were investigated in this paper.Seventeen simply supported beams with the dimensions of 150 × 250 × 2600mm include nine secondary-load reinforced concrete beams reinforced by CFRP, six RC beams strengthened with CFRP directly and two unstrengthened control beams were experimentally investigated. Concrete intensive grade is C25,the main variable parameters such as initial load and load history, CFRP amount, reinforcement ratio, anchor measure was adopted. The following items were observed and measured in the experiment: the shape and propagation of cracks, concrete strain ,the steel strain, CFRP strain, the deformed curves, crack load, the maximum crack width and ultimate load under the every load, failure mode.The results indicate that after being strengthened,the flexural capacity and stiffness of beams is significantly increased and crack width and average crack spacing is less compare to normal RC beams.Different initial load causes different lag strain ,therefore,the flexural capacity,stiffness and cracks of beams was influenced. CFRP amount also affects the strengthening effect of beams ,the more CFRP amount,the larger flexural capacity of beams.However, the extent of increase is not linear.The results of experiment also indiate that anchor measure largely affects flexural capacity of beams and exertion of high strength of CFRP. failure mode of beams includes tensile rupture of CFRP failure,concrete crushing failure,peeling failure of the concrete cover and impending failure of the adhesive.On the basis of experimental research,through compartmentalizing experimental beams into plenty of tiny cell,according to constitutive equation of each materials including steel bar,concrete,CFRP, this paper presents numerical simulation study of flexural all course of RC beams strengthened with CFRP, the theoretical results agree closely with those of the test.