Prestressed Carbon Fiber Reinforced Flexural Performance Of Reinforced Concrete Beams Pilot Study

Engineering practice and experimental research show that strengthening action of CFRP mainly is fully taken after the steels yield ,however,deficiently before that.Thus the action that CFRP enhance cracking load and yield load of the beams strengthened with CFRP isn't apparent and the improvement to the performance in bending in the regular service course is limited.To make full use of the strength of CFRP,the prestressing technology is used in the experiment to overcome the disadvantage of CFRP and improve strengthening action of CFRP.The test shows that prestress can improve the performance of CFRP in all course. Prestressed CFRP can exert its full contribution to the beams strengthened with CFRP. If the steel bars in initial state do not yield ,whether the beam is cracked or not , bearing capacity is similar.Prestressing force is transferred to the concrete through bond. U style stirrups only take the action of pretection and the key what can ensure the the strengthening action of CFRP is good bond between CFRP and concrete.Academic analyse and calculation show that bearing capacity is enhanced and the width of cracks and the deflection in the regular service course is limited for prestressing force can improve the exertion of CFRP. 30 percent of the strength of CFRP is proper prestressing value.0.01 is the proper number of strain of CFRP when the ultimated moment is calculated.This paper put forward a technics on cracking moment. Preliminary research effort on the losses of pretress is taken and the calculation formula is put forward accordingly.