Experimental Study On The Impact Of Adhesive Layer Thickness And Initial Stress Of Prestressed Carbon Fiber Sheet Reinforced Concrete Beam Interface Temperature Stress

Studies have shown that the coefficient of thermal expansion of carbon fiber sheets is larger different than concrete and steel. when the ambient temperature changes between the carbon fiber sheets bonded interface and the concrete beam will inevitably produce temperature stress. And study on the influence of the adhesive layer thickness and the initial stress of prestressed carbon fiber Sheets strengthen ing concrete beams under the temperature changes is less.The study use the beams of adhesive layer thickness of 2mm, 4mm, 6mm and the initial stress of 10%, 20%, 30% carbon fiber sheets tensile strength to carry out temperature test,measured by test fitting and analysis of numerical data, combined with infinitesimal segment of the force analysis under the ideal state of bonding conditions, seeking distribution of interface temperature stress and the impact of the thickness of the adhesive layer and initial stress. The results show:1. For the beams of different initial stress and the same thickness adhesive layer The larger initial stress, the value of carbon fiber sheets strain distribution along the beam is larger. For the beams of different thickness adhesive layer and the same initial stress,the larger thickness adhesive layer, the value of carbon fiber sheets strain distribution along the beam is smaller. For the beam with 2mm and 4mm thickness adhesive layer, the larger initial stress, the region of CFRP sheets strain changed dramatically is larger. But for the beams with 6mm thickness adhesive layer, the value of carbon fiber sheets strain distribution along the beam are relatively stable, and there is no region of strain sharp changed. The strain rate of change is basically remain unchanged.2. The equation of prestressed CFRP sheet strain and temperature change in the end position of beams is obtained by numerical fitting. Relationship curves show that under the same thickness adhesive layer conditions, the larger initial stress, the strain values of CFRP sheets is smaller,and when the strain rate changes in the end position of beams,the corresponding temperature is higher.The corresponding temperature is higher when the strain rate changes in the end position of beams with 4mm thickness adhesive layer.3. For the same initial stress conditions, the smaller thickness of adhesive layer, The maximum interface temperature stress of the anchor end and mid span of the test beams is larger.for the same thickness adhesive layer, the larger initial stress,The maximum interface temperature stress of the anchor end and mid span of the test beams is larger. Under the same thickness adhesive layer,the suggestion is using prestressed CFRP sheets of initial stress of 0.1P stress on the structure reinforcement.4. For the same initial stress conditions, when the temperature changes at 0 centigrade ~ 20 centigrade range, the interface temperature stress of the concrete beams with 4mm thickness adhesive layer is the smallest;when the temperature changes at 20 centigrade ~ 47 centigrade range, the interface temperature stress of the concrete beams with 6mm thickness adhesive layer is the smallest; the suggestion for prestressed carbon fiber sheet reinforced concrete beam is using 4 mm thickness adhesive layer in winter,and in a relatively high temperature summer using 6 mm thickness adhesive layer is more appropriate.