Study On Flexural Behavior Of Steel Reinforced Concrete Slabs Strengthened With External Prestressed FRP Tendons

As a kind of active strengthening method, external pre-stress strengthening can reduce the stress and strain lagging phenomenon, and make the appended prestressed part and original structure combined force, collaborative work, improve the bearing capacity of structure. The traditional prestressed strengthening use high-strength prestressed reinforcement or steel strand mostly, cannot solve the steels corrosion problem. Fiber Reinforced Polymer (FRP) have caused the special attention in engineering, because of its lightweight, high-strength, excellent corrosion, fatigue resistance and nonmagnetic, and in recent years FRP have been used in the concrete structures extensively at home and abroad.In this text, a total of six RC slabs, each having 500 mm width,100 mm thickness, and 2000 mm length, were constructed and tested to failure under four-point bending. Each slab was reinforced with four No.8 deformed steel bars at tension side that corresponded to 0.5% steel reinforcement ratio. One slab was used as a control while the other fivex slabs were strengthened with external prestressed GFRP tendon. The flexural behavior of sluice bridge deck strengthened with external prestressed GFRP tendon is imitated to study and the main contents are as follows:(l)The influences of GFRP strengthening quantity and tension control stress on cracking and ultimate load of slabs are studied. It is shown that the cracking and ultimate load are increased significantly with the quantity of GFRP tendon strengthened with; when the strengthening quantity is the same, the cracking and ultimate load are not increased with the tension control stress, and the cracking and ultimate load is the largest while the suitable tension control stress.(2)The influences of GFRP strengthening quantity and tension control stress on short-term stiffness of slabs are studied. It is shown that the short-term stiffness improved obviously, and the deflection of concrete slabs got smaller at the same load with the increase of strengthening quantity of GFRP tendon strengthened with; there is no influence of the tension control stress on the improving degree for short-term stiffness.(3) Combine existing relevant regulations, according to the basic flexural theory based, The calculating formulas of normal section bearing capacity of reinforced concrete slabs strengthened with external prestressed GFRP tendons are proposed.