Experimental Studt On Bending Behavior Of Damaged Bemams Reinforced With High Ductile Concrete

The development of reinforced concrete has now become the most widely used structural form.Due to the aging of buildings,changes of use functions,design and construction defects,and natural disasters,they will face the problems of reinforcement and repair.Therefore,the repair and reinforcement of damaged reinforced concrete structure has a broad application prospect.Compared with the traditional reinforcement method,the high ductility concrete(HDC)reinforcement method has better ductility and durability,and the construction is convenient and the cost is low.In order to make this reinforcement method widely used in engineering practice,this paper mainly does the following work:(1)In this paper,19 simply supported beams are tested by four point bending test,and the failure pattern and crack development law of each group of beams before and after reinforcement are analyzed.The results show that the bearing capacity and ductility of damaged concrete beams strengthened by HDC have been significantly improved.Among them,the peak load and cracking load are greatly increased compared with before the reinforcement;the maximum deflection,ductility coefficient,and flexural rigidity at the time of failure are improved to different degrees;The shape of the broken ring changed from the original brittle bending failure to obvious ductile shear failure.The cracks after the failure were finer and more evenly distributed than before the reinforcement,and the average value of the crack spacing of the three groups of reinforced beams was significantly reduced.(2)The influence of different HDC thickness and stirrup ratio on the bearing capacity,crack distribution,ductility and stiffness of strengthened beams is analyzed by comparison.The results show that the larger the thickness of the reinforcement layer is,the more obvious the improvement of its bending capacity and deformation capacity is,but the peak load and cracking load are not in direct proportion to the thickness of the reinforcement layer,that is to say,when the thickness of the reinforcement layer is too large,the increase of the characteristic load has a downward trend.In addition,addition stirrup ratio can further improve the bearing capacity and deformation capacity of the strengthened beam.With the increase of stirrup ratio,the improvement is not obvious.Therefore,the recommended thickness of the reinforcement layer is 10 mm,and the stirrup ratio is 0.75%.(3)Based on the test,the calculation formula of flexural capacity of the strengthened beam considering the tensile strength of HDC strengthened layer is given.The results show that the calculated value of bearing capacity is in good agreement with the test results,which provides a reference value for the practical engineering application.