Experimental Study On Fatigue Behavior Of Prestressed Concrete Beam Under Overload And Corrosion Damage

Prestressed concrete structure has good mechanical properties due to light weight,small crack development,and it is widely used in civil engineering.With the increasing heavy traffic,the fatigue of the prestressed concrete structure has been concerned by researchers all over the world.In addition to bearing the service load and natural load during the structure’s service life,reinforcement corrosion caused by atmospheric environment or marine environment is another common threat.The mechanical properties of materials are changed because of corrosion damage and fatigue damage,which significantly affects the load carrying performance of structure.Based on the current situation,the static performance,constant-amplitude fatigue performance and overloaded variable-amplitude fatigue performance of 10 prestressed concrete beams are experimentally investigated by changing the corrosion rate of non-prestressed tendons,the amplitude of fatigue load and the cycle of heavy loading.The main research works and results are listed as follows:(1)Two prestressed concrete beams were tested under static load.The influence of corrosive damage in non-prestressed steel on static behavior of prestressed concrete beams was investigated.The static bearing capacities of corroded beam and uncorroded beam were determined,which provided the reference for fatigue load amplitude.(2)Four prestressed concrete beams were tested under constant-amplitude fatigue load by changing the corrosion rate and fatigue load amplitude.By measuring the development of steel strain,concrete strain and mid-span deflection of test beams after different fatigue cycles,the effects of the fatigue load amplitude and corrosive damage on fatigue performance of prestressed concrete beams were exposed,and the degradation of residual stiffness and residual strength for test beams under constant-amplitude fatigue loading was analyzed.Based on the cumul ative damage characterized by stiffness degradation,the expression cumulative damage f(n/N)is proposed,and the degeneration of fatigue residual bearing capacity R(n)was also preliminarily discussed.(3)Four prestressed concrete beams were tested under overloaded variableamplitude fatigue loading.Two-stage variable-amplitude fatigue tests with loading sequence from high to low were carried out on two corroded beams and two uncorroded beams,to investigate the effect of heavy-loading cycles on the fatigue performance and fatigue life of the test beams.The fatigue performance of corroded and uncorroded beams subjected to heavy-loading were compared and discussed.Based on the theory of cumulative fatigue damage under two-stage variable-amplitude fatigue loading,the fatigue life of corroded and uncorroded beams after heavy-loading was predicted,which provides a reference for the fatigue life assessment of prestressed concrete beams subjected to heavy-loading and corrosive damage.