| When the bridge structure is strengthened by enlarging section method,the closed traffic will cause great economic losses.When the bridge is strengthened under the open traffic condition,the vehicle driving will induce the vibration of the bridge,which will affect the new pouring concrete.Based on this,the time before the final setting of concrete is divided into the initial setting period and the middle setting period and divided into seven periods.24 cube specimens and 48 new and old concrete Z-type direct shear specimens are designed together with the reference group.The disturbance is provided by the indoor vibration table.At the same time,the damage process of the specimen is monitored in real time by acoustic emission equipment,and the influence mechanism is analyzed from the macroscopic strength and micro-cracks.In the compressive strength test of concrete cube specimens,the anti-disturbance coefficient K_i is used as the evaluation index of anti-disturbance.It is found that compared with the reference concrete,the anti-disturbance coefficient of the specimen after initial disturbance increases first and then decreases.The anti-disturbance coefficient of the specimen gradually increases after the disturbance in the middle stage of condensation,and the fitting equation of the anti-disturbance coefficient K with respect to the disturbance time t is established through the measured data.By means of acoustic emission b value and energy,the reason of strength change of concrete cube specimen is revealed from the angle of initial micro crack number.In the direct shear test of new and old concrete,according to the different interface treatment methods,the specimens are divided into groove(KC)specimens and planting bar(ZJ)specimens.It is found that the peak load of grooved specimen increases gradually at the initial stage of setting,and it is disturbed at the middle stage of setting.The peak load of specimen is lower than that of reference specimen but still increases.Combined with DIC analysis,the damage stage of the grooved specimen was divided,and it was found that the damage of the disturbed specimen in the middle stage of condensation was larger.At the same time,by analyzing the AE event point distribution,it is found that the damage of the specimen is mainly concentrated in the groove.According to the acoustic emission energy and load curve,the damage stage of the specimen is divided,and the damage of the specimen is divided into shear failure and tensile failure by Gaussian mixture model clustering method.It is found that the larger the initial damage is,the higher the proportion of shear failure event points of the specimen is,the larger the RA value of the failure mode classification boundary is,and the smaller the converse is.The damage of specimens is classified by fuzzy C-means method.It is found that the less the initial micro-cracks are,the higher the interface cracking ratio is.At the same time,the functional relationship between the anti-disturbance coefficient K of the specimen after early-age disturbance and the disturbance time t is obtained,which can be used for engineering reference. |
