Study On Defect Detection Of Prefabricated Shear Wall Grouting Sleeve

Because of its advantages of convenient construction and green environmental protection,prefabricated structure.Because of its advantages of easy construction and green environmental protection,prefabricated buildings occupy an increasing proportion in residential buildings.Shear wall is the main stress component of prefabricated building,and its difficulty lies in the connection with the main body.The research shows that sleeve grouting connection is a main connection mode of prefabricated shear wall,which can be divided into single row sleeve connection and double row sleeve connection.The overall performance of the force wall is affected by the quality of the sleeve grouting,and because of the particularity of the sleeve position,the detection of the sleeve grouting quality becomes a research difficulty.The existing sleeve grouting quality detection methods include embedded strain gauge method,core drilling detection method,etc.these methods are more complex,and also have some damage to the shear wall.Based on this,this paper uses the impact echo method to detect the single row sleeve,and the ultrasonic transmission method to detect the double row sleeve.Compared with the traditional method,this method is not only simple,efficient and accurate,but also has no damage to the shear wall.The main contents of this paper are as follows.(1)Based on the basic theory of shock wave propagation,the basic equation of shock wave and the reflection and diffraction phenomenon of shock echo,the propagation equation of shock wave in shear wall under different working conditions is proposed,and then the influence law of sleeve grouting defect on shock wave is analyzed;At the same time,the propagation characteristics of ultrasonic wave and the detailed steps of ultrasonic transmission method to detect sleeve grouting are introduced.(2)In order to avoid the influence of the free boundary on the test results,the measuring point is set at the position more than 6 cm away from the boundary.If the thickness frequency of the shock wave drifts to the low frequency,the impact echo method is used to measure 22 sets of sleeves(including 20 sets of single row sleeves and 2 sets of double row sleeves)in a prefabricated shear wall,It indicates that there is a defect in the grouting sleeve.The test results show that the detection effect of the impact echo method for single row sleeve is obviously better than that for double row sleeve.(3)The accuracy of the formula and the reliability of the test results are verified by the finite element simulation.Based on COMSOL software,the refined finite element models of prefabricated shear wall with single row sleeve connection and double row sleeve connection are established respectively.The results show that if there are grouting defects,the thickness frequency of shock wave will drift to low frequency,and the detection effect of shock wave method for large-scale defects is obviously better than that for small-scale defects.For the single row sleeve,the sleeve is set at the center and edge of the shear wall,and the thickness frequency will drift to the low frequency;When the frequency of shock wave is close to the thickness frequency of shear wall,the simulation effect is the best.The results show that the finite element simulation of ultrasonic testing of grouting quality of double row sleeve is better than the impact echo method,and the influence of different strength of concrete on ultrasonic is small.