Performance Analysis And Test Research Of Prefabricated Concrete Structure With Defective Joints

With the adjustment of the national industrial structure,the implementation of building industrialization and the concept of green and energy-saving buildings,prefabricated buildings have ushered in a golden period of development in China,and prefabricated concrete structures are the main direction of building industrialization.The quality of the connection joints of prefabricated concrete structures directly determines the overall safety performance of prefabricated concrete structures and affects the engineering application of prefabricated concrete structures.At present,sleeve grouting connection is the most widely used joint connection method of prefabricated concrete structures.However,due to some factors in actual construction,such as poor precision of reserved steel bars and difficulty in controlling grouting quality,sleeve grouting connection often has various construction quality defects,which adversely affect the overall performance of prefabricated structures.In this paper,aiming at the defects of sleeve grouting joints,the forms and causes of common defects are expounded,the static and dynamic performances of prefabricated concrete structures with joint defects are numerically simulated and analyzed,and the dynamic detection and evaluation method of sleeve grouting joints defects is explored and put forward,and the joint defects of reinforced concrete prefabricated columns are actually detected and verified.The main contents and research results are as follows:（1）On the basis of synthesizing the characteristics of sleeve grouting connection construction technology and on-site construction investigation,the common defects of sleeve grouting connection joints of fabricated concrete structures are summarized,and their causes are analyzed.（2）By using the numerical simulation method and ABAQUS finite element software,the models of prefabricated concrete columns with different degrees of grouting defects in sleeve grouting joints are established,and the influence of grouting defects on the static performance of prefabricated concrete columns under monotonic horizontal load is studied by numerical simulation calculation.The finite element numerical analysis of the horizontal ultimate load on the top of the fabricated reinforced concrete column shows that the defect of insufficient grouting will lead to the decrease of the peak bearing capacity of the fabricated reinforced concrete column.With the increasing degree of defects,the peak bearing capacity of fabricated concrete columns decreases.Compared with the intact prefabricated concrete column,when there are 10%,20% and 30% grouting defects in the sleeve grouting joint,the peak bearing capacity decreases by 3.5%,12.5% and 22.3% respectively.（3）Using ABAQUS finite element software,the dynamic performance of prefabricated concrete columns with different types and degrees of defects in sleeve grouting joints is numerically analyzed.The results show that,compared with the intact structure,the defects of sleeve grouting joints will lead to the decrease of the natural frequency of fabricated concrete columns,and with the increase of defects,the degree of natural frequency decrease will also increase.（4）Through finite element numerical analysis of the dynamic performance（parameters）of prefabricated concrete columns,it is found that the first-order frequency of prefabricated concrete columns decreases by 6.8%,10.8% and 14.9%respectively when there are 10%,20% and 30% insufficient grouting defects in connection joints,compared with columns without joint defects.When 10% and 20%of the joints are not compacted by grout,the first-order frequency of prefabricated concrete columns decreases by 5.0% and 8.9% respectively.According to 12 kinds of prefabricated concrete columns with different types and degrees of defects in connection joints,the quantitative relationship between the degree of defects in connection joints and the dynamic characteristic parameters（frequencies）of prefabricated concrete columns is established.（5）The dynamic testing and evaluation method for the defects of sleeve grouting joints is preliminarily studied and put forward,that is,the dynamic performance parameters（frequencies）of prefabricated reinforced concrete structures are obtained by using the structural dynamic testing technology,and the defects of joints are judged and quantitatively evaluated according to the quantitative relationship between the structural dynamic performance parameters（frequencies）and the defects of sleeve grouting joints.In the laboratory,six fabricated reinforced concrete column specimens with grouting sleeve joints with different degrees of defects were made,which verified the feasibility and effectiveness of the dynamic detection and evaluation method of joint defects.