Study On The New End Connections With Steel Tongue For Prestressed Concrete Double Tees

Prestressed concrete double tees have the advantages of clear force transmission path and good mechanical properties.They are one of the most widely used prefabricated concrete components.They can be used as floor slabs and exterior wall slabs.In the structure using double tees,the end connection is the keypoint of overall performance.There are many types of double tees end connections.On the basis of summarizing the current research and application,two new end connection for the end of chinese double tees are proposed refer to the existing two connection modes of Cazaly Hanger and Loov Hanger.The new end connections are more suitalble to Chinese double tees with narrow rib and complicated reinforcement at ends.Then performance of the new end connections were studied and design method was proposed.The main contents and results of this article are as follows:1.The research and application of the two end connections methods of Cazaly Hanger and Loov Hanger were summarized.According to the characteristics of chineses double tees,two modified types of end connections were proposed and named as steel(strap)dapped ends and steel(tiepiece)dapped ends.The design principles of each component were analyzed;design method of the new steel dapped ends connection were proposed,which are consistent with Chinese codes.2.The static loading tests about two kinds of new end connections made of steel at the prestressed concrete double-tee ends with 14 different parameters were carried out,the two kinds of new end connections is steel dapped end with steel strap connection and steel dapped end with reinforcement connection.The failure modes,bearing capacity,initial crack,load-displacement curve at loading point,and load-strain curve at reinforcements about the connections were studied.The test results show that there are two failure modes of steel dapped end with steel strap connection,one is bending failure of the specimen at the loading point,and the other is end shear failure due to the yield of reinforcement at the bottom of the notch,and it's mechanical performances are good and the design method is safe and feasible.The ratio of the height of the U-shaped steel strap to the height of the specimen should not be less than 0.7.The failure mode of steel dapped end with reinforcement connection is shear failure at the ends,it's mechanical performances are greatly affected by the initial cracks,and the design method is feasible but the constructional reinforcement of ends is not good,and measures to improve the constructional reinforcements of ends are given,and the extension length of the diagonal tensile reinforcements should not be less than 40 d.3.Used Abaqus finite element analysis software to carry out non-linear finite element numerical simulation of 6 steel(strap)dapped ends.The simulation results agreed well with the test results.The test results are corroborated and the test phenomena can be explained by the simulation results.4.Quality inspection methods for steel dapped ends were given,including appearance inspection and performance inspection.In engineering applications,the quality can be guaranteed to be reliable,and the quality of construction and installation and the safety of the building structure can be ensured.