Experimental Research On The Ultimate Lap Length Of The Resttraint Grouting-ancjoring Overlap-joint Of Steel Bar

The key of precast concrete structure is solving the joints of the steel bar and concrete, only the joints of precast concrete can be solved, the structure can work as a whole. The research group of Harbin institute of technology think up the Restraint grouting-anchoring overlap-joint of steel bar, and use it to the lap connection of precast concrete shear wall system. Since2008, lots of experimental and theoretical studies have been done by the research group,and determined that the lap length is as long as the anchorage length. The result of early experiment shows that improving the ratio of spiral reinforcement stirrup can reduce the lap length, but we don’t know how much the lap length can be reduced. If the lap length is shorter, there will be more convenience for the use of engineering and also the transport and installation, but it’s hard to make sure the safety of lap connection, the ability of the lap connection should be assessed.Depending on the result of preliminary study, this article research the ultimate lap length of he Restraint grouting-anchoring overlap-joint of steel bar, the ultimate lap length meants the shortest lap length when the spiral reinforcement stirrup is reasonable. This article designed a series of test specimen to research the ultimate lap length of different diameter of steel bar, and design parameter include the diameter of steel bar, the lap length, the ratio of spiral reinforcement stirrup as parameter, and54test specimen was completed. the loading method referred to Technical specification for mechanical splicing of steel reinforcing bars (JGJ107), and improved the test method. For the steel bar which diameter is12mm,16mm,20mm, change their lap length and the radio of spiral reinforcement stirrup, then the ultimate lap length of three kind of steel bar can be determined through the test data and the destroying phenomenon.Using the ultimate lap length to the precast concrete shear wall, so the ability of the lap connection can be proved. This article designed three precast concrete shear wall specimens with the diameter of the longitudinal bars in the edge constraint part12mm,16mm,20mm, and the lap length is determined by the ultimate lap length. There are three cast-in-place concrete shear wall with the same steel bar reinforcement, specimen size, loading condition as the precast shear wall. Through the pseudo-static test of six shear wall, obtained the hysteretic curve, skeleton curve, degradation stiffness, ductility and energy dissipation capacity of the precast concrete shear wall, also the corresponding cast-in-place shear wall. Comparing two kind of shear wall, they are the same on the part of hysteretic curve and skeleton curve, but on the part of ductility and energy dissipation capacity, the precast concrete shear wall is much better than the cast-in-place concrete shear wall, having a good seismic performance. The experiment showed the ability of overlap-joint of steel bar is safe, also the ultimate lap length is reasonable. Depending on the two experiments, and the theoretical analysis, the advised formula of the ultimate lap length was provided.