Study On A New-type Grouted Deformed Pipe Splice

Precast concrete structural elements were produced in the industralized mode and were assembled on the construction site. Advantage of mass producton could be shown and the capability, speed and quality of construction could be developed and ensured. In the mean time, large quantities of labor, engery, waste and pollution could be saved, and this was in accordance with the strategy of green buildings of our country. Grouted pipe splice was one of the key technologies in the connection and assembly of precast elements. It could ensure the reliablity of precast concrete structures and thus promote the use of precast concrete structures.This thesis introduced and summarized the grouted pipe splice from the perspective of engineering application and structural performace. The existing problems of high costs and complicated techniques in the process of manufaction were pointed out and a new kind of grouted deformed pipe splice(GDPS splice) was proposed. Using seamless steel tubes as the material, concentric ribs on the inner surface and the concentric inverted trapezoid grooves on the outer surface were made by cold rolling techniques with simple manufacturing techniques at a low cost. The trapezoid grooves and concentric ribs could effectively improve the bond between the splice and the grout as well as the splice and the surrounding concrete. Thus, the reliability of precast concrete connetions could be ensured. In this thesis, the structural performance of the splice was studied by structural experiment, theoretical analysis and finite element analysis.1. The structural performance of 9 GDPS splice in 3 specifications under monotonic tensile load was investigated. (1) The strain distribution on the spleeve surface was tested and it was found to be correlated with the inner surface structure. (2) The strain distribution on the rebar surface was tested by bragg optical gratings. The strain was distributed symmetrically and the peak value was close to both sides of the splice and with the increase of the load, the position of strain peak value was intended to move to the middle part.(3)Two failure modes including rebar fracture failure and bond slip failure occured in the experiment. The tensile strength of the splice was larger than 1.10 times the tensile strength of the rebar, and the residual deformation was smaller than 0.10mm. The requirements for Type Ⅰ joint by JGJ 107-2010 were satisfied.2. The structural performance of 18 GDPS splice in 3 specifications under cyclic load was investigated. (1) The relationship between strain of the sleeve and the load was analyzed and a linear relationship was found between the strain and the load. (2) The residual deformation of the splice was found to be smaller than 0.30mm, and two failure modes including the rebar fracture failure and bond slip failure occured in the experiment. The strength and residual deformation of the splice satisfied the requirements for Type Ⅰ splice by JGJ 107-2010.3. Theoretical analysis of the bond strength for cylindrical grouted splice was conducted. (1) Based on the thick-walled cylinders in elastic mechanics, the initial confining stress between the grout and the rebar, as well as the initial confining stress between the grout and the sleeve were deduced. The grout-rebar firiction and grout-sleeve friction were calculated, and it could be found that the bond slip failure was more likely to happen between the rebar and the grout. (2) Based on the bond strength theory between rebar and concrete, the bond strength and ultimate strength of 23 sleeves with bond slip failure were calculated and they were in accordance with the experemental value.4. The finite element models of the sleeves in 3 specifications were established and the ultimate strength, load deformation relationship and stress distribution of the sleeves were calculated. (1)The calculated relationship between load and deformation was in accordance with the experiemental value, so the finite element model could properly represent the structural performance of the splice. (2) The largest von mises stress of the sleeves of 3 specifications all located at the inner trapezoid grooves near the smooth part without ribs, so the sleeve fracture failure at this point should be avoided.