Full-Scale Model Experimental Study of the HDPE Multitube Saddle of an Extradosed Bridge

Abstract

For an extradosed bridge, the main function of the saddle structure is to steer the cable in the pylon. The saddle is one of the most important and key structures in the cable prestressing system. Focusing on the high-density polyethylene (HDPE) multitube saddle structure and cement slurry filling, the mechanical properties of the saddle are analyzed and verified in detail by a full-scale model test. It is shown that the numerical analysis results are consistent with the test results. Under 1.8 times the designed load (7171.4 kN), the test strain values of each section are less than the calculated strain values, which indicates that the saddle structure design is safe and that the saddle structure meets the design requirements. Friction resistance between the steel strands and the HDPE tube can resist unbalanced cable forces on either side of the saddle during construction and operation. According to the test, the maximum value of the static friction coefficient between cable and HPDE tube is 0.093. The cement slurry stress is basically in the linear elasticity range under the test conditions. After further increasing the cable tension, the cement slurry inside the saddle is compacted, without any cracks or crushing phenomena. This demonstrates that the saddle is safe and reliable.