Construction Technology of Mid-span Jacking Closure of Long-span Hybrid Beam Cable-stayed Bridge

The actual line type of the Shishou Yangtze River Highway cable-stayed bridge structure tends to the theoretical line while meeting the force requirements of the cable, main tower, and main girder. At the same time, it can ensure the safety of the bridge structure closure construction. It established a geometric control method closure scheme of the Shishou Yangtze River Highway Bridge based on theoretical analysis based on many factors such as the characteristics of the bridge structure, mechanical characteristics, estimated closing time and process implementation risks.
First, after comprehensively analyzing the advantages and disadvantages of the geometric control method and the temperature-matching cutting method, the geometric control method was used for closing construction. Secondly, it studied the mid-span push-closure scheme. First the special conditions related to the mid-span closure was found, and then the implementation control conditions of the push-closing process were found out, such as:arrange of the closing time, calculation of the length of the closure section and the pushing displacement, etc., and then analysis on the top reasoning. Once again, the mid-span was closed according to the steps. Finally, the key technology of mid-span closing was analyzed. 1) Before closing the dragon, the longitudinal jacking device of the South Tower was installed. The jacking device must not only be equipped with a forward jack, but also a reverse jack. 2) When the dragon was closed, it needed to be adjusted within the allowable range through the previous control process in advance, and the body deviation would not be adjusted when the dragon was closed. 3) The locking device of the closure must have good vertical and lateral flexural rigidity to ensure that the axis of the main beam was offset and the shape of the closure could maintain the adjusted state after the push was completed. After adjusting the shape of the closure, a tie rod was installed to complete the locking of the closure section, restricted the horizontal and vertical freedom of the closure section, and bore part of the weight of the closure section at the same time, so as to meet the requirements of the circular seam welding of the closure section.
By applying jacking force to the closure, the closure section of the one-sided lifting was embedded in the closure, eliminating the difference between the length of the closure section and the width of the closure due to the influence of temperature, and the lack of space for closure operations. It was safe, fast, and accurately realized the construction of the whole bridge closure.