Research On Several Key Issues In The Construction Of An Open-spandrel Variable Cross-section Continuous Bridge With A Reinforced Concrete Composite System

An open-spandrel variable cross-section continuous bridge system with a steel box girder at mid-span is a newly developed bridge form derived from regular variable cross-section continuous bridges.Its purpose is to reduce the self-weight of the bridge and to improve its spanning capacity by caverning out the web at the root of the box girders and then replacing the concrete girder at mid-span by steel box girder.The paper has mainly conducted the following work that can be concluded in three aspects on the basis of the construction techniques on the key issues of an open-spandrel variable cross-section continuous bridge.(1)Research on the key issues in the seismic analysis of bridge structures and friction pendulum bearing in large bridgesA spatial dynamic model of a bridge was established for the research of dynamic characteristics combining with the geological condition and ecological environment of the area where the engineering project is located.Through a dynamic time-history analysis method,the elastic and elastic-plastic seismic responses of the main girder structure were analyzed and calculated,and corresponding countermeasures were studied and a new form of friction pendulum bearing was developed which suits the construction requirements of large bridges.(2)Research on the key issues in the construction and anti-cracking of the V-shape supportThe length and inclination of the open-spandrel area in an open-spandrel continuous bridge have significant impact on the overall stress condition of the structure and the economical efficiency of the engineering project,which is more complex and with much larger local stress at the merge area of the top and bottom internal surfaces comparing with those in regular continuous rigid bridge.Thus,the paper studied the structure designing of the length of open-spandrel area,the length,inclination and key points of the internal bottom surface to make clear the design method of this new bridge form.(3)Research on the installation construction techniques of the steel box girder at mid-spanThe transportation of steel box girder in the river,the positioning of the ship,the stress analysis of hoisting super-long or super-heavy components and corresponding hoisting techniques to ensure the smooth and safe hoisting of the steel box girders.