Research And Application On Fabrication And Installation Of The Arch Rib Of Concrete Filled Steel Tubular Tied Arch Bridge In The 2^nd Bridge Across Han River In Yun Prefecture

The concrete filled steel tubular arch bridge has many particular advantages such as less weight, longer span and better adaptability, larger carrying capacity, upstanding plasticity, fatigue resistance, impact resistance, construction convenience, attractive appearance and better economic benefits. But on the other hand, it has its own disadvantages.The development of the concrete filled steel tubular arch bridge, to some extent,has been delayed because of many factors such as theoretical research, manufacturing technology and anticorrosive coating technique so that the number of building those bridges is very limited. It is hard to guarantee the compactness and continuity of the pump concrete and honeycomb or interspace will be often formed on the back side of the caulking ring because of rough fabrication, poor welding quality, unreasonable structure, inappropriate caulking ring or even the inner diaphragm designed in the steel tube. The processing and welding quality of the steel tubular arch have a direct effect on the structure safety and working life of the bridge engineering. The difficulty lies in the processing and welding quality control of the blanking of the steel tubular arch rib. It is always a construction problem to guarantee the welding structure with enough toughness and plasticity because all the welding positions lie in the upper air and there are many kinds of welding positions which are horizontal, vertical, sideward and upward so that the factory operation can not be conducted.The construction and maintenance of the concrete filled steel tubular arch bridge still leg behind the engineering pratice. The key technology of each link has not been unified and lacks systemic and scientific guidances. Therefore, the optimum construction scheme, advanced techniques and methods should be used in the process ofimplementation to guide the construction work so as to guarantee the construction quality will be qualified.The contents are shown as follows:I. The key to construct the steel tubular arch bridge is how to guarantee its processing and welding quality because the fabrication, processing and welding quality of the steel tubular arch rib have a direct effect on the life span of the bridge engineering.The fabrication, processing and installation techniques of the steel tubular arch include materials, lofting, line drawing, blanking, bending, welding, assembling, coating,transportation, installation, quality test, quality assurance system and other things. In view of the site installation problems of the steel tubular arch rib, we should analysis the characteristics of its installation technique by comparing various hoisting plans from different views. In view of specific natural environment and the solutions to solve the problems, we should take innovative working methods and techniques to make the steel tubular arch rib close smoothly in the process of installation.II. Study on the pumping and jack-up technique of the concrete-filled steel tube of the main bridgePumping and jack-up technique can be used if the C50 micro-expansion concrete is poured into the concrete filled steel tubular arch rib. The raw materials and the concrete mix ratio should be selected properly and scientifically by testing and analysising the performance of raw materials in order to know the main technological parameters and guideposts constructed by the pumping and jack-up technique. Some methods such as improving the pumping method, taking measures on the arch and designing to change the structure of batten plates can be used to guarantee the steel tube will not be blocked by the concrete and the wall of the steel tube will be free from disjointing. The density of the concrete will be tested by the ultrasonic.