Study On The Design Parameters Of Small Radius Curve Box Girder Bridge Of Addis Ababa Light Rail

At present, cities around the world in order to adapt to or to guide the development of the city are all trying efforts to plan and build urban rail transit system which has large capacity, fast speed, low energy consumption, less pollution, safety and reliability. Urban rail transit system generally located in the city where are more buildings. In order to steer away from these buildings, the small radius curve line is common used in urban rail transit line. Ethiopia’s capital Addis Ababa plan to construct two light rail lines firstly, two lines are all located in center city and most are elevated line, so there are many small radius curve bridge. Based on the project, paper carry on the research on the small radius curve box girder bridge design parameters.This paper based on the summary of the basic form and characteristics of the curve box girder bridge and the analysis of small radius curve box girder’s mechanical characteristics. With the background of light rail line bridge engineering in Ethiopia’s capital Addis Ababa light rail south-north line and east-west line, established the finite element model of a typical small radius curve continuous box girder, and studied the dynamic response of continuous box girder bridges that has different curve radius and span when moving load series through under different speed. The main research work are as follows:(1) Summarized the research status of the curve box girder bridge domestic and overseas, analyzed the basic form and structure characteristics of curve box girder bridge, stress characteristics of box girder bridge and small radius curve box girder bridge design parameters like central angle, bending-twisting stiffness ratio, curve radius, load and others are studied.(2) Light rail lines in Ethiopia’s capital Addis Ababa as engineering background, using finite element analysis software ANSYS established a typical space model of small radius curve continuous box girder, calculated and analyzed the natural vibration characteristics of the bridge structure. The results show that the small radius curve continuous beam bridge has all the characteristics of continuous girder bridge, the established continuous beam bridge analysis model is close to the actual status.(3) As concerns three span continuous box girder bridge under different span (20m,25m,30m,35m,40m) and curve radius(50m,65m,100m,146m,190m), analyzed load influence under the most unfavorable load position. Take the bridge deformation, the construction cost and other factors into consideration, compared the analysis result, get the optimal bridge span of 30 m, curvature radius of 50 m finally.(5) On the basis of optimal bridge spans and curvature radius, calculated the action of the dynamic response of the bridge when moving load series through under the speed of 10 km/h,20 km/h,30 km/h,40 km/h and 50 km/h. The results show that the speed has low influence on the maximum deflection of key position. With the increase of speed, the maximum acceleration value of different position increases gradually, and when speed come to 50km/h, maximum acceleration value are almost the same on every point.