The Suitable Bridge Structural System Of The Span Between300Meters And500Meters

Currently, the main structural systems of bridges with300~500m span arecontinuous rigid frame bridge, arch bridge, cable-stayed bridge and suspension bridge,and most of them rely on the ordinary concrete and steel structure, while the mainspan of continuous rigid frame bridge has not yet reached400m. UHPC（Ultra HighPerformance Concrete）has the advantages of high strength, less shrinkage and creep,high durability and outstanding volume stability, and it can significantly reduce theself-weight, improve the crossing ability and reduce the life-cycle economic costwhen applied to the bridge structure.This article applied the UHPC to the long-spanbeam bridge structural system in order to achieve a breakthrough in the spanningcapacity of the beam bridge structural system and redefine the appropriate bridgestructural system of the span between300m and500m based on the sustainability andlife cycle analysis. So, the main researches made by the author in this paper are asfollows:(1) Firstly, define the concept, classification, development and application scopeof the bridge structural system, to lay a foundation for the research of structuralsystem. Then introduce the material properties, sustainability, economy andapplications in domestic and overseas of UHPC in detail, and then clarify the wideapplication prospects of UHPC in bridge engineering especially in long-spanstructures.(2) Introduce the design concept of ultra long-span UHPC continuous girderbridge and select the typical beam bridge, arch bridge, cable-stayed bridge andsuspension bridge structural system with the main span in the range of300m to500mas real cases to conceptually design the UHPC continuous box girder bridge based onthe results of the research team.(3) Carry out an overall stress analysis on the four UHPC continuous box girderbridges with different main spans by the finite element method, and then check theirstrength and stiffness to ensure the safety and reasonability of the structural design.The finite element analysis shows that the design of the four span bridge force isreasonable and the structural system is safe and feasible.(4) According to the amount of material, calculate the initial construction costand energy consumption of the real bridge and designed bridge, and then make a contrast. The results show that the sustainability of the UHPC continuous box girderbridge is obviously better than the real bridge and the cost-effectiveness is betweenthe arch bridge and the other three bridge structural systems.(5) Determine the time of maintenance and repalcement and frequency of thebridges’ components in the whole service life by forecasting the life of the maincomponents of real and designed bridges, and then calculate the life-cycle economiccost of the bridge structural systems and make comparisons. The analysis shows thatthe UHPC continuous box girder bridge has a good durability, long service life andthe percentage of its later maintenance cost is lower than the real bridges. What’smore, its100-year life cycle cost is between the arch bridge and three other realbridges and the200-year life cycle cost is significantly lower than all of the realbridges.