The Study On Structural Forms, Mechanical Behaviors And Design Calculation Methods Of Orthotropic Monolithic Steel Bridge Decks On High-speed Railway

Orthotropic monolithic steel bridge deck has been applied in more and more domestic high-speed railway large span bridges and highway-railway bridges and fast developments have been achieved because of its lightness, integration, large carrying capacity and comfortability in operation. Sponsored by scientific research and development plan projects of railway department "Research of design technology of special passenger railway-- Research of technology of orthotropic monolithic steel bridge deck on special passenger railway bridges" (Contract number 2008G007-B), systematical studies on structural forms, mechanical behaviors and design calculation methods of orthotropic monolithic steel bridge deck were done with the methods of theoretical analysis, FEM comparative analysis and test study by taking Nanjing Dashengguan Yangtze River Grand Bridge on Beijing-Shanghai high-speed railway, Anqing Yangtze River Grand Bridge on Fuyang-Jingdezhen railway and Hanjiatuo Yangtze River Grand Bridge on Chongqing-lichuan railway as examples. Creative results listed below were achieved.1. Influences of rib forms (plate rib, reversed T rib and U rib) on mechanical behaviors and stability of orthotropic monolithic steel bridge deck were studied. Results show that by maintaining steel of ribs themselves and vertical bending stiffness's equal, under various same loads, difference among vertical displacements of orthotropic monolithic steel bridge decks stiffened by three types of ribs is no more than 1.4%; difference among horizontal displacements is no more than 5.1% and horizontal stiffness of U rib plan is larger than other plans; difference among stresses of deck system is generally no more than 6.7%; elastic globe stability coefficients of U rib plan is generally more than 23% larger than other plans; ribs of various forms can be used in orthotropic monolithic steel bridge decks and U rib behaves well in all aspects of stiffness, strength and stability.2. Influences of height of U rib, thickness of steel deck(flange of U rib), thickness of U rib and thickness of web of floor beam on mechanical behaviors and stability of orthotropic monolithic steel bridge deck were studied. Reasonable value ranges of these parameters were given. Concept of reasonable general applicable degree of match of various design parameters of U rib and its formula were proposed. In reasonable value ranges of these parameters, three sets of most reasonable matches of design parameters of U rib were given by considering stiffness, strength, stability and economy(steel) comprehensively and calculating reasonable general applicable degrees.3. Mechanical behaviors and applicability of stringer-floor beam orthotropic monolithic steel bridge deck on which floor beams are only set at joints of bottom chords were studied. Results show that under deck loads, forces of bottom chords are relatively small and burden is light. The in-plane forces and deformations of stringers (ribs) and floor beams are relatively large. The participation extent in the 1st system action of deck system is more than that of bottom chords. The out-of-plane forces and deformations of floor beams are relative large. Stringers and floor beams with relatively large sections are required. Stringer-floor beam orthotropic monolithic steel bridge deck is fit for bridges with short spans and without strict requirements of construction height of deck system.4. Mechanical behaviors and applicability of multi- and dense-floor beam orthotropic monolithic steel bridge decks on which floor beams are set not only at joints but also in segments of bottom chords were studied. Results show that under deck loads, forces of bottom chords are relatively large and burden is heavy. The in-plane forces and deformations of stringers (ribs) and floor beams are relatively small. The participation extent in the 1st system action of multi-floor beam deck system is a little smaller than that of bottom chords. The out-of-plane forces and deformations of floor beams are relative small. Only stringers and floor beams with relatively small sections are required. Multi-floor beam orthotropic monolithic steel bridge deck is fit for bridges with large to grand spans and strict requirements of construction height of deck system. The participation extent in the 1st system action of dense-floor beam deck system is a little larger than that of bottom chords. The out-of-plane forces and deformations of floor beams are also relative small. Generally no stringer and floor beams with smaller sections are required. Dense-floor beam orthotropic monolithic steel bridge deck is fit for bridges with medium to large spans and with stricter requirements of construction height of deck system (e.g. curved bridges).5. The expression of steel deck effective width of members of orthotropic monolithic steel bridge deck system was derived and then Space Frame Simplified Method (SFSM) was proposed. It is verified by examples that with this method computing workload is greatly reduced with high accuracy. SFSM can be used at beginning and middle stages of bridge design.6. Plane Beam Simplified Method (PBSM) of members of orthotropic monolithic steel bridge deck system under the 2nd system action was proposed and calculation parameters graphs and tables were given. With these graphs and tables members of bridge deck system are simplified to plane beam model and internal forces and stresses are calculated. It is verified by examples that with this method the calculation is simple with certain accuracy. PBSM can be used at beginning stage of bridge design.7. Three panels of deck system of Anqing Yangtze River Grand Bridge were chosen as study object and a three-panel 1:4 scale test model was produced. Tests on various forms of orthotropic monolithic steel bridge deck system were conducted. The mechanical characteristics of orthotropic monolithic steel bridge deck and the correctness of simplified calculation methods were verified.The above-mentioned research results have already been applied in design of several orthotropic monolithic steel bridge decks on high-speed railway and good economic and social benefits have been achieved. Theoretical support and technical reserves can be also provided for similar bridges in the future.