Study On Thermal Effect Of Three Super Great Railway Steel Bridges With Large Spans

With the rapid development of railway construction, there emerged more and more long bridges with large spans. The greater the bridge, the more remarkable the thermal effect is. Super great railway steel bridges with large spans in different structural forms have diverse thermal effects. The paper studied the thermal effects of three selected under construction or newly-built great railway steel bridges with large spans which are representative in structure. One of the selected bridges is Dongtinghu three-tower two-lane railway cable-stayed bridge with double main span(DTRB), taking span arrangement for (98+140+406+406+140+98)m; The second one is Beijiang twin-tower four-lane railway cable-stayed bridge with single main span (BTRB), taking span arrangement for (57.5+109.25+230+109.25+57.5)m; The final one is Dongpingshuidao double-track railway steel-truss arch bridge (DRAB), taking span arrangement for (85.25+286+85.25)m. The main work done and results are as follows:1.10temperature conditions had been selected to study the thermal effect of three great bridges, including structure warming (or cooling) overall, the temperature difference of different structure components due to sunshine and varied heights, basing on detailed inspection of different countries’ specification and documentation’s provisions and research about bridge temperature effect.2. The three-dimensional finite element model of DTRB had been built; Calculation and analysis of thermal effects had been completed as well. The results showed:the overall warming (or cooling) had greatest impact on DTRB among the various temperature conditions, which not only generated main beam’s great stretch (or shrink), but also the top of side-tower columns’ great displacement along the bridge and biggish stress on the body of side-pylons. The displacement on the top of side-pylons along the bridge and stress on the body were comparable to those generated by the most unfavorable live load, while beam deflection and rotation in the end were not obvious. The other temperature conditions left had little influence on DTRB.3. The three-dimensional finite element model of BTRB had been built; Calculation and analysis of thermal effects had been completed as well. The results showed:The overall warming (or cooling) not only generated main beam’s great stretch (or shrink), but also the top of tower columns’ great displacement along the bridge and biggish stress on the body of pylons; However, the main pylons’ sunshine temperature difference (10℃) along the bridge generated even greater displacement on the top of pylons, which was comparable to that generated by the most unfavorable live load. The other temperature conditions left had little influence on BTRB. The beam deflection, rotation in the end and stress in the beam were not obvious under all the temperature conditions.4. The three-dimensional finite element model of DRAB had been built; Calculation and analysis of thermal effects had been completed as well. The results showed:In addition to the main girder’s biggish stretch (or shrink) caused by the overall warming (or cooling), the temperature difference (15℃) between the lower and upper arch rib would generated the main girder’s great deflection and rotation in the end, which were half about those of the most unfavorable live load, the stess in the upper and lower arch rib were comparable to those of the most unfavorable live load. The temperature difference (15℃) between the part above and below the bridge deck system also had a certain impact on DRAB, while the other temperature conditions left had little influence on the beam displacement and stress in DRAB.5. The main girder’s stretch (or shrink) generated by the overall warming (or cooling) of the three bridges in different stuctrure forms was almost equivalent to that of the main girder in free state; As a result, the beam expansion joints in the end and shifting bearing stroke could be estimated by Δl=αΔTl.The research results of this thesis provide reference for the design of super great railway bridges with large spans.