The Study Of Huge Hollow Aqueducts Thermal Stress In Running Phase

A large number of project experiences have shown that thermal stress is one of the primary factors to cause mass concrete structures, for example dam, sluice pier, bridge, etc. to crack and wreck. It has also been probed by concrete aqueduct. Owning to the thermal stress, there are few aqueducts that have no cracks.There will be large quantities of super-huge aqueducts to be built in the middle line of the project of South-to-North water transfer, also the investments of the aqueducts are huge. So we should attach importance to the designs of huge aqueducts in order to ensure theirs credibility, economy and rationality. Since the thermal stress is a very disadvantageous factor on sometime, we should do some study on the thermal stress of huge aqueducts.In this thesis, the major works as following:(l)Summarize the classification of the crack, the reasons, the characteristics of the thermal crack, as well as the harm to the building, and proposed some ways of the prevention, the control and the repair.(2)Calculate the thermal boundary conditions of the aqueduct influenced by solar radiation in detail, and back analyzed the heat transfer coefficient between the aqueduct surface and the atmosphere.(3)With the finite element theory and the software ANSYS7.0, a huge aqueduct in middle line of South-to-North water transfer has been calculated, including the transient thermal field and thermal stress in the summer temperature rise and under the winter temperature drop operating mode transient state temperature field and the temperature stress.(4)In order to reduce the thermal stress, Professor Wang Changde proposed a new structural style, the hollow aqueduct. In this paper, the author carried on the contrast analysis with the original aqueduct's thermal stress.(5)Compare two kinds of hollow aqueducts which frontier walls thickness, and select one that is more effective to reduce the thermal stress.The final result indicated that, because of the influence of the solar radiation orthe atmospheric temperature decreasing ,the quite great thermal tension force should occur inside aqueduct. The hollow aqueduct can reduce effectively the thermal stress in each direction. But, the c aqueduct that has different frontier wall thickness can reduce the thermal stress dissimilarly. Therefore, it should be very necessary to choose reasonably the frontier walls thickness.