| Natural ventilation cooling tower is one of the most widely used cooling tower structure, but our country is behind the developed countries in Europe and America in the design concept of the super-large indirect air cooling tower. Compared German VGB standard for cooling tower structure design considering the geometric nonlinearity and material nonlinearity of the structure, the design of cooling tower in our country is mainly on the linear elastic range. Therefore, it is necessary to compare and study the cooling tower which is designed by the two existing kinds of specifications in order to provide reference for the revision of relevant codes in our country.In this paper, a numerical analysis method is used. From different views, the paper analyzes the load carrying capacity of two cooling towers high up to 220 m, which are designed by our country’s standard and German VGB standard. And it also analysis the reliability of the typical structure of the super-large indirect air cooling tower. According to our country’s Unified Standard for Reliability Design of Engineering Structures(GB50153-2008), the evaluation of the reliability of the structure of the ultra large indirect air cooling tower was given based on different standards. In the reliability analysis section, the HDMR(High Dimensional Model Representation) response surface method is used to obtain the structural approximate structure function in this paper. Then, the structural reliability is analyzed with the help of FORM and MCS.According to research and analysis, the wall of the cooling tower adopting Germany VGB standard design(Model B) was thicker than that in our country through the cooling tower design specification(Model A). But the Model B meridional reinforcement area is larger than the Model A, the ratio of reinforcement is obviously improved. It can be seen through the analysis of the load response that bearing capacity of the two models both meet the requirements under the action of our country. Wind load is controlled by cooling tower, and the windward side of the tower to the main tension, tower on the windward side of the concrete layer prone to cracking, the reinforcement layer is mainly to bear the tensile stress. Through the reliability analysis it can be seen that the most unfavorable cross-section of two models appeared at the tower larynx(0° meridian near 110 m height). The reliability index of Model A was significantly larger than that of Model B, and the reliability index of the bearing capacity of each layer of the Model A meets the requirements of our country. The reliability index of the bearing capacity of the B concrete layer is lower than the standard limit of our country, but the reliability index of the steel bar can meet the requirements of our country.And the two model meets our specifications on the normal use limit state corresponding reliability index.It can be seen through the analysis of this article that in fewer design variables and the reasonable choice of the reference point, using the Cut-HDMR response surface method can obtain structure approximation function with high accuracy, and can accurately calculate the reliability index of a shell. Although the wall thickness is thin, but because of the higher ratio of reinforcement, shell tensile bearing capacity is greatly improved by using German VGB standard design of cooling tower structure. And the regulated load bearing and structural reliability are meet the requirements of our country’s code. |
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