| In recent years,with the rapid development of domestic tourism,a new type of straddle monorail tourism transportation system with both traffic and amusement properties has been widely used.For the convenience of erection,the track beam of this system is usually an unpaved steel box girder or I-beam.However,there is a lack of theoretical research on the regional differences of insolation temperature field and temperature gradient load of unpaved steel beams,and there are difficulties in the engineering design that no clear code provisions are available while similar code provisions are not applicable,which affects the safety and economy of the structure.It is highly necessary to study the insolation temperature field of the steel beam of this system to determine its accurate temperature gradient distribution.From the perspective of the distribution law of the solar radiation temperature field of unpaved steel beams,combined with the onsite measurement experiment and the numerical simulation method,this thesis studies the vertical temperature gradient,regional differences and national divisions of two types of unpaved steel beams.The specific work is as follows:(1)An experimental study on the insolation temperature field of unpaved steel beams was carried out.According to the division of solar radiation intensity,the long-term measured tests of two kinds of crosssection steel beam specimens were carried out at five representative locations to explore the regional difference of temperature gradients.The influence factors of the insolation temperature field of unpaved steel beams were analyzed and the horizontal and vertical time-history variation laws and distribution characteristics were summarized.By comparing the selected typical standard temperature gradient curve with the measured data,the positive and negative temperature difference curves of unpaved steel beams were determined.(2)The solar radiation intensity was calculated by ASHRAE clear sky model,and the finite element models of the insolation temperature field of two kinds of steel beams were established by using the APDL parameterization module in finite element software ANSYS.The calculation of relevant parameters of the element model was verified by comparing the calculated values with the measured values.The key parameters of temperature field were determined by comparing the values of model parameters of each location.By analyzing vertical temperature difference distribution of different beam heights,the curve distribution of the general model of temperature gradient was determined.(3)Based on the extreme value analysis method of the GEV distribution model,combined with the measured data and historical meteorological data of the past 58 years,the simulated samples of temperature difference at the top of the steel beam were calculated by using the verified finite element model,and then the representative values of the most unfavorable temperature gradient with return periods of 50 years and 100 years were calculated.(4)Based on the regression analysis of the finite element calculation value of the insolation temperature field of steel beams in 34 major cities in China,the empirical formula of temperature difference representative value for the three parameters of altitude,latitude,and annual maximum temperature corresponding to daily temperature difference was deduced.The formula could be used to calculate the representative value of temperature difference at any place,and the regional difference of temperature gradient of unpaved steel beams in China was explored.For the convenience of use,the partition map of the temperature gradient of unpaved steel beams in China was calculated and drawn based on the empirical formula,and the temperature base value table of each zone was given.By analyzing the variation of the temperature difference value of different beam height models outside the range of 600 mm from the top of the beam,combined with the representative value of the top temperature difference,a complete general temperature gradient model of unpaved steel beam was established. |
