Experimental And Numerical Investigation Of The Non-uniform Temperature Field And The Effect On Spatial Steel Structures Under Solar Radiation

Because of larger scale,numerous components and higher-degree indeterminacy,large-span spatial steel structures are usually sensitive to temperature effect.In particular,open-air steel members and spatial structures covered by transparent roof material or under construction are directly exposed to time-dependent thermal environment changes due to solar radiation.Temperature effects will be more significant and seriously affect component assembly efficiency and structure closure.Moreover,as thermal deformation is restrained by redundant constraints,internal residual temperature stress appears and leads directly to large differences between actual stress state and design state.These may cause potential safety problems that are not generally considered in common structural design.However,this temperature effect,mainly influenced by solar radiation,ambient air and shadows,has the characteristics of sharp changes and non-uniformity.Previous studies are rarely conducted in this field and there is only general requirement and no clearly design reference in current codes.Therefore,quantitative analysis of solar temperature effect for spatial structures is an innovative study and has practical engineering guiding significance.This thesis focuses on the following contents.1.Experimental study of temperature field and effect on steel members under solar radiationFrom the design of multipurpose test platform,monitoring scheme,test conditions and so on,the non-uniform temperature field and effect test of common steel members such as rectangular tube,I-shaped steel and circular tube are designed in detail.Through continuous monitoring of temperature field effect and various thermal boundary conditions,the non-uniform distribution and timedependent characteristics of temperature field,thermal stress and deformation are obtained from the analysis of test results.The solar-induced bending stress is proposed and the relationships of temperature to thermal stress and deformation are summarized.2.Numerical methods and parametrical studies for temperature field of steel members under solar radiationConsidering the heat exchange process and shadow effect,the numerical method is put forward to simulate the temperature field of test specimens,and the validity is also evaluated with the test data.Parametrical studies of member properties and environmental factors are carried out to explain the influence regularity and effect mechanism on their solar temperature distribution.Then based on the theory of solar radiation and steady-state thermal analysis,a simplified calculation method for temperature field of steel members is presented,and also compared with test data.These will provide theoretical support for practical engineering.3.Mechanism and influence factors of temperature effect on steel members due to solar radiationConsidering different constraint conditions and actual temperature distribution,the numerical method is used to simulate the temperature effect on test specimens,and the validity is also evaluated with the test data.Parametrical studies are also carried out to analyze the influence of restraint stiffness,member properties and environmental factors.The concept of the influence coefficient of bending stress is proposed and the influence of various factors on this coefficient is analyzed.The coefficients of commonly used steel members are calculated to simplify the consideration of non-uniform temperature effect in practical engineering.4.Experimental and numerical investigation of temperature action process on spatial structural systems under solar radiationThe temperature distribution and effect of typical spatial structure systems are investigated by experimental and numerical methods to accurately capture the distribution rules of different structural components.The thermal boundary conditions are also measured,and the numerical method is validated by the test data.The thermal effects caused by solar radiation are analyzed to evaluate the effect of solar temperature field on internal force and deformation of main bearing members.From the contrastive analysis between temperature effect and temperature field of main bearing members,the influence of solar-induced temperature change on spatial structures is fully grasped.5.Engineering example: evaluation of solar temperature field and the effect for Sheshan 65 m diameter telescopeNumerical method for solar temperature field is applied to practical structure which is affected obviously by the solar temperature effect.Takeing Sheshan 65 m diameter telescope as an example,its shadow distribution and non-uniform solar temperature field in summer are simulated.The distribution and time-dependent regularities of the temperature field are obtained.The influence of solar temperature effect on shape accuracy of reflector is also evaluated.The study provides valuable technical references for thermal design,monitoring and precision control of similar telescopes.