【作者】 刘哲；

【导师】 丁阳；

【作者基本信息】 天津大学 ， 结构工程， 2018， 博士

【摘要】 钢结构施工过程中因环境温度作用和焊接会产生变形和残余应力,可能影响结构的施工安全。钢结构运营过程中环境温度在改变结构内力的同时也会改变结构模态参数,从而影响结构损伤预警的精度。复杂钢结构的静力性能和动力特性受温度影响更为复杂,因此亟需对其施工和运营过程中的温度效应进行研究。本文采用数值模拟、现场监测和试验研究相结合的方法,对复杂钢结构施工过程中的环境温度效应、焊接残余应力和运营过程中的环境温度效应进行了研究。主要内容和成果如下:(1)建立了复杂钢结构施工温度场模型。基于应力等效原则对太阳辐射下构件有效温度进行修正,采用2个正态分布函数对监测所得构件有效温度进行非线性拟合,建立了复杂钢结构施工温度场模型。将所建立温度场模型应用于白浪河摩天轮结构施工过程模拟,结果表明:构件有效温度日温差符合Boltmann分布,温度效应分析时应依据构件有效温度对极限温度值进行调整;基于所建立温度场模型的数值模拟结果与实测结果吻合较好。(2)分析了复杂钢结构施工过程中的环境温度效应。基于所建立温度场模型分析了构件安装温度和安装过程对复杂钢结构静力性能的影响,研究了施工合拢温度对结构最大应力的影响。结果表明:考虑构件安装温度和安装过程会影响竣工后结构的节点位移和构件应力,白浪河摩天轮结构应力最大相差分别为48MPa、72MPa;确定合理的施工合拢温度可减小结构最大应力,白浪河摩天轮结构最大应力降低40MPa。(3)分析了宽对接焊缝焊接残余应力对复杂钢结构静力性能的影响。复杂钢结构施工过程中焊缝宽度难以控制,分别采用盲孔法和SYSWELD对宽对接焊缝残余应力分布进行了试验研究和数值模拟,分析了宽对接焊缝焊接残余应力对复杂钢结构静力性能的影响,以及超声波冲击法消除应力的有效性。结果表明:焊接残余应力峰值随焊缝宽度的增大而增大,最大值接近母材的屈服强度;焊缝收缩变形对白浪河摩天轮结构合拢处构件内力的影响不容忽视;采用超声波冲击法可有效消除宽对接焊缝残余应力,试验中4条焊缝的横向和纵向残余应力峰值分别平均降低了22%、28%。(4)分析了环境温度对复杂钢结构静力性能和模态频率的影响。探讨了环境温度对结构静力性能和模态频率的影响机理,通过白浪河摩天轮结构数值模拟结果和实测数据对比,揭示了复杂钢结构静力性能和模态频率的温度影响规律,并采用BP神经网络技术对环境温度影响的消除进行了研究。结果表明:环境温度主要通过改变材料弹性模量以及结构内力和几何状态来改变结构模态频率;白浪河摩天轮结构模态频率随温度升高而降低,在监测期内前四阶频率最大变化幅度为3.04%;BP神经网络模型可以正确反映模态频率和环境温度之间的变化关系,利用建立的频率-温度回归模型可有效消除环境温度对结构模态频率的影响。(5)建立了考虑环境温度影响的复杂钢结构损伤预警方法。采用粒子群(PSO)算法对支持向量回归-时间序列(SVR-ARMA)组合模型进行参数优化,并结合均值控制图法建立了复杂钢结构的损伤预警方法,通过假设检验方法模拟不同程度损伤对所建方法的有效性进行验证。结果表明:PSO算法可提高SVR-ARMA组合模型的泛化能力和预测精度,所建立的PSO-SVR-ARMA模型与基本SVR模型相比,频率预测精度提高了22%;基于PSO-SVR-ARMA频率预测模型的损伤预警方法可识别由轻微结构损伤造成频率的异常变化,具有良好的损伤预警精度。更多还原

【Abstract】 Due to environmental temperature and welding,there will be deformation and complex residual stress during the construction of steel structure,which may affect construction safety.The environmental temperature during the service stage will change the internal force and the structural modal parameters of steel structure,thus affecting the accuracy of damage warning.The influence of temperature on the static performance and dynamic characteristics of complex steel structures is more complicated,therefore,it is an urgent demand to research the temperature effect in the course of its construction and service.In this paper,the environmental temperature effect in construction stage,welding residual stress and environmental temperature effect in service stage of complex steel structure are studied by via field test combined with numerical simulation.The main contents and achievements are as follows:(1)A model simulating the construction temperature field of complex steel structure was established.The effective temperature of components under solar radiation was corrected based on the principle of stress equivalence,and the monitored effective temperature of components is nonlinear fitted by two normal distribution functions.So the model simulating the temperature and construction field of complex steel structure was established,which was applied to simulate the steel construction of Whitewave River Ferris Wheel.The results showed that the daily temperature difference of the effective temperature of the components was consistent with Boltmann distribution;the limit temperature should be adjusted according to the effective temperature of components when temperature effects analyzed;the simulation results based on the temperature field model were relatively well matched with the measured results.(2)The environmental temperature effect during the construction of complex steel structure was analyzed.The influence of installation temperature of components and installation process on static performance of complex steel structure was analyzed based on the construction temperature field model,as well as the influence of the healing temperature of construction on maximum stress of the structure.The results showed that both the installation temperature and the installation process of the components would affect node displacement and rod piece stress after completion.The maximum stress difference of Whitewave River Ferris Wheel was 48 MPa and 72 MPa respectively.To determine the healing temperature of construction by considering the mechanical response on different parts of the structure could reduce the maximum structure stress of Whitewave River Ferris Wheel by 40 MPa.(3)The influence caused by the residual stress of wide butt welds on complex steel structures was analyzed.The weld width was difficult to control during the process of steel structure construction.The residual stress distribution pattern of the wide butt weld in complex steel structure was tested by blind hole method and numerical simulated by SYSWELD,based on which the impact of wide butt weld residual stress on static performance of complex steel structures was analyzed,as well as the effectiveness of stress relief treatment via the ultrasonic impact method.The results showed that the peak value of welding residual stress increased with the weld width,and the maximum value was close to the yield strength of base metal.The influence of weld shrinkage deformation on the internal force of rod pieces at the joint of Whitewave River Ferris Wheel should not be neglected.The ultrasonic impact method could effectively eliminate the residual stress of wide butt weld.In the test,the peak values of transverse and longitudinal residual stress of the four welds were reduced by 22% and 28% respectively.(4)The effects of environmental temperature on static performance and modal frequency of complex steel structure were studied.The influence mechanism of environmental temperature on structural static performance and modal frequency was discussed.Comparison of numerical simulation results and measured data of Whitewave River Ferris Wheel revealed the temperature influence law of the static performance and the modal frequency of the complex steel structure.The effect of BP neural network technology to eliminate the influence of environmental temperature was studied.The results showed that the environmental temperature changed the modal frequency mainly by changing the elastic modulus of materials and the internal force and geometric state of structure.The displacement of the upper structure of Whitewave River Ferris Wheel was sensitive to temperature changes,while the stress of the lower structure was sensitive to temperature changes.The modal frequency decreased while the temperature increased,and the maximum amplitude of variation of the first 4 frequencies during the monitoring period was 3.04%.BP neural network could reflect correctly the relation between modal frequency and environment temperature.The influence of environment temperature on modal frequency of the structure could be effectively eliminated by the established frequency-temperature regression model.(5)An early warning method of damage for complex steel structure taking account of environmental temperature influence was established.The particle swarm optimization(PSO)algorithm was used to optimize the parameters of the support vector regression-time series(SVR-ARMA)combination model.The damage warning method of complex steel structure was established by mean control chart and the PSO-SVR-ARMA model.The effectiveness of the proposed method was verified by hypothesis testing method simulating different degrees of damages.The results showed that PSO algorithm could improve the generalization ability and prediction accuracy of SVR-ARMA combination model.Compared with the basic SVR model,the frequency prediction accuracy of the established PSO-SVR-ARMA model was improved by 22%.The damage warning method based on PSO-SVR-ARMA frequency prediction model could identify the abnormal changes in the frequency caused by slight structural damage and had good damage warning precision.更多还原