| With the support of the new round of western development strategy and the "the Belt and Road" policy,large-scale public buildings in the frigid plateau regions represented by Tibet will usher in a peak period of construction.Long-span steel structures are often used as the metal roof of large-scale public buildings,with large solar radiation area and high requirements for construction molding quality,but the rationality of the design temperature load and construction closing temperature values will directly affect the construction safety and operational durability of long-span steel structure buildings,especially in the frigid plateau regions with special climatic environments.Therefore,it is necessary to study the time-varying distribution characteristics of solar radiation temperature field and temperature effect of longspan steel structures in the frigid plateau regions,so as to provide a theoretical basis for engineering practice,and promoting the deepening of steel structure specifications in terms of non-uniform temperature loads under solar radiation.The main research work and achievements of this article involve the following four aspects:(1)Taking the right metal roof truss long-span steel structure of a large hospital in Tibet as the research object,the temperature time-history curve of long-span steel structure was collected based on the field test,and the solar position parameters and thermal boundary parameters in the frigid plateau region were recorded,and the temperature time-variation characteristics and distribution law of long-span steel structure under the alpine environment in mid-March were clarified,At the same time,the applicability of different theoretical formulas in frigid plateau regions is analyzed,which provides a reference basis for the design temperature load value of long-span steel structures and the numerical simulation of solar radiation temperature field in frigid plateau regions.(2)Based on engineering drawing information,the finite element model of thermal analysis of long-span steel structure shell-surface effect element is established by using geometric modeling software and mesh division software.The algorithm of sunshine shadow of surface effect element is compiled based on computer graphics,and the distribution of sunshine shadow obtained by the joint simulation of Python software and finite element software is verified by using the field shadow photos,Finally,the accuracy of the numerical simulation method is verified by the measured temperature data,which provides a referential numerical simulation method for the accurate calculation of the solar radiation temperature field in the frigid plateau region.(3)Based on the thermal-structural indirect coupling method,the thermal analysis model is transformed into a structural analysis model by using APDL parametric design language,and the solar radiation temperature field is applied to the structural analysis model as a body load.Through the transient analysis,the time-varying characteristics of the solar radiation temperature effect of the long-span steel structure in the alpine region of the plateau are obtained,and the coupling mechanism of strong solar radiation heating and strong air convection heat transfer in the frigid plateau region is revealed.At the same time,the solar radiation temperature response characteristics of the components of the long-span steel structure are compared and analyzed,which provides guidance for the structural design of the truss long-span steel structure.(4)Based on this numerical simulation method,the solar radiation temperature response characteristics of long-span steel structures under different initial solar radiation intensity,air convection heat transfer coefficient and thermal strain reference temperature(construction closing temperature)are studied,and the relationship between plateau strong solar radiation warming and cold air convective heat transfer was clarified,and the calculation principle of optimal construction closing temperature in the frigid plateau region are proposed,which laid a theoretical foundation for the high-standard forming of long-span steel structures in frigid plateau regions. |
