Determination of changes inthermal stress state of steel beams in LIRA-SAPR software

Abstract

Abstract. In this article, the authors conducted a study of the stress-strain and temperature state of the steel frame of the building.Verification analysis of steel section for fire resistance in the homeland software package is carried out.The obtained results were compared with the results of a similar analysis in a foreign software package.The analysis of the dynamic problem of thermal conductivity of the cross section of the beam is carried out.The basic equations for solving the boundary problem of nonstationary thermal conductivity are given.Also, the algorithm of realization of analysis of temperature deformations on section of a steel beam by finite element method is given.The process of designing analytical model of structural elements and analysis of the stress-strain state when operating temperature is changed is considered.The analysis of kinematic and static characteristics of the calculated model under study is carried out.Based on the obtained analysis results, the temperature fields of the beam at certain time intervals are determined.Due to the uneven distribution of temperature in the cross section of the element, temperature deformations are occured.Also, due to the limitation of deformations by external connections, their appearance is accompanied by the development of temperature stresses.Therefore, the study of the peculiarities of thermal deformations in steel structures has considerable practical importance.Due to the urgency of the problem of determining thermal stresses and strains in structures, it is necessary to clarify and improve existing calculation methods, which can not sufficiently take into account changes in time of physical and mechanical characteristics of steel.Therefore, the authors of the article calculated the coefficients of reduction of the physical properties of the section and performed a static analysis of the structure. The change of the stress-strain state of the floor elements under the influence of fire is shown.The results of the analysis showed the importance of taking into account the influence of temperature on the strength and deformation characteristics in the calculation of structures.The authors of the article developed and presented an algorithm for analysing the strength of steel structures for flexibility, taking into account the thermal conduction analysis and the fire resistance analysis.