Study On Dynamic Reliability Of Time-varing Resistance Of Portal Frame Girder

With the large number of steel buildings put into operation,and with the increasing service life of engineering structures,The basis of the reliability of civil engineering facilities Has become a widespread concern in the field of civil engineering structures and the forefront of important research topic. Especially in recent years, in several major snow disasters, Portal frame structures have a more serious damage. During using after years of engineering structures subjected to various loads, by the external environment and against various corrosive media, Portal frame structures have different degrees of damage or defect. People naturally concerned about the current state of these structures and future structural reliability. The safety of the structure depends on the resistance of structural members; therefore, resistance of structural elements gradually formed structural reliability of one of the most important study.To predict the structure of the resistance level of a few years later, model of resistance must be established evaluation change over time. When the analysis by the parameters resistance changes, further consideration of the uncertainty component resistance, establish service component attenuation model of resistance has opened the door to research with the portal frame structure in use. For the time-varying resistance, most studies of reinforced concrete structures, but corrosive environment are committed to the study specifically for the steel. The steel members for the atmospheric environment of time-varying resistance, also in the level of qualitative analysis, almost no quantitative conclusions of the research presented.Considering the environment, the role of aging and other factors coupled, study of the general atmosphere and acid rain environment, marine environment, Portal frame structure beam material properties over time degeneration and damage mechanism of the time, Main tasks are as follows:Analysis of influencing factors that atmospheric corrosion and the characteristics of the climate station. Research Institute of the metal corrosion of steel based on the experimental results atmospheric corrosion of different environments, consider the comprehensive climate stations and the corrosion protection characteristics, calculated for different atmospheric conditions representative of five areas of Q235 steel corrosion depth and corrosion rate. Statistics of the 16 kinds of practical engineering application of more size of the beam portal frame, using the principles of mathematics and mechanics, then calculate the five regions of different atmosphere, different sizes of portal frame girder corrosion in service during the considered time-varying flexural capacity and shear capacityIn the above, based on further analysis of the resistance to fading, comparative analysis of existing portal frame girder resistance degradation model; calculated beam out of the door frame after the expiration of 50 years in service, the amount of decay and the attenuation coefficient. By contrast, analysis of various models, exponential model obtained agrees well with the actual.Time-varying resistance and the "structures load code" as the basis to calculate the regional representative of 5 different sizes in different beam portal frame time-varying atmospheric environment reliability and proposed structures based on static Comparative analysis of reliability and norms.