Simplified Modeling And Robustness Evaluation Of Steel Frame

Progressive collapse is typically the result of a chain action arising from local damage to one or more structural elements caused by overloading or extraordinary loading.The source and magnitude of loads may vary,but in any case when the local capacity of resisting element is reached,failure of a lager portion or of the complete may occur.The main purpose of the research on progressive collapse is to find a practical method which can be used in the design of progressive collapse resisting structure.Progressive collapse of steel structures is a complex dynamic nonlinear process.When studying the collapse characteristics of structures,it is generally necessary to establish a series of finite element analysis models,which can accurately reflect the structural load response characteristics and structure failure characteristics and so on.In the study of the continuous collapse problem,the focus of the study is usually in the elastic-plastic stage,as well as part of the catenary line effect stage,so in the establishment of the model,the overall structure of the geometric nonlinearity and material nonlinearity in the model are required to be accurately modeled.Progressive collapse resisting capacity of steel structure generally depends on their capacity of resisting local damage;however this ability to resist progressive collapse depends on many factors that have yet to be identified in a methodical and reliable manner.Many studies have been carried out on the topic of progressive collapse in recent years.Most existing literature focuses on modeling of the structure at the component level and on schemes for representation and application of the loading.Generally speaking,component based method have been thought as a useful method to simulate the progressive collapse of steel structure.In this article,a series of studies based on the component method were carried out to study the simplify modeling steel frame,and the progressive collapse propertiesof steel frames were studied further.Detailed research contents have been carried out from following aspects:(1)Three component based models were developed to simulate the response of different types of steel beam-column connections.Three types of connections include:simple single-plate shear connection ? top and seat with web angle(TSWA)connection ? welded unreinforced flange-bolted web(WUF-B)connection.These component based models consider the behavior of connections under large tension forces,which was so important that must be considered in the the large deformation stage of progressive collapse cases.(2)The proposed component-based connections models and their constitutive laws were implemented into the business software LS-DYNA to simulate three two bays steel frames against progressive collapse.The comparison study showed the capabilities of the component based models in researching the property of structure with different types of connections.These component based models were implemented into the double bays steel frames to study catenary action due to the loss of middle column.It was proved that the catenary action can enhance the bearing capacity of two bays steel frames.(3)Modeling approaches for analyzing the robustness of 3D steel frame buildings against column loss are presented,including the nonlinear behavior and failure of the top and seat with web angle(TSWA)connections and welded unreinforced flange-bolted web(WUF-B)connections.Analysis results are presented,and the behavior of steel frames buildings under column loss is compared.