Investigations On Critical Problems Of Static Analysis Method Of Progressive Collapse Of Steel Framed Structures

Progressive collapse is a complex process in which failure of a single component of a structure under accidental load leads to collapse of a disproportionately large part of the system.Although the probability of progressive collapse is extremely low,once it occurs,it will cause huge economic losses and even casualties.Therefore,it is very important to study the progressive collapse of structures.Progressive collapse of the building structure is a complex dynamic process.Although the dynamic analysis method has high accuracy,it is often complicated,difficult to model,and takes a long time to calculate.The static analysis method is relatively simple and is more suitable for the collapse-resistant design of the structure.However,it is necessary to ensure that it can accurately evaluate the response of the structure under the failure condition of the column and the collapse-resistant mechanism.In order to solve the key problem of static analysis method of continuous collapse of building structure,this paper has conducted the following researches:(1)Establish refined finite element models of planes and three-dimensional steel frame structures,including plane hinged steel frame structure,plane semi-rigid steel frame structure,plane rigid steel frame structure,3D hinged steel frame structure,3D semi-rigid steel frame structure and the 3D rigid steel frame structure,and the existing test data are used to systematically verify the model to ensure the accuracy and reliability of the models.(2)The static analysis of three types plane steel frames is carried out to explore the static resistance mechanism.The dynamic analysis of the plane composite frame is carried out using the alternate load path method,and its dynamic resistance mechanism is obtained through numerical processing.Finally,the dynamic resistance mechanism and static resistance mechanism of plane composite frames are compared respectively.When the bending effect of the beam is the main resistance mechanism,the resistance generated by the bending of the beam during dynamic loading is generally larger than that of static loading;When the catenary effect is the main resistance mechanism,the resistance between the catenary effect and the dynamic loading is not much different between the dynamic loading and the static loading.Therefore,it is considered that the static resistance mechanism and the dynamic resistance mechanism of the plane composite steel frame are similar.(3)Obtain the dynamic amplification factor(DIF)of the plane and the 3D steel frame structure.Through comparison with the DIF specified in the mainstream codes at home and abroad,it is found that these codes underestimate the DIF of the structure,resulting in a design that is not safe enough.Based on the calculation results,the calculation method of the DIF of the steel frame structure that can be used for the static analysis of progressive collapse of the structure is finally proposed.