Measurement Method of Initial Geometric Deflections of T-Section Steel Struts

Initial geometric deflection is one of the important factors impacting on the overall stability bearing capacity of steel struts. The common initial geometric deflections of the steel strut with T-section include the initial bending deformation of the component, the initial eccentricity of the load and the initial torsional deformation of the member. In the process of the study on the overall stability bearing capacity of steel struts, in order to measure the initial geometric deflection more accurately and conveniently, the relationship between the initial geometric deflection of steel struts and the parameters such as load, strain, lateral displacement and torsion deformation of the section are utilized. Based on the traditional theory of elastic stability, the calculation formulas of the initial geometric deflections are derived, and the inverse parameter measuring method is put forward to obtain the initial geometric deflections by using the relationship between the load and deformation of the compression member in the elastic stage.
Using ANSYS, the 3 D model of a T-section steel strut with initial geometric deflections was created, and the geometric nonlinear analysis of the strut was performed. Comparing the data of the initial geometric deflections of the 3 D model with the results calculated by the inverse parameter measuring method, the accuracy of the calculation formula to get the initial geometric deflections was verified. Finally, based on the overall stability capacity test of T-section steel struts, the measured values such as load, strain, lateral displacement and torsion deformation of the section in the elastic stage were obtained. By the inverse parameter measuring method, the actual initial geometric deflections of the steel strut were calculated. The results were compared with those obtained by the traditional optical instrument measuring method, and the correctness of the inverse parameter measuring method was verified.
It is shown that the inverse parameter measuring method of the initial geometric deflections of T-section steel struts was correct and feasible. Since the deflections can be measuring with the equipment in the overall stability capacity test without extra devices, the artificial measurement errors are reduced. Moreover, the influence of the end constraint on the critical force of actual struts is taken into account during the process of the overall stability bearing capacity test. Most of all, the common initial geometric deflections of the steel strut with T-section, not only the initial bending deformation of the component and the initial eccentricity of the load, but also the initial torsional deformation of the member can be obtained. The initial geometric deflections, which are obtained by the inverse parameter measuring method, can be directly used in the subsequent finite element analysis, that it can provide an essential reference for the study of the overall stability bearing capacity of the steel struts with T-section.