STICK MODEL OF RECTANGULAR HOLLOW STRUCTURAL SECTION STEEL COLUMNS WITH LOCAL BUCKLING UNDER HIGH AXIAL FORCE

Abstract

 1. Introduction

 Local buckling is one of critical behaviors to determine the plastic flexural strength and deformation capacity of rectangular hollow structural (RHS) section steel columns. Several researchers have proposed numerical models to capture the strength deterioration of the RHS columns under axial loads due to local buckling. The authors proposed a fiber model using a phenomenological model (phenomenological fiber model) to simulate the yield area extends to a broad axial range from the end. This study presents the accuracy of the fiber model for RHS columns under cyclic high axial loading compared to stick or FEM models.

 2. Composition of Phenomenological Fiber Model

 The composition of the phenomenological fiber model is constituted based on the numerical simulations of RHS columns subjected to shear forces with axial loads. 10 specimens, based on a past research article, are referred to clarify the accuracy of the phenomenological fiber model, to develop the yield lines of local buckling of RHS section. The collapse mode of local buckling forms a kind of hip roof shape on the steel tube wall, and the lengths of each yield line are estimated by numerical and tests results. The stress-strain relationship of the fiber element of the phenomenological fiber model is almost identical with the shell elements of the FEM models, except for 33 width-thickness ratio RHS columns.

 3. Validation of Phenomenological Fiber Model with Numerical Model for RHS Columns

 The accuracy of the phenomenological fiber model for RHS columns, subjected to shear forces under high constant or variable axial loads, is validated by FEM numerical results. 12 models of the RHS columns are created using shell elements based on the specimens in the Chapter 2. The phenomenological fiber model captures the strength, the force-deformation relationship, and the local buckling behavior of the FEM numerical results under high axial loads, except for the 33 width-thickness ratio RHS columns.

 4. Validation of Phenomenological Fiber Model with Test results Based for RHS Axial Members

 The accuracy of the phenomenological fiber model for RHS axial members is examined. 8 specimens are extracted from a past research article as samples for the validation. The phenomenological fiber model almost captures the buckling strength, overall flexural and local buckling behavior of the test results.

 5. Validation of Phenomenological Fiber Model with Test Results and Other Analytical Model Based for RHS Columns

 The accuracy of the phenomenological fiber model for RHS columns subjected to shear forces under axial loads is validated by tests and FEM numerical results. 25 specimens are extracted from 9 past research articles as samples for the validation. The results of the phenomenological models are almost identical with the results of the test results, as well as those calculated by another phenomenological model developed by the extended skeleton curve theory, except for the 33 width-thickness ratio RHS columns.

 6. Conclusion

 This paper presents the accuracy of the phenomenological fiber model for evaluating the buckling behavior. As a result, the phenomenological fiber model could capture the strength, the force-deformation relationship, and the local buckling behavior of the RHS columns subjected to shear forces with high axial loads. This phenomenological fiber model also simulates the overall flexural and local buckling behavior of RHS axial members, except for RHS sections larger than and equal to 33 width-thickness ratio.