Presenting a generalizable numerical model for the nonlinear behavior of rigid steel connections

Document Type : Original Research

Authors
Y. hejazi 1
A. Mirzakhani 2
E. Kashi 3
A. Sarvghad Moghaddam 4
1 iau student
2 Faculty Member
3 Assistant professor, Department of Civil Engineering, Shahrood Branch, Islamic Azad University, Shahrood, Iran
4 iiees
10.22034/24.1.53
Abstract
The degree of connection rigidity has a significant effect on the seismic behavior of steel frames. However, the lack of proper modeling methods or not considering the degree of rigidity of the connection in the design of structures, destroys the accuracy of the design. In conventional methods for the analysis and design of steel frames, the behavior of beam-to-column connections is assumed to be joint or fully braced. With these assumptions, the analysis and design of steel frames becomes easier. But the results of the tests show the existence of a degree of flexibility in the hypothetical clamp joints and a degree of stiffness in the common joint joints. Therefore, for accurate and economic analysis and design of steel frames, it is necessary to consider the tightness of the connections. Few researches have been done on the nonlinear modeling of steel connections with nonlinear shock absorbers, and most of these studies are also on the modeling of connections using the finite element method. This shows the need to deal with the correct and practical modeling of connections. There are various methods for numerical modeling and calibration of experimental and nonlinear behavior of structures, among them, the modeling method with nonlinear springs, plastic joint models, fiber models, and models can be used. Designing finite elements pointed out. One of the advantages of modeling with non-linear springs and plastic joints is the non-linear modeling of the failure zone with minimal degrees of freedom. In this method, calibrated functions are used to model the nonlinear behavior of the structure. But in the method of fiber models and finite elements, the nonlinear behavior of the structure is determined by assigning the nonlinear behavior of the materials. Disadvantages of the fiber modeling method include the absence of shearing and twisting effects, sliding between components, and cracking and crushing of materials. Finite element modeling also provides the ability of three-dimensional behavior, including complex geometries and multiaxial stress and strain states. In the finite element modeling method, determining the size of the elements requires a convergence test. Also, due to the high volume of calculations and its time-consuming nature, this method is used in detailed models to model a part of the structure. In this paper an accurate estimate of the seismic behavior of these joints and damage modes in them is obtained, using the behavior of valid laboratory samples, to be used as a criterion in numerical modeling. For this purpose, four common steel connections, have been investigated and numerical models are presented to consider the nonlinear behavior of the mentioned connections in the Opensees software. Cyclic behavior of experimental samples has been used to calibrate the characteristics of the proposed numerical model. The results show that with the proposed method, the seismic behavior parameters of the studied connections such as load bearing stiffness and ductility capacity in the experimental and numerical model are well matched and can be used to more accurately model in analyzing and applied designing to obtain an accurate estimate of the behavior of the connections and the degree of rigidity in the designs leading to the operation. It is important to compare the plasticity capacity, maximum bearing capacity and initial stiffness in the examined connections compared to their corresponding numerical models, and the difference between 0.29% and 8.42% in different situations confirms this.

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Modares Civil Engineering journal
Volume 24, Issue 1
March and April 2024
Pages 53-67