Numerical Evaluation of Shear Strength of Members with I, H, Tubular and Box Sections in the panel zone of steel moment-resisting frames

Introduction: One of the important topics in the design of steel structures is the selection of member cross-section types. I-shaped, H-shaped, box-shaped, and tubular sections are the most common steel sections used in building structures, bridges, and industrial structures. In the design of these types of structures, one of the design criteria is controlling shear in steel members. If the lengths of the flexural members are short, controlling this limit state can be very necessary. Study of theoretical and regulatory relationships: In this article, first, theoretical and codebased relationships of nominal shear strength of H-shaped members with respect to the strong axis, tubular, box-shaped, and H-shaped members with respect to the weak axis were studied. Then, the nominal shear strength of each mentioned section was evaluated using numerical modeling in Abaqus software. The material and geometric modeling of the created members in Abaqus software were validated based on laboratory models. For numerical parametric evaluation, 35 members with different cross-sections were used. Each of these members was modeled in Abaqus software and each of them was subjected to both pushover and cyclic analyses. The lengths of each of these models were such that in all models, the shear limit state was more decisive than the flexural limit state. Conclusion: Based on this research, the results of the relationships presented in the AISC 360 for determining the nominal shear strength of H-shaped members with respect to the strong axis have very close conformity with the results of numerical modeling in Abaqus software, and the difference of approximately 10% between them is due to the fact that in the AISC 360, for calculating the shear strength of these types of sections, in order to make calculations easier, the same value for the elastic and plastic section modulus is assumed. Also, the results of this research show that in this type of sections at higher drifts, the results of the AISC 360 method are approximately 10% less conservative. At lower drifts, the results of the relationships presented in the AISC 360 for determining the nominal shear strength of tubular sections have very close conformity with the results of numerical modeling in Abaqus software. The reason for this is that in the AISC 360, for determining the shear strength of these types of sections, the maximum shear stress of the section has been used. Also, the results of this research indicate that in this type of sections at higher drifts, the results of the AISC 360 method are approximately 20% more conservative. At lower drifts, the results of the relationships presented in the AISC 360 for determining the nominal shear strength of box-shaped members have very close conformity with the results of numerical modeling in Abaqus software.The reason for this is that in this types of sections due to the closed section, conditions for redistribution of shear stress are available, and each of the flanges resists shear equally. In this case, the insignificant difference between the results of the AISC 360 method and the results of numerical modeling is due to the fact that in the AISC 360, for determining the shear strength of these types of sections, in order to make calculations easier, the same value for the elastic and plastic section modulus is assumed. The results of the relationships presented in the AISC 360 code for determining the nominal shear strength of H-shaped members with respect to the weak axis do not have close conformity with the results of numerical modeling in Abaqus software, and the nominal shear strength obtained from the AISC 360 is about 20% non-conservative. The reason for this difference is that in these types of sections, the difference between the nominal stress obtained from the AISC 360 approach and the average stress of the section is about 35%, and in higher drifts, it is not possible to redistribute 100% of the shear stress and only 15% of these stresses are redistributed.