The effect of Number and Position of Braced Frames on Failure Distribution and Column Behavior of the Dual Steel Structural System (MRF and EBF)

Subject Areas : Analysis of Structure and Earthquake

Alireza Faroughi ¹ , Sajjad Mohammadi ² , Abd-ol-Reza Sarvghad Moghaddam ³

1 - Assistant Professor, Department of Civil Engineering, Islamic Azad University, East Tehran branch, Tehran, Iran
2 - lecturer, Department Civil Engineering Department, East Tehran branch, Islamic Azad University Tehran, Iran
3 - عضو هیأت علمی تمام وقت، گروه مهندسی سازه، پژوهشگاه بین المللی زلزله شناسی و مهندسی زلزله

Received: 2020-03-07 Accepted : 2020-08-18 Published : 2020-08-19

Keywords: interaction, Number and position of braced frames, Over-strength factor, Dual system of steel, Fourth revision of Iranian 2800 standard of seismic provision, Amplified seismic load,

Abstract :

In the seismic design of structures, determination of the number and position of braced frames, according to the architectural scheme of projects, is usually encountered with obstacles. This has made it difficult in some cases to choose the best location and number of braced bays and especially in dual frames, has led to differences in the design forces of their adjacent members (columns). One of the seismic design requirements of lateral resisting system is to control the columns adjacent to braced bays for load combinations of intensified seismic load, which is a function of over-strength factor of the structure. This research aims to present and introduce the best structural model regarding the number and position of braced frames in a structural system, such as steel moment resisting frame and eccentric braces dual system. Though the intensified seismic load function is controlled in models which columns are connected to the braces in 2 directions, and seismic loads are applied in those 2 directions, the number of damaged hinges (Exceeding CP) is significantly increased in comparison with the models with straggly braces. Since the increase in axial force of these columns reduces their moment capacity (despite controlling the amplified seismic load provision), columns in dual systems that resist flexure, would be damaged and exceed the collapse threshold much sooner than other columns. Therefore, it is suggested that, like the publication 360, the control of these columns in an amplified earthquake should not be based solely on axial force, but on the interaction of forces.