An Analysis on the Structural Behavior of the y-Shaped Concentric Steel Bracing

Document Type : Original Article


Faculty of Structural Engineering Department, Road Housing and Urban Development Research Center


Lateral bearing systems utilizing concentric braces are considered to be the most common types of these systems. Among the types of concentric braces, some forms such as X and V are better known and some are less common such as y-shaped. Meanwhile, the y-shaped brace is a usable solution in frame spans that have openings. The lack of documented scientific and technical information about the y-shaped brace causes its incorrect use and the occurrence of damages under the effect of earthquakes. In this research, the behavioral characteristics of this brace have been investigated by conducting theoretical studies. It has been shown that the y-brace in its conventional form is quite susceptible to out-of-plane buckling. By analyzing the in-plane and out of plane buckling of bracing, the critical buckling length coefficient has been obtained and it is presented for the location of the convergence point in different locations of the span. In order to satisfy the requirements of Iran Standard 2800 which prohibits carrying the total lateral force only by compression or tension in the bracing members, it is necessary to observe the location of convergence point for the y-shaped bracing. Finally, with the help of displacement coefficients method, the level of seismic performance of the y-braced frame was estimated and it was determined that this bracing system has the ability to provide the life safety performance in design earthquake.


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