Abstract
The most important feature of the behavior factor is that it allows the structural designer to be able to evaluate the structural seismic demand, using an elastic analysis, based on force-based principles quickly. In most seismic codes, this coefficient is merely dependent on the type of lateral resistance system and is introduced with a fixed number. However, there is a relationship between the behavior factor, ductility (performance level), structural geometric properties, and type of earthquake (near and far). In this paper, a new and accurate correlation is attempted to predict the behavior factor (q) of EBF steel frames, under near-fault earthquakes, using the genetic algorithm (GA). For this purpose, a databank consisting of 12960 data is created. To establish different geometrical properties of models, 3−, 6−, 9−, 12−, 15, and 20− story steel EBF frames were considered with 3 different types of link beam, 3 different types of column stiffness, and 3 different types of brace slenderness. Using nonlinear time history under 20 near-fault earthquake, all models were analyzed to reach 4 different performance levels. 6769 data were used as GA training data. Moreover, to validate the correlation, 2257 data were used as test data for calculating mean squared error (MSE) and correlation coefficient (R) between the predicted values of (q) and the real values. In addition, the MSE and R were calculated for correlation in the train and test data. Also, the comparison of the response of maximum inelastic displacement of 5 stories EBF from the proposed correlation and the mean inelastic time-history analysis confirms the accuracy of the estimate relationship.
Highlights
One of the prevalent methods for building seismic design is the force-based design (FBD) method which is used in common codes such as Eurocode 8 [1]
In the FBD method, the maximum displacement and nonlinear interstory drift ratio can be obtained by multiplying the elastic values by the behavior factor R. is method assumes that the displacement equivalent rule which exists for SDOF structures is applicable to multidegree of freedom (MDOF) structures
E coefficient multiplied by the maximum displacement and the interstory drift ratio indicates the fact that the main drawback to the FBD method is that it assumes the displacement and the interstory drift ratio profile remains constant at height during seismic excitation
Summary
One of the prevalent methods for building seismic design is the force-based design (FBD) method which is used in common codes such as Eurocode 8 [1]. Is article proposes a simple expression for estimating of behavior factor of the EBFs. ese formulae are expressed based on geometrical characteristics of EBFs and are obtained based on parametric study including numerous nonlinear time-history analyses of 162 EBFs with 4 performance levels under 20 near-fault ground motions. E main emphasis is on introducing of the potential of the proposed relationships to fit them into the framework of design methods based on elastic analysis In this process, for a given behavior factor, R, the presented relationships can provide the designer with an acceptable estimate of the maximum roof displacement, the maximum interstory drift, and other structural demands
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