EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS Earthquake Engng Struct. Dyn. 2008; 37:535–555 Published online 14 November 2007 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/eqe.771 A design-variable-based inelastic hysteretic model for beam–column connections Gun Jin Yun 1, ∗, † , Jamshid Ghaboussi 2 and Amr S. Elnashai 2 1 Department of Mechanical, Aerospace and Structural Engineering, Washington University in St. Louis, St. Louis, MO 63130, U.S.A. 2 Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S.A. SUMMARY This paper presents a design-variable-based inelastic hysteretic model for beam–column connections. It has been well known that the load-carrying capacity of connections heavily depends on the types and design variables even in the same connection type. Although many hysteretic connection models have been proposed, most of them are dependent on the specific connection type with presumed failure mechanisms. The proposed model can be responsive to variations both in design choices and in loading conditions. The proposed model consists of two modules: physical-principle-based module and neural network (NN)-based module in which information flow from design space to response space is formulated in one complete model. Moreover, owing to robust learning capability of a new NN-based module, the model can also learn complex dynamic evolutions in response space under earthquake loading conditions, such as yielding, post- buckling and tearing, etc. Performance of the proposed model has been demonstrated with synthetic and experimental data of two connection types: extended-end-plate and top- and seat-angle with double-web- angle connection. Furthermore, the design-variable-based model can be customized to any structural compo- nent beyond the application to beam–column connections. Copyright 2007 John Wiley & Sons, Ltd. Received 9 July 2007; Revised 6 October 2007; Accepted 8 October 2007 KEY WORDS: design-variable-based models; neural networks; hysteretic models; beam–column connec- tions; nonlinear analysis; inelastic behavior 1. INTRODUCTION The cyclic behavior of connections is very important for seismic performance evaluation of building structures in highly seismic zones. Because of their complexities in geometrical properties and ∗ Correspondence to: Gun Jin Yun, Department of Mechanical, Aerospace and Structural Engineering, Washington University in St. Louis, St. Louis, MO 63130, U.S.A. † E-mail: gunjin.yun@gmail.com Copyright 2007 John Wiley & Sons, Ltd.