Practical advanced analysis for semi-rigid space frames Seung-Eock Kim a, * , Se-Hyu Choi b a Department of Civil and Environmental Engineering, Sejong University, 98 Koonja-dong, Kwangjin-ku, Seoul 143-747, South Korea b Construction Technology Research Institute, Sejong University, 98 Koonja-dong, Kwangjin-ku, Seoul 143-747, South Korea Received 15 November 2000; in revised form 15 May 2001 Abstract A practical advanced analysis of semi-rigid space frame is developed. Herein, the nonlinear behavior of beam- to-column connections is discussed, and practical modeling of these connections is introduced. The proposed analysis can predict accurately the combined nonlinear eects of connection, geometry, and material on the behavior and strength of semi-rigid frames. Kishi±Chen power model is used to describe the nonlinear behavior of semi-rigid con- nections. Stability functions are used to capture second-order eects associated with P-d and P-D eects. The column research council tangent modulus and a parabolic function for gradual yielding are used to represent material non- linearity. The load±displacements predicted by the proposed analysis compare well with those available experiments. A case study has been performed for a four story semi-rigid frame. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Advanced analysis; Semi-rigid connection; Geometric nonlinearity; Material nonlinearity; Steel frame 1. Introduction Conventional analysis of steel frame structures is usually carried out under the assumption that the beam-to-column connections are either fully rigid or ideally pinned. However, most connections used in current practice are semi-rigid type whose behavior lies between these two extreme cases. In the AISC- LRFD Speci®cation AISC, 1993), two types of constructions are designated: type fully restrained con- struction; and type partially restrained construction. The LRFD Speci®cation permits the evaluation of the ¯exibility of connections by rational means when the ¯exibility of connections is accounted for in the analysis and design of frames. The semi-rigid connections in¯uence the moment distribution in beams and columns as well as the drift P-D eect) of the frame. One way to account for all these eects in semi-rigid frame design is through the use of a direct second-order inelastic frame analysis known as ``advanced analysis''. Advanced analysis indicates a method that can suciently capture the limit state strength and stability of a structural system and its individual members so that separate member capacity checks are not required. Since the power of International Journal of Solids and Structures 38 2001) 9111±9131 www.elsevier.com/locate/ijsolstr * Corresponding author. Tel.: +82-2-3408-3391; fax: +82-2-3408-3332. E-mail address: sekim@sejong.ac.kr S.-E. Kim). 0020-7683/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII:S0020-768301)00141-X