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CONTENTS
Volume 1, Number 3, September 2001
 

Abstract
In this paper the results of an experimental program devoted to the assessment of the cyclicrnbehaviour of full scale, European type, beam-column subassemblages with welded connections are presented.rnSix tests (five cyclic and one monotonic) have been carried out on three different series of specimens,rnencompassing a total of eighteen tests. The three specimen series have been designed with the aim of definingrnthe effect of the column size on the connection behaviour, under different applied loading histories. The testsrnhave evidenced the effect of the column size and panel zone design and of the applied loading history on therncyclic behaviour and failure modes of the connections.

Key Words
welded connections; cyclic tests; loading histories; rotation capacity; panel zone;failure modes.

Address
Elena Mele, Dipartimento di Analisi e Progettazione Strutturale (DAPS), Universita di Napoli \"Federico II\", P.le Tecchio 80, 80125 Napoli, ItalyrnLuis Calado, Departamento de Engenharia Civil (DECivil), Instituto Superior Tecnico, Av. Rovisco Pais,1049-001 Lisboa, PortugalrnAntonello De Luca, Dipartimento di Analisi e Progettazione Strutturale (DAPS), Universita di Napoli \"Federico II\", P.le Tecchio 80, 80125 Napoli, Italy

Abstract
In the present work a constitutive model is developed which permits the assessment of the structural performance through a criterion based on cumulative damage. For it, a damage index is defined and is evaluated through the application of the Miner\'s rule in low-cycle fatigue. However, the damage index is not considered as a posteriori variable since is incorporated explicitly as an internal variable in the constitutive equations which produces a direct coupling between the damage and the structural mechanical behaviour allowing the possibility of considering as a whole different coupled phenomena. For the elaboration of this damage model, the concepts of the mechanics of continuum medium are applied on lumped dissipative models in order to obtain a coupled simplified model. As a result an elastoplastic model coupled with damage and fatigue damage is obtained.

Key Words
continuum damage mechanics; low cycle fatigue; steel structures; seismic design; simplified model

Address
R. Perera, S. Gomez and E. Alarcon, Department of Structural Mechanics, Technical University of Madrid (UPM), Spain

Abstract
The purpose of this paper is to propose a new type of steel reinforced concrete (SRC) beam-columnrnjoints and to examine the structural performance of the proposed joints, which simplify the construction procedurernof steel fabrication, welding works, concrete casting and joint strengthening. In the proposed beam-column joints,rnthe steel element of columns forms continuously built-in crossing of H-sections ( ), with adjacent flanges ofrncolumn being connected by horizontal stiffeners in a joint at the level of the beam flanges. In addition, simplifiedrnlateral reinforcement ( ) is adopted in a joint to confine the longitudinal reinforcing bars in columns.rnExperimental and analytical studies have been carried out to estimate the structural performance of the proposedrnjoints. Twelve cruciform specimens and seven SRC beam-column subassemblage specimens were prepared andrntested. The following can be concluded from this study: (1) SRC subassemblages with the proposed beam-columnrnjoints show adequate seismic performances which are superior to the demand of the current code; (2) The yieldrnand ultimate strength capacities of the beam-to-column connections can be estimated by analysis based on thernyield line theory; (3) The skeleton curves and the ultimate shear capacities of the beam-column joint panel arernpredicted with a fair degree of accuracy by considering a simple stress transfer mechanism.

Key Words
new type of SRC beam-column joint; simplifying construction procedure; structural performance;limit analysis; yield line theory.

Address
Masaru Teraoka, Technology Development Division, Fujita Corporation, 2025-1 Ono, Atsugi-shi, Kanagawa, JapanrnKoji Morita, Department of Design and Architecture, Faculty of Engineering, Chiba University 1-33 Yayoi-cho, Chiba-shi, Chiba, JapanrnSatoshi Sasaki and Daisuke Katsura, Technology Development Division, Fujita Corporation, 2025-1 Ono, Atsugi-shi, Kanagawa, Japan

Abstract
This paper presents a three-dimensional finite element analysis methodology for a quantitativernevaluation of confinement in concrete-filled box-shaped unstiffened steel columns. The confinement effectsrnof concrete in non-circular sections can be assessed in terms of maximum average lateral pressure. A briefrnreview of a previous method adopted for the same purpose is also presented. The previous method is based onrna two-dimensional finite element analysis method involving a concrete-steel interaction model. In both thernpresent and previous methods, average lateral pressure on concrete is computed by means of the interactionrnforces present at the concrete-steel interface. Subsequently, the strength enhancement of confined concrete isrnempirically related to the maximum average lateral pressure. The results of the former and latter methods arernthen compared. It is found that the results of both methods are compatible in terms of confined concreternstrengths, although the interaction model yields a somewhat overestimated estimation of confinement thanrnthose of the present method when relatively high strength concrete is used. Furthermore, the confinement inrnrectangular-shaped sections is investigated and the reliability of previously adopted simplifications in suchrncases is discussed.

Key Words
concrete-filled tubes; box-shaped CFT columns; confinement; confined concrete; concrete-steel interface; composite action.

Address
K.A.S. Susantha, Hanbin Ge and Tsutomu Usami, Department of Civil Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan

Abstract
Cyclic response of \"shear\" connections between steel outrigger beams and reinforced concrete core walls is presented in this paper. The connections investigated in this paper consisted of a shear tab welded onto a plate that was connected to the core walls through multiple headed studs. The experimental data from six specimens point to a capacity larger than the design value. However, the mode of failure was through pullout of the embedded plate, or fracture of the weld between the studs and plate. Such brittle modes of failure need to be avoided through proper design. A capacity design method based on dissipating the input energy through yielding and fracture of the shear tab was developed. This approach requires a good understanding of the expected capacity of headed studs under combined gravity shear and cyclic axial load (tension and compression). A model was developed and verified against test results from six specimens. A specimen designed based on the proposed design methodology performed very well, and the connection did not fail until shear tab fractured after extensive yielding. The proposed design method is recommended for design of outrigger beam-wall connections.

Key Words
collector element; composite construction; cyclic testing; floor diaphragm; hybrid structures; outrigger beam; reinforced concrete wall; shear stud; walls.

Address
Jeremy T. Deason, LJB Engineers, 3100 Research Blvd., P.O. Box 20246, Dayton, OH 45420-0246, U.S.A.rnGokhan Tunc, Cantor Seinuk Group, Inc. (WSP), 600 Madison Avenue, New York, NY 10022, U.S.A.rnBahram M. Shahrooz, Department of Civil and Environmental Engineering, University of Cincinnati, P.O. Box 210071, Cincinnati, OH 45221-0071, U.S.A.

Abstract
This paper provides a state-of-the-art review on advanced analysis models for investigating thernload-displacement and ultimate load behaviour of steel and composite frames subjected to static gravity andrnlateral loads. Various inelastic analysis models for steel and composite members are reviewed. Compositernbeams under positive and negative moments are analysed using a moment-curvature relationship whichrncaptures the effects of concrete cracking and steel yielding along the members length. Beam-to-columnrnconnections are modeled using rotational spring. Building core walls are modeled using thin-walled element.rnFinally, the nonlinear behaviour of a complete multi-storey building frame consisting of a centre core-wall andrnthe perimeter frames for lateral-load resistance is investigated. The performance of the total building system isrnevaluated in term of its serviceability and ultimate limit states.

Key Words
advanced analysis; core-braced frame; composite beams; nonlinear analysis; performance-based design; plastic hinge analysis; semi-rigid frames; steel and composite structures; tall buildings.

Address
J.Y. Richard Liew, Department of Civil Engineering, National University of Singapore, Blk E1A, 1 Engineering Drive 2, Singapore 117576, Singapore

Abstract
An experimental research program on end-plate beam-to-column composite joints under cyclicrnloading is presented. The major focus relates to the identification of the contribution of the concreternconfinement in composite columns to the behaviour of the joint, on internal nodes and external nodes,rntogether with an assessment of degradation of strength and stiffness in successive loading cycles. From thernexperimental results it was possible to identify the various failure modes and to fit the correspondingrnhysteretic curves to the Richard-Abbott and Mazzolani models. These curve-fitting exercises highlighted thernneed to adapt both models, either for improved ease of application, or to deal with some aspects previously notrncovered by those models.

Key Words
composite joints; cyclic behaviour; end-plate; composite columns; hysteretic curves.

Address
Rui Simoes and Luis Simoes da Silva, Departamento de Engenharia Civil, Universidade de Coimbra, Polo II, Pinhal de Marrocos, 3030 Coimbra, PortugalrnPaulo J.S. Cruz, Departamento de Engenharia Civil, Universidade do Minho,rnAzurem, 4800-058 Guimaraes, Portugal


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