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Inelastic behavior of steel beam-to-column subassemblages

Krawinkler, Helmut; Bertero, Vitelmo V.; Popov, Egor P.

UCB/EERC-71/07, Earthquake Engineering Research Center, University of California, Berkeley, 1971-10, 290 pages (530/K7/1971)

An efficient earthquake resistant design of unbraced multistory steel frame buildings requires a knowledge of the elastic and inelastic behavior of the basic structural elements (beams, columns and their connections) as well as a clear understanding of the interactions taking place between them when combined into subassemblages within the frame. To attain this objective, a thorough experimental investigation of the simplest structural subassemblage, a column with two beams framing into it, was carried out. The selection of a model of such a subassemblage suitable for laboratory testing is discussed, followed by a description of the experimental setup and the testing procedure. Most of the important experimental data obtained from the tests on four specimens are presented in form of tables and graphs. These data include the section properties, loading histories, comprehensive tables of all load and deformation parameters, load-deformation hysteresis diagrams, as well as deformation fields and strain (stress) distributions in the connection areas. A detailed interpretation of the test results is presented thereafter. In this interpretation it is attempted to evaluate the significance of the most important geometrical and loading parameters with respect to strength, stiffness and ductility of the subassemblage. The effect of these parameters on the energy absorption capacity and energy dissipation is carefully studied. The behavior of beam-to-column connections in the elastic and inelastic range is also studied analytically. Simplified mathematical models of connections are discussed. The accuracy of these models is investigated by means of a finite element analysis. Conclusions are drawn regarding (1) the strength and ductility requirements for structural elements, (2) the effect of panel zone distortions on the stiffness of the subassemblage, (3) the effect of P delta and story drift limitations resulting therefrom, (4) the hysteretic behavior and the energy characteristics of the subassemblage. Recommendations for the design and the analysis of unbraced mulistory steel frames are presented.

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