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As part of a United States/New Zealand/Japan/China collaborative research project, interior and exterior beam-column joint subassemblages with floor slabs of prototype two-way and one-way reinforced concrete building frames were designed for earthquake resistance using the current New Zealand concrete design code, NZS 3101:1982. Three full-scale subassemblages as designed were constructed and tested under quasi-static cyclic loading which simulated severe earthquake actions. The overall performance of each subassemblage during the tests was satisfactory in terms of strength and ductility. The joint core and column remained essentially undamaged while plastic hinges formed in the beams. The strong column-weak beam behaviour sought in the design, desirable in tall ductile frames designed for earthquake resistance, was therefore achieved. Although the joint cores of the subassemblages remained in the elastic range, joint core shear deformations contributed significantly to the interstorey drifts. Also, a significant proportion of the slab bars in tension contributed to the negative moment flexural strength of the beams. The performance of the one-way joint was superior to the performance of the two way joints.

SP123 This volume is a collection of technical papers on the aspects of design of beam-column joints for seismic resistance. Nineteen papers are divided into the following groups. - Tests conducted on specimens designed using current codes but with the same general geometry and a specified loading history. (4 papers) - Design recommendations -- Japan. (1 paper) - Influence of joint geometry on strength and deformation characteristics. (8 papers) - Influence of bond on joint performance. (4 papers) - Joint in precast systems and with high-strength materials. (2 papers)

Proposes mechanisms of the transfer of forces to beam-column joints, generated under typical seismic actions in cast-in-place reinforced concrete slabs. One of the main objectives of the paper is to review behavioral models that should assist designers in visualizing the flow of internal forces in beam-column-slab subassemblages. It is postulated that membrane forces play a dominant role and that contributions of other actions, such as bending in slabs and torsion in transverse beams, are relatively unimportant, particularly when significant ductility demands arise during seismic motions. Locations at which slab reinforcements transmit tensile forces by means of bond to the surrounding concrete are considered to be particularly important in the assessment of the enhancement of beam flexural strength. The description of these phenomena is related to observations made during the testing of isolated reinforced concrete beam-column subassemblages with slabs simulating one-and two-way cast-in-place floor systems. Subsequently, the findings are extended to describe the perceived behavior of continuous floor slabs supported by beams of multibay ductile frames. The relevance of the flexural strength enhancement of beams to the design of beam-column joints and columns is briefly examined. Design recommendations are made, particularly with respect to the effective width of the tension flanges.

Two series of experiments have been conducted to study the performance of wide beam-to-column subassemblages under lateral loadings. Results indicate that in moment-resisting frames: 1) the maximum effective beam width should be twice the column width, if all beam reinforcing bars are expected to yield within 2 percent of story deformation, and 2) the maximum amount of beam reinforcement not placed in the joint core should be limited in terms of resulting torsional stress in the outside beam portions. The torsional strength c åt = 24çb (by Kanoh and Yoshizaki) is a good design criteria for wide beam-column joints.

Geometrical configurations of reinforced concrete beam-column joints in actual building structures are quite varied because the configurations depend upon the number of structural members connecting the joints, the shapes of cross section of the members, the eccentricity among the axes of members, and so on. Focusing the interest mainly on the eccentricity from these factors, studies on seismic behavior of reinforced concrete interior beam-column joints in one-way frames with eccentricity are carried out with a classificatory examination, an investigation of a building destroyed by a strong earthquake, and a survey of previous studies and the authors' experiments. From the investigation of the destroyed building, it is suggested that the heavy eccentricity between columns and beams caused torsional moments in the columns and joints, causing severe damage. From the survey of three previous experiments in which one-sided eccentric joint specimens with wide columns and deep beams were subjected to lateral loading, it is shown that effective width and/or torsional moment should be considered for calculating the strength and stiffness of frames. Experimental results indicate that such eccentricities caused twisting of the columns and joints, resulting in reduction of the shear strength of the members. From the results of the classification examination and of the authors' tests in which five beam-column subassemblages with several types of eccentricity and beam width were subjected to cyclic lateral forces, it is observed that joints with one-sided eccentric beams suffer larger torsional moment around column axes, narrowing the effective joint width. Therefore, the shear cracking stress and the deformability of joints are reduced.