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)

Reversed cyclic loading tests were carried out for 18 reinforced concrete exterior beam-column subassemblages designed in accordance with the principle that yielding of adjoining beam or column precedes joint shear failure. Column axial force, amount of joint hoop reinforcement, existence of intermediate column bars, and moment-resisting capacity ratio of beam to column were selected as experimental variables. Test results showed that the ductility of the subassemblages increased by column axial compressive force and the amount of the joint hoop reinforcements. The existence of the intermediate column bars was also effective in increasing the ductility. On the basis of thorough consideration of the test results, a critical cumulative displacement ductility factor was quantified as a function of the test variables, and was ascertained to be a very effective value to evaluate the aseismic performance of exterior beam-column subassemblages.

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.

In structures subjected to lateral loading, slab reinforcement acting as effective tensile reinforcement of the beams has been found to increase significantly the beam flexural strength. The enhanced beam flexural strength has several effects on the structural behavior, including a shift in the ratio of strengths between the beams and other members. This may result in a failure mechanism different from that anticipated. The slab contribution depends on several variables, including the connection type (interior or exterior), lateral deformation level, and lateral load history (uniaxial or multiaxial). This paper summarizes general behavior observed during isolated and multiple beam-column-slab connection tests. An approximation is given for estimating the amount of slab reinforcement to be considered as effective tensile reinforcement of the beams.

The Architectural Institute of Japan (AIJ) published its 1988 draft design guidelines for earthquake-resistant reinforced concrete buildings based on ultimate strength concept as a first attempt to develop an ultimate strength design procedure in Japan. This paper introduces the general concept of the design procedure, and explains in detail the design requirements and background information for reinforced concrete beam-column joints of the AIJ guidelines. Based on experimental evidence, the amount of lateral reinforcement in the joint required is significantly reduced from ACI requirements.