International Concrete Abstracts Portal

Precast concrete systems are mainly used to construct residential buildings in Japan. The systems include precast concrete wall structures for low-to-medium-rise buildings and frame structures for medium to high-rise buildings. Most of the precast members are produced in fabricating plants and shipped to the site. Beam-column joints in precast systems are designed using essentially the same design philosophy but considerably different details, as used in cast-in-place construction. The details of the joints are usually examined from the structural viewpoint by experimental tests and from the construction viewpoint by mock-up tests. This paper is intended to give an overview of beam-column joints used in precast concrete moment-resisting frame structures. Aseismic design and details of the joints are described and a few examples of construction practice are illustrated. Emphasis is placed on joints in high-rise construction using precast concrete systems.

Presents a critical review of current design provisions for shear and anchorage in beam-column joints subjected to large seismic actions. When current design limits are compared with experimental data, the results indicate that if short anchorage lengths and large shear stress are used simultaneously, large losses of bond transfer capacity and stiffness will occur. The performance of joints based on different levels of joint shear stress and anchorage lengths is discussed, and an empirical formula linking anchorage and shear is proposed based on the limited tests data available on bar slip.

Describes a theoretical investigation into the hysteretic behavior of hinges in reinforced concrete members subjected to seismic loading. The most important feature of this study is the quantitative evaluation of bond deterioration process between the main reinforcement steel and concrete. An analytical procedure is formulated and a computer program for assessing bond deterioration is developed. End hinges and adjacent bond regions in reinforced concrete members are represented by mathematical models that consist of steel elements, concrete fiber elements, and bond links. Assuming appropriate constitutive curves for these elements, the equilibrium condition of section forces in a hinge is obtained iteratively. This analytical method is applied to the problem of slippage of beam bars in reinforced concrete cruciform beam-column joint subassemblages. The analytical results aptly explain the transient processes of structural behavior observed in experiments, and the quantitative assessment of bond deterioration processes is accomplished satisfactorily.

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.

Cyclic loading tests of eight half-scale interior beam-column subassemblages using high-strength materials were carried out to investigate their seismic behavior under high joint shear stress vn ranging from 140 to 200 kg/cmý. Concretes with three nominal compressive strengths; 400, 600, and 800 kg/cmý was used. High-strength reinforcing bars with a yield strength of 4000 and 6000 kg/cmý were provided as beam longitudinal reinforcement. Reinforcing bars with a yield strength of 8700 kg/cmý were used for joint transverse reinforcement. To prevent premature shear failure in joints and significant slippage of beam bars through joints, four different types of joint detail were planned. They included high-strength bars for joint reinforcement, anchor plates attached to beam longitudinal bars in the joint, relocation of beam plastic hinges away from the joint, and joint reinforcement using steel plates. The beam-column joints using high-strength concrete of 600 kg/cmý or higher showed ductile behavior up to 5 percent story drift, even under conditions of high join-shear stress. No significant bar slippage or bond deterioration was observed, including the joints using high-strength beam main bars. The high-strength transverse reinforcement worked effectively as joint reinforcement, as indicated by considerably high strains measured in joint hoops. The relocation of beam plastic hinges away from the joint reduced damage of the beam-column joint. Based on the test results, guidelines for design of such reinforced concrete beam-column joints are presented.