International Concrete Abstracts Portal

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.

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.

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.

A set of shear-resistant actions is presented to analyze reinforced concrete interior beam-column joints in weak beam-strong column ductile frames. The proposed analysis explains the results of experiments of beam-column joints with and without bond at beam bars and with various horizontal shear reinforcement. Local bond strength at beam bars affects horizontal hoop stress. Under or up to the limit of enough bond, larger local bond strength demands larger horizontal hoop stress. Over this limit, larger local bond strength demands smaller horizontal hoop stress. Joint shear reinforcement improves anchorage of beam bars because horizontal hoop stress guarantees bond stress outside diagonal strut. This results in smaller compressive stresses of joint concrete, preventing compressive shear failure.