| In tall buildings high-strength concrete is often used in columns while lower strength normal concrete is used in beam-slab systems. For ease of constuction, concrete of beam-column joints and that of beam-slab systems are placed synchronously, i.e. lower strength concrete is used in beam-column joints. While the variation in concrete strength between beams and columns is great, the capacity of joints may be lower than that of columns. Thus,in order to improve the capacity, joints must be strengthened. Test of 6 different-strength concrete beam-column joints is presented in the paper. The difference between axial compressive capacity of beam-column joints and that of columns is introduced when joints are strengthened by various measures. Influence of shapes , spiral hoops and ratio of beam depth to side dimension of square column upon axial compressive capacity of beam-column joints is discussed . Then economy and security of the relative article in current code are demonstrated and the design recommendations of beam-column joints are given.
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