Development of High Reliability Steel Structural System Using Structural Joints as Energy Dissipating Elements against Strong Earthquake

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A steel structural system which consists of wide-flange beams and columns connected by using buckling restrained knee brace dampers are proposed. The knee brace dampers are made of low yield strength steel and connected to beams and columns by high-strength bolts. These bolted dampers are intended to produce advantages on the steady quality assurance related to the construction work of the structural joints and the seismic resistance of the frames against strong earthquakes. In order to actualize this system, following investigations were conducted.1) The configuration of joint elements and the buckling restraining method for knee brace dampers are indicated. According to the proposed procedures, the full-scale experimental connections for loading tests are designed and fabricated.2) Loading tests for full-scale beam-column subassemblies of the proposed structural system are conducted. The fundamental mechanical properties, namely, the elastic stiffness of joint elements, the yield limit and the collapse limit of structures are experimentally inspected.3) The effective restraining method against the lateral buckling of a beam which is connected to the columns at the both ends by the knee brace damper system is suggested and its effectiveness are experimentally confirmed. The design procedures for the buckling restraining of the beam is indicated.4) The issues concerned with construction works for the proposed structural system are investigated, namely, the shop fabricating process, the erection at the construction site, the administration of fastening ultra high-strength bolts, the development of an efficient fastening machine.5) The calculating method of the stiffness and the strength of the knee brace damper systems are indicated. An example of a structural design for a 3 story building is shown and the structural performance and the cost for construction are compared with an ordinary moment resisting frame.