Analysis On Negative Effects On Internal Forces And Displacement Of Members Of Frame Structure For Eccentric Beam-Column

Frame structure is a common structural system of multiple-story building and tall building. At present, frame structure is designed based on the condition that the central axis of beam and that of column are the same one. Actually, the central axis of beam and that of column are not the same one for the need of architectural design. Technical specificiation for concrete structures of tall building divided it into two situations: when the eccentricity of beam and column is less than a quarter of the wide of the column,the effects for eccentricity can be ignored; when the eccentricity of beam and column is more than a quarter of the wide of the column,the beam must be haunched and the effects for eccentricity must be considered,but the specificiation didn't specify what negative effects that eccentric beam-column would bring and how to consider it.In view of this situation,the paper builded three models which their eccentricity of beam and column equaled zero,was more than a quarter of the wide of the column and less than a quarter of the wide of the column for haunched beam through structural analysis program for general purpose—SAP2000, analysised their internal forces and displacement under vertical load and their earthquake resistant capability under horizontal earthquake load.By collating and summing up the results of the analysis,the paper concluded that the eccentricity of beam and column will bring negative effects on members especially on column indeed,so the specificiation requirements that the central axis of beam and that of column should be the same one.When they are not the same one,the negative effects must be considered. Haunched beam can reduce the eccentricity of beam and column and has been proved that can improve the performance of bearing load of eccentric beam-column joints by many trials,but when the size of hauched beam is not appropriate,it may bring negative effects to the structure,so the specificiation restricts the size of the hauched beam.In addition,the eccentricity of beam and column can increase the natural period of vibration of structure,so when the frame structure is builed on soft foundation, the eccentricity of beam and column should be avoided in case bringing more negative effects to structure.