Experimental Study On Seismic Performances And Preliminary Study On Design Method Of Steel Reinforced Concrete Beam Transfer Structure With Energy Dissipation Haunch Brace

To meet the multifunctional requirements of high-rise buildings, more and more transfer structures are adopted in high-rise buildings, and become one developing trend of high-rise buildings. However, deformation concentration and energy accumulation at transfer storey more likely occur in transfer structures, and damage may easily be induced by earthquake excitations. To improve the poor seismic behaviors of transfer structures, steel reinforced concrete beam (SRCB) transfer structure with energy dissipation haunch brace (EDHB) was proposed in this dissertation. In the paper, low frequency cyclic loading tests was adopted to study the seismic behaviors of SRCB transfer structure with EDHB, and numerical analysis method was performed to study the influences of different design parameters on performances of the new type of transfer structure. Finally, the design method of SRCB transfer structure with EDHB is established based on the ductility concept. The main works and conclusions are as follow:(1) Normal SRCB transfer structure, Normal SRCB transfer structure retrofitted with EDHB and SRCB transfer structure with EDHB were tested by using low frequency cyclic loading experimental method. Seismic behaviors such as failure modes, load-displacement curves, structural ductility, strength and stiffness degradation and energy dissipation of the three specimens were studied. Results show that the cracks at the end of the beam can be effectively controlled by adding EDHB, the formation and development of the plastic hinges at the ends of the transfer beam and on the top of the CFST column can be delayed and controlled, the structural stiffness, strength and energy-dissipating capacity are greatly enhanced, and the stiffness degradation of the structure can be mitigated. Tests results prove that adding EDHB in the transfer structure is an effective way to retrofit and improve the seismic behaviors of the transfer structure.(2) Based on the experimental researches, numerical simulation analysis is carried out to study the influences of parameters, axial compression ratio of frame columns and columns supported by the transfer beam, arrangement of EDHB, stiffness ratio of EDHB to beam ( K_h~C) and linear stiffness ratio of transfer beam to column ( K_b~C), on the seismic behaviors of the SRCB structure with EDHB. Results show-that the seismic behaviors of the tramsDr structure can be more obviouslyimproved by adding EDHB when the axial compression ratios of frame columns andcolumns supported by the transfer beam are relative large By summarizing the resultsofthe structural responses,internal forces and the deformation and energy dissipationof the haunch braces,the optimization values of the design parameters of EDHB arethat (E|'),the haunch brace angle(T)should be between 30 to 45 degree,thedistance(α)from the haunch tip to the beam end be kept L_b/6-L_b/5,and K_h~C bebetween 0 2to 0 45(3) A simplified calculation model of the SRCB transfer structure with EDHB is established. Formulas of the internal forces at the controlled cross sections and the relations between the deformation of the haunch braces and storey displacement are derived by the theoretical analysis method. A design method based on the ductility concept of"strong column-weak beam","strong shear-weak bending"and"strong joint-weak members"is established using the formulas, which can be the theoretical references for the design of the new type of transfer structure.