Study On Seismic Behavior And Design Method Of Replaceable Steel Coupling Beam

The energy dissipation of the coupling beam directly affects the safety of the whole structure.At present,high-rise building shear wall structure usually use reinforced concrete coupling beams,however,a large number of tests and post-earthquake observations show that reinforced concrete coupling beams always occur shear failure,its strength and stiffness retrograde seriously,energy dissipation capacity is poor.The deformation and energy dissipation capacity of steel beams is much better than that of reinforced concrete coupling beams.Using steel beams instead of ordinary reinforced concrete coupling beams,composing mixed joint shear wall structure,has become an ideal form of structure.However,the node area of steel beam and shear wall is often seriously damaged,affecting the mechanical performance of wall limbs,and difficult to repair after the earthquake.Therefore,domestic and foreign scholars put forward the concept of replaceable steel coupling beam,that is dividing the steel coupling beam into three sections: two ends of the steel coupling beam and the weakened mid-span,they are connected with bolted splice plates or end plates.Replaceable steel coupling beams focus breakage on the middle weakened segment,it is convenient and cost-effective because we only need to replace the middle section after earthquake.In order to make the replaceable steel beam safe and reliable and has good seismic performance,the main work of this paper is:(1)Using the finite element analysis software ABAQUS to simulate the existing test data,by the comparison of the hysteresis curve,skeleton curve,energy dissipation index and stress cloud diagram obtained by the experimental and finite element simulation,the scientific and effective of finite element modeling are verified.(2)Established four finite element models with different mid-span web thickness,studied the influence of the mid-span web thickness on the bearing capacity,ductility and energy dissipation capability of replaceable steel coupling beam.With the increase of the thickness of the web in the middle weakened section,the ultimate bearing capacity of the replaceable steel beam is gradually increased,but the increase rate tends to be gentle;Both ductility coefficient and energy dissipation coefficient improve with the increase of the thickness of the mid-span web,when the mid-span web thickness increases to a certain extent,the ductility coefficient and energy dissipation coefficient slightly decline;When the web thickness ratio increases to 0.7,the damage occurs on the flange of the beam end,does not concentrate on the mid-span.Considering the influence of the web thickness of the replaceable section on the seismic performance of the beam,the best web thickness ratio is 0.5 ~ 0.6.(3)Established six finite element models with different mid-span length,studied the influence of the mid-span length on the bearing capacity,ductility and energy dissipation capability of replaceable steel coupling beam.With the increase of the mid-span length,the bearing capacity of the replaceable steel beam gradually decreases,When the length-span ratio is between 0.35~0.55,the bearing capacity reduces scarcely;The energy dissipation coefficient increases first and then decreases,when the length-span ratio is between 0.39~0.55,the energy dissipation capacity is better;Considering the replacement of length-span ratio on the seismic performance of the coupling beams,the most suitable length-span ratio is 0.39~0.55.(4)Concisely introduced the principle of seismic design of replaceable steel coupling beam,and on the basis of finite element analysis,the formula of shear calculation of ordinary I-beam in the specification is modified,and the formula for calculating the shear capacity of replaceable steel beams with mid-span is given.