Seismic Performance Research On Haunch Connection Of Steel Frame Middle Column And Beam

As one type of improved strengthen connection,the haunch connection strengthen beam section by haunch in the local position,which make plastic hinge move from the beam-column connection to protect connection weld.The beam with haunch only on bottom flange is convenient for concrete floor construction.The seismic performance research on haunch connection of steel frame middle column and beam had been conducted by theoretical analysis,experimental study and numerical analysis.On the basis of analyzing the calculation model of haunch connection,the force analysis of beam with haunch connection is carried through to research the?value’s influence on mechanical property of haunch connection;Combining American design specification with Chinese design specification,the design procedure for welded haunch connection is concluded,and the differences in design between two countries are summarized.By theoretical calculation,the influence of main parameters including haunch length,haunch height and beam span and so onto for the mechanical property of haunch connection are gained.The results show that with the increase of the value of?,the beam moment at column face becomes smaller,which will be better to protect the beam form brittle fracture.But if?is larger than one,beam web shear in the haunch region and haunch flange shear will increase.The value of?is more close to one but should be less than two.With the increase of haunch length,The value of?and?_min became smaller;The top and bottom beam flange groove weld stressf_{w t},f_wb reduce gradually;The haunch flange required minimum sectional area,haunch flange axial stress and haunch web shear stress increase gradually.When haunch height is invariant,the reasonable haunch length should be near the middle range of（0.5-0.6）times of the high beam.The reasonable haunch flange section area should make?close to?_min,such materials are made full use.With the increase of haunch height,The value of?_min and?increases gradually;The top beam flange groove weld stress,haunch flange required minimum sectional area,haunch flange axial force gradually reduce;The bottom beam flange groove weld stress and haunch web shear stress increase.When haunch length is unchanged,it is more reasonable to properly increase haunch height.With the increase of the beam span,the value of?_min and?is larger;The top and bottom beam flange groove weld stress,haunch flange axial force,haunch web shear stress decreases.In order to research on the seismic performance of haunch connection,the low cyclic loading tests have been carried out to the four specimens designed according to the proportion of 1:2,which three specimens with only bottom haunch and one with bottom haunch and top flange with steel concrete composite floor slab.The haunch dimension parameters and the floor slab on the influence of seismic performance of haunch connection have been researched through experiment.The results show that the plastic hinge of haunch connection occurs on the place from the haunch end about the range of 1/3 times of beam height;the hysteresis curves of haunch connection are relatively full and the haunch connection has good seismic performance.The plastic angle and total corner are higher than the minimum value of which has good seismic performance.The plastic deformation capability is good.The bearing capacity of specimens with floor slab is better than that of without floor slab,but deformation capacity and energy dissipation is less.On the basis of theoretical analysis and experimental research,ANSYS numerical analysis is used to study the bearing capacity,stress distribution,the law of plastic hinge formation,ductility,energy dissipation,hysteresis properties,etc about the asymmetric haunch connection under low cycle load.The influences of node parameters（height,length,beam span）on the seismic performance of asymmetric haunch connection are systematically studied.The reasonable size range for haunch connection parameters is gained.The haunch length takes（0.54-0.58）times of beam height,the haunch angle should be close to the 300 or so.The seismic performance of asymmetric haunch connection meeting the design requirements is optimal when beam span-depth ratio is around 12.Also the influence of different nodes types for seismic performance of haunch connection have been researched.the connections of top flange with plate reinforcement and bottom flange with haunch are designed,which are contrasted with connections of only bottom flange with haunch and connections of top flange with cover plate and bottom flange with haunch.The results show that the three kinds of haunch connection move the plastic hinge outward from the beam-column interface,the plastic hinge occurred the place from the haunch end about 1/4-1/3 times of beam height and the seismic performance is good.The bearing capacity of haunch connection with the flange cover plate is largest,the connection with haunch only on bottom flange is second and the connection with plate reinforcement on top flange is least.Finally,on the basis of systematic analysis,the current design formula is revised which the position of plastic hinge takes 1/3h_b.