Flexural Mechanism And Theoretical Model Of Reverse Channel Prefabricated Connections Between Square Tubular Column And H- Shaped Beam

With development of structural industrialization,the requirement of steel structure assembly get improved.Square tubular columns have great mechanical property.But square tubular column is close section,it is difficult to connect it with H-shaped beam by high-strength bolt,which limits the application of square tubular column in fabricated structures.In view of the problem,horizontal reverse channel fabricated connections were proposed on the basis of vertical reverse channel connections,which is a connection welded two horizontal reverse channels on column to fabricate with beam.Experiment and numerical and theoretical method was used to analysis the flexural property of connections.The bending mechanism of the reverse channel connections were discussed.Theoretical model and design method of reverse channel connections was established.Research contents and conclusions are as follows.（1）In-plane bending experiments of four different reverse channel connections were tested.Flexural property of vertical reverse channel connections and horizontal reverse channel connections were compared.The results indicate the following conclusions.Compared with the Test-V,the flexural capacity of Test-IS increased by50%,the ductility increased by 13%,but the initial stiffness reduced by 22%.The flexural capacity of Test-US and Test-MS is lower than that of Test-IS,but the rotation capacity of Test-US and Test-MS is greater.The moment have not decreased until the rotation reached 0.12.（2）Finite element model of reverse channel connections were established.And parametric analysis was conducted.The failure model and influencing factors were reached.The results indicate that t_ch2/t_b0 is the main influencing factor for different failure models.With the change of tch2/tb0,two failure models appeared for each kinds of reverse channel connections,witch are synergistic and independent out-of-plane bending appeared on the flange of channel and beam end-plate for each kinds of reverse channel connections.And for IS-RCC,the failure model of independent out-of-plane bending for beam end-plate was also appeared.In addition,when the hb/lb,hch/bch and tch2/tch1 is so large,the shear failure will occur on channel.Define ratio of the rotation of the beam and the joint as the shear effect coefficientγ.And the influence of shear failure in channel can be ignored when theγis larger than 0.85.（3）The influence for flexural capacity of geometric parameters were researched.Bending capacity of different reverse channel connections were compared by finite element analysis.The results indicate that t_ch2 and t_b0 is the key factor for each kinds of reverse channel connections.The rate of change of flexural capacity and initial stiffness can reach 40%.For US-RCC and MS-RCC,the bch and tch1 is also main factors.The rate of change of flexural capacity and initial stiffness can reach 15%.In addition,when shear failure of channel can be ignored,the flexural capacity of US-RCC and MS-RCC is similar.When shear failure can not be ignored,the flexural capacity can increased by40%.Otherwise,the flexural capacity and initial stiffness of IS-RCC is 2 to 3 times larger than MS-RCC.IS-RCC can be designed as semi-rigid connections.And MS-RCC can be designed as simple connections.（4）The bending mechanism of the reverse channel connections were discussed.Research indicates that the bending mechanism of US-RCC and MS-RCC is decided by channel and beam end-plate.The force state of the channel is the same as that of the rigid frame.The force state of beam end-plate is out-plane bending.The bending mechanism of IS-RCC is decided by channel web and beam end-plate under tension.The force state of channel web and beam end-plate is out-plane bending.The plastic line of channel web is same as beam inner end-plate.（5）Flexural capacity and initial stiffness calculation model of reverse channel connections was established by component method.Channel tension component,channel compression component and shearing component,channel web tension component,channel stiffening compression component and tension component,beam end-plate component and column web component were established.The calculation model of connections were verified by finite element results.The average error of the flexural capacity calculation result for US-RCC and MS-RCC is about 5%.The average error of the initial stiffness calculation result for US-RCC and MS-RCC is about 10%.The average error of the flexural capacity calculation result for IS-RCC is about 15%.The average error of the initial stiffness calculation result for IS-RCC is about 5%.（6）The design method of reverse channel connections was proposed.The US-RCC and MS-RCC can be designed as simple joints.Design formula of initial stiffness and rotation capacity were simplified.For common narrow flange beam,the connection is suit for the beam with high span ratio smaller than 25.The IS-RCC can be designed as semi-rigid joint.The bending capacity calculation formula was simplified.And the results of the design formula are fit well.