analytical study on reduce beam section connection by tubular accordion web

the basic strategy of reduce the ductility demand and related concentrated tensions at moment resistance connections is reduce the section of the beam at connected region to column. by this method plastic hinge done at the reduced cross section and this local reduction decreases the demand of the components of connection. on this basis, in present study a new beam-to-column moment connection with reduced beam section using tubular accordion web that called taw-rbs is studied analytically. the results show that taw-rbs create a ductile fuse away from beam-to-column connection components, through removing web from beam flexural capacity. reduction of beam flexural capacity in the plastic hinge is calculated based on the dimensions of beam and tube. so bending strength of the remaining tubular web would be proportional with square of the thickness of tube and inversely related with the thickness of flat web and the diameter of tube. the optimal location of the tubular web is determined due to the length of beam and the plastic modulus ratio at the plastic hinge to the total cross section.  also shear control at tubular web according to local and global shear buckling are other points of this study. the results show that taw-rbs reduces flexural stiffness about 14 to 19% in the plastic hinge locations that is equal with the rbs20%. also the proposed connection, depending on the size of the beam, reduces bending strength between 22 to 28% in the plastic hinge location that is intermediate between rbs20% and rbs50%.