Design Rules of Moment Connections
Symbols
Cpr: Stiffening in the joint, etc. a coefficient that takes into account the circumstances and is used to calculate the maximum possible bending moment strength
Fu: Structural steel characteristic tensile strength
Fy: Characteristic yield stress in structural steel
lh: The distance of possible plastic hinge point at the beam ends to the column face
ln: Beam span between possible plastic hinge points at the beam ends
Mpr: Possible bending moment capacity
Mpri: Possible bending moment capacity at the left end i of the beam
Mprj: Possible bending moment capacity at the right end j of the beam
Muc: Required bending moment strength of the joint at the face of the column
Ry: ratio of possible yield stress to characteristic yield stress
Vd: Simple beam shear force arising from vertical loads at the plastic hinge point of the beam.
Vuc: Required shear strength of the joint at the face of the column
Design Acceptance
Moment connections are rigid and full / partial restarined joints.
For rigid joints, end plate, bolted flange plate and welded moment connections are classified according to rotational rigidity and rotational stiffness ratios are defined in the earthquake code depending on the ductility level.
General Design Rules for End Plate Connections
The strength of end plate joint is determined by the assumption that the tensile force of the bolts in one flange is controlled by rupture limit state under compressive force in the other.
If there is no axial load on the joint, total tensile and compressive forces are equal and opposite in both flange, so that total force creates a force pair.
It is accepted that the center of rotation is in the center of compression flange.
Column / Beam Splice Connections Design Rules
In order to be suitable for design with reversible forces such as seismic forces, symmetrical and equal number of bolts are used on both flanges and web. ideCAD does not allow asymmetrical structure during modeling.
While it is assumed that flanges carry the moment effect and web carries shear force, the axial force is equally shared between both flanges.
AISC 358-16 Design Acceptance
Depending on the ductility level, the joints that are determined to provide a relative angle of translation of at least 0.04 or 0.02 radians should be used. End plate joints and flange plate joints are designed in ideCAD Structural.
The required bending moment strength Mu and the required shear strength Vu on the column face of the joints are calculated over the plastic joints at the end of the beam. The formulas in the image below are used in the design.
The Vu used in the dimensioning of the joint is determined according to the equation in the above image by summing the shear force determined on the basis of the yield state and the shear force calculated from the combination of 1.2G + 0.5Q + 0.2S on the plastic joint at the end of the beam.
Plastic joint length is specified separately for each joint in AISC 341-16 and automatic calculation is made in accordance with these rules. Details will be given in each respective combination.
The shear strength required for the shear zone is calculated by using the column shear force generated by possible plastic moments of beams connecting to the column.
Next Topic