The seismic load resisting system's (SLRS) beam-to-column connections must meet the following requirements:
An interstory drift angle of at least 0.02 radians must be maintained by the link.
At an interstory drift angle of 0.04 radians, the measured flexural resistance of the connection, measured at the column face, must equal at least 0.80Mp of the linked beam.
For the earthquake load impact E, the required shear strength of the connection shall be derived using the following quantity:
The required shear strength must not be more than the shear resulting from the amplified seismic load applied in accordance with the applicable building code.
In plastic hinge zones, abrupt changes in beam flange area are not permitted.
If testing or qualification shows that the resulting design may create stable plastic hinges, drilling of flange holes or trimming of beam flange width is allowed.
Both flanges must be supported laterally in some way, either directly or indirectly. Between the lateral braces, the unbraced length must not exceed 0.17ryE/Fy.
Where research shows that a plastic hinge will form during inelastic deformations of the IMF, lateral braces should be positioned near concentrated loads, changes in cross-section, and other areas.
The required strength of lateral bracing close to plastic hinges is
An interstory drift angle with at minimum 0.04 radians must be maintained by the link.
At an interstory drift angle of 0.04 radians, the observed flexural resistance of the connection, evaluated at the column face, must approximate at minimum 0.80Mp of the linked beam.
For the earthquake load impact E, the required shear strength of the connection shall be derived using the following quantity:
The required panel zone thickness must be calculated using the same approach that was used to measure the panel zone of the verified or preapproved connection.
The necessary shear strength of the panel zone shall be established at a least by adding the predicted moments at the plastic hinge points to the column faces and calculating the total of the moments at the column faces.
Doubler plates must be welded to the column flanges employing a completejoint-penetration groove-welded or fillet-welded joint that creates the whole doubler plate thickness's potential shear strength.
When doubler plates are welded against the column web, the top and bottom edges must be welded together to develop the proportion of total force transmitted to the doubler plate.
When doubler plates are installed away from the column web, they must be symmetrically arranged in pairs and welded to continuity plates in order to develop the proportion of total force transmitted to the doubler plate.
Welds and/or high-strength bolts are required for beam-to-column connections. As seen below, connections can be fully restrained (FR) or partially restrained (PR) moment connections.
The required flexural strength of FR moment connections that are part of the seismic load resisting system (SLRS) shall be equivalent to
3.2. FR Connections Shall Meet the Following Requirements.
Steel backing and tabs must be removed from connections with complete-joint-penetration (CJP) beam flange groove welds, with the exception of top-flange backing joined to the column by a continuous fillet weld on the edge below the CJP groove weld.
Where weld access holes are required, they must be positioned. The surface roughness of the weld access hole must not exceed 500 in. (13 m), and it must be free of notches and gouges.
Notches and gouges must be corrected according to the engineer of record's specifications. In bolted moment end-plate connections, weld access holes in the beam web adjacent to the end-plate are prohibited.
The necessary strength of double-sided partial-joint-penetration groove welds and double-sided fillet welds in connections that withstand tensile forces is 1.1RyFyAg (LRFD) or (1.1/1.5)RyFyAg (ASD) of the connected element or part, as appropriate. To resist tensile stress in the connections, single-sided partial-joint-penetration groove welds and single-sided fillet welds must not be employed.
For FR moment connections, the needed shear strength, Vu or Va, is obtained by multiplying the earthquake load impact E by
When the following conditions are met, PR moment connections are permitted:
such connections must be designed for the requisite strength.
The connection's notional flexural strength, Mn, must be at least 50% of the connected beam or column's Mp, whichever is lower.
The stiffness and strength of the PR moment connections, as well as the effect on overall frame stability, must be considered in the design.
For PR moment connections, Vu or Va should be calculated using the load combination above plus the shear caused by the maximum end moment that the connection can withstand.