§9.2 Beam-to-Column Joints and Connections

Connections in Special moment frames require pre-qualification according to Section 9.2b to achieve the performance requirements of 9.2a. The engineer is referred to commentary on 9.2b which references FEMA350 as a source for several connections that are considered prequalified.

When calculating the shear (Vu) based on 1.2D + 0.5L + 0.2S + 2Mpe/L, all combinations of 1.2D, 0.5L and 0.2S are calculated so as to determine the maximum shear load on the beam from the gravity loads. This is added to the contribution of 2Mpr/L. L is taken as the distance between reduced beam sections, if they exist, otherwise L is the distance between the face of the columns supporting the beams. Mpr is the ultimate strength of the beam in bending at the reduced beam section, if it exists, otherwise it is from the full beam section.

§9.3 Panel-Zone of Beam-to-Column Connections

Only connections parallel to the column web are considered and checked by the program.

The required shear strength of the panel-zone is determined from the summation of moments at the column faces as determined by projecting the expected moments at the plastic hinge locations (RBS if they exist) to the column faces. The material factor φv is taken as 1.0 in all cases.

Pu is taken as the maximum axial load on the column at the joint from all standard provision load combinations.

If the beams frame into the flange of the column at some angle other than parallel to the column web, then the component of the beam force parallel to the column web is used.

Panel Zone shear is calculated as the moment divided by the distance between the center of the beam flanges.

Not that the requirements of §9.3b are irrespective of the magnitude of the panel shear force. The program can consider the use of plug-welds to reduce the required web plate thickness, refer to the Criteria - Joints menu command to select this plug weld option.

§9.4 Beam and Column Limitations

Refer to the requirements of 8.2.

Per table I-8-1 footnote 3, SMF columns will be checked to comply with λps in Table I-8-1 when Equation 9-3 is less than 2.0, else they will be checked against LRFD Table B5.1.

§9.6 Column-Beam Moment Ratio

The calculation of ΣM×pb is determined by summing the projections of the expected beam flexural strength(s).

If the beams frame into the flange of the column at some angle other than parallel to the column web, then the component of the beam force parallel to the column web is used to calculate M×pb

If no reduced beam section is specified on a member than the capacity of the full member is utilized.

For the Exception (if necessary) the design shear strength of a story is calculated as the component of the major axis shear strength, of all the columns in the direction of the column under consideration, added together. All columns, not only those columns of the special moment frame type, are considered.

§9.7 Beam-To-Column Connection Restraint

A column will be assumed to remain elastic only if the ratio from Equation 9-3 is greater than 2.0.

A joint is considered restrained if contained within a deck, is a beam frames into the weak axis of the column, or by the user specifying that the column is braced.

If the user indicates that the minor axis of the joint column is unbraced then the physical bracing (deck or beams) is ignored and the joint is considered unrestrained.

The deck is only considered to brace the joint at the elevation of the top flange of the beams framing into the flanges of the column.

If a beam (not a joist) is determined to frame into the minor axis of the column at the joint, then RAM Frame assumes that the joint is restrained at the elevation of both the top and bottom flanges of the framing beams.

§9.8 Lateral Support of Beams

Beams framing into the side of a lateral girder are assumed to brace both the top and bottom flange of the girder.

Joists framing into the side of a lateral girder are assumed to brace only the top flange of the girder.

If required the engineer can assign user brace points to all lateral beams to meet this provision. The user brace points should represent actual physical bracing to be provided on the constructed beam.