E1-Ordinary Moment Frames (OMF)

Basis of Design

OMF are expected to provide minimal inelastic deformation capacity in their members and connections.

Member Requirements

Width-to-thickness ratios of members for OMF are no limitations. Also, stability bracing of beams or joints in OMF is no requirenements. Structural steel beams in OMF are permitted to be composite with a reinforced concrete slab to resist gravity loads.

According to AISC 341-16, width-to-thickness ratios and stability bracing of beams or joints do not controlled by programme.

Connections

There are two type of beam-to-column connections as fully restrained (FR) and partially restrained (PR) moment connections.

FR. Moment Connections

FR moment connections should provide at least one of the followings:
(a) FR moment connections are designed for a required flexural strength that determines 1.1R_yM_p, and divided by α_s, where α_s = LRFD-ASD force level adjustment factor = 1.0 for LRFD and 1.5 for ASD.
The required shear strength of the connection, V_u or V_a, is determined using the equation E1-1. The capacity-limited horizontal seismic load effect, E_cl,

(b) FR moment connections are designed for a required flexural strength and a required shear strength. They’re equal to the maximum moment and corresponding shear that can be transferred to the connection by the system, including the effects of R_y.
The bending moment used to control for continuity plates is 1.1R_yM_n/α_s or the maximum moment that can be transferred to the connection by the system.

PR. Moment Connections

PR moment connections should provide the followings:
(a) Connections are designed for the maximum moment and shear from the applicable load combinations
(c) The nominal flexural strength of the connection, M_n,PR, is no less than 50% of M_p of the connected beam.(d) V_u or V_a, as applicable, are determined per Section E1.6b(a) with M_p in Equation E1-1 taken as M_n,PR.