According to the AISC 341-10 Section E3.5.c, the region at each end of the beam subjected to inelastic straining (plastic hinge formation) shall be designated as a Protected Zone. Each prequalified moment connection in AISC 358-16 has its own section on what is considered a Protected Zone. Figure 1 shows the requirements from the Los Angeles Department of Building and Safety (LADBS). A clear marking denoting the protected zone is required, as well as a sign prohibiting penetrations and welds to this zone as it would negatively affect the performance of the moment connection. AISC Code of Standard Practice for Steel Buildings and Bridges (ANSI / AISC 303-16) also has a similar requirement where the Fabricator shall permanently mark the protected zones designated in accordance with AISC 341. If markings are obscured in the eld after application of re protection, then it shall be re-marked.
Figure 2 shows the protected zone for an RBS connection, and Figure 3 shows the protected zone for a bolted flange plate moment connection. As can be seen in these examples, the protected zone encompasses the beam flange and the beam web, because this is the location where the expected inelastic deformation will occur. This means that during construction, the owner’s designated construction representative will have to confirm with the Mechanical, Electrical and Plumbing (MEP) trades that no penetrations will be made through the beam web at these locations. In addition, someone will have to physically mark these locations on each moment connection, as seen in Figures 4 and 5.
Figure 1 — LADBS Protected Zone Marking Requirements
Figure 2 — Protected Zone for an RBS Moment Connection
Figure 3 — Protected Zone for a Bolted Flange Plate Moment Connection
Figure 4 — Protected Zone Marking for an RBS Connection in the Field
Figure 5 — Protected Zone Marking for an RBS Connection in the Field (Sprayed on Top of Fire Proofing)
Figure 1 (below) shows the protected zone for the Strong Frame SMF connection. Since the beam is not the yielding element, the protected zone only includes the elements in contact with the link at the beam flanges and shear tab at the beam web.
(a) T-Stub Links
(b) End-Plate Links
Figure 1 — Protected Zone for Strong Frame SMF Connection