We thought we would start off the new year with a series of Structural Engineering 101 emails about a relatively new type of patented moment connection that has become popular on the east coast. A significant portion of our work requires we use moment frames. Many of our clients (hospitals in particular) would like to have unobstructed space when they renovate so moment frames are an obvious solution for multi-story buildings.
A BRIEF HISTORY
The SidePlate® connection was the early 1990s' brain child of California engineer, David L Houghton, SE, in response to concerns about the seismic performance of the traditional fully welded beam/column moment connection. Forensic investigations of failed connections following the 1994 Northridge earthquake revealed unexpected failure modes due to significant stress concentrations at the beam column interface all of which were highly sensitive to workmanship in the field (part of the reason we now have such stringent special inspection requirements). The geometry of the pre-1994 connection made it difficult to weld without large defects.
The popular pre-1994 moment connection was basically a traditional fully welded moment connection with some special detailing requirements. Due to the high seismicity out west, member sizes get very large quickly and welding the beam flanges to the column flanges gets more complicated and time consuming.
Mr. Houghton developed a new type of connection that eliminated many of the failure modes from the pre-1994 connection, moved the majority of welding back into the controlled environment of the fabricator's shop and reduced the field welding requirements to fillet welds in lieu of the more time consuming full penetration welds. The use of field fillet welds dramatically improved erection time. One of our projects saw a 2-3 week improvement in the contractor's estimated schedule for a typical moment framed building.
Over the next few emails, we'll introduce you to both the welded and bolted SidePlate connections and when each is appropriate, discuss why we model the connections in our models particularly when they aren't really an interference for other construction and how the design and licensing process works.
A LITTLE TRIVIA
BTW, a little piece of trivia - FEG was fortunate enough to be in the right place at the right time and designed the first SidePlate Bolted™ building that was constructed on the planet.