In this post, we follow up on our April 17 webinar, Meeting Braced-Wall Requirements: A New Portal Frame Solution, by answering some of the interesting questions raised by attendees.
During the webinar, we discussed how the Strong-Wall site-built portal frame system (PFS) provides designers, builders and contractors in prescriptive jurisdictions with a new alternative to IRC wall-bracing methods. In case you weren’t able to join our discussion, you can watch the on-demand webinar and earn PDHs and CEUs here. Continue Reading
This blog was co-written for the webinar by Curt Haselton, Ph.D., P.E., Founder and CEO Haselton Baker Risk Group and Jeff Ellis, P.E., S.E., SECB, Director of Codes and Compliance at Simpson Strong-Tie. Continue Reading
This year the NASCC (North American Steel Construction Conference) will be in Baltimore, Maryland. The conference is the annual educational and networking event for the structural steel industry, which attracts attendees and exhibitors from all over the world. With more than 130 sessions this year, the conference will provide attendees the opportunity to learn the latest in research, design, technology and best practice in the steel industry. Continue Reading
The April SE blog article, What Makes Strong Frame® Special Moment Frames So Special, explained the features and benefits of the Yield-Link® structural fuse design for the Strong Frame® special moment frame (SMF) connection. In this blog, I will be introducing the Yield-Link end-plate link (EPL) to the Strong Frame connection family.
What is the EPL? The EPL connection (Figure 1) is the latest addition to the Strong Frame Strong Moment Frame (SMF) solution. The new EPL connection can accommodate a W8X beam which is approximately a 33% reduction in beam depth from a W12X beam. The frame is field bolted without the need for field welding which means a faster installation. The snug-tight bolt installation requirement means no special tools are required. The EPL SMF connection has the same benefit of not requiring any additional beam bracing as the T-Stub connection. The frame can be repaired after a large earthquake by replacing the Yield-Link connection. Since the shear tab bolts will be factory installed, installation time for the frame is reduced by 25% making the EPL connection one of the most straightforward connections to assemble.
Figure 1: New Yield-Link EPL connection
Why Did We Develop the EPL? The development of the EPL came from strong interest and numerous requests to offer a solution with more head room for clearance of retrofit projects or enhancement for new construction using a shallower beam profile. The original T-stub link design has the shear tab welded to the column flange. The geometry of the shear tab meant that a W12X beam is required to accommodate the Yield-Link Flange. In Figure 2, you can see that a shallower beam profile will bring the Yield-Link flange closer to each other and limit the attachment of the shear tab. A new connection was needed.
Figure 2: Yield-Link flange interference with shear tabFigure 3: 3 Bolt configuration with notched flange plate. (The 3rd bolt is on opposite side of beam.) The asymmetric layout produced uneven force distribution in the bolts.
How Did We Develop the EPL? Multiple configurations were studied, including a notched flange plate with 3 bolts (Figure 3) to avoid interference with the shear tab connection to the column. In the end, a compact end plate link combining the shear tab and Yield-Link stem in a single connection was the final design. However, many questions loomed over the prototype. How will the single end plate design perform in a full scale test? Will the new configuration change the limit state? These questions needed to be studied prior to launching an expensive full-scale test program with multiple samples and configurations. Numerous Finite Element Analysis (FEA) models were studied and refined prior to full scale testing of a prototype. Modeling included ensuring the stem performs as a fuse (Figure 4) as discussed in the April blog and the integrity of the shear tab is maintained in the compact design. Figure 5 shows a graph comparing the analytical model to the actual full scale test. The full scale test with a complete beam and column assembly was performed to the requirements under AISC 341 Section K. The full scale test passed the requirements for the SMF classification as can be seen in Figure 6 for the specimen with 6-inch columns and 9-inch beam.
Figure 4: Equivalent Plastic Strain Plot of Yielding-Link StemFigure 5: Full Scale Test vs. Analytical modelFigure 6: Moment at Face of Column vs. Story Drift
Where Can I Get More Information? The EPL is now recognized in the ICC-ES ESR-2802 code report as an SMF. EPL solutions are also offered in the Strong Frame Moment Frame Selector Software. Want to see how the new connection and member sizes can expand your design options? Visit www.strongtie.com to download the new Strong Frame Design Guide or contact your Simpson representative for more information.
