Simpson Strong-Tie offers fixed-base frame design. Moment frame performance differences between pinned column bases and fixed column bases were discussed previously in Section D7. In order to have a fixed-base connection, footing design needs to account for the added moment as well as the stiffness required to perform as a fixed base. Currently Simpson Strong-Tie uses the embedded column base approach (see Figure 1), similar to design Example 4.4.4 in the AISC Seismic Design Manual (2nd Edition). Consult with Simpson Strong-Tie for available non-embedded options. By designing the column as a fixed base, designers should be aware that the fixed-base connection will be stiffer than beam-to-column moment connections, and yielding may occur at the base of the column. Once plastic hinges are formed at the column base, the frame will behave as a pinned-base frame.
Currently Simpson Strong-Tie offers a pinned-column-base design minimizing moment transfer at the base of the column by utilizing base plates with anchor rods closely spaced to the column center line. However, there is still some moment resistance at the column base attributable to the moment couple formed by the anchor rods in tension and compression at the edge of the base plates. Because of the desire to know the true ultimate capacity of the moment frames when using the FEMA P-807 guideline for retrofit, Simpson Strong-Tie also offers a single-bolt pinned-base solution for soft-story retrofit projects (see Figure 2). The Designer will need to indicate on their structural plans if a single-bolt pinned-base solution is desired.
Designers can coordinate with Simpson Strong-Tie if column splices are required to facilitate erection. Column splice solutions offered by Simpson Strong-Tie are all field bolted. DTI washers are provided with the connection kit (see Figure 3).
Currently we offer a set number of link types for production reasons. However, if the Designer has a need for links to be designed specifically for projects using our AISC 358-16 Chapter 12 procedure, we can fabricate design-built links as needed by the Designer.
The Weak Story Tool with Simpson Strong-Tie Strong Frame Moment Frames can provide pushover (load vs. deflection) curves for one-story, one-bay frames. If pushover curves are required for other configurations, Simpson Strong-Tie can provide these at the request of the Designer.