Importance of Grout in Baseplate Design
How much consideration do you give to the type of grout used for your baseplates? Do you stop short after specifying a given compressive strength, or do you consider the stiffness of the grout mix design? Do you ensure the grout is placed well in the field, according to your construction documents?
In the June 2022 SEU session, Barry Arnold, PE, SE, from ARW Engineers, presented Baseplates, Embeds, and Disasters, Oh My! Barry explained the design parameters that affect the performance of baseplates and embeds and showed how even small changes to the design parameters can have huge impacts on the performance of, and the stresses in, anchor rods, baseplates, columns and gusset plates.
Barry noted that the column base connection detail is one of the most important elements in steel structures. The code requires that “the designer should use caution and good judgment… for this very important class of connection.” Designers often use software to model these connections which requires the input of a spring constant, k, for the grout beneath the baseplate. To hear Barry explain the importance of using an accurate spring constant, watch this short 3 minute video:
Also, Barry stressed the importance of the placement and performance of the grout beneath the column base plate, and noted that this item is often overlooked considering how critical it is to the column base connection. Grout beds are notoriously littered with debris and large voids. As you can see in this slide, Barry suggested this important action item be added to your special inspection schedule, given the critical role the grout plays in the performance of your lateral load bearing columns to prevent situations such as the one shown on the slide.
Using an incorrect spring constant value or poor grout installation could cause unintended stresses to develop which could lead to disaster down the road. Paying closer attention to the grout properties and installation are critical to achieving a connection that performs the way the designer intends.