We are looking to install some new beam seats in an existing columns. Loads are too high for CSA Annex D with any type of adhesive or mechanical anchors. We're looking at through-bolting but I found the CSA to be silent on this. The ACI Chapter 17 (similar to CSA Annex D) does mention that multiple through-bolts connected to a single plate are not to be designed with the anchorage provisions but does not provide any additional information on procedures. Have you seen this detail successfully achieved with your product? Do you have any documents to help with the design of such connection?
Hi JD,
If your application is anchoring all the way through the column than Hilti does not have testing to support adhesive anchors in a through bolting situation. The published values do assume a minimum concrete thickness with sufficient concrete at the back of the hole.
However, here are some tips that may be helpful with installation. First, it is important that the hole is cleaned thoroughly through some combination of flushing or blowing with compressed air, and brushing with a wire brush that is the same tolerance as the drilled hole. Next, it is important to create some mechanism that will not allow the epoxy to flow from the bottom of the hole when the rod is inserted. This is commonly done by drilling a slightly larger tolerance hole than the anchor rod through a piece of plywood and filling the hole with a filler foam (such as Hilti CF 810). This will essentially create a “bottom” of the hole when injecting the epoxy. So once that form is set up, you will fill the hole with the epoxy. Depending on the depth and width of the hole, using an extension tube with piston plug may be wise in order to remove the possibility of having air voids entrapped in the epoxy. Once the hole is filled (typically 2/3 the depth of the hole), the rod can be inserted. Prior to insertion, the end of the rod should be taped to prevent the epoxy from bonding to the threads where the plate, nut, and washer will later go. As the rod is being inserted, it should pierce the foam material at the “bottom” of the hole. Excess epoxy can be wiped or scrapped prior to gel time, but the form should remain attached to the concrete during the full cure time of the adhesive.
If you have any other questions please contact us at CA.EngineeringTechnicalServices@hilti.com .
Do you have any design procedures you can suggest for such a situation? Design shear capacity of through-bolt anchors in a concrete column with close edge distances.