We have a project where the contractor already cut the bolts flush with the top of the nuts without approval from the EOR (me). The steel baseplate has oversized holes. The contractor has proposed using a serrated hex flange nut and washer. We are concerned that these nuts will still pull thru the bolt holes.
The project has been installed with 3/8" diameter Hilti TZ anchor bolts & the steel baseplate has 3/4" diameter bolt holes. The application is the base of a pedestrian handrail. The city has asked that the loading is applied at the top of the fence line. So, the anchors need to be designed for a 200# live load applied at an elevation of 6'-0".
We are looking for a solution. EOR (me) has recommended reviewing with Hilti if a lower profile nut would work with the Hilti TZ anchor. The anchors are already installed, so if they loosen the current nuts and reinstall with new nuts, will the bolts still have adequate capacity? Aside from requiring pull-out testing, what would Hilti recommend to confirm that these anchors will have adequate capacity.
Hi Mark,
Unfortunately, Hilti only has supportive testing for the HIT-Z rod with the included nut and washer. Additionally, Hilti has only tested a fixture hole size up to 1/2" for a 3/8" HIT-Z rod, per Table 1 of Section 3.2.2 in the Anchor Fastening Technical Guide. Therefore, the decision to use an alternate nut and washer will ultimately be up to your engineering judgement.
For additional assistance, please reach out to hnatechnicalservices@hilti.com or give us a call at 877-749-6337.
Regards,
Matthew