Is there any guidance or recommendation for using HY-200A adhesive for post installed anchorage of a structural supporting member that will be anchored to a large concrete pedestal that supports in service rotating equipment and creates some vibration within the pedestal?
Hi Shane,
Thank you for reaching out.
There are currently no test standards for dynamic loading of post-installed anchors in North America. However, simplified methods have been developed in Europe to support the evaluation of an anchor's resistance to fatigue; specifically adhesive anchoring systems such as Hilti's HIT-RE 500 V3 and HIT-HY 200 A/R V3 used with threaded rods.
Design Considerations
The design premise is that in a high-cycle fatigue application with 2,000,000 cycles, you would perform an ACI 318-19 Ch. 17 static anchor design with the following considerations:
- The strength of the carbon steel rod in steel failure is reduced to 25% of the static capacity.
- For stainless steel anchors, there is no clear fatigue limit. If the number of cycles considered does not exceed 2 million, this approach is conservative for stainless steel; otherwise, a further reduced steel capacity may need to be considered, depending on the specific material properties.
- The concrete strength is reduced to 55% of the capacity
- For core-drilled hole without use of a roughening tool for HIT-RE 500 V3 applications, this would be reduced further to 40%.
- The bond strength is reduced to 55% of the capacity
- For core-drilled hole without use of a roughening tool for HIT-RE 500 V3 applications, this would be reduced further to 40%.
In PROFIS Engineering, the design would need to be such that the static utilization does not exceed 25% for the carbon steel rod and 55% for concrete or bond failure modes (40% for cored holes).
Additional Considerations
The following items can help reduce the fatigue forces into the anchor and help to distribute those forces:
- Making sure that the anchor is installed with the published installation torque to increase the pre-stress force and help distribute some of the fatigue forces into the fixture and concrete. Installing the anchor with the correct Tinst, and then periodically inspecting the nut and washer throughout the service life of the anchorage, can help reduce the potential of overstressing the bolt from fatigue stress. Additionally, the use of the proper Tinst and pre-stress forces help with group anchorages. In a group, if some anchors are “tighter” than the others, the fatigue forces will be distributed unequally which may reduce the steel capacity of the “looser” anchors.
- After the provided nut and washer are installed with the correct Tinst , providing a lock nut on top may reduce the potential of the nut and washer coming loose.
- The anchor should be installed no more than 3% from perpendicular to the fixture to make sure that the nut and washer are bearing fully so they do not induce a higher stress into the rod. Installing at angle also increases the bending forces in the bolt which will reduce the steel capacity over time (even less than 25% of the static capacity). Additionally, installing at an angle will not permit the proper clamping of the nut and washer. Even if the nut has the proper Tinst applied, the pre-stress force may not be distributed evenly, which may reduce the steel capacity.
- For anchor groups, the proper Tinst is needed for load distribution in between the anchors. For equal load distribution in shear, it is recommended that the adhesive is injected after the steel fixture has been placed on the concrete surface; this is also referred to as a through-set anchor installation. Under this practice, the adhesive will fill up the annular gap in between the rod and the concrete (for bonding) when the rod is inserted, and it should also fill up the annular space in between the rod and the fixture. This will support the equal distribution between all of the anchors in shear as all of the anchors should be bearing against the fixture at the same time regardless of the direction that the shear forces are applied.
In the end, since these studies and tests were not performed in North America, it will be left to engineering judgement to determine if this is applicable to the design/project.
Regards,
Kevin