-Which is more appropriate, cracked or uncracked concrete, shall be adopted for concrete as base material during anchor bolt failure checking? Any related Code can be referenced to?
-Any Hilti bolts that are not suitable for use in cracked/uncracked concrete?
Dear Kelly,
Thank you for your enquiry.
When it comes to safety in concrete anchoring, the base material condition with regard to cracks plays a critical role, as according to the Eurocode 2 Part 4 (EN 1992 -4). EN 1992-4 suggested that it is generally conservative to assume that the concrete is cracked over its service life. If uncracked concrete is assumed, verification is required (see 4.7).
The stress in the concrete induced by external loads must be in constant compression status to define it as uncracked concrete. For applications on a compressed wall, pre-stressed concrete may be considered as uncracked, but this must be checked carefully. Moreover, as per EN 1992-4 9.2.2 and D.1 (2), fasteners under seismic conditions or exposed to fire should have a European Technical Product Specification for use in cracked concrete. To establish the base material as uncracked concrete under all circumstances is obviously quite cumbersome, so to stay compliant with the Eurocode we recommend always considering cracked concrete for your concrete anchor fastening design.
Hilti offers a wide range of anchors that perform extremely well in cracked conditions (e.g. HST3-R,HUS4, HIT-HY 200-R, RE500V3). Generally, you can easily check in the Hilti online, Hilti Anchor Fastening manual or the ETA document of the anchor system whether the anchor is suitable for cracked concrete.
Regards,
Ron Siu
Technical Engineer