How to interpret seismic approval for anchors

approval anchors to seismic - What Does It Mean and What Not?

Seismic approval for anchors — what it means, and what it does not

In recent years the demand for seismic approval of anchors has grown across a wide range of projects. But what exactly is this approval? What does it actually mean, and how should it be used correctly?

What the approval is — and what it is not

A “seismic approval” for a given anchor certifies that the manufacturer paid an accredited laboratory to test that anchor according to the procedure set out in the European standard ETAG Annex E for seismic design. It does not mean the anchor is “good” for seismic use. It means only that the anchor was tested.

Naturally, a manufacturer will rarely spend money testing an anchor that performs poorly in this respect. But the approval itself is no guarantee that the anchor will perform effectively under seismic action, relative to its performance under normal loads.

A worked example

A wedge anchor such as the MTP-X M12 carries 16 kN in cracked concrete, but only 9 kN in a seismic calculation — a 43% drop in load capacity. By contrast, the SLPT M12/18 anchor carries the same load in cracked concrete and under seismic design. The reason is simple: wedge anchors are less suited to dynamic loads. In other words, a European seismic approval confirms that the anchor was tested for seismic action — not that the anchor is good for it.

The two European categories: C1 and C2

In the European standard — the basis for anchor design in most Israeli design offices — there are two seismic approval categories:

Category	Intended for
C1	Non-structural elements
C2	Structural elements

In most building projects, seismic design concerns structural elements — so C1 is not relevant in the majority of cases. In Israel, however, many designers are unaware of this distinction and approve mechanical or chemical anchors for structural elements on the basis of a C1 approval alone.

The American standard

In the American standard, each application type is denoted by a different letter, and the more letters an anchor is approved for, the wider the range of conditions it suits. That said, approvals under the American standard do not state a clear load capacity for each case; instead they refer the designer to clauses that reduce the anchor's load capacity according to the conditions. In practice, few Israeli designers use the American standard for seismic design.

Common mistakes in design

In most seismic anchor designs in Israel, the calculation is carried out for cracked concrete under static or quasi-static loads, and the designer simply requires that the anchor hold a seismic approval — C1 or C2 — without examining the anchor's actual seismic performance. That is a double error.

The two mistakes

If this is structural seismic design, a C2 approval is mandatory — C1 will not do.
The design must use the load capacity given by the C2 approval in the anchor's European Technical Assessment — not the ordinary static load capacity.

A designer who approves an anchor on the basis of C1 for a structural element, or who fails to check the specific load capacity under the C2 approval, is behaving like a practice manager who hires a candidate that enrolled in an engineering degree without ever asking whether they finished it. It is neither sound nor professional.

Chemical rebar connections under seismic action — a critical limitation most designers do not know

One point deserves particular emphasis: at present there is no chemical adhesive anywhere in the world holding a C2 seismic approval. This means that, under the European anchoring standard, structural seismic design using chemical rebar connections cannot be carried out within the C1/C2 categories at all.

So what is the answer? EAD 330087-01-0601

The correct solution is to use EAD 330087-01-0601, which is written specifically for the design of post-installed chemical rebar connections. This document works on a different basis from the standard anchor route, and it permits full, standards-compliant seismic design of chemical rebar connections — outside the C1/C2 framework entirely.

Unfortunately, most Israeli designers are not familiar with this document and do not use it. The result is either incorrect design, or an inability to approve standard rebar-connection solutions on seismic projects.

In conclusion

Principles of sound design
A seismic approval tells you that a test was carried out — not that the anchor is optimally suited to the application.
For structural design with threaded rods, require a C2 approval, and base the calculation on the C2 values in the European Technical Assessment — not on the static load capacity.
For structural design with chemical rebar connections, require a seismic approval under EAD 330087-01-0601, and design the rebar connection to that document.
Compare anchors on their actual seismic performance — not on the mere existence of an approval.

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