7.1.3.1 Basics

During the construction period of the first nuclear power plants no general authoritative approvals for headed studs had existed. Anchorings were designed and built based on consent orders from the building authorities concerned. These orders and their associated expert opinions governed the permissible combinations of stresses for tension and shear loads for headed studs and covered any boundary or group influences individually.

When designing anchor plates, a distinction is made between safety-related and non­safety-related units.

The design and construction of fastenings for non-safety-related components is based today on the general technical approval (ETA) for the significant combination of characteristic loads concerned.

Beyond the provisions of the General Technical Approvals, safety-related components are subject to additional requirements in terms of the structural load-bearing and deformation behaviour of the anchorings.

As well as for the effects of actions from characteristic loads, safety-related anchorings with headed studs must also be designed to withstand the effects of actions from accidental external events such as earthquakes or for internal anomalies. Designing anchorings for special load cases also includes the effects of impulsive actions and the occurrence of cracking in reinforced concrete structure with wide cracks.

The design of anchor plates within headed studs for attaching safety-related compo­nents is not covered by General Technical Approvals; nor has any such General Technical Approval for accidental actions (K-approval) yet been applied for at the Deutsches Institut fuur Bautechnik. That means using anchor plates for safety-related components is still subject to approval by the supreme building authority in each case. This involves verifying structural strength and serviceability of anchor plates in accordance with DIBt Guidelines [67], the successor to [63]. Finally, the suitability of the anchoring for the specific intended purpose in nuclear power plants must then be assessed by an expert opinion.