Information Notice No. 86-94: Hilti Concrete Expansion Anchor Bolts

                                                            SSINS No.:  6835
                                                            IN 86-94 

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555

                              November 6, 1986

Information Notice No. 86-94:   HILTI CONCRETE EXPANSION ANCHOR BOLTS 

Addressees: 

All nuclear power reactor facilities holding an operating license or a 
construction permit. 

Purpose: 

This notice is provided to inform recipients of a revision to the published 
ultimate tensile capacities for 1/2-inch-diameter Hilti Kwik bolts that 
could potentially affect pipe support designs covered by IE Bulletin 79-02. 
This revision resulted from a Hilti review bf all, onsite test data 
developed at nuclear power plants after a 10 CFR Part 21 report identified 
that onsite tests at the Susquehanna plant produced results that were 
significantly below the published values contained in Hilti's "Architects 
and Engineers Anchor and Fastener Design Manual" for several sizes of anchor 
bolts. 

It is expected that recipients review this information for applicability to 
their facilities and consider actions, if appropriate. However, suggestions 
contained in this information notice do not Constitute NRC requirements; 
therefore, no specific action or written response is required. 

Description of Circumstances: 

Testing of various sizes and embedment depths of Hilti Kwik and Super Kwik 
expansion anchor bolts was performed at the Susquehanna Steam Electric 
Station during March 1985 and during March/April 1986. The results of these 
tests established average ultimate tensile capacities of some expansion 
anchor bolts that were substantially lower than the published values in the 
Hilti manual. These results were reported to the NRC by Dravo Constructors, 
Inc. in a Part 21 report in May 1986. The worst-case result from the 
Susquehanna onsite tests established an average ultimate tensile capacity 
for the 1/2-inch anchor bolt with a 5-1/2-inch embedment that was 59% of the 
value published in the Hilti manual. Other significantly lower values 
reported by Dravo included 5/8", 3/4", 1", 1-1/4-inch Kwik bolts and the 
1-inch Super Kwik bolt. All of these lower values were associated with the 
deeper embedment depths where failure is governed by anchor pull out. In 
response to the data generated at Susquehanna, Hilti performed a statistical 
evaluation of its available onsite test results and provided these results 
to the NRC in September 1986. Hilti's evaluation of the onsite test data 
supported the values published in its manual for all anchor bolt sizes 
except for 1/2-inch bolts. Hilti stated it would revise the 


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                                                       IN 86-94 
                                                       November 6, 1986 
                                                       Page 2 of 2 

values for the 1/2-inch-diameter Kwik bolt. A copy of the revised ultimate 
tensile capacity values for the 1/2-inch-diameter Hilti Kwik bolts is 
provided in Attachment 1. 

Discussion: 

A substantial amount of data scatter in the testing of concrete expansion 
anchor bolts is expected and this data scatter was considered in selecting 
the appropriate safety factors for design purposes. Although Hilti's 
evaluation of all plant test data confirmed its ultimate tensile capacities 
for most sizes of anchor bolts published in the manual, it appears that a 
greater amount of data scatter exists in the results for deeper embedment 
lengths. Apparently, the higher capacities that can be achieved for deeply 
embedded bolts are more sensitive tp the exact concrete mix properties 
and/or installation techniques. Licensees using the ultimate capacities from 
the Hilti manual should be aware that the concrete mix and installation 
techniques at their facilities could have a significant impact on the 
results for the deeper embedment capacities. These concerns should not 
impact licensees with facilities that have established allowable working 
loads for expansion anchors based on onsite tests or facilities that 
establish allowable working loads based on the shorter embedment lengths. 

No specific action or written response is required by this information 
notice. If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate regional office or this office. 


                                   Edward L. Jordan, Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  J. R. Fair, IE 
                    492-4509 

Attachments: 
1.   Revised Ultimate Tensile Values for 1/2-Inch-Diameter Kwik Bolt
2.   List of Recently Issued IE Information Notices