Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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
8611040026
.
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