ML19276G665
| ML19276G665 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Byron, Braidwood, Quad Cities, Zion, LaSalle  |
| Issue date: | 05/31/1979 |
| From: | SARGENT & LUNDY, INC. |
| To: | |
| Shared Package | |
| ML19276G664 | List: |
| References | |
| NUDOCS 7908060120 | |
| Download: ML19276G665 (24) | |
Text
ATTACHMENT
' g RESPONSE TO IE rdi.LETIN No. 79-02 FOR Byron /Braidwood - Units 1 and 2 LaSalle County - Units 1 and 2 Zion - Units 1 and 2 Quad Cities - Units 1 and 2 Dresden - Units 2 and 3 Dresden - Unit 1 Co=onwealth Edison Company Chicago, Illinois 1.
The pipe support baseplates for Byron /Braidwood Units 1 and 2, LaSalle County Unita 1 and 2, Zion Units 1 and 2, Quad Cities Units 1 and 2, Dresden Unitt 2 and 3 and Dresden Unit 1 have been designed based upon rigid plate theory.
The rigid plate analysis procedure has been compared with a flexible plate analysis procedure.
The design of expansion anchored plate assemblies using rigid plate theory provides factors of safety ranging from a minimum of 4.0 to a maximum of 8.7 against manufacturer's recoc= ended ultimate failure loads.
It has been shown in the attached report, entitled,
" Evaluation of Analysis Procedures for the Design of Expansion Anchored Plates in Concrete," dated May 31, 1979, that, when the flexibility of the expansion anchored baseplate assemb],y, in conjunction with the load versus displacement behavior of the expansion anchor, is accounted for in a finite element solution, the " prying action" forces are largely relieved, and the flexible plate solution approaches the rigid plate solution. This has been concluded for the typical expansion anchor assemblies used to support mechanical cocponents in our stations for various expansion anchor types, embedmont depths, preload levels and applied load patterns which may typically be encountered in such installations.
It is, therefore, Cc=onwealth Edison Company's opinion that adequate margin exists in the present design of expansion anchored plate assemblies to accommodate the effect of the ficxibility of the baseplate assemblies as required by the Nuclear Regulatory Co=1ssion.
The load-displacement curve illustrated.in the attached report were obtained from field tests at several nuclear stations currently under construction, and are judged to be conservative.
Co=onwealth Edison Co=pany will perform a comprehensive static testing program for concrete expansion anchors under the direction of an Independent Testing Laboratory to verify these load-displacement curves.
It is estimated that these static tests will commence on or about August 15, 1979. Estimated completion of static testing would be approximately 6 months after tests have begun.
Also, the test program will include testing to failure, flexible expansion anchored plate assemblies designed using rigid plate theory, and demonstrating that the failure load equals or exceeds four times the design load.
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7908060) to The static test program to verify the load-displacement curves and ultimate loads will enco= pass the following combination of variables:
a) Expansion anchor types
- 1) Wedge type anchors
- 2) Self-drilling type anchors b) Anchor diameter
- 1) 1/4"
- 4) 5/8"
- 2) 3/8"
-5 M 4" g.
- 3) 1/2" 6Ww 3g c) Embedment Depth
^
- 1) 4-1/2 anchor diameters
- 2) S anchbr diameters d) Embedmen p terial
- 1) Con' crete - f'
= 3500 psi and 5500 psi
- 2) Masonry mortar - ASIM C-270, Type M and Type N
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In addition, this testing program will also assess the long term preload relaxation characteristics of wedge type anchors.
It is estimated that this test progren will commence on or about August 15, 1979 and will run concurrently with the static tests. Estimated complecion of this series of tests would be approriantely 18 months after tests have begun.
The results of the static test program will be available for review by the Nuclear Regulatory Commission upon completion.
2.
Commonwea17.h Edison Company has verified that concrete expansion anchor bolts have been designed using a minimum factor of safety of 4.0 between the bolt design load and the bolt ultimate capacity determined from manufacturer's static data for wedge and self-drilling type anchors.
This factor of safety has Leen traditionally recommended by manufacturers of both wedge and self-drilling type expansion anchors for static loads.
3.
The dynamic / cyclic loads for which the pipe support baseplates have been designed were obtained from either a response spectrum or time history method of analysis, and,therefore, properly accounts for any dynamic load factora. The concrete expansion anchor design allowables were based upon maintaining a minimum factor of safety 4.0 between the dynamic / cyclic design loads, corresponding to an OBE event, and the bolt ultimate capacity, as determined from manufacturer's static load test data for wedge and self-drilling type anchors.
Commonwealth Edison Company will perform a t,omprehensive dynamic test program under the direction of an Independent Testing Laboratory
to verify the dynamic behavior of wedge and self-drilling type expansion anchors. Thece tests will be performed on rigid plate expansion anchored assemblies under the following dynamic conditions:
a) Pipe transient cyclic loads b) OBE seismic loads It is esti=ated that this test program will commence on or about August 15, 1979 and will run concurrently with the static and relaxation tests. Estimated co=pletion of this series of tests would be approximately 6 months after tests have begun.
The results of the dyna =ic test program will be available for review by the Nuclear Regulatory Coc=ission upon completion.
4.
Byron /Braidwood - Units 1 and 2 Wedge type expansion anchers with an embedment depth equal to 8 anchor diameters have been used exclusively in safety related areas for Byrtn/
Braidwood Units 1.and 2.
All concrete expansion anchors have been installed in accordance with approved QA/QC procedures.
These procedures require, as a minimum, verification of the following items:
a) Installation torque b) Test torque (a measure of exparsion anchor preload relaxation)
-)
Embedment depth d) Anchor size The design of the concrete expansion anchors for Byron /Braidwood Units 1 and 2 has assured that the expansion anchor bolt preload is greater than or equal to the design load.
Documentation of existing expansion anchor installations at Byron /Braidwood Units 1 and 2 will be available for review by the Nuclear Regulatory Commission upon completion.
LaSalle County - Units 1 and 2 Wedge type concrete expansion anchors have been used exclusively in safety related areas for LaSalle County Units 1 and 2.
Embedment lengths of both 4-1/2 anchor diameters and 8 anchor diameters have been used for the wedge type anchors. All concrete expansion anchors have been installed at LaSalle County Units 1 and 2 in accordance with approved QA/QC procedures. These procedures require, as a minimum, verification of the following items:
a) Installation torque b) Test torque (a measure of expansion anchor preload relaxation) c) Embedment depth d) Anchor size 9
M
4-
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The design of the concrete erpansion anchors for LaSalle County Units 1 and 2 has assured that the expansion anchor bolt preload is greater than or equal to the d<iign load.
Documentation of existing expansion anchor installations at LaSalle County Units 1 and 2 will be available for review by the Nuclear Regulatory Cocmission upon completion.
Zion - Units 1 and 2 A mixture of wedge and self-drilling type concrete expansion anchors have been used in safety related areas at Zion Units 1 and 2.
The minimum embedmenx length for wedge type anchors is 4-1/2 anchor diameters. Self-drilling anchors were predominantly used prior to 1976. All concrete expansion anchors were specified to be installed at Zion Units 1 and 2 in accordance with manufacturer's reco=endations.
Commonwealth Edison Company will inspect wedge and self-drillirg type erpansion anchors supporting safety related piping in which the calculated factor of safety (ultimate anchor capacity divided by the calculated applied load) is less than or equal to 10, at Zion, Units 1 and 2, to assure conformance to manufacturer's installation recommendations. Wedge type expansion anchors will be inspected to verify the following iters:
a) Minimum test torque level b) Minimum embed:ent length c) Expansion anchor size Wedge type expansion anchors which do not meet the required test torque value will be retorqued to the insta11aticn value and reinspected within seven days to assure that relaxation has not' exceeded the required test torque value. Wedge type expansion anchors which do not have the correct embed =ent length or size will be reanalyzed and, if inadequate to support the design loads, will be replaced, or the expansion anchored plate assembly modified accordingly to support the design loads.
Manufacturers of self-drilling concrete expansion anchors typically have not specified initial installation torque values. The torquing of a self-drilling anchor does not seat the anchor in the concrete hole, and, thereby, minimize anchor displacement as in the case of wedge type anchors.
Cc=onwealth Edison Company, however, will perform a test program for self-drilling type erpansion anchors under the direction of an Independent Testing Laboratory to determine appropriate test torque levels to assure that the preload in the self-drilling expansion anchors is greater than or equal to the design loads. Self-drilling expansion anchored assemblies supporting safety related piping will be inspected by applying the test torque to the individual anchors, and be inspected for correct size. The self-drilling expansion anchors will be inspected subsequent to the application of the test torque to assure that the shell of the self-drilling expansion anchor is not in contact with the back of the expansion anchor baseplate. Self-drilling expansion anchors which are in contact with the back of the expansion anchor baseplate will either be replaced with a wedge type anchor, or the expansion anchored plate assembly modified accordingly to support the design loads.
e
Future expansion anchor installations at Zion Units 1 and 2 will consist of wedge type only, with an embedment length equal to 8 anchor diameters.
These anchors will be insta2 ed in accordance with approved QA/QC procedures, ana the design load for these anchors will be less than the specified anchor preload.
An inspection and testing plan will be implemented at Zion in order to systematically evaluate anchor bolts that were used for category 1 pipe supports.
This inspection and testing plan will be implemented by August 1, 1979 and will be completed by the end of each units scheduled refueling outage.
Documentation of existing expansion anchor installations at Zion Units 1 and 2 will be available for review by the Nuclear Regulatory Cocnission upon completion.
Quad Cities - Units 1 and 2 A mixture of wedge and self-drilling type concrete expansion anchors have been used in safety related areas at Quad Cities Units 1 and 2.
The minimum embed =ent depth for wedge type expansion anchors is 4-1/2 anchor diameters.
Self-drilling anchors were predominantly used prior to 1977. All concrete expansion anchors were specified to be installed in accordance with manufacturer's recommendations.
Commonwealth Edison Company will inspect wedge and self-drilling type erpansion anchors supporting safety related piping in which the calculated factor of sarety (ultimate anchor capacity divided by the calculated applied load) is less than or equa3 to 10, at Quad Cities, Units 1 and 2, to assure conformance to manufacturer's installation recommendations. Wedge type expansion anchors will be inspected to verify the following items:
a) LEnimum test torque level b) lunimum embedment depth c) Expanaion anchor size Wedge type expansion anchors which do not meet the required test torque value will be retorqued to the installation torque value and reinspected within seven days to assure that relaxation has not exceeded the required test torque level. Wedge type expansion anchors which do not have the correct embedment length or size will be reanalyzed and, if inadequate to support the design loads, will be replaced, or the expansion anchored plate asse:bly modified accordingly to carry the design loads.
Manufacturers of self-drilling concrete expansion anchors typically have not specified initial installation torque values. The torquing of a self-drilling anchor does not seat the anchor in the concrete hole, and, thereby, minimize anchor displacement as in the case of wedge type anchors.
Commonwealth Edison Company, however, will perform a test program for self-drilling type expansion anchors under the direction of an Independent Testing Laboratory to determine appropriate test torque levels to assure that the preload in the self-drilling expansion anchors is greater than or equal to the design loads. Self-drilling expansion anchored assemblies supporting safety related piping w.111 be inspected by applying the test torque to the individual anchors, and be inspected for correct size.
The
9 self-drilling expansion anchors will be inspected subsequent to the applicatien of the test torque to assure that the shell of the self-drilling expansion anchor is not in contact with the back of the expansion anchor baseplate.
Self-drilling expansion anchors which are in contact with the back of the expansion anchor baseplate will either be replaced with a wedge type anchor, or the expansion anchored plate assembly modified accordingly to support the design loads.
Future expansion anchor installations at Quad Cities Units 1 and 2 will consist of wedge type anchors only, with an embedment length equal to 8 anchor diameters. These anchors will be installed in accordance with approved QA/QC procedures, and the design load for these anchors will be less than the specified anchor preload.
An inspection and testing plan will be implemented at Quad Cities in order to systematically evaluate anchor bolts that were used for category 1 pipe supports. This inspection and testing plan will be implemented by August 15, 1979 and will be completed by the end of each units scheduled refueling outage.
Documentation of existing expansion anchor installations at Quad Cities Units 1 and 2 will be available for review by the Nuclear Regulatory Co=ission upon completion.
Dresden - Units 2 and 3 A mixture of wedge and self-drilling type concrete expansion anchors have been used in safety related areas at Dresden Units 2 and 3.
The minimum embedment depth for wedge type expansion anchors is 4-1/2 anchor diameters.
Self-drilling anchors were predominantly used prior to 1977. All concrete expansion anchors were specified to be installed at Dresden Units 2 and 3 to be in accordance with manufacturer's reco=endations.
Commonwealth Edison Company will inspect wedge and self-drilling type expansien anchors supporting safety related piping in which the calculated factor of safety (ultimate anchor capacity divided by the calculated applied load) is less than or equal to 10, at Dresden, Units 2 and 3, to assure conformance to manufacturer's installation reco=endations. Wedge and self-drilling type expansion anchors will be inspected to verify the following items:
a) Minimum test torque level b) Minimum embedment depth c) Expansion anchor size Wedge type expansion anchors which do not meet the required test torque value will be retorqued to the installation torque value and reinspected within seven days to assure that relaxation has not exceeded the required test torque level. Wedge type expansion anchors which do not have the correct embedment length or size will be reanalyzed and, if inadequate to support the design loads, will be replaced, or the expansion anchored plate assembly modified accordingly to carry the design loads.
Manufacturers of self-dri' ling concrete expansion anchors typically have not specified initial installation torque values.
The torquing of a self-drilling anchor does not seat the anchor in the concrete hole, and, thereby, minimize anchor displacement as in the case of wedge type anchors.
Cc=monwealth Edison Co:pany, however, will perform a test program for self-drilling type expansion anchors under the direction of an Independent Testing laboratory to deter:Ine appropriate test torque levels to assure that the preload in the self-drilling expansion anchors is greater than or equal to the design loads. Self-drilling expansion anchored assemblies supporting safety related piping will be inspected by applying the test torque to the individual,
anchors, and be inspected for correct size.
The self-drilling expansion anchors will be inspected subsequent to the application of the test torque to assure that the shell of the self-drilling expansion anchor is not in contact with the back of the expansion anchor baseplate.
Self-drilling expansion anchors which are in contact with the back of the expansion anchor baseplate will either be replaced with a wedge type anchor, or the expansion anchored plate assechly nodified accordingly to support the desigr. loads.
Future expansion anchor installations at Dresden Units 2 and 3 will consist of wedge type anchors only, with an embedment length equal to 8 anchor diameters.
These anchors will be installed in accordance with approved QA/QC procedures, and the design load for these anchors will be less than the specified anchor preload.
An inspection and testing plan will be implemented at Dresden in order to systematically eraluate anchor bolts that were used for category 1 pipe supports.
This inspection and testing plan will be implemented by August 15, 1979 and will be completed by the end of each units scheduled refueling outage.
Documentation of existing expansion anchor installations at Dresden Units 2 and 3 will be available for review by the Nuclear Regulatory Co==ission upon completion.
Dresden - Unit 1 Co==onwealth Edison Company is currently reviewing the design for Dresden Unit 1 in order to verify that adequate factors of safety exist.
It is anticipated that a visual survey of category 1 pipe supports and associated concrete expansion anchors will be made and that the inspection and testing techniques utilized for Dresden Units 2 & 3 will be used.
Results from the static, dynamic and relaxation tests used for all other Commonwealth Edison Company units, would also be applicable for Dresden Unit 1.
Currently Dresden Unit 1 is down for chemical decontamination with start-up anticipated for the summer of 1980.
The inspection and testing plan for Dresden Unit 1 will be completed prier to start-up.
5.
Commonwealth Edison Company has inspected a random sa=ple of ten self-drilling expansion anchors at Zion, Units 1 and 2.
All anchors tested exceeded the ultimate capacity of the expansion anchor divided by a factor of safety of 4.0.
These test results, along with continued operation of safety related piping systems under pipe transient cyclic loadings at all operating stations justify continued operations of these facilities.
Commonwealth Edison Company has developed and is implementing a comprehensive inspection and testing program for all operating stations to further sub-stantiate continued operations.
t EVALUATION OF ANALYSIS PROCEDURES FOR THE DESIGN OF EXPANSION ANCHORED PLATES IN CONCRETE PREPARED BY:
REVIEWED BY:
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APPROVED BY:
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May 31, 1979 Sargent & Lundy Engineers Chicago, Illinois 8
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r EVALUATION OF ANALY9IS PROCEDURES FOR THE DESIGN OF EXPANSION ANCHORED PLATES IN CONCRETE' 4
TABLE OF CONTENTS 1.0 PURPOSE 2.0 INDIVIDUAL CONCRETE EXPANSION ANCHORS 2.1 Concrete Expansion Anchor Types 2.2 Behavior of Individual Concrete Expansion Anchors 2.2.1 Pre-load Levels In Wedge And Sleeve Type Expansion Anchors 2.2.2 Pre-load Levels in Self-drilling Type Expansion Anchors 2.2.3 Modes of Failure For Concrete Expansion Anchors 2.3 Idealized Load-Displacement Curve For Individual Concrete Expansion Anchors 3.0 EXPANSION ANCHORED PLATE ANALYSIS PRCCEDURES 3.1 Rigid Versus Flexible Plate Analysis 3.2 Rigid Plate Analysis 3.2.1 Rigid Plate Analysis Theory 3.2.2 Rigid Plate Analysis For Direct Tension Loads 3.2.3 Rigid Plate Analysis For Pure Moment Couple Load 3.2.4 Rigid Plate Analysis For Applied Shear Loads 3.3 Flexible Plate Analysis 3.3.1 Description of the Flexible Plate Model 3.3.2 Behavior of the Flexible Plate Assembly
4.0 CONCLUSION
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'y EVALUATION OF ANALYSIS PROCEDURES FOR THE DESIGN OF EXPANSION ANCHORED PLATES IN CONCRETE i
LIST OF TABLES TABLE NO.
. TITLE 1
Typical Expansion Anchor Installation and Test Torque Values 2
Results of Analysis for Typical Expansion Anchor Assemblies-4 O
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EVALUATION OF ANALYSIS PROCEDURES FOR THE DESIGN OF EXPANSION ANCHOPED PLATES IN CONCRETE LIST OF FIGURES g
FIGURE NO.
TITLE 1
Typical Expansion Anchored Plate Assemblies 2
% Idealized Load-displacement Curve For Concrete Expansion Anchors 3
Idealized Load-displacement Curve For 1/2" Diaceter Expansion Anchors 4
Idealized Load-displacement Curve for 3/4" Diameter Expansion Anchors 5
Rigid Plate Behavior Under Direct Tension Load 6.
Rigid Plate Behavior Under Pure Moment Couple Load 7
Plate Deflection Due To Applied Tension Lcad And Prying Acton 8
Finite Element Model Of A Quarter Section Of A Typical Plate Assembly 9
Load-reaction Curve For a 1/2" x 9" Expansion Anchored Plate Assembly 10 Load-reaction Curve For A 5/8" x 12" x 12" Expansion Anchored Plate Assembly e
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8 6
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1.0 PURPOSE The purpose of this report is to demonstrate'that the rigid plate analysis procedure used for the design of expansion anchored plate assemblies pro-vides factors of safety ranging from a minimum of 54.0 to a maximum of 8.7, against manufacturer's recommended anchor failure loads.
It will subse-quently be shown that when the flexibility of the baseplate in conjunction with the true load versus displacement behavior of the expansion anchor is accounted for in a finite element solution, the
" prying action" for~ces are largely relieved and the' flexible plate solution approaches the rigid plate solution.
This report analyzes four typical expansion anchor plate assemblics used to support mechanical com-ponents in nuclear power stations using both rigid plate theory and flexible plate theory, and compares the maximum anchor loads and displacements for each type of analysis.
The following variables are considered in both the rigid plate and flexible plate analysis presented herein:
a.
Expansion Anchor Type al.
Wedge Type a2.
Sleeve Type a3.
Self-9 rilling b.
Expansion Anchor Embedment Depths bl.
4-1/2 Diameter Embedment Depth b2.
8 Diameter Embedment Depth c.
Expansion Anchor Pre-load Level cl.
Zero Pre-load c2.
Pre-load Levels Specified in Table 1 d.
Applied Load dl.
Direct Tension Load d2.
Moment Couple The rigid plate analysis is presented in Section 3.2 and the flexible plate analysis is presented in Section 3.3.
Table 2 compares the results of both the rigid plate and flexible plate analysis.
S s
2 2.0 INDIVIDUAL CONCRETE EXPANSION ANCHORS 2.1 Concrete Expansion Anchor Types Three types of concrete expansion anchors have traditionally been used for the attachment of mechanical componer.ts to concrete in nuclear power stations.
They are:
a.
Wedge Type Anchors b.
Sleeve Type Anchors c.
Self-drilling Anchors The wedge and sleeve type anchors are predominantly used today by the nuclear industry.
Self-drilling anchors were used prior to 1976, however, today they are used primarily for the support of small loads.
2.2 Behavior Of Individual Concrete Expansion Anchors 2.2.1 Pre-load Levels In Wedge And Sleeve Type Expansion Anchors Wedge and sleeve type expansion anchors are installed to a specified initial torque referred to as the
" installation torque".
This installation torque provides the wedge and sleeve type expansion anchors with an initial pre-load force.
This initial pre-load is reduced in time due to a combination of such factors as stress relaxation in the concrete expansion anchor and concrete creep.
Field tests have demonstrated that a major
.part of this pre-load relaxation takes place immediately after installation.
It is estimated that the initial expansion anchor pre-load ultimately relaxes to approximately 60% of its initial value.
Sargent & Lundy's installation procedure raquires'
~
that expansion anchors be tested after installation to assure a minimum pre-load value after relaxation.
This minimum pre-load value is verified by applying a test torque to the expansion anchors after installation anci requiring that the test torque achieve a minimum of 60% of the installation torque.
Typical values for the installation torques and test torques for 1/2" diameter and 3/4" diameter wedge and sleeve type expansion anchors are given in Table 1.
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.s 3
2.2.2 Pre-load Levels In Self-drilling Type Expansion Anchors The initial installation torques and test torques
'have*not been typically specified by manufacturers for self-drilling type expansion anchors.
The torquing of a self-drilling. expansion anchor does not seat the anchor in the concrete hole, and, thereby minimize anchor displacement, as in the case of wedge and sleeve type anchors.
Any torque requirement for self-drilling anchors would induce a preload in the anchors, but not influence the ultimate load capacity of the anchor.
2.2.3 Modes Of Failure For Concrete Expansion Anchors There are three postulated modes of failure for a concrete expansion anchor.
They are:
a.
Yielding of The Expansion Anchor '
b.
Excessive Displacement Of The Anchor c.
Concrete Cone Failure The expansion anchor failure referenced in Item 2.2.3a is defined by the yielding of the anchor material
~
at the neck of the anchor and the displacement of the anchor at failure is controlled by the clastic deformation of the anchor.
The anchor failure referenced in Item 2.2.3b is controlled by an assigned maximum displacement of the 3xpansion anchor relative to the concrete.
Sargent & Lundy typically specifies this maximum displacement to be one anchor diameter for anchors embedded greater than 4-1/2 diameters.
The failure referenced in Item.2.2.3c is governed by the expansion anchor embedment depth and the strength of the concrete.
Anchors embedded 4-1/2 diameters or less, are usually susceptible to concrete cone failures referenced in Item 2.2.3c; therefore, Sargent &
Lundy has specified a maximum displacement of 3/4 anchor diameters to preclude anchor failure.
Anchors embedded greater than 4-1/2 diameters are usually controlled by the mode of failure referenced in Item 2.2.3b.
In addition to controlling the mode of failure, the anchor embedment depth also effects anchor flexibility, i.e.,
the greater the anchor length, the greater the anchor flexibility.
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4 Concrete expansion anchors are not usually controlled by the modes of failure referenced in Items 2.2.3a and 2.2.3c; mode failure 2.2.3b typically predominates.
2.3
' Idealized Load-Displacement Curve For Individual
' Concrete Expansion Anchors Figure 2 illustrates an idealized load-displacement curve for individual concrete expansion anchors with and without initial pre-load.
It can be seen that the initial pre-load level does.not effect the ultimate capacity of the anchor.
This fact has been verified by numerous field tests.
When a concrete expansion anchor is pre-tensioned to a level P by torquing the nut, the corresponding g
deformation A is taken up by the movement of the f
anchor as shown in Figure 2.
When a pre-tensioned anchor is loaded in tension, it has negligible displacement until the external load reaches Pg at which point it follows the original load-displacement curve to the specified ultimate load.
Thus, the only effect of pre-tensioning the concrete expansion anchor is to reduce the ultimate anchor displacement by an amount equal to A1 The idealized load-displacement curves for 1/2" diameter expansion anchors and 3/4" diameter expansion anchors are shown in Figures 3 and 4, respectively.
Two load displacement curves are given for each anchor diameter dependent upon the anchor embedment depth.
Sargent & Lundy has defined anchor failure as an anchor displacement
. equal to 3/4 anchor diameters for anchors embedded 4-1/2 diameters.or less, and equal to one diameter for anchors embedded greater than 4-1/2 diameters.
These conservative idealize load-displacement o
curves have been verified by static load tests performed in the field at several nuclear power stations currently under construction.
3.0 EXPANSION ANCHORED PLATE ANALYSIS PROCEDURES 3.1 Rigid Plate Versus Flexible Plate Analysis The analysis of expansion anchored plates is traditionally performed using rigid plate theory.
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5 The forces in the expansion anchors are computed by static equilibrium and the resulting expansion anchor loads are limited to the ultimate capacity
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of the expansion anchor divided by an appropriate factor of safety.
The ultimate load is typically provided by the expansion anchor manufacturor and a factor of safety equal to 4.0 is used to obtain the allowabic design load.
Recognizing the flexibility of the baseplate relative to the concrete expansion anchor, a load applied to the concrete expansion anchor assembly may cause the expansion anchor plate to deform such that compressive " prying action" forces are developed between the contacting areas.
A finite element approach is used to properly account for the effects of plate flexibility and anchor-flexibility.
In the following sections it will be shown that these " prying action" forces are relieved due to the flexibility of the concrete expansion anchor (as demonstrated by the idealized load-displacement curves indicated in Figures 3 and 4) relative to the flexibility of the baseplate.
3.2 Rigid Plate Analysis 3.2.1 Rigid Plate Analysis Theory In a rigid plate analysis, che forces in the concrete expansion anchors are calculated on the basis of the rigid body movement of the baseplate.
Stresses in the concrete and in the concrete expansion anchors are calculated by equating the internal forces to the external forces by' maintaining the compatibility of the linear strain relationship in both the steel baseplate and concrete bearing surface.
3.2.2 Rigid Plate Analysis For Direct Tension Loads For direct tension loads, the baseplate displacements are constant over the entire. surface of the base-plate; therefore, the tensile forces in all concrete expansion anchors are equal and the sum of the tensile forces in the concrete expansion anchors are equal to the externally applied direct tension load.
Figure 5 illustrates the displacement of the baseplate and equilibrium of the anchor forces and the externally applied direct tension load.
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6 3.2.3 Rigid Plate Analysis For Pure ftoment Couple Load Under a pure moment couple, the rigid plate will rotate about a neutral axis.
The rotation will induce compressive forces.where the baseplate and
, concrete are in contact and tensile forces in the concrete expansion anchors on the opposite side.
The concrete expansion anchor forces are calculated assuming equilibrium of the forces over'the entire plate and by assuming compatibility of the linear strain relationship between the steel and concrete.
The design of the expansion anchor p. late assembly for a pure moment couple using rigid plate analysis is shown in Figure 6.
3.2.4 Rigid Plate Analysis For Applied Shear Loads Shear loads applied in the plane of the expansion anchor plate assembly do not induce " prying action" forces in the concrete expansion anchors, regardless of plate flexibility.
Concrete expansion anchored plate assemblies are designed to resist applied shear loads using the following interaction equation:
f f
~
pb+p1 5 1.0 (1) t v
where f
= tension force in the anchor t
F
= allowable tensile capacity of the anchor t
f
= shear force in the anchor y
F
= allowable shear capacity of the anchor.
y Equation 1 can be educed to ft+
vE I
t v
Taking F /F
= 0.7, Equation 2 reduces to y
f It+07 5F t 8
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7 This is equivalent to the shear friction theory of
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ACI-349, Appendix B, where the shear force in anchors is converted into an equivalent tension force and added to the force due to tension and/or moment.
This approach is conservative compared to published test results on expansion anchors for tensile and shear loading, which indicate that the ratio F /F is always larger than 1.0.
y 3.3 Flexible Plate Analysis In a flexible plate analysis the deformation of the plate under applied load results in additional
" prying action" forces in the concrete expansion anchors.
Figure 7 illustrates these " prying action" forces on a flexible plate under a direct tension load.
It will be demonstrated that these additional " prying action" forces are eliminated due to the flexibility of the anchor relative to the flexibility of the baseplate and, therefore, do not reduce the required factor of safety.
3.3.1 Description Of The Flexible Plate Model' The SLSAP Computer P::ogram was used for the non-linear finite element analysis of the expansion anchor plate assemblies referenced in Figure 1.
Figure 8 illustrates the typical finite element model of a quarter section of a plate assembly.
The plate is modeled using quadrilateral plate elements.
The concrete under the baseplate is represented by one-way (compression only) springs and the stiffness of these springs is computed on the basis of the elastic half-space appresch.
The anchors are represented by truss elements as
' indicated in Figure 8 and the stiffness of the concrete expansion anchors are based upon the idealized load displacement curve shown in Figures 3 and 4.
Pre-load in the concrete expansich anchors is simulated by an equivalent negative temperature load.
Due to the non-linear nature of the idealized load displacement curve, the plate assemblies are analyzed by the ultimate design approach in which the design loads are multiplied by a load factor equal to four.
The resulting expansion anchor reactions are compared with the ultimate capacity of the expansion anchors as defined in Figures 3 and 4.
The load factor equal to four was selected to be consistent with the minimum required factor of safety used in the rigid plate analysis.
4
8 3.3.2 Behavior Of The Flexible Plate Assembly Comparing the results of the rigid plate analysis
,and the flexible plate analysis listed in Table 2, it can be seen that the anchor forces obtained from a flexible plate analysis approaches those obtained from a rigid plate analysis.due to the flexibility of the anchor relative to the baseplate.
Figures 9 and 10 show the external force and anchor reaction for plate Assemblies 1 and 2 listed in Figure 1.
These figures demonstrate a minor amount of " prying action" force in the.early load stages which disappears as the load is increased.
Figures 3 and 4 show that four timcs the design load is substantially less than the ultimate load.
4.0 Conclusion The results for the flexible plate analysis listed in Table 2 indicate that a factor of safety of at least 4.0 is maintained against manufacturer's recommended ultimate failure loads.
This verifies that the rigid plate analysis utilizing.a factor of safety equal to 4.0 can be used for the design of expansion anchored plate assemblies.
It has been demonstrated that " prying action"
~
is a self-limiting phenomenon in expansion anchored plate assembly design and does not effect the ultimate capacity of the anchored plate assembly.
This has been demonstrated for the typical expansion anchored plate assemblics used to support mechanical components in nuclear power stations for various expansion anchor types, embedment depths, preload levels and applied load patterns which may typically be encountered in such installations.
e 9
e 5
e 9
/
9 l
TABLN 1 Typical Expansion Anchor Installation and Test Torcue Values Installation Anchor Size Torque Test Torque Inches ft-lbs ft-lbs 1/2 60-75 45 3/4 230-270 160 i
g
~
e e
O
.g, e
't e
D e
O 5E
<4
,, rv...
'm*=
klGID PLATE ANALYSIS FLEX 1BLE LA E A :M.YSI S
^
^
E u
u 3^
65 EM n
0" E
b~
v5 c
n m
n
.c 81
- 1
'8 8E e1 h
1
- 5 a
u
- t Ro
- m
?,
5%
3 23
?" 21 8
23 E
- 0 00 5" 8m Oc 00 5" 8m 3c
"~
o 5
5
- t k'
m" e8 "t
t v t-e8 U
84 80 t5 35 Et 8%
80 85 38 50 8%
8-v ta ta 80 tt 18 t"
ta tt ax 18 t"
t u
En no 48 28 Re E%
34 3K R<
in 3%
4" 0
12.8 3.2 6.8
.06 TENSION kips h
3.2 3.2 0.8 6.9
'.0003 5
kips kips 2.1 12,8 3.2 6.8
<.001 g
' kips 4.5d 5.5
- R 0
43.6 2.85
>4
<.06 M
110 MENT k-in g
10.9 10.9 0.8 6.9
.0003 2
k-in k-in 2.1 43.6 2.94
>4
<.001 k-in c' :
4 c' 0
12.8 3.2 8.7
.06
~
X TENSIOi kips 3.2 3.2 0.8 8.7
.0006 cn kips kips 2.1 12.8 3.2 8.7
<.001 x
kips
- O Bd 7.0 0-43.6 2.85
>4
<.06 d
l!0 MENT k-in 10.9 10.9 0.8 8.7
.0006 A
k-in k-in 2.1 43.6 2.92
>4
<.001 k-in
'O 33.6 8.4 4.8
.12 E
TENSION kips 9
8.4 8.4 2.1 4.8
.0006 kips kips 4.4 33.6 8.4 4.8
<.001 kips it 4.5d 10.15 h
0 159.2 7.43
>4
<.12 e:
l!0 MENT k-in S
'39.8 39.8 2.1 4.8
.0006 k-in k-in 4.4-159.2 7.35
>4
<.001 m _'
k-in
. ~n O"
0 33.6 8.4 7.6
.10 TENSION kips n
8.4 8.4 2.1 7.6
.001
~
kips kips
'.4' J -
33.6 8.4 7.6
<.001 kips 8d 16.0
,<.10 m
0 159.2 7.45
'> 4 84
!*0 MENT
.kJin h
39.8 39.8 2.1 7.6
.001 A
k-in k-in 4 '.'4 159.2 7.53
>4
<.001 k-in M
R1G1D PLATE Alta35IS TLEXI BLE P L_A_T__E AN A.L._Y S I S En NU NU
" 8.
83
?
EO 5
3%
5 u?
8.o n'E u?
8-o e
x
-l S
E" 5
E5 E
?E m0 Eh E
BE m
D w" BR 81 E6 U
8e E6 U
?"
S c
E N
Gx x3 "3 <c RD En a
"# <e sh 25 uE ud
$c Ic
$3 ud uY u$
$3 90 7
9 3
2*8 2E 6 '?
n.'i RU Se 38 23 n*
BU 28 28 0
E$
EE Eu Eu c
< sa
<u
,a
<o 1: x
<o
<c
<m
>; c:
c.,
0 19.2 4.02 5.4
.07 TENSION kips m
4.8 4.8 0.8 6.9
.0003 5
kips kips 2.1 19,.2 4.02 5.4
<.00]
Q
~ kips 4.5d 5.5
- 0 0
66.0 3.41
>4
<.07
\\\\
MOSENT k-in d
d 16.8 16.8 0.8 6.9
.0003 k-in k-in 2.1 66.0 3.39
>4
<.001 k-in ci n Z"
0 19.2 3.99 7.0
.075 TENSION kips in 4.8 4.8 0.8 8.7
.0006 x
kips kips 2.1 19.2 3.99 7.0
<.001 kips O
Sd' 7.0 H
0 66.0 3.38
>4
<.075 y
MOFENT k-in
~
16.8 16.8 0.8 8.7
.0006 k-in k-in 2.1 66.0 3.35
>4
<.001 k-in 0
67.2 9.33 4.3
.13 E
TENSION kips 16.8 16.8 2.1 4.8
.0006 g
kips kips 4.4 67.2 9.33 4.3
<.001.
kips 4.5d 10.15 N
O 512.8 8.87
>4
<.13 s
MOMENT k-in G
128.2 128.2 2.1 4.8
.0006
~
E k-in k-in 4.4 512.8 9.21
>4
<.001 i
k-in EN O
67.2 9.44 6.7
.11 x
TENSION kips 16.8 16.8 2.1 7.6
.001 N
kips kips 4'. le 67.2 9.44 6.7
<.001 x
kips 8d 16.0 0
512.8 9.14
>4
~< 11 g
MOMENT
.kJin gs 128.2 128.2 2.1 7.6
.001 h
k-in k-in 4.4 512.8 9.55
>4
< 001
~~
k-in
.gu 1.-0"
~
l" 1
1" 1"
m
_. "l i
5 hr.
3
=)
H c--- -
y m
-d
-.)>-
o I
l 1
3 l
m a
0 j
=
y- -
e 5,
y
-o-1
?
a J
j ASSEMBLY NO. 1 ASSEMBLY NO. 2 Plate 1/2" x 9" x 0'-9" Plate 5/8" x 12" x l'-0" Anchors 4-1/2" Dia.
Anchors 4-3/4" Dia.
t
-.. 9" l '.9 "
=
c lh" 6" 1" 1h" 9"
9" lh" C
-a
=
=
= r
=
1 x-
~~
A_
3
)\\
x
)-
s
-. u - -
rd.
p - -- --.c o-l 1
e m
j
.E 7
1-
,A
~-
+--
g l
l L
=
I 8,
m i
I 54 1
J' y-- ---t-1 p
- -4 f
x_
a, g
o ASSEMBLY NO. 3 ASSEMBLY NO. 4 Plate 1/2" x 9" x l'-3" Plate 3/4" x 21" x l'-9" Anchors 6-1/2" Dia.
Anchors 8-3/4" Dia.
TYPICAL EXPANSION ANCHORED PLATE ASSEMBLIES FIGURE 1 e
l h,
Pg 7
/
'k Corresponds to Pre-Load
/
_ _ pecified S
p._
1 Pre-Load P g a<
O Corresponds to No Pre-Load l
I l
t.--
/M An g
=_
b a.
. Origin for Pre-Tension ase Displacement P
Ultimate Anchor capacity u
P
= Specified Pre-Load
/
f 8: = Initial Displacement with no Pre-Load 1
b
= Displacement at Ultimate Anchor Capacity FIGURE 2 IDEALkZED LOI.D-DISPLACEMENT CUINE FOR CONCIW fb LAPANSlOh ANCliORS
6--P 5.5k With Prc-Load
=
u 5,--
Without Pre-Load 4--
n g)
L x Design Load a
~
4 3-l Pre-Loa T
2-o 2.Ik l
l 1 - - - - --- - - - - Desi gn Load 0
1
.2 3
.4 3 d 3
a Displacement (Inches)
(a)
- 4. 5 d Embedment Pu = 7.Ok With Pre-Load Without Pre-Load 6-l s-I E
I 4--
~~
l 5
4x Design Load 3_
o l
c re-Load o
2-I d
2.Ik 1-.. _
d - De s i g n Lo a d 0
.1
.2
.3
.4
.5
.6 ld Displacement (Inches)
(b) 8d Ensedment Figure 3
IDEALIZED LOAD-DISPLACEMENT CURVC POR 1/2" DIAMETER EXPhNSION AliCHORS O
e
10 --
9--
I
~
8--
- _ L-4x' Design Load l
With Pro-Load 7--
l 6-Without Pre-Load g
5-pre-Load'
~
l o.
w 4--
4.4k x
3--
l j
2-
- -l- - Des i gn Load o4 1
l 0
.2
.4
.6
.8 Displacement (inches) 3-d 4
(a) 4.5d Embedment 16 u _._= 1 _6. 0 k _ __
P 15
(
With Pre-Load Without Pre-Load l
i 10 --
l 1 - -
4 x Design Load m
o.
l
.a I
x I
e 5
- Pre-Load l
oA 4--
4.4k l-3 2-. _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _L _ De s ign Loa d i
1--
0 O.2 0.4 0.6 0.8 ld Diaplacement (inches)
(b) 8d Embedment FIGURE 4
IDEALIZED LOAD-DISPLACE *iENT CURVE FOR 3/4" DIAMETER EXPANSION AN,' HORS e
e Anchor
////// ////////////////
Base Plate Plate in Loaded Position T
[i t bt VT BY EQUILIBRIUM t + t = T FIGURE 5 RIGID PLATE BEHAVIOR UNDER DIRECT TENSION LOAD T = Applied Tensile Load t = Corr,caponding Anchor Reaction 9
8 4
A w w, xot
/////
/
/ /' / / f l/ //////
.d D
d
.=
~
y
't, f~,
d Ec J
k l
STRAIN DISTRIBUTION NN T o fc5 g
L %
C N
3 e
STRr.;SS DISTRIBUTION Unknowns are cc& k D+d-k
~
ct" E
- c k
f
=E E
cb
" ^s s t
E C
=
c c
c C-T=0 Ch - T h
(D+d)
=M Where:
M = Applied moment d = Edge distance of. anchor c
= Compressive strain in concrete A
- Area of anchor c
s e
= Tensile strain in anchor t
k = Length of compression block b = Width of plate f
= Maximum stress in concrete c
E
= Modulus of elasticity of steel s
E
= Modulus of elasticity of concrete C = Total compression in concrete T.= Total tension in steel FIGURE 6 RIGID PLATE BEIIAVIOR UNDER PURE MO1ENT COUPLE LOAD
, 2 i.
3 A
s
.\\
3 T
M
\\
N h.(P/2 + Q)
M (P/2 + Q) 0 Q
1[1[y y y
~%
i l p PLATE DEFLECTION DUE TO APPLIED TENSION LOAD AND PRYING ACTION FIGURE 7 P = Applied Tension Load Q = Force Due to Prying Action 9
9 e
a B
D
PLATE SIZE = 1/2" x 9" x O'-9" ANCItOR BOLT SIZE = 1/2"#
L
\\
s l
o k
,_ Anchor
/
l,,'/
i I
m v
11 I
vNm e
4 k
Y 6 @ J/4" = 4.5"
=
d d
i OliE-WAY CO:1?RESSIO" a
][
~
/
ji 3
SPRING REPRESENTING e
e CONCRETE SLTPO.*1T h
Ar r;v fr/
nr ANCHOR 77 FIGURE 8
'Pinite Element !!odel of a Quarter Section of a TJpical Plate Assembly, 9
4
t 6
s 1
5 Tri fh
- e w
z4 o
x 5
m c
3 LE_ G2ND e
=
k)z Anchor reaction if there -
2
. M J,[ Pre-Load was no prc-load and no
~
f prying action.
p
/
- - -- Anchor reaction if there was
/
pre-load but no prying actic:'
/
- Anchor reaction including 1.0
/
the effect of pre-load and
/
prying action.
/
/
/
l.O 2.0 3.0 4.0 50 60 APPL:C0 FOT.C2 PIR ANCliOR (MIPS)
F10!!!:.2 9
m ---=.=:.=2 Load-rcaction Curve for a 1/2" x 9" Expansion Anchored Plate Assembly 9
e
e
~
7.0 6.0 n
E E
SD o
/
,(
l' ' ' "
- 6
.xw
/
c:
4.0 f
e
/
o
/
b
/
=
/
/
. LEGET.D a0
/
/
Anchor reaction if there
~~~~
/
was no pre-load and no
/
prying action.
EO y
Anchor reaction if there was
/
pre-load but no prying action
/
/
Anchor reaction including y
the effect of pre-load and 1.0 y
prying action.
/
/
/
/
l.O 2.0 3.0 4.0 SO 6.0 7.0 8.0 APPLIED FORCE FZR ANCHO?. LO'J (K!PS)
FIGURE 10 Ioad-reaction Curve for a 5/8" x 12" x 12" Expansion Anchored Plate Assemb]y e