ML20217H782

Paper 716 Entitled, Dynamic Behavior of Anchors in Cracked & Uncracked Concrete, Presented at 14th Intl Conference on Structural Mechanics in Reactor Technology in Lyon,France on 970817-22

ML20217H782
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Issue date:	08/17/1997
From:	Costello J, Graves H, Klingner R NRC, TEXAS, UNIV. OF, AUSTIN, TX
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NUDOCS 9804300072
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14th Intsrnational Conferance on l Structural Mechanics in Reactor Technology Lyon, France, August 17-22,1997 PAPER NO. 716 TITLE: " Dynamic Behavior of Anchors In Cracked and Uncracked Concrete" AUTHORS: H. L. Graves, J. F. Costello United States Nuclear Regulatory Commission, USA R. E . Klingner, J. M. Hallowell, Y. Zhang The University of Texas, Austin, TX USA I

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l l l l ABSTRACT: In early 1993, the US Nuclear Regulatory Commission began a research l l program at The University of Texas at Austin, to determine the dynamic behavior and l strength of anchorages used to attached nuclear power plant piping and equipment to the concrete building structure. In this paper, a general summary of the test program is given.

l DitTerences between the dynamic and static behavior of a cast-in-place anchor loaded in shear in uncracked and cracked concrete are also discussed.

i i 1. INTRODUCTION AND BACKGROUND l It is usually assumed that the behavior and strength of anchor bolts under static loads do

! not differ much from that of dynamic or earthquake load conditions. Based on a data survey, the adequacy of this assumption could not be verified from available data sources.

Therefore, there was a need for test data that provides a basis for comparing the static and dynamic behavior of anchorages. The objective of the research program at The University

of Texas at Austin (UT), was to develop needed data and verify by tests the above

assumption.

l l A research program test matrix was developed and included the following 5 tasks:

Task 1: Static and Dynamic Behavior of Single Tensile Anchors Task 2: Static and Dynamic Behavior of Multiple Tensile Anchors Task 3: Static and Dynamic Behavior of Near-Edge Anchors Task 4: Static and Dynamic Behavior of Multiple-Anchors l Task 5: Final Report i

in this paper an overall description of the UT research program is presented and the results of tests on a cast-in-place anchor loaded in shear are discussed.

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. 2. RESEARCH PROGRAM

SUMMARY

Test Parameters Concrete used in the UT research program had (Se same conspressive strength found in existing nuclear plants. The range of the compressive strength used was 28.1 MPa (4000 psi) to 38.7 MPa(5500 psi). The test also included some test in 21.1 MPa(3000 psi) i concrete. Concrete with soft limestone aggregate was used in most cases since this represents a conservative case. However, some concrete with river gravel aggregate and granite aggregate was also used to provide additional data points.

Anchorages used included those anchors generally used as post-installed anchors (installed after the concrete has set) and a cast-in-place anchor, headed bolt. Specific anchor types l

were: 1) wedge-type expansion anchors; 2) undercut anchors (two different designs); 3) j heavy-duty sleeve-type single-cone expansion anchors; and 4) a headed steel bolt. The l diameters of the anchors tested ranged from 9.5 mm (3/8 inch) to 25 mm (1 inch). Anchor installations were in accordance with anchor manufacture. s recommendations.

l Specimens were cast as rectangular-shaped concrete slabs without reinforcement in the area that would be affected .v concrete cone breakout. Specimens that were considered to i be reinforced had top and bottom steel reinforcement bars spaced to simulate a heavily reinforced wall. The steel reinforcement bars had 38 mm (1.~ ;us;y o.~,o..u ete cover.

l Test Loading l Most static loads for Tasks 1 and 2 were applied using a hand-controlled electric pump, l applying displacement at a constant rate, failure occurs in minutes. For dynamic loads, the failure occurred between 0.1 and 0.2 seconds. Figures 1 and 2 show the load rates used.

General Procedure Used For Cracked Concrete Testing Cracks were formed in the concrete test slabs once an anchor location was determined.

Cracks were made by using split tubes placed on both sides of the planned anchorlocation.

The split tubes are expanded by wedges to open the crack to the desired width. This

procedure allows one to place cracks anywhere on the surface of the concrete slab. The l following sequence was used

• The crack was started using wedges, and reduced to hairline width.

• The anchor was installed at the location of the crack.

• The crack was widened to 0.3 mm at the surface.

• The anchor was tested. The crack width was monitored by a linear potentiometers but was not controlled during testing.

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, 3. TEST RESULTS To date n!! testing under the UT research program has been completed. Results from Task I have been reported in a paper by Rodriguez et al,1994 [Ref. 2). Results from Task 2 have not been published but are expected to be available in late 1997. Task 3 results have been published by IIallowell,1996 [Ref. 3). In this paper, due to space limits, discussion is limited to tests performed under Task 3 for a cast-in-place anchor, see table I for test matrix. All tests were conducted in concrete with a compressive strength of 32.4 MPa, an embedment depth of 100 mm (4 inches), an anchor diameter of 19 mm (3/4 inches), and with an edge condition of 100 mm (4 inches). For the cracked concrete tests a 0.3 mm initial track was used.

DESCRIPTION CONCRETE ANCIIOR TEST NO.

Static shear test on single anchors 32.4 MPa (4700 psi) Cast -in-p .ce 3.1 in uncracked concrete River Gravel Aggregate (headed bolt)

Dynamic shear test on single 32.4 MPa (4790 psi) Cast-in-place 3.?

anchors in uncracked concrete River Gravel Aggregate (headed holt)

Static shear test on single anchors 32.4 MPa (4700 psi) Cast-in-place 3.3 in cracked concrete Riser Gravel Aggregate (headed bolt)

Dynamic shear test on single 32.4 MPa (4700) Cast-in-place 3.4 anchors in cracked concrete River Gravel Aggregate (headed bolt)

Table 1 Test Matrix (each test represents 5 replicates)

For static tests, a 534-kN (60 ton) centerhole hydraulic ram controlled by an electric pump applied load to the anchor. Dynamic tests were conducted with a 534-kN (60 ton) Enerpac double action hydraulic centerhole ram. Figure 3 shows the shear test setup.

Test Procedure For Test Numbers 3.1 - 3.4 For the cracked test the split tubes mentioned in section 1 above were inserted into drill holes at proper location. The linear potentionmeters were than positioned and the cracks

! were formed. The test reaction frame shown in Figure 3 was put into position along with I the ram and load cell. Load was applied and the data was transferred to a computer for analysis. The load displacement curves for the tests listed in table 1 are shown Figures 4-7.

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Discussion of Typical Load Displacement Curves Figure 4 shows that for the static test the anchor reached an average maximum load of 39 kN (8.8 kips) before significant deformation occurred. In Figure 5, dynamic tests, the maximum loaad was 49.9 kN (11.2 kips). For the tests in cracked concrete Figure 6 shows for static test that the anchor reached an average maximum load of 32 kN (7.2 kips). For the dynamic test Figure 7 shows the anchor average maximum load was 46.1 kN (10.4 kips).

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SUMMARY

AND CONCLUSIONS To determine the difTerence between static and dynamic behavior and strength of a cast-in-place bolt loaded in shear, data for each test type is compared. Figure 8 shows the load at concrete cone breakout for cast-in place anchors. In Figure 9 the concrete cone breakout load for a single-anchor connection is normalized by the breakout load for anchors under static !9ading in uncracked concrete (Test No. 3.1). The normalized graphs show the percentage change in capacity for different test conditions.

Thefollowing conclusions are madefor Test numbers 3.1 - 3.4.

e The dynamic capacity exceeds the static capacity in all cases.

o For cracked concrete, the capacity is reduced by approximately 18%

DISCLAIMER The findings and opinions are those of the authors artd do not reflect positions of the U.S.

Nuclear Regulatog Commission or the University of Texas at Austin.

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6. REFERENCES 1

1. Rodriquez, Miltun. Benavior of Anchors in Uncracked Concrete Under Static and Dynamic Tensile Loadings," M.S. Thesis, The University of Texas at Austin, August 1995.

2. Rodriquez, M., Zhang, Y., Lotze, D., Graves, H.L., and Klingner, R.E., Dynamic Behavior ofAnchors in Cracked and Uncracked Concrete," 5th Symposium Current Issues Related to Nuclear Power Plant Structures, Equipment and Piping, Orlando, Florida, December 14-16,1994.

3. Hallowell, J., Tensile and Shear Behavior ofAnchors in Uncracked and Cracked Concrete Under Static and Dynamic Loading," M.S. Thesis, The University of Texas at Austin, December,1996.

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. 1 l- Load vs. Time itatic Tests

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Figure 1. Applied Load for Static Tests, [Ref. 3l Load vs. Time - Dynamic Tests

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Typical Load-Disp,acement Curva - Cast-in-Place Anchor, Static Shear Lcteding, Uncracked Conc: rete Displacement (mm) 127 2.54 3.81 5 08 . 6 35 7.62 0 00 44.5 10 0 ,

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Figure 4. Load-Displacement Curve, Test Number 3.1 Typical Loa 60splacement Curve - Cast 4r> Place Anchor, l

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DM(nun) 1 27 2.54 3.81 5 G8 6.35 7.62 0.00 06.7 15.0 I l f

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6 Typical Load-Displacement Curve - Cast-in-Place Anchor, Static Shear Loading, Cracked Concrete Displacement (mm) 2.54 3 81 5.08 6.35 7.62 0 00 1.27 44 5 to 0 ,

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! Dynamic Shear Loading, Cracked Concrete i

Cisplacement (mm) 2 54 5.08 7.62 10.16 12.70 15.24 I . 0.00

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. ENed of Loading Rate and Cracked Concrete on Concrete Cone Breakout Load of Cast-ir>. Place Anchor Loaded in Shear 20 0 89 0 16.0 71.2 l'

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l Normalized E5ect of Loading Rate and Cracked Concrete on Concrete Cone Breakout Load of Cast 4n-Place Anchor Loaded in Shear 1.50 m

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