Text

Containment Vessel Tendons Stress Relaxation Properties of Retensioned Wires
	ML17255A719
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Site:	Ginna
Issue date:	12/31/1983
From:	Fulton J, Herr J, Hsieh S; GILBERT/COMMONWEALTH, INC. (FORMERLY GILBERT ASSOCIAT
To:	;
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ML17255A717	List: ML17255A716; ML17255A718; ML17255A719;
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	GAI-2499, NUDOCS 8403290189
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GAI REPORT NO ~ 2499

DECEMBER, 1983 ROBERT E.

GINNA NUCLEAR POWER STATION CONTAINMENT VESSEL TENDONS STRESS RELAXATION PROPERTIES OF RETENSIONED WIRES PREPARED FOR:

ROCHESTER GAS AND ELECTRIC COMPANY WRITTEN BY:

e F.

FULTON/S.

ST HSIEH REVIEWED BY:

kkX-J C

HER APPROVED BY:

C.

CHEN PREPARED BY:

GILBERT/COMMONWEALTH READING, PENNSYLVANIA Qbert ICenmonwealth r

8403290189'840326 t

II PDR ADOCK 05000244 P

PDR

0 TABLE OF CONTENTS SECTION TITLE PAGE

1.0 INTRODUCTION

2.0 RETENSIONED WIRE TEST RESULTS 2.1 2.2 2.3 Curve Extrapolations Factor Method Superposition Method 13 3.0 TENDON FORCE PREDICTIONS 14 3.1 3.2 3.3 Retensioning Ratio Values for Actual Tendons Base Curves for Actual Tendons Predicted Tendon Forces at July 1981 Surveillance 14 14 17

4.0 CONCLUSION

S 18 REFERENCES 20 TABLES Table 1 Stress Relaxation Test Conditions of Retensioned Wires Table 2 - July 1981 Surveillance Forces Compared with Predictions Table 3 Percent Difference in Measured Versus Predicted Forces Gilbert/Commonwealth

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TABLES OF CONTENTS (Cont'd)

FIGURES Figures 1-A through 1-I Base and Retensioned Stress Relaxation:

Log-Log Scale Figures 2-A through 2-I - Base and Retensioned Stress Relaxation.

Semi-Log Scale Figures 3-A through 3-K Retensioned Stress Relaxation Ratio Figure 4 Base Relaxation for Actual Tendons Figure S - Base and Retensioned Relaxation for Actual Tendons Figures 6-A through 6-R Comparison of Predicted and Measured Forces APPENDICES Appendix A Stress Relaxation Test Report 11

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e INTRODUCTION The R. E. Ginna containment structure is post tensioned by 160 vertical tendons.

The tendons were originally stressed in March and April 1969, and lift-offtests were performed on six occasions subsequent to this date over a period of 11 years.

From these tests, it was found that 'the measured tendon lift-offforces were generally lower than the predicted values.

As a result, Gilbert Associates, Inc.'GAI) was requested to investigate the possible causes for the lower-than-predicted tendon forces.

Reference 1

describes the details of this investigation, from which it was concluded that stress relaxation of the tendon wires is the only significant cause for the lower-than-predicted tendon forces.

By the time of the eight year surveillance in 1977, the average force of the tendons was marginally above the design requirement of 636 kips.

Rochester Gas and Electric Corporation (RG&E) decided to retension 137 of the 160 tendons.

This work was completed in June 1980.

The 23 tendons which were not included in the June 1980 retensioning program had been retensioned previously in May 1969, approximately 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months after their original stressing.

In order to develop data which would enable a determination of the stress relaxation property for the retensioned

tendons, retensioning tests on sample tendon wires were conducted at the Fritz Engineering Laboratory of Lehigh University.

The retensioning test program was actually an extension of the original wire relaxation tests initiated in March 1980 at the same laboratory.

After the specimens had been under load for a specified duration, seven (7) were restressed to their initial stress level.

Table 1 presents the test conditions of the seven (7) retensioned tendon wires.

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As discussed later in this report, the relaxation property of a retensioned wire is significantly different from that of an unretensioned wire.

In general, the former exhibits a lower stress relaxation.

Therefore, using stress relaxation property data from unretensioned wires to predict the stress relaxation in the retensioned tendons will lead to an over-estimation of the stress loss.

As a result, the predicted tendon forces based on these losses will be artifically low, which is unconservative for purposes of comparison with forces measured at future surveillances.

This report evaluates the Lehigh retensioning test data for the purpose of determining how to establish a representative retensioned stress relaxation curve for the Ginna tendons.

Two prediction techniques, referred to as the Superposition Method and Factor Method, were evaluated.

The Superposition Method basically assumes that superposition principles apply to the stress relaxation property and, consequently, relies only on unretensioned data.

The Factor Method, on the other hand, relies on the test results from both the unretensioned and retensioned wires.

The Lehigh retensioning test results were compared with those predicted by both the Superposition Method and the Factor i

Method.

The method providing the best representation of the retensioned stress relaxation property was concluded to be the Factor Method, and this method was then applied to reevaluate the data from the July 1981 surveillance.

The Factor Method was also used for predicting the forces for the tendons selected for the July 1983 surveillance.

2.0 RETENSIONED WIRE TEST RESULTS The results of the original stress relaxation tests and the retensioning tests have been summarized in a Lehigh report entitled "Relaxation Tests on 1/4" Prestressing Wires," which is included in this report as Appendix A.

Some later data, not GilberL/Commonwealth

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~I included in the Lehigh report, was subsequently r'eceived under the cover of a transmittal letter dated March 23, 1983 from professor Roger G. Slutter to GAI.

This data is also included in Appendix A.

The combined data set was used in the present analysis.

2.1 Curve Extrapolations The test data from the seven (7) retensioned wires reported in Appendix A was replotted on a log-log scale.

These are shown in Figures 1-A through 1-G.

In the figures, the curves designated "BASE" represent the stress relaxation versus= time-under-load prior to retensioning.

The curves designated "RETENSIONED" represent the stress relaxation versus time-under-load after the wires were retensioned.

The time corresponding to the last data point on the Base curve is the time at which tPe wire was retensioned.

From the figures, all the results display the fundamental characteristic that the stress relaxation of a retensioned wire is less than its Base relaxation.

The dashed lines beyond the last data point represent the extrapolations out. to 350,000 hrs.

(40 years).

The extrapolations I

shown in the figures for the Base curves were determined visually, and they are consistent with those in the semi-log plots in Reference 1.

The extrapolations for the Retensioned curves were also determined visually.

For both sets of curves, a linear extrapolation was used as a reasonable approximation.

As a way of "smoothing out" the data, the circled data points on the Retensioned curves are those selected as the reference points for the linear extrapolation.

This approach applies well to the curves of Wire g3 (Sl-B) in Figure 1-A, Wire f19 (76-Bl) in Figure 1-E, and Wire g7 (76-B) in Figure 1-C.

Their ret'ensioned stress relaxations at 40 years are predicted as

12Z, 16Z and

10Z, respectively.

Some judgement,

however, was required for the extrapolation of the curves for Wire g8 (76-C), Wire 810 (76-B2),

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Wire ij4 (51-C) and Wire gl2 (150-C2).

These are discussed separately below.

2.1.1 Wires 88 and f10 (Figure 1-D and Figure 1-F)

Table 1 indicates that sample wires g8,

($9, and fP10 are all from the same test wire pulled from Tendon 76 and were tested at the same temperature, 104o F, and the same initial stress, 70/ GUTS.

The only difference is that Wire f19 was retensioned at 100 hrs.,

Wire $ 10 at 1,000 hrs.

and Wire f18 at approximately 10,000 hrs.

Figures 1-D, 1-E, and 1-F show the Base and Retensioned curves for Wires 8'8, 89, and 810, respectively.

Figure 1-H presents the Base curves and the extrapolations of the three wires on a single plot.

In the figure, all three curves lie very close together.

This confirms that the three wires exhibited the same stress relaxation property before retensioning.

The Retensioned curves of the three wires are plotted together on Figure 1-I.

A deviation among these three curves is evident.

The curves start separating at around 5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months after retensioning, and out to approximately 10,000 hours0 days 0 hours 0 weeks 0 months under load the amount of relaxation which the wires experience is inversely proportipnal to the time at which they were retensioned.

Ho~ever, beyond 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months the relaxation values of the'ires j

which were retensioned at 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months (810) and 10,000 hours0 days 0 hours 0 weeks 0 months (88) slowly converge.

By approximately 15,000 hours0 days 0 hours 0 weeks 0 months , it appears that Wires 88 and 810 exhibit the same retensioned stress relaxation.

However, the relaxation for Wire g9, retensioned at 100 hours0.00116 days 0.0278 hours 1.653439e-4 weeks 3.805e-5 months , does not display a tendency to converge to the values of Wires 88 and gl0.

Figure 1-I also presents linear extrapolations consistent with those made in Figures 1-D, 1-E and 1-F.

From the figure, the extrapolated curve of Wire 88 appears to cross over that of Wire if10.

However, there is no reason to believe that the wires would actually exhibit this characteristic.

It is more reasonable GilberC/Commonwealth

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to interpret the data as indicating that somewhere in the 15,000 hour0 days 0 hours 0 weeks 0 months to 20,000 hour0 days 0 hours 0 weeks 0 months time range, the retensioned curves for Wire f18 and Wire 810 converge to approximately the same curve and continue as one curve thereafter.

In light of this, the extrapolations for Wires g8 and ij10 were adjusted.

Since data beyond 20,000 hours0 days 0 hours 0 weeks 0 months was not available, the average of the two extrapolation curves was constructed as the extrapolation curve estimated for Wires t8 and 810.

This adjusted extrapolation curve predicts a

13% stress relaxation at 40 years.

This curve was

used, as indicated in Figures 1-D and 1-F.

2.1.2 Wire

/$4 (Figure 1-B)

Figure 1-B shows two possible extrapolations for the Retensioned curve of Wire 84, indicated as dashed lines A and B.

Extrapolation A represents an extension of the straight line which passes through most of the data points located within the range from 1,000 hrs. to 10,000 hrs.

This line crosses over the Base curve and gives a

24% stress relaxation at 40 years.

Extrapolation B was based on the last two data points marked by squarest This extrapolation gives a

13% stress relaxation at 40 years.

Line B is considered to be more realistic than line A for two reasons.

First, line B seems to be more consistent with the concave-downward shape of the retensioned curve between 200 hrs.

and 10,000 hrs.

Secondly, the figure shows that the Base and Retensioned curves start approaching each other at 200 hrs.,

and they seem very likely to converge together somewhere in the 10,000 to 20,000 hr. range.

There is no reason to expect the Retensioned relaxation to become greater than the Base relaxation, which would occur if curve A were used.

Therefore, it was decided to use extrapolation B for Wire g4, as indicated in Figure 1-B.

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2.1.3 Wire

$512 (Figure 1-G)

It is seen from Figure 1-G that the two data points on the Retensioned curve at around 8000 hrs.

and 10,000 hrs. are displaced higher than would be expected based on the trend of the data between 1000 hrs.

and 6000 hrs.

Because of this, there exists a wide range of possible extrapolations, depending on the reference points selected.

One possible extrapolation is to extend a straight line which connects the data points at 8000 hrs.

I and 10,000 hrs. (line A) out to 40 years, at which time it becomes equal to the Base curve.,

This extrapolation gives a 3.8% stress relaxation at 40 years.

Another possibility is to use the two data points at approximately 6000 hrs.

and 4000 hrs. for extrapolation.

Line B was drawn through these two points and extended out to 40 years.

This results in a 2.5X stress relaxation at 40 years.

Other possible extrapolations give a 40-year stress relaxation of somewhere between 1.7/ to 3.8X.

By inspection, line B seems to agree better with the overall trend of the Retensioned

curve, and is therefore considered as the representative extrapolation for Wire 812.

The extrapolated line A was considered as an upper bound.

All the extrapolations discussed above were made linearly on a log-log scale.

To aid in the visual extrapolation process, the test results from the seven (7) retensioned wires were re-plotted on the semi-log plots in Figures 2-A through 2-I.

2.2 Factor Method As discussed earlier, the test results indicate that the stress relaxation of the retensioned wires is generally lower than that for the unretensioned wires.

Therefore, the retensioned stress relaxation may be obtained from the unretensioned results by applying a multiplying factor of between 0 and 1.

The Qbcrt ICommonwca! th

determination of the appropriate factors is the key point of this method.

These factors rely on the test data presented in Figures 1-A through 1-I or, alternatively, Figures 2-A through 2-I, which were used in this work.

At any time-under-load the original stress relaxation and the retensioned stress relaxation of each wire can be read from the Base curve and the Retensioned curve, respectively.

The factor corresponding to a particular time is obtained as the stress relaxation v'alue from the Retensioned curve divided by the value from the Base'urve.

Factors from each of the seven retensioning tests were plotted on a semi-log scale, as shown in Figures 3-A through 3-H.

The vertical axis represents the factor value, which's referred to as the stress relaxation "retensioning ratio".

The horizontal axis represents the time at which the wire was retensioned.

Each of the figures represents the retensioning ratio values at a particular time after retensioning.

Data exists for 104 F (four specimens) and 68 F (three specimens).

In each figure, it is apparent that the retensioning ratio varies with the time of retensioning and the temperature.

Based on the data points, curves were established and used to predict the

. i retensioning ratio'alues

~for the wires with different temperatures and different retensioning times.

Before describing the curve fitting process that was used, the effect of several parameters will be evaluated.

Retensioning Time Wires $8, 99, and 810 As listed in Table 1, wire specimens g8, g9 and f10 came from the.

same test wire and were subjected to the same test temperature and initial stress',

only the time of retensioning varied.

It is reasonable to consider these three wires collectively for evaluating the retensioning time effect.

Wires 88, iP10 and g9 were retensioned at approximately 10,000, 1,000 and 100 hours0.00116 days 0.0278 hours 1.653439e-4 weeks 3.805e-5 months , respectively.

As Figures 3-A through 3-H indicate, generally the Qbert IConeenwealth

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retensioning ratio values for Wire 88 are the lowest, and the ratio values for Mire f10 are lower relative to Wire 89.

From this it can be concluded that, generally, a lower percentage of the original unretensioned stress relaxation occurs for later retensioning times.

However, after a sufficient duration (time after retensioning),

the effect of the retensioning time becomes less significant to the extent that as the retensioning time increases beyond a particular range, the retensioning ratio tends to approach a constant value.

This is seen from Figures 3-E through 3-H where beyond >10,000 hours0 days 0 hours 0 weeks 0 months after retensioning, Mire jP10

'and Wire 88 have approximately the same retensioning ratio values although they were retensioned at different times.

The data from Wire iP3 provides supporting evidence, which is discussed in the next section.

The condition described above apparently does not hold true for very early retensioning times.

Wire 89, retensioned at 100 hrs ~,

still exhibits retensioning ratio values that are higher than those for Wires 758 and iP10 even at 350,000 hrs. after retensioning (Figure 3-H).

2.2.2 Wire Heat Figures 3-A through 3-H indicate that the retensioning ratio values for Wire f$8 and Wire g3 are in the same neighborhood.

As can be seen from Table 1, Wire g3 has the same test temperature and initial stress as that of Wire $8.

But Mire 83 is from a different heat and it was retensioned at a different time'.

6000 hours0.0694 days 1.667 hours 0.00992 weeks 0.00228 months versus approximately 10,000 hours0 days 0 hours 0 weeks 0 months for Wire 88.

Recall that Wire f10 was retensioned at 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months and its retensioning ratio is slightly larger than that of Wire 88 when the duration after retensioning is less than 10,000 hours0 days 0 hours 0 weeks 0 months .

For duration longer than 10,000 hours0 days 0 hours 0 weeks 0 months , there exists no difference in the retensioning ratio values between Wire F10 and Mire g8.

Therefore, it would be expected that for Wire 83 and Wire g8, the difference in Gilbert/Commonwealth

retensioning time of 6000 hrs. versus 10,000 hrs. would not produce any significant difference in retensioning ratio values=,

after 10,000 hrs., if there were no effect of the different wire heats.

In fact, the retensioning ratio data indicates that this is indeed the case, even as early as 1000 hrs. after retensioning (Figure 3"C).

Also, comparing Figure 2-A with Figure 2-D, it is interesting to note that the shapes of the Base curve and Retensioned curve of Wire 83 are very similar to those of Wire 98, although there exists a significant difference in magnitude of the stress relaxation curves.

Based on the preceding observations, it seems reasonable to conclude that the retensioning ratio values are the same for different wire heats, all other parameters being equal.

2.2.3 Temperature Since the comparison above for Wires /j3 and 88 indicates that the wire heat has no effect on the retensioning ratio, it is reasonable to consider Wires 84, 812, and g7 as one group all with the same temperature of 68 F, and Wires 89, 810, 83 and 88 as another group all with the same temperature of 104 F, even though more than one wire heat is involved in each group.

Figures 3-A through 3-H show that the wires at 68 F generally have higher retensioning ratio values than the wires at 104o F.

The data of Wires 84,

$ 12, and 87 are comparable with those of Wires 8107

$3y and 88 in the sense that they were retensioned at about the same times, respectively.

The figures indicate that the retensioning ratio data points for 68 F do not behave quite as well as those at 104 F, particularly at the relatively early times after retensioning of 10 hrs.

and 100 hrs (Figures 3-A and 3-B).

For these

times, the 68o F

retensioning ratio values

increase, rather than decrease, with the time of retensioning.

However, beyond 1000 hrs. after retensioning (Figure 3-C through Figure 3-H), the 68o F data

exhibits the s'arne basic characteristic of the 104 F data, namely a generally decreasing retensioning ratio as the time of retensioning increases.

Another observation is that after about 4000 hours0.0463 days 1.111 hours 0.00661 weeks 0.00152 months (Figure 3-D), the data for Wires f12 and 87, retensioned at 5500 hrs.

and 11,600 hrs.,

approach the 104 F

results; and at a time after retensioning of 100,000 hours0 days 0 hours 0 weeks 0 months (Figure 3-G) and thereafter, the temperature effect becomes insignificant.

From Figure 3-G and Figure 3-H, Wires

/$ 10', 83, 88, gl2 and 87 all have the same retensioning ratio at 100,000 hrs.

and beyond, regardless of the time at which they were retensioned.

However, Wire d4 which was retensioned at 1000 hrs. still exhibits a different retensioning ratio, apparently due to its temperature difference (compare Wires g4 and 810).

Based on the observations

above, two groups of curves, each group representing a temperature condition, were established as shown in Figures 3-I and 3-J.

Each curve represents, Eor a particular retensioning time, the retensioning ratio versus time after retensioning.

These were based on the curves in Figures 3"A through 3-H.

The procedure used Eor connecting the data points in Figures 3-A through 3-H Eor each temperature condition is described below.

2.2.4 Curves Eor 104o F

Since the quantity of data was somewhat limited, only a linear connection of the data points was considered to be practical.

As shown in Figures 3-A through 3-H, data points 9R, 10R and 8R are connected with straight lines since the test conditions and heat numbers of these wires are the same.

Data point 3R (different heat) lies only slightly below the 10R-8R line for times after retensioning up to 100,000 hrs.,

and the data point is only slightly above the line at 350,000 hrs. after retensioning.

These deviations are regarded as insignificant, and data point 3R is considered to be a confirmation of the retensioning ratio values set by the results from Wire 88.

A horizontal line was extended Qbcrt /Comnenwealth 10

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from point 8R out to 350,000 hours0 days 0 hours 0 weeks 0 months as the extrapolation.

This seems to be justified as discussed in the preceding section.

The retensioning ratio becomes a constant as the retensioning time increases beyond a particular value.

A comparison between points 3R and 8R indicates this occurs for retensioning times as early as 6000 hours0.0694 days 1.667 hours 0.00992 weeks 0.00228 months for the 104 F condition.

Certainly the results indicate that for retensioning times beyond 10,000 hours0 days 0 hours 0 weeks 0 months , the retensioning ratio has reached a constant value at each specific time after retensioning.

However, it is seen that the retensioning ratio increases as the time after retensioning increases.

The curves for the 104 F data were replotted in Figure 3-I.

In this figure, the retensioning ratio is plotted as a function of the time after retensioning, and each curve represents a

particular retensioning time.

2.2.5 Curves for 68 F

A similar approach was used to establish 68 F curves.

Three data points 4R,

12R, 7R were first connected by straight lines.

The lines were extended for extrapolations to 100 hrs.

and out to 350,000 hrs.

However, upper and Lower bounds to the extrapolated Lines were imposed as indicated below.

As the retensioning ratio is defined, it cannot exceed a value of 1.

Thus, the linear extrapolations back to 100 hrs. in Figures 3-D through 3-H are cut-off at a ratio value of 1.

In the extrapolation out to 350,000 hrs.,

the Line for the 68o F curve appears to intersect with the horizontal line for 104o F.

Beyond the intersection point, it is conservative to assume that the 68 F curve will merge into, but not fall below, the 104o F curve.

The data alone is not sufficient to indicate if this assumption is justified.

Nevertheless, there is no reason to expect the retensioning ratio data for 68 F to reverse its previous trend and become less than the 104 F values.

Qbert /Commonwealth 11

Figures 3-A and 3-B are particularly discussed here.

Obviously from the figures it is very difficult, if at all possible, to justify a reasonable extrapolation curve for the 68 F condition when the time after retensioning is less than 1000 hrs.

However, in this work, it is reaLly not necessary to determine the retensioning ratio values at times after retensioning any less than 1000 hrs. since none of the tendons were retensioned prior to this time.

Therefore, the curves in Figures 3-A and 3"B were not considered in the tendon force predictions.

Only the 68 F and 104 F curves shown in Figures 3-C through 3-H were used and these are replotted in Figure 3-J.

In the figure, the time after retensioning now appears on the horizontal coordinate line, and each curve represents a particular retensioning time.

With Figures 3-I and 3-J, the retensioned stress relaxation can be predicted by applying the retensioning ratio values to the Base curves.

The Base curves appear in Figures 2-A through 2-G.

At any particular time after retensioning, the retensioning ratio for a particular temperature and time of retensioning can be directly read or obtained by interpolation using both Figure 3"I and Figure 3-J.

This ratio value can then be used as a multiplier on the stress relaxation value from the Base curve obtained at the same time as the time of interest after retensioning.

The resulting value is the predicted stress relaxation for the retensioned wire at a particular temperature, and a particular retensioning time and time after retensioning.

For comparison, the Retensioned curves which were predicted by the Factor Method described above are identified as "F.M." and shown together with the Lehigh test data in the Figures 2-A through '2-G.

Also shown in the figures are the Retensioned curves predicted by the Superposition Method (Labeled by S.M.).

This method is discussed below.

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3.0 TENDON FORCE PREDICTIONS Up to this point, the discussions have been limited to the Lehigh test program on the retensioned wires.

By using the retensioned test data, a prediction technique called the Factor Method was developed which offers a reasonable approach for determining the retensioned stress relaxation in the test wires.

However, the final objective is to apply this technique to the prediction of stress loss in the retensioned tendons.

For this purpose, retensioning ratio values which are suited to temperature conditions of the actual

tendons, and Base curves which represent the stress relaxation properties of the tendons were established in the manner described below.

3.1 Retensioning Ratio Values for Actual Tendons During plant operation the air temperature inside the containment is approximately 100 F, and the temperature of the tendons is expected to range as high as 85 F to 95o F (page 2-38, Reference 1). It is believed that this temperature range has been experienced by the tendons during most of their life.

Therefore, an average temperature of 90 F was selected as the representative temperature for the prediction of tendon relaxation.

A's a result, it was necessary to establish retensioning ratio values corresponding to 90o F in order to apply the Factor Method to the actual tendons.

Either Figures 3A through 3H, or alternatively Figures 3I and 3J, may be interpolated to obtain the ratio values for 90 F.

Figures 3A through 3H were actually used, for better accuracy.

The resulting 90 F curves are presented in Figure 3K.

3.2 Base Curves for Actual Tendons Figures 3-1 and 3-2 of Reference 1 show the unretensioned (Base) stress relaxation of all the specimens involved in the Lehigh Test Gilbert /Commonwealth 14

Program.

The wires fog1 these specimens were extracted from Tendons 51, 76 and 150st In the figures it is seen that the unretensioned relaxatign property varies depending on test temperature, initial. sggess, and material heat.

Among these

curves, four representative ones were selected and replotted in Figure 4 herein.

TheyFgre curves 76-C (Wire 88, 0.7

GUTS, 104 F) a 76 B (Wile $7 a 0 ~ 7 GUTSa 68 F) a 51 B (Wire 83a 0 ~ 7 GUTSY 104 F) and 51-C (Wirevg4, 0.7

GUTS, 68o F).

The Base curves for tendon 150 were not <uspd because, as explained in Reference 1, the data of interest at:,g 7CGUTS and 104 F was suspect.

Wt, By using a linear intprpolation between the curves at 68 F and

...104o F, the curves foehn'tendon 76 at 90o F and Tendon 51 at 90 F

were established..t,.ghgycare labeled as76-90o F and 51-90o F in Figure 4.

Thesetwo pprves are considered as representative unretensioned relaxation curves, or Base curves, at 90 F for tendons,76 and 51.

Thy. figure shows that curves 76-90 F and 51-9Qz F are very similar in shape, although somewhat different in magnitude

'(16.6% versus, 14.2% at 100,000 hours0 days 0 hours 0 weeks 0 months ).

of From Figures 2.9-2~ 2.gt 3, and 2.9-4 in Reference 1, it was shown that the average eEfeggive stress relaxation at 100,000 hours0 days 0 hours 0 weeks 0 months for all tendons compri'qedppldly of wires from any of the three different test heats was in the neighborhood of 15%.

This value is noted between the curves 76-90 F and 51-90o F in Figure 4.

The 15% value for average effective stress relaxation is within 10 percent of the test;tvalues of 16.6% (Curve 76-90o F) and 14.2%

(Curve 51-90 F).

Therefore, it seems feasible to establish a

single Base curve for use in determining the stress losses in all tendons.

At the very,/east, all the Base curves, if there exists more than one, should, have a sabhae similiar to the 76-90 F or 51-90o F Base curves.

~bTo investigate this further, two different approaches to establishing unretensioned relaxation curves (Base curves) for the tendons.

were considered, which are discussed below.

.Qbert /Commonwealth 15

4

e 3.2.1 16% Relaxation Curve It was assumed that a

common unretensioned relaxation curve (Base curve) can be used for all the tendons.

This common Base curve has a relaxation of 15% at 100,000 hours0 days 0 hours 0 weeks 0 months , and has a shape similar to Curve 76-90o F.

The shape of Curve 76-90

'F was selected over Curve 51-90 F because longer-term test data was available for this curve, which would provide a more accurate extrapolation out to 40 years.

At 100,000 hrs.

the ratio of 0.9 was established (15% divided'y 16.6%),

and the 15% curve was constructed by scaling Curve 76-90o F by this factor.

The resulting curve is shown in Figure 5 and is noted as "16% Base Curve", since the 40 year relaxation turned out to be nearly 16%.

The other two curves shown in Figure 5 were constructed by applying the retensioning ratio values, obtained from the 1,000 hr. and 100,000 hr.

curves in Figure 3-K, to the 16% Base Curve.

Thus, the two resulting curves in Figure 5 represent the retensioned stress relaxation property of a 16% relaxation grade of wire after the wire is restressed either at 1,000 hrs. or 100,000 hrs.

I

'following its original stressing.

3.2.2 Effective Stress Relaxation Curve As an alternative to using.a common relaxation curve, a unique Base curve was determined for each tendon.

The effective stress relaxation which each tendon had exhibited as of June 1980 (100,000 hrs.)

was determined first.

Then, a scaling factor similar to that obtained for the 16% curve was determined for each

tendon, based on its unique effective stress relaxation value at 100,000 hrs.

Based on the value of the factor, the 76-90o F curve in Figure 4 was scaled to provide a corresponding Base curve for each tendon.

For comparison, both types of Base curves described in sections 3.2.1 and 3.2.2 were used to reevaluate the stress loss in the GlberC/Commonwealth 16

K

tendons for the July 1981 surveillance.

The approach which results in the best agreement with the lift-offforces, using the retensioning ratio values described in'ection 3.1, can be used for force predictions at future surveillances.

3.3 Predicted Tendon Forces at July 1981 Surveillance The July 1981 surveillance was performed one year and one month (9490 hours0.11 days 2.636 hours 0.0157 weeks 0.00361 months ) after the June 1980 retensioning.

Eighteen tendons were selected for the surveillance.

Among the 18 tendons under surveillance, 14 were from the tendons retensioned in June

1980, and the remaining four tendons were from those retensioned in May 1969.

The tendon numbers, lift-offsequences, last lock-off

forces, and measured lift-offforces at the surveillance, are presented together with,the predicted results in Table 2.

The retensioning ratio values described in Section 3.1 were used for predicting the stress relaxation in the tendon wires.

These ratio values were obtained from Figure 3K and applied to the two different types of Base curves discussed in Section 3.2.

Other force losses due to such as shrinkage,

creep, and elastic shortening in concrete were calculated using the methodology I

described in Reference 1.

The combined force loss was then substracted from each tendon lock-off force appearing in column (1) of Table 2.

The results are listed in either column (3) or column (4), depending on whether the 16K Base curve or an Effective Stress Relaxation curve was used as the Base curve.

These forces are to be compared with the measured values appearing in column (2) of Table 2.

A comparison of the percent I

difference between measured and predicted forces for the two types of Base curves is presented in columns (1) and (2) of Table 3.

The mean of the absolute sum of the percent differences for the 16/ Base curve approach is 1.64/,

compared to 2.64/ for the individual Base curve approach (Effective Stress Relaxation curves).

Without considering Tendon 74, because its effective Gilbert ICommonwcalth 17

~

stress relaxation value was somewhat questionable, the values reduce to 1.55% compared to 2.21%.

Comparing all the results in columns (1) and (2), it seems reasonable to conclude that both types of Base curves result in predicted tendon forces that generally agree about equally well with the forces measured.

The predicted force-versus-time curves for each tendon are shown in Figure 6.

The solid curves represent predicted forces based on (1) the Effective Stress Relaxation (E.S.R.) of the particular tendon, modified by the retensioning ratio values, and (2) 16%

relaxation, modified by the retensioning ratio values.

The 1981 surveillance data are also indicated in Figure 6.

Returning to Table 3, columns (3) and (4) show the percent difference between the measured forces and 95% times the predicted forces.

The 95% predicted force value is the acceptance limit that is specified in a new subsection in the ASME Code on Inservice Inspection of Concrete Containments (2). It is seen from columns (1) and (2) that the measured forces are generally slightly below their predicted values for 9 of the tendon forces predicted using the 16% Base curve and for 7 of the tendons using the Effective Stre s Relaxation Base Curves.

However, all but-one I

of the measured fo ces are greater than 95% of the predicted values for both approaches.

4.0 CONCLUSION

S, 1.

Compared to the Superposition Method, the Factor Method, which uses retensioning ratio values, provides the best means for accounting for the retensioning effect on stress relaxation in the tendon force prediction process'.

The curves for the retensioning ratio values presented in Figure 3K are to be applied to a Base curve relaxation for future force predictions for the Ginna tendons.

Gilbert/Commonwealth 18

~

3.

Both the 16% Relaxation Base Curve and the Effective Stress Relaxation Base Curve resulted in predicted tendon forces that generally agree about equally well with the forces measured at the July 1981 Surveillance.

Although the 16%

Base Curve has the advantage of simplicity, since one curve applies for all the tendons, both types of Base curves will be used for the July 1983 Surveillance in order to provide a

further comparison.

Gijlert /Commonwealth 19

REFERENCES Robert E. Ginna Nuclear Power Station Containment Buildin Tendon 2.

ASME Boiler and Pressure Vessel Code Section XI Rules for Inservice Ins ection of Nuclear Power Plant Com onents Draft Subsection IHX Inservice Ins ection of Concrete Containments, May 1982.

Gilbert ICommonwea! th 20

~

TABLE 1 STRESS RELAXATION TEST CONDITIONS OF RETENSIONED WIRES Tendon I.D.

Specimen No.

Heat

'No.

Stress Temperature

(%GUTS)

( F)

Time at Retensioned Retensioning Duration (Hours)

(Hours) 51-B 51-C 19477 19477 70 70 104 68 6000 1000 18214 11137 76-C 76-Bl 76-B2 76-B 10 30091 30091 30091 30091'0 70 70 70 104 104 104 68 10190 100 1000 11600 14229 8635 19229 3575 150>>C2 12 10355 70 68 5500 9720 Stbert/Commonwealth 21

TABLE 2 JULY 1981 SURVEILLANCE FORCES COMPARED WITH PREDICTIONS Tendon No.

Sequence of Lift-Off Last(>>

Lock-Off (Ki s)

Measured Lift-Off (Ki s)

(2) 16K Relexation with Retensioning Eff. Stress Relax. with Retensioning (3)

(4)

Predicted Lift-OffForce (Ki s)

June 1980 Retensioned Tendons 13 155 17 21 51 53 62 63 74 761 754 776 765 765 761 773 769 749 730 738 727 725 710 734 716 722 731 721 713 734 723 723 722 730.

730 708 707 718 738 723 728 710 733 717 664 76 84'3 125 133 10 12 13 14 754 753 761

'68 757 713 714 713 705 734 714 713 721 726 718 707 711 714 746 712 May 1969 Retensioned Tendons 33 36 116 16 17 18 770 763 744 757 679 657 646 690 670 664 647 658 679 689 660 663 In June 1980, except for the tendons retensioned in May 1969 Qbert /Commonwealth 22

~

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TABLE 3 PERCENT DIFFERENCE IN HEASURED VERSUS PREDICTED FORCES Tendon No.

Predicted 16% Relax.

E.S.R. with with RT RT E.S.R. with RT 16% Relax.

with RT 95% Predicted (2)

(3)

(4) 13 155 17 21 51 53 62 63 74 76 84 93 125 133 33 36 116 1.2 3.5

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g=l 1.64 2.64 5.71 5 ~ 92 N

Z (An[

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850 e. FIGURE 6A COMPARISON OF PREDICTED AHD MEASURED TEHDOH FORCES INCLUDING R ETEHSIOHIHG FOR TEHDOH HO. 13 .luffJAN.flilftftflfifffffffftfllff 0 PREVIOUS SURVEILLANCE LIFT OFF 800 IG OR IN LOCK 0 F AL OCK OF VAL 750 'X Q CL 700 I-SUR LAN IL FT 0 F (2) 16%o RELAX. WITH RT 650 (I) E.S.R. WITH RT I I I IIIlllllllllll 95%o X (2) 600 X ttCI- 'X0OX ~ I-z 0 wUX w D w I wU 'X w D 1.4 2.0 2.5 95% X (I) IIIIIIIIIIIIII I-R 0 I-X gg w w w w. UX w tt:D ~ E.S. R. WITHOUT RT FF V FT0 ~ I ~ I-T LI I I i w ALUE I- ~ lY ~ a. w oL I-CI. & C w Io' tL w I sI ~ P I 4.5 9.6 12.0 13.6 15.6 17.6 22.6 27.6 32.6 37.6 42.6 12.6 TIME AFTER CONTAINMENTWALL CONSTRUCT!OH (YEARS)
850 FIGURE 6B COMPARISON OF PREDICTED ~ AHD MEASURED TENDON FORCES IHCLUDIHG R ETEHSIOHING FOR TEHDOH NO-155 ~f8:ftftLtNlftftfltftf fltfmNfffllllfl ~ PREVIOUS SURVEILLANCE LIFT OFF 800 sc 750 X O 700 O I ORIGINAL LOCK OFF VALUE SU E RT LOCK OFF YALU IHIillHmlfllml YEILLANCELIFT OFF (I) E.S.R. WITH RT I HI IIIIIIIIIIIIII (2) 16% RELAX WITH RT 650 600 'X 2:0 CIX I-1.4 0 tUuz IU CCD W I I Wu 2: IU D 2.0 2.5 W. V 'X IIJ Wu'X UJ CL D IIJ I: IL RT I X X O I-K Cg IJII-w wl I LIFT I I 0 OF F VALUE --- O ~>> IIL ~ IL'U MI t' CC ~ I-tU O CV I- 'L ~ CC'- CC 0-O lllllllllllllll 95% X (I) lllltllllllltt 95% X (2) I4 ~il.~ IjilII ~ ~ ~ E.S. R. WITHOUT RT 4.5 9.6 12.0 13.6 15.6 17.6 22.6 27.6 32.6 37.6 42.6 12.6 TIME AFTER CONTAIHMEHTWALL CONSTRUCTION (YEARS)
850 FIGURE 6C COMPARISON OF PREDICTED AHD MEASURED TENDON FORCES INCLUDING RETEHSIOHIHG FOR TEHDOH NO. 17 . itUtiittitiittltiiitmliHNtftttltliil ~ PREVIOUS SURVEILLANCE LIFT OFF 800 RT LOCK OFF VALUE 750 u CJ 'X CJQ 700 I 650 0 RI Gl LOCKO SURVEILLANCE LIFT OFF W .V (1) E.S.R. WITH RT I I I I IIIIII IIIII I I (2) 16% RELAX WITH RT ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ I ~ ~ ~ ~ ~ I 95% X (1) E.S.R. WITHOUT RT I ~ I ~ I ~ ~ ~ I ~ I I ~ ~ I I ~ 95% X (2) 600 X0' I-0 Wu 2: UJ tt:D IU I I tUu 2'. lU W I X LL" z I-ce 2 I I/I W)I ~ 4 tg I UJ RT LIFT OFF VALUE I- 'L 'i" tU I O-I- tt. C tU In L ] I-JJ: e i W i I o'- ~ I >-. Ill ~ C4, I- 't: 'I 1.4 2.0 2.5 4.5 TIME AF T E R CONTA 9.6 12.0 13.6 15.6 17.6 12.6 INMENT WALL CONSTRUCTION (YEARS) 22.6 27.6 32.6 37.6 42.6
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850 FIGURE 6D COMPARISON OF PREDICTED ~ AND MEASURED TEHDOH FORCES INCLUDING R ETEHSIONIHG FOR TENDOH HO. 21 ttMt~ttftHlNtlfltN!tttNtftttttlttt 4I PREVIOUS SURVEILLANCE LIFT OFF 800 IG OR IN OCK 0 F VA U RTLO 0 ALUE 750 W LI K O 700 CI I UR IL IFT OF L (I) E.S.R. WITH RT IIIIIIIIIIIIIIIII (2) 16oo RELAX. WITH RT 650 600 x Vl wRI- ~ ~ 'X. O'. OX ~ I-1,4 0 wV 2: w D w I wUX w D 2.0 2.5 I I W w ~ Uz w 4.5 TIME AFTER COHTAIHM - wVX w OC ~l gg w l CI R 0 I-X W wlL ~ LIFT OFF V LUE I-;- c j. C w ~L s IL: i + 1 o'V-IIIIIIIIIII' I 95io X (1) 95% X (2) I I I I 0 II 1 III 'IIII S.R E. WITHOUT RT I- 'C ~ ID 9.6 12.0 13.6 15.6 17.6 22.6 27.6 32.6 37.6 42.6 12.6 EHT WALL CONSTRUCTIOH (YEARS)
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850 FIGURE 6E COMPARISOH OF PREDICTED AND MEASURED TENDOH FORCES IHCLUDIHG RETENSIONING FOR TENDOH HO. 51 8Wf&Cf~lf.Nflflftfllf fffffftlftllffl 4 PREVIOUS SURVEILLANCE LIFT OFF 800 RT LOCK OFF VALUE R 750 III O CI IL 'X Q 700 Cl I-650 RT LOCK OFF VALUE SURVEILLANCELIFT OFF IUU (I) E.S.R. WITH RT I I I I I I IIIIIIIIIII (2) 16% RELAX. WITH RT 95% X (I) E.S.R. WITHOUT RT 600 00 1 I-I- 0 UJUr W 'D CC IU I IUUr IU tYD I l gg W W 'r IU 10: 'n r Wf W Ur ln Q I-r WI-I W W. 0 1 .I-I ~r .Wl RT LIFT OFF VALUE I-W s Qt W I o'- 'V I- 'Y ~ 95% X (2) 1.4 2.0 2.5 4.5 T IIl0 h I-TF R I.A 9.6 12.0 13.6 15.6 17.6 22.6 12.6 NThINI4FNT WAI.I. CONSTRIICTIOH (YEARS) 27 6 32 6 37 6 42 6
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850 FIGURE 6F COMPARISOH OF PREDI TED. AHD MEASURED TENDON FORCES IHCLUDIHGRETEHSIOHIHG FOR TENDOH HO. 53 ltWf~tttNttttttiNtttmtttttttttttttt ~ PREVIOUS SURVEILLANCE LIFT OFF 800 T LO R CK OFF VALUE 750 ttI LI r CIQ 700 I-0RI G A C LO 0 FF YAL E URYEILLANCELIFT OFF (2) 16% RELAX. WITH RT IIIIIIIIIIIIIIIII 650 600 I/1 I- 'X OO ] I-X O tttUz ttt tU UX ttt I 0-ttt Oz ttl D X 1I-g w 4 ttt U -0. x I-a AI an w(ttL RT z I O I-tL X ltt ttt I LIF I I-M I TOF I III-F VALUE O ~ g I ~ t ttt I ot tU ~ E.S. R. WITHOUT RT 95% X (\\) I- 'C ~ CI ~ 2.0 2.5 4.5, 9.6 12.0 13.6 15.6 17.6 22.6 27.6 32.6 37.6 42.6 12.6 TIIAC A FTFR CAHTAIHtlFNTWhl I. (.ANSTRIICTIAN(YEARS)
850 ~ ~ F IGUR E 6G COMPARISOH OF PREDICTED-AND MEASURED TENDOH FORCES INCLUDING RETENSIOHING . FOR TEHDOH HO. 62 tfMl&ClitH3lltttfllN'llNffff ffffllllll 0 PREVIOUS SURVEILLANCE LIFT OFF coo RT LOCK OFF VALUE I LL 750 IlI U CCOIL X O ClK 700 ILII-650 ORIGINAL LOCK OFF VALUE SURVEILLANCE LIFT OFF .- W O'x 'I) E.S.R. WITH RT ~ rer ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ (2) 16% RELAX, WITH RT 95% X (I) } 95% X (2) E.S.R. WITHOUT RT 600 K I. OOX WI-I-
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850 F IGUR E 6H COMPARISOH OF PREDICTED At<D MEASURED TEHDOH FORCES It(CLUDlt(G R ET EtkSIOHIHG FOR TEt(DOH HO. 63 ttl t IIL t t l Ilt I ltlll14tlllltll1lllllllllltlltlll 0 PREVIOUS SURVEILLAHCE LIFT OFF 800 RT LOCK OFF VALUE 750 Ittu O X CI Clx 700 I 650 ORIGIHAL LOCK OFF VALUE SURVEILLANCE LIFT OFF (2) 16% RELAX WITH RT I I I Iltlltlltlltll (1) E.S.R. WITH RT I I I I I I I I I I III I III 600 W 00Ir ',4 x I 0 I 4 WUr W D W I I WUr W D 2.0 2.5 W ' X IU D ~ I I W Pl 1 4.5 TIME AFTER COHTA -WUX D lY W U ~Il X0 I-X WI-w W 9.6 12.0 13.6 12.6 IHMEHT WALLCOHST RUCTIOH 95% X (2) Illllllllllllll 95% X (I) lljlllllllllllt E.S.R. WITHOUT RT I-i. w[ I I-I g'- I o' C4. I-lC W I-tL W Pl 1 W ~ C4 I CI ~ 15.6 17.6 22.6 27.6 32.6 37.6 42.6 (YEARS)
850 F IGUR E 6T. COMPARISOH OF PR EDICTED. AND MEASURED TENDON FORCES INCLUDING RETENSIOHING FOR TENDOH HO. 74 ttMf~tttftflltNINtllfttfftff fttfllftf PRE VIOU5 EIL FF SURV IFT 0 LANCE 800 ~ >50 u O K OO 700 I- ... ORIGINAL LOCK OFF VALUE RT LOCK OFF VALUE mllllmllllllllmlllllllll!Ilillf Ill J'URVEILLANCE LIFT OFF 650 (2) 16/o RELAX. WITH RT 600 00 f X I-X 0 WuX W 'D W I W'uX W lL D W X I-g I<< ~ Wl Ur X I-lL'I: lL' ~ I-o I-CL X X0 I-tL X lL lUI-W lU gg lL lU M I I- ~ 'U e ) ~ C7 I- ~ tL: lL-UJ. I I l ~ ~ W I >-: I o C4 ~ f I-I I z I >- 95oo X (2) (I) E.S.R WITH RT 1.4 2.0 2.5 4.5 9.6 12.0 l 13.6 I5.6 17.6 22.6 27.6 32.6 37.6 42.6 12.6 TIME AFTER COHTAINMEHTWALL CONSTRUCTIOH (YEARS)
850 FIGURE 6J COMPARISOH OF PREDICTED AHD MEASURED TEHDOH FORCES IHCLUDIHG R ET ENSIOHIHG FOR TENDON NO. 76 11&fNtHII.Htflftifmtflftfffifflllllfl PREVIOUS SURVEILLANCE LIFT OFF 800 R 750 IJJu 'x QQ 700 I 650 ORIGINAL LOCK OFF VALUE RT LOCK OFF VALUE SURVEILLANCE LIFT OFF (2) 16% RELAX WITH RT (I) E.S.R. WITH RT I I I I I I I II IIII I III 600 X UJ I-XOG j 'X 1.4
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I 2.0 2.5 W OX W D Tll~ ~. r gg I W Cl W' 'X UJ D ~ Vl -.- UJ X WI-'w Ol x I-a I W ~ I- ~ RT LIFT OFF VALUE X CI I-CL' gg UJ0 w W J I UJ I-Q: W 0-O IIY: C UJ MI L ~ I Ik ' UJ I >-'- I I o'V I- ~ UJl>. 95% X (2) llIllllllllllll 95% X (1) E.S.R. WITHOUT RT I- ' ~ IX 'J ~ 9.6 12.0 '3.6 15.6 17.6 12.6 4.5'2.6 27.6 32.6 37.6 42.6 rnaIT J lilrltaITIrr J I I rnarCTrrllrTlnir Jvtl nCI
850 FIGURE 6K COMPARISOH OF PREDICTED AHD MEASURED TENDON FORCES INCLUDING RETENSIONIHG FOR TENDON NO. 84 . t~~tU.ttilltNitNllimtittltilili PREVIOUS SURVEILLANCE LIFT OFF 800 750 W O X O 700 Q I-650 ORIGINAL LOCK OFF VALUE RT LOCK OFF VALUE SURVEILLANCE LIFT OFF (2) 16,o RELAX. WITH RT I I I I I I I I I I I I I I I I I I I (I) E S.R. I WITH RT 95.o X (2) 600
X r0O l X
~ I-1.4 I-X0 UI OX Ul D Ul I IU OX UI CL'.0 2.5 Ul I OX IU CCD ~ 'I (Y Ul I 4.5 T IllP h P T I-R CA IU OX Ul CCD I CC 'Q X X0ill8 IUI-IU I RT LIFT OFF VALUE I')')I I-(Y K ~ C ~ IU. Ul I I IL 'l U'l CI I-27.6 22.6 9.6 12.0 13.6 15.6 17.6 12.6 NThlNMENTWAI.I CONSTRUCTIOH (YEARS) I-Ul I I CC ~ CC sn c'o ~ l-1O. cv 32.6 37.6 42.6 95.o X (I) E. S. R. WITHOUT RT
0
850 F IGUR E 6L COMPARISON OF PREDICTED ~ AHD MEASURED TENDON FORCES IHCLUDIHGRETEHSIONIHG FOR TEHDOH HO. 93 .~~tNtftltfHNHllNNHtmllttl ~ PREVIOUS SURVEILLANCE LIFT OFF 800 ORIG N LOCK OF F VALUE RT LOCK OFF VALUE 750 UJ LI CC CJ 'X O 2: 700 I-650 SURVEILLANCELIFT OFF (2) 16%o RELAX. WITH RT ~ et I&AICttH (I) E.S.R. WITH RT 95% X (2) 600 OD 1X I-0 UJV 'X W D W I WVX UJ IL W ' 'X UJ lY ' ~ PI W fj IJ: L UJVX (Y D (Y W C I-RT )I I I LIFT OFF VALUE O I ~ R" ~ I UJ IoI IIIIIIIIIIIIIII 95%o X (I) I I I I I I I I I I II I I II E.S.R. WITHOUT RT I I-W ~ 1.4 2.0 2.5 l 4.5 9.6 12.0 13.6 15.6 17.6 22.6 27,6 32.6 37.6 42.6 12.6 TIME AFTER COHTAIHMENTWAI L CONSTRUCTION (YEARS)
'l ~
850 FIGURE 6M COMPARISON OF PREDICTED ~ AHD MEASURED TENDON FORCES INCLUDING RETEHSIONIHG FOR TEHDOH HO. 125 ttMf~lHWlftftffl Nllfttffffflfflf fill ~ PREVIOUS SURVEILLANCE LIFT OFF 800 C 0 0 ALUE 750 IQu OIL 'X OO 700 IQ 0 R A LOCK 0 F F V LU SU AN E LIFTOF (I) ESR. WITH RT 650 600 X X0A 0 wVX w D CC w I I wUX w D w z w wVZ wf-w u c- > x I-a W Ij lL ~L w~ mL X O I-an IZ X gg w w w. I-w 0 T LIFT OFF VALUE R I-i. (L: C-w 'n L I I >-'- I I o I- 'V 95% X (I) IIIIIIIIIIIIIII (2) 16% RELAX WITH RT ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ E.S. R. WITHOUT RT 95% X (2) I-CI. 1.4 2.0 2.5 1 4.5 9.6 12.0 ~ 13.6 15.6 17.6 22.6 27.6 32.6 37.6 42.6 12.6 TIME AFTER COHTAINMEHTWALL CONSTRUCTION (YEARS)
e
850 FIGURE 6N COMPARISON OF PREDICTED. AND MEASURED TENDOH FORCES INCLUDING R ET EHSIONIHG FOR TEHDOH HO. 133 t~ttNlltNlltftfNNfftffff ffffffffill ~ PREVIOUS SURVEILLANCE LIFT OFF 800 LL 750 leu CI IL K O 700 O IllI-LOCK OFF VAL RT LOCK OFF VALUE lliiiliiiliiliiliilliNlNNHEi--- SURVEILLANCE LIFT OFF 650 600 I-1.4 WVr lU IA x ~ 0 WVr lU D 2.0 2.5 (2) 16% R ELAX. WITH RT ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ (I) E.S.R. WITH RT ffffftllffflllttf 95% X (2) I II I I I I I I IIIIII 95% X (1) r w f-w V rr I-gg an I I I ~ I I ~ I I ~ ~ ~ 1I ~ E.S. R. WITHOUT RT RT LIFT OFF VALUE CC rrO 0Ir WI-lU III I-0- t I-p IY ' W ~L I-W 0-I- CL W I gg P ~ f. W I >--I I o'V I ml g ~ f 4.5 9.6 12.0 13.6 'I5.6 17.6 22.6 27.6 32.6 37.6 42.6 12.6 TIME AFTER COHTAIHMENTWALL COHSTRUCTIOH (YEARS)
850 FIGURE 60 COMPARISOH OF PREDICTED. AND MEASURED TENDON FORCES INCLUDIIIG R ET ENSIOHING FOR TENDOH HO. 33 .. f~lHTHfftftffffNfftftiftfffffffl ~ PREVIOUS SURVEILLANCE LIFT OFF 800 ORIGINAL LOCK OFF VAL RT I OCK OFF VALUE 750 IUu O X OQ 700 I-RT OFF LUE UR EILL IF 650 600 O I O Cl I x ~ I-
. r0 lU OX lU Ck lU I
WuX Ul CLD I I W W' X Wt W ur ) ~ll lU I l & Ul L >. L O I-X gg W I Ul~I ~ o I I CL'U 0-O I-i. IL lU Ml L o ~ I. lU I o'V I-Ul 0-CV (I) E.S.R WITH RT I I I I I I I I II I IIII II (2) 16% RELAX. WITH RT IIIIIIIIIIIIII 95% X (1) IIIIIIIIIIIIIII 95%o X (2) I- 'L CI 1.4 2.0 2.5 4.5 9.6 12.0 13.6 12.6 CTION L CONSTRU TIME AFTER COHTAIHMEHTWAL 15.6 17.6 22.6 27.6 32.6 37.6 42.6 (YEARS)
C s
850 FIGURE 6p COMPARISON OF PREDICTED AND MEASURED TENDON FORCES IHCLUDIHGRETE NSIOHING FOR TEHDOH NO. 36 ttWf~l1-.MINWNlltttttHlttilflilt 0 PREVIOUS SURVEILLANCE LIFT OFF 800 RT LOCK OFF VALUE 750 'X O 700 I-AL IG OR IN LOC F F LU SU R EIL FT 0 FF (1) E.S.R. WITH RT 650 RT LIFT OFF VALU (2) 16% RELAX WITH RT IIII\\II ~IIIIIII 95%%uo X (1) 600 0O 1 wr ~ I-X I r O UlUr w lr.D Ul I I Ulur Ul D 'I II w'r Ul I-wh ur w Ik lr. I ml r Ul D I-. lr. Llrr0 I-r lg UlI-Ul UlK ~ ) ~ Ul I-IY Ul O I-t lL'. L LU, IL ~ I Ul I >-'- I o'V I- '4, 1IIII1I1[IIIIII 95%o X (2) 1.4 2.0 2.5 4.5 9.6 12.0 13.6 15.6 17.6 22.6 27.6 32.6 37.6 42.6 12.6 TIME AFTER COHTAIHMENTYIALLCONSTRUCTION (YEARS)
'Ci, I
850 FIGURE 6Q COMPARISOH OF PREDICTED AHD MEASURED TEHDOH FORCES IHCLUDIHG R ET EHSIOHIHG FOR TEHDOH HO. >>> ttMlttttilttltilmii!tH1llliiliiiililililii ~ P R EYIOUS SURVEILLANCE LIFT OFF 800 IL 750 IjIu O X O Cl 700 ILI I 0 GINAL Rl CK 0 0 0 FF 0 F F YA YALUE RT LIF 0 FF AL E (I) E.S.R. WITH RT I I I I I I I I I II IIIIIII ( 2) 16 1o R E LAX. WITH RT 650 600
X Q
! Xl 1.4 XI-
r I
Q I WVX W D W I 2.0 2.5 WVX W D OFF LIFT
[l LLANCE 3--I-~
W ~ W Vr x I-a W El SUR QX l I gg I + I I Q I-X UjI-W W 11.6 ~ I -"' i I 13.6 15.6 12.6 CTIOH (YE 4.5 6 12.0 ARS) TIME AFTER COHTAltIMEHTSALL COl(STRU I i IL'J 22.6 27.6 I CE' o'I I o-CV I-
1. 6' 32.6 3
1IJIIIIJIIIIII 95~to X (I) IIIIIIIIIIIIII 95~o X (2) lC Pl 2.6
850 FIGURE 6R COMPARISON OF PREDICTED AND MEASURED TEHDON FORCES INCLUDIHG R ETEHSIOHING FOR TENDOH HO. 116 ttftlttNtttNtttmiewtttte 0 PREVIOUS SURVEILLANCE LIFT OFF 800 0 750 tQV CLO tt X0 700 IJJI-RT LOCK OFF VALUE ORIGINAL LOCK OFF VALUE'URV EIL ANCE LIFT 0 FF 650 600 RT LIFT OFF VALUE X an lU l K o I-I. Z '. 0OX ~ I- ' lUVZ an IU CUVX Ul - IU O
lU D
Ct: IU I 'X X lU a.g I I gg I lU 0-Ct: CL'U "I 0 O I- >> Ct:- IU I , I-CC CL. lU I o'- f% e I-Cat (1) E.S.R. WITH RT ltlllllllllllllll (2) 16% RELAX WITH RT IIIIIIIIIIIIIII 95% X.(l) ~ ~ ~ ~ ~ ~ ~ 95% X (2) 1.4 2.0 2.5 4.5 9.6 12.0 13.6 I5.6 I7.6 12.6 TIME AFTER COHTAINMENTWAl L COHSTRUCTION (YEARS) 22.6 27.6 32.6 37,6 42.6
APPENDIX A STRESS RELAXATION TEST REPORT Qtbere /Commonwealth
k II 1 l li ~
RELAXATION TESTS ON 1/4" PRESTRESSING MI,RE BY ROGER G ~ SLUTTER REPQRT No. 200,79.100.5
200.79.100.5 LEHIGH UNIVERSITY Bethlehem, Pennsylvania 18015 Telephone 215 661 3515 Fritz Engineering Laboratory Building 13 January 21, 1982 y ~ Mr. Ken Murray Gilbert Associates, Tnc. P. 0. Box 1498
Reading, PA 19603
Dear Mr. Murray:
Enclosed is a report on the relaxation tests that we have 'been doing on 1/4" wire. We put this report together because the testing is substantially completed. We are still continuing all of the wire under load and the 104 F temperature is being main-tained in one cabinet. report. Please let us know if you need additional copies of the Sincerely yours, ,?, Roger G. Slutter RGS/df Enclosure Research hl Civil Engineering and Related Fields
1 ~
200.,79.100.5 RELAXATION TESTS ON 1/4" PRESTRESSING WIRE I TRODUCTION In March of 1980 relaxation tests were started in Fritz Engineering Laboratory on 1/4" diameter prestressing wire received from the Robert E. Ginna Nuclear Power Station of Rochester Electric and Gas, Company. The wire samples were obtained from the tendon sur-veillance wires in the plant and were ASTM 'A421 type BA wire (240 ksi UTS). The relaxation tests were conducted under conditions and procedures meeting ASTM A328-78 specifications in controlled envir-onment cabinets originally constructed for conducting similar tests on 1/2" diameter 7-wire prestressing strands. Fourteen wires were included in the testing program. Tests were conducted at temperatures of 68 and 104 F with initial tension of 0.70 UTS and 0.75 UTS. Some tests were conducted for 10,000 hours while others were under load for a longer period of time. Modifications to a conventional relax-ation test procedure were made to simulate loading history of actual tendons in the Ginna Nuclear Power Plant. Guidance for the program was provided by Mr. Jim Fulton and Mr. Ken Murray of Gilbert Associates.
l 0 0
200.79.100.5'EST SPECIMENS ~ ~ / Specimen identification'numbers were assigned to wire specimens prior to their arrival at Fritz Engineering Laboratory. All of the wires supplied were used in testing except epecimen No. 2, which was badly bent in several places along the length. Several other wiies were bent at one point along the length. These kinks probably were
the result of difficulty in removing the wire from the tendons.
In order to determine the effect of these kinks on.relaxation, two tests were run for approximately 100 hours in a testing machine at room temperature; A short piece of specimen No. 6 was straight while a similar length of specimen No. 12 was tested with a kink in the center of the gage length of 20 inches. These tests demonstrated that a kink somewhere in the 10 foot gage length in the relaxation tests would have only a negligible effect on the results. In cutting the specimens down to fit in our cabinets, it was possible to eliminate kinks in several specimens. 'In the final tests only Specimen Nos. 8 and 15AB had plastically deformed wire within the 10 foot gage length. The deformation in Specimen No. 8 was a large radius bend of approximately 10 feet and 15AB had a kink in the gage length. Specimen Nos. 1, 3 and 5 had'aw marks on the wire but it was possible to keep these outside the gage length by properly 0 " selecting the specimen length for testing. In the 68 F cabinet the -length of wire under test was 21 feet and in the elevated temperature cabinet the length was 16 feet. The original length as shipped was
~ ~ ~ ~ a
200.79.100.5 approximately 22 feet. Table 1 provides a list of test specimens. Specimen No. 2 is not included since it was never tested. TESTING PROCEDURE The cabinets for relaxation tests were constructed of plywood with insulation on the inside surface and windows for. access to instru-mentation. The 68 cabinet was equipped with an air conditioning system and the'wo cabinets. for elevated temperature were provided with heating mats and cicrulating fans. Each wire was placed in a separate frame consisting of two angles 5" x 3-1/2" x 3/8" with spacers and 3/4" 'thick bearing plates at each end. Wires were held at each end using chucks for 1/2" diameter 7-wire strand with one jaw removed. These chucks were tested in a testing machine prior to use to be sure that they would not slip with time under load. The frames were stored on steel racks so that each frame was free to expand and contract independent of the others. Chucks which ancored the wires were centered on the center of gravity of.the pair of angles with the wire between the angles. Each specimen had a 10 foot gage length near midspan. At each end of the gage length steel clamps were attached to the wire and to a gage length rod supported on rollers resting on top of the pair of angles. Figure 1 shows the dial gage mounted on one end of the rod with plunger bearing on the bracket at one end of the 10 foot gage length. This photograph was taken through the window in the cabinet located near the jacking end of the wire. The dial gage is
~ ~ ~ I 200.79.100.5 graduated in mils and enables the 10 foot gage length to be set within + 0.000002 in/in. The brackets were attached to the wire by bolting spring loaded plates on each side of the wire. Loads were read by a 20 kip BLH load cell incorporated in the pulling rod of a 30 ton hydraulic ram. This loading assembly is shown in 'Fig. 2. A threaded lug attaches to each chuck and is engaged by a pulling yoke attached to the load cell. The hydraulic ram is a center
hole ram and load is applied by a pull rod connected to the load cell and passing through the ram.
The BLH load cell was carefully cali-brated on one of our testing machines to read the load directly, in pounds. During initial tensioning of each specimen the initial,load for the relaxation test was applied in five equal increments over a period of five minutes. When the exact load was reached at the end of five minutes, the dial gage on the 10 foot gage length was read. Thereafter, all loads were read at the same dial reading. Thus any slip of the grips would not affect the test results'lthough no slip of grips was observed. In order to hold the correct load in each wire when the jacking assembly was removed, shims were carefully fitted r between the chuck and bearing plate by trial and error until the dial gage read essentially the same as the specified reading for measuring the load. 'The correct shims could be. found so that the dial reading was within + 0.002 inch of the load reading value. During the first 24 hours the load was held by the hydraulic ram with the load cell under load. After the 24 hour reading the shims
200.79.100.5 were fitted and the jacking assembly was removed for use on other specimens. Since the load cell was not under load it was possible to che'ck zero settings and check the calibration of the load cell at any time. The zero load setting was checked each day that readings were taken. 1 The procedure for taking readings after the first 24 hours was to install the jacking assembly in position by means of a hand operated 'ork lift. Load was applied until shims could be removed. The gage length was adjusted to the correct value and the load cell was read. Tension was then increased until shims could be replaced and the jacking load was released. It was necessary to overload approximately 225 lbs. or approximately 2% of UTS for each reading. This overload was applied for approximately one minute for each reading. The effect of this over-loading for readings is considered to be negligible in view of the small magnitude and short duration. The advantage of t'his procedure is that it minimizes the time 'that the load cell is loaded and thus eliminates problems related to stability of the load cell. Temperature was maintained within + 1 F in the cabinet at 104 F and within + 2 F in the 68 F cabinet. The heating control 0 0 0 was more precise .than the air conditioning control depending on the ambient temperature. It was not necessary for the temperature to be so exact but experience has shown that the wire and angles do not change length at the same rate during a temperature change. Therefore, the'emperatures were held very exact to eliminate the possibility that readings might be taken while the temperature was changing. It was
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200.79.100.5 found that a rapid change of temperature could produce an error of 12 lbs. per F in the load. 0 4 . All data was kept in a date book with the following being recorded each time readings. were taken. Date Watch Time Time from Start of-Test Dial Gage Reading (always constant) Load Temperature % Load of Load Since relaxation data is plotted on.a log scale for time, the readings were taken at time intervals that would be properly spaced on a log scale. Table 2 gives a tentative minimum schedule for taking readings. Constraints of working hours,
weekends, and holidays resulted in the readings being tak'en at slightly different times for each specimen.
However, for the first 'week of each test the schedule was carefully followed. TEST RESULTS As data was accumulated the pattern of the curves became obvious and additional test plans were evolved through discussions between Fritz Engineering Lab and Gilbert personnel. Since these additional tests complicate the interpretation of the test curves, an outline of the entire program as completed is given in Table 3. Only specimens 1, 6 and ll were allowed to remain as initially tensioned.
0
200.79.100.5 For all other specimens th'ere was an ad)ustment of tension or tempera-ture to simulate the load history of the tendons. Specimen Nos. 5 and 15AB were unique in that they were installed in the unused side of the 104 F cabinet with no heaters and the window open. Due to heating in,the opposite 'side of the cabinet it'was necessary to begin these tests at 80 F instead of 68 F. Tem-perature was increased to 104, F after 1000 hours to simulate the 0 effect of a vessel being put, into operation. After 8640 additional hours the wires were returned to 80 F or below so that the effect of 0 this temperature change could be observed. Specimen No. 13 exhibited very low losses compared to all other specimens. This specimen was released after 13,270 hours and \\ allowed to set 0t no load for a week. It was then retensioned to the original load to observe the results. All other specimens were re-tensioned without unloading. The data from all tests are plotted in Figs. 3 through 11 in the form of percent loss of load as ordinate and time in hours as abscissa. A log scale was used for both percent loss and time because of the advantage.offered in checking each new data point as it was obtained. The specimens are grouped for convenience in comparing different wires under comparable conditions of loading or temperature. Figures 7, 8 and 10 show comparison'of the retensioned curve and the original relaxation curve for Specimen Nos. 7, 9 and 13. Retension curves for other specimens are shown on the same graph with
~ ~ 200.79.100.5 the family of original curves. The curves showing the effect of tem-perature change are given for Specimen Nos; 5 and 15AB in Fig. 11. The effect of returning the wires to a temperature of 80 F can not be 0 plotted in Fig. 11 because of the time scale. In a period of 800 hours following the temperature reduction there was no change in load in the wires.
SUMMARY
AND CONCLUSIONS The wire under test was expected to exhibit a loss of 15% at 40 years. This is based on room temperatures. Projections to 40 years from our results for wires at room temperature indicate that Specimen No. 4 would reach 13%, Specimen 'No. 7 would reach 15%, Specimen No. 12 would reach 5% and Specimen No. 15AB10 would reach 7.5%.
However, the tests conducted at 104 F are probably more indicative of loss to 0
be expected in actual tendons. The 40 year prediction for 104 F 0 specimens is that Specimen No. 3.would reach 15%, Specimen No. 5 would reach 16%, Specimen No. 8 would reach 20%, and Specimen No. 13 would reach 9.5%. Specimen No. 13 does not seem to be typical and the average pro)ected 40 year loss would appear to exceed 18% at 40 years. The effect of retensioning of the wires at any time from 1000 hours to 11,600 hours was considerable and would appear to reduce 'I the loss to approximately a 12% level or lower depending on the time at which retensioning was performed. Retensioning at 100 hours on Specimen No. 9 was. not conclusive in that the loss of the retensioned projects to approximately 14.5% in 40 years.
200.79.100.5 Other conclusions from analysis of this data are: 1. Tensioning to 0.75 UTS initially should not be done because losses are very high and the actual wire tension becomes lower than for wires tensioned to only 0.70 UTS after a period of time.. '2. Temperature increases that occur at some time after wires are tensioned have a significant effect and essentially shift the amount of loss to the cur've for the higher temperature. 3. The.variation in the rleaxation rate among wires is significant, but an increase in temperature significantly increases the relaxation rate in all wires. 4. A temporary overstress of 6% for short durations which occur in tendon surveillance checks does not significantly affect relaxation loss. f i 5. A drop in temperature appears to produce a delay in the relaxation rate. More data would be necessary to substantiate this conclusion. The testing program is continuing in that none of the wires have been unloaded. The 104 F.temperature is being maintained con-0 stant, but the other wires are. being held under load at whatever the room temperature is. '
~ ~ q
200. 79. 100. 5 ~ TABLE 1 TEST SPECIMENS Specimen . No. 3 4 ' 9 10 12 13 15AB 15AB10 Tendon No. 51 51 51 51 76 76 76 76 76 150 150 150 150 150 Position from Top of Tendon (ft.) 0-23 46 - 69 69 91.33 91.33 114.33 0-23 23 46 46 69 69 91.67 91.67 114.67 0 - 23 23 46, 46 69 91.67 114.67 69 91.67 Initia'1 Test Temperature ('F) 104 104 68 80 104 68 '104 104 104 104 68 104 80 68 TABLE 2 READING INTERVALS FOR RELAXATION READINGS ~Readia 3 4 5 6 7 8 10 Time from. Start of Test 2 min. 6 min. 30 min. 1 hr. 2 hrs. 4 hrs. 7 hrs. 20 hrs. 40 hrs.'0 hrs. ~Readia 12 13 14 15 17 18 19 20 Time from Start of Test 4 days 8 days 16 days 29 days 6 weeks 12 weeks 24 weeks 12 months 21 months 28 months
Specimen Initial Test Initial No. Temperature Tension ( F) (lbs.) TABLE 3 DESCRIPTION OF TESTS Description of Tests CD CD CD CD Ln 10 12 13 15AB 15AB10 ~ 104 104 68 80 104 68 104 104 104 104 68 104 80 68 8,840* 8,250 8,240 8,240 8,840 8,240 8,250 8,240 8,240 8,840 8,240 8,240 8,240 8,240 Continued relaxation test beyond 10,000 hrs. with no adjustments in load Retensioned to original load after 6000 hrs. Retensioned to original load after 1000 hrs. Temperature was raised to 104 F after 1000 hrs. 0 0 0 Temperature was reduced to 80 F after 8640 hrs. at 104 F Continued relaxation test beyond 10,000 hrs. with no adjustments in load Retensioned to original load after 11,600 hrs. Retensioned to original load after 10,190 hrs. Retensioned to original load after 100 hrs. Retensioned to original load after 1000 hrs. Continued relaxation test beyond 10,000 hrs. with no adjustments in load Retensioned to original load after 5500 hrs. Retensioned to original load after 13.,270 hrs. Unloaded and retensioned after one week to original load 0 Temperature was raised to 104 F after 1000 hrs. Temperature was reduced to 80 F,after 8640 hrs. at 104 F -The effect of 6% overstress was studied after 10,000 hrs.
8840 lbs. corresponds to 0.75 UTS and 8240 or 8250 corresponds to 0.70 UTS.
~ ~
200.79.100.5 1 Zp C ~ ~ I I V~ ~4WPk Vg V Fig. 1 Dial Gage and Gage Length Rod 44 4vv r, If'l 'E E I T i3 P ~ pp Fig. 2 Loading System for Tensioning and Checking Load
IOO 8 104 F started at 0.70 UTS ~- 8l 8 104 F started at 0.75 UTS 50
~- 810 8 104 F started at 0.70 UTS 0
(1'oad increased to initial I load at 1000 hrs.) 0 0)M O I.O 0 0 O. I O.l =-I.O IO IOO TIME IN HOURS Fig. 3 IOOO IO,OOO
IOO 50 84 8-68 F started at 0.70 UTS (load increased to initial load at 1000 hrs. 810 9 104 F. started at 0.70 UTS (load increased to initial load at 1000 hrs.) <<D <<D CD CD Ln IO M M O I.O 0 0 . g~e O.l 0:I I.O IO IOO TIME IN HOURS Fig.4'OOO '. I0,000
IOO 50 88 8 104 F started at 0.70 UTS 86 9 104 F started at 0.75 UTS 86 9 68 F Ln testing machine 28" length with 20" gage . length to determine if wire from this tendon exhihits high loss of load at other conditions. 0 V) M O I.O 0 0 O.l O.l I.O IO IOO TIME IN HOURS C Figt 5 IOOO IO,OOO
IOO 50 87 ~ 8 68 F started at 0.70 UTS 812 8 68 ' started at 0.70 UTS 815 AB10 8 68 F started at 0.70 UTS (follows 812 for first 24 hrs.) 84 8 68 F started at 0.70 UTS (load increased to initial load at 1000 hrs'.) CC I-CC V O 0 0 Z V) O I.O 0 0 nslOA O.l O.l I.O IO IOO TIME IN HOURS. Fig. 6; IOOO l0,000
IOO ~ II7 g 68 F started at 0.70 UTS 87 Retensioned at 11,686 hrs. to 0 ~ 70 UTS CC I-CC V V) O I,O 0 0 O. I O.l . 1.0 IO lQQ TIM E IN HOURS Fig. 7 IGLOO.: IO,OQO
IOO 50 ~lI'9 8 104 F started at 0.70 UTS ~ (load increased to initial load at 100'rs.) 0 M (0O. I.O 0 O. I O.l I.O IO .IOO TIME IN HOURS Fig. 8 IOOO l0,000
IOO
813 8 104 F started 8 0.70 UTS I/11 8 104 F started 8 0.75 UTS 812 8 68 F ub testing machine 10-3/8" bent with 3/16" camber at center, s traigh tened and tes ted with 7" gage length to evaluate effect of "kinks" in wire. Cl c( 0 V) V) O I.O 0 0 O. I O.l ~ I.O IO IOO .TIME IN HOURS Fig. 9: IOOO l0,000
I [00 ~ 013 8 104 F seeeeed 8 0.70 UTS 50 -o-813 Rethnsioned after a week at nearly zero load 104 F and 0.70 UTS s Cl 0 M M O I.O 0 0 O. I O.l I.O Io IOO TlM E IN HOURS Fig. 10 IOOO ~l0,000
l00 o'/5 8 78 F started at.0.70 UTS increased to 104 l at 1000 hrs. 50 ~ //15AB 8 78 F started at 0.70 UTS increased to 104 F at 1000, hrs. Temperature to be increased to 104 F at 1000 hrs. 0' 0 OH e V) V) O l.0 0 0 O.l O.l l.O lo l00 T l M E lN HOUR S l000 l0,00'
200.81.100.5 LEHIGH UNIVERSITY Bethlehem, Pennsylvania 18015 Fritz Engineering Laboratory eulldlng 13 March 23, 1983 Mr. S. S. Shieh Gilbert Associates Building G2A 3143 P. 0. Box 1498
Reading, PA 19603
Dear Mr. Shieh:
Enclosed is a copy of the data taken since August 17, 1981 on the relaxation tests of 1/4 inch diameter wire. Sincerely yours, e~g~ xg&>( Roger G. Slutter RGS/df Enclosures Research ln Civil Engineering and Related Ftetds
200.81.100.5 LEH IG H 0 NIVERSITY Bethlehem, Pennsylvania 18015 Fritz Engineering Laboratory Bulldlng 13 March 23, 1983 Mr. S. S. Shieh Gilbert Associates Building G2A 3143 P. 0. Box 1498
Reading, PA 19603
Dear Mr. Shieh:
Enclosed is a copy of the data taken since August 17, 1981 on the relaxation tests of 1/4 inch diameter wire. Sincerely yours, gjrr. ~gj~gd( Roger G. Slutter RGS/df Enclosures Research In Civil Engineering and Related Plaids
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ML17255A719

Contents

Text

1.0 INTRODUCTION

4.0 CONCLUSION

4.0 CONCLUSION

Dear Mr. Murray:

SUMMARY

Dear Mr. Shieh:

Dear Mr. Shieh:

Navigation menu

ML17255A719

Text

1.0 INTRODUCTION

4.0 CONCLUSION

4.0 CONCLUSION

Dear Mr. Murray:

SUMMARY

Dear Mr. Shieh:

Dear Mr. Shieh:

Navigation menu

Search