ML13311A720
| ML13311A720 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 02/29/1984 |
| From: | COMPUTECH ENGINEERING SERVICES, INC. |
| To: | |
| Shared Package | |
| ML13310B339 | List: |
| References | |
| R557.09, NUDOCS 8404170498 | |
| Download: ML13311A720 (37) | |
Text
SAN ONOFRE NUCLEAR GENERATING STATION. UNIT 1 SEISMIC EVALUATION OF REINFORCED CONCRETE MASONRY WALLS AASONRY WALL TEST PROGRAM RESULTS FROM TESTING WALLS 1A. 1B AND IC Prepared For:
BECHTEL POWER CORPORATION Los Angeles. California Prepared - By:
COMPUTECH ENGINEERING SERVICES.
INC.
Berkeley. California Report No. R557.09 February 1984 8404170498 840412 PDR ADOCK 05000206 P
TABLE OF CONTENTS 1
INTRODUCTION................................
2 TEST FACILITY................................
2 2.1 Test Setup..........................
.... 2 2.2 Capacity of Test Equipment.
.... 2 2.3 Description of Instruments......................
2 2.3.1 Stroke Measurements.....................3 2.3.2 Joint Opening Measurements.................3 2.3.3 Displacement Measurements..................4 2.3.4 Acceleration Measurements 4
2.3.5 Rebar Strain Measurements.......
5 2.4 Data Acquisition........................
.... 6 3
QA/QC PROCEDURES....................
.......11 3.1 Procurement of Documents..................... 11 3.2 Construction of Specimens
..................... 11 3.3 Testing of Material Samples......
11 3.4 Instrumentation.....................
......11 4
TEST SPECIMENS..
.....13 4.1 Construction of the Test Specimens........
13 4.2 Dimensions of Test Specimens................... 13 4.3 Boundary Conditions................................
14 4.4 Attachments......................
14 5
INPUT TIME HISTORIES.
........ 17 5.1 Duration.....
17 5.2 Modifying the Time Histories 18 6
TESTING OF THE FUEL STORAGE BUILDING WALL SPECIMENS
.... 26 6.1 Tests Performed 26 6.1.1 Material Property Tests.................... 26 6.1.2 Low Level Pull Back Tests.................. 26 6.1.3 High Level Dynamic Response Tests............. 27 12 REFERENCES................................
126
1 INTRODUCTION As a part of the Systematic Evaluation Program Topic 111-6. Seismic Design Considerations, the masonry walls at San Onofre. Unit 1 were evaluated using a nonlinear inelastic time history analysis methodology. This analysis was performed by Computech Engineering Services. Inc. (CES) and is presented in References 1 through 4. Although many walls exhibited considerable inelastic response. all were within the limits set forth in the acceptance criteria.
The NRC staff indicated in References 5 and 6 that the analytical methodology could not be accepted without additional confirmatory testing. Details of a test program were discussed in a meeting on May 11 through 13. 1982. The main objective of the test program was to demonstrate the overall conservatism of the analysis results.
The original description of this test program was Included in a letter dated July
- 29. 1982.
NRC review and comments on the program were provided in letters dated September 29. 1982 and January 3. 1983.
Responses to the NRC comments were submitted in letters dated November 22, 1982 and March 2, 1983.
The main objective of the test program was to demonstrate the overall conservatism of the analysis methodology and not to proof test the walls.
This report provides a detailed description of the test procedures and results of testing walls 1A. 1B and 1C which represented typical walls of the Fuel Storage Building of the San Onofre Nuclear Generating Station. Unit 1.
2 TEST FACIUTY The tests were performed at the structural laboratories of the Earthquake Engineering Research Center. University of California Berkeley.
The facility is capable of accommodating full sized test specimens utilizing either dynamic or static loads. The sections below provide a description of the program related aspects of the test facility. including a specially constructed unidirectional "shake table' used for the testing of the walls.
2.1 Test Setup The test setup consisted of four reaction frames (A-frames) as shown in Figure 2.1 and two MTS actuators located towards the top and bottom of the reaction frames. The test walls were placed on top of a specially constructed *shake table' made up of a 1" thick steel plate 8' by 4' in plan. The plate rested on four Thomson Dual Roundway Bearings sliding on top of hardened steel rods allowing unidirectional motion with minimal friction force (friction coefficient equal to 0.007). These four main bearings carried the gravity load of the test specimens.
A second set of Thomson Bearings were located such that they prevented uplift of the base of the walls.
The details of the "shake table' are shown in Figure 2.2.
Spreader beams were attached to the test specimen at the top of the wall.
The actuators were attached to these beams so as to provide horizontal motions normal to the specimen. The connection of the top spreader beam to the wall was similar to the insitu walls.
2.2 Capacity of Test Equipment The actuators that were used to supply the required excitation are high performance equipment and were oriented normal to the test specimens.
The actuators are capable of developing a maximum dynamic load of 75 Kips using a hydraulic pressure of 3.000 psi for a relatively short time.
Normal use of the hydraulic system requires a hydraulic pressure of 2.500 psi thus reducing the dynamic load to 62.5 Kips.
The maximum stroke of the actuators is + 6 inches, the maximum piston velocity is 30 in/sec and the flow capacity of the servovalves is 200 gal/min.
The actuators were controlled by a displacement command signal that was capable of following a prescribed displacement pattern which could be any earthquake time history.
sine wave, step function, etc.
The only restriction was that the above listed capabilities of displacement, velocity or force were not exceeded.
2.3 Description of Instruments The instruments used for measuring the various response parameters were Accelerometers. Wire Potentiometers. Direct Current Displacement Transducers (DCDTs) and Strain Gages. In addition, built into the actuators are Linear Variable Differential Transformers (LVDTs) for measuring the actuator stroke.
2
Each of these instruments is described in some detail in the following sections.
2.3.1 Stroke Measurements The position of the hydraulic actuator (Stroke) is measured by a Unear Variable Differential Transformer (LVDT) built into the actuator and conditioned by an MTS controller.
An LVDT is a transformer with a moveable ferromagnetic core, one-primary winding and two secondary windings arranged so that movement of the core from its center position causes the voltage in one secondary winding to increase and the voltage in the other to decrease.
This difference in voltage is translated by a phase-sensitive demodulator into a DC voltage proportional to the core displacement.
At zero displacement, the voltage in both windings is equal and the output from the demodulator is zero. A schematic representation of an LVDT is shown in Figure 2.3.a.
The MTS controller provides a 10 kHz carrier to the LVDT primary and demodulates the secondary signals to give a + volt to DC output.
This output is compared by the controller electronics to the command signal to complete the displacement feedback outer loop.
Actuator position is displayed on the front panel of the controller, and the DC output of the demodulator is accessible at a panel jack. This output was connected directly to the data acquisition system to provide stroke measurements. The system was calibrated by an MTS factory representative.
2.3.2 Joint Opening Measurements The opening of joints on the specimens was determined by measuring the change in distance between the center of one block to the next (spanning over a joint).
This measurement was made with Hewlett Packard Series 7 Direct Current Displacement Transducers (DCDTs).
The DCDT is an LVDT, packaged in an assembly that contains an integral carrier oscillator and a phase sensitive demodulator.
Hence, the operation is the same as that of an LVDT. but both the input and output are direct current.
The DCDTs were supplied from a regulated 5 Volt power supply. The
+/-5 Volt output was amplified by Burr-Brown Model 3088/16 amplifiers.
located in the same chasis with the power supply, to give +10 Volt output over the expected range of operation of the DCDT.
The 2.4 kHz carrier frequency of the DCDT is present in the output as a 5 Volt common-mode noise signal, but it is practically absent in the transverse-mode, which is where measurements are normally taken.
Unfortunately the common-mode rejection ratio of the Burr-Brown amplifiers is not sufficient to reduce the noise in the output to an acceptable level.
The noise would be entirely unacceptable in a high speed data acquisition system and could lead to allasing problems as 3
well as loss of small signals to noise.
To correct this, a set of 50 Hz. two pole low pass analog filters were built. After Inserting the filters into the circuitry labo 'ratory measurements showed practically complete elimination of the noise above 250 Hz.
The DCDTs were calibrated in a jig which permitted insertion of blocks of various thicknesses under the DCDT rod.
The thickness of various machined steel blocks was measured using a micrometer, then the thickness of various stacks of the blocks was measured to account for any Inaccuracies which might result from stacking them.
One suitable set of blocks was chosen and used in calibrating all DCDTs.
2.3.3 Displacement Measurements The displacements at various points on the wall were measured with Celesto Wire Potentiometers.
A Wire Potentiometer is a highly accurate.
multiturn helical potentiometer which is attached to a spool which is rotated by a cable attached to the specimen.
The spool is returned to one extreme position by a constant force spring motor which maintains tension on the cable.
Intermediate positions are read from the variable voltage in the wiper of the potentiometer.
Signal conditioning for the Wire Potentiometers was provided by a Validyne MC-1 power supply. which provides 5V 3kHz excitation, and by Validyne CD-19 demodulation units mounted in the MC-1 chasis, which convert the output of the Wire Potentiometer to a +10 Volt DC signal.
The CD 19 unit also provides 50 Hz low pass filtering.
Because the Validyne CD-19 does not operate well at very low gains.
the output of the Wire Potentiometers was reduced by installing two 604 ohm resistors in series with them, as shown in Figure 2.3.b. AC conditioning was chosen for its superior rejection of 60 Hz and other AC or radio frequency interference.
The Wire Potentiometers were calibrated using a jig with notches machined every three inches with 0.001" accuracy in a bar.
The jig allows the cable to be extended to any notch and left there while a reading is taken.
2.3.4 Acceleration Measurements Two types of Accelerometers are available at the EERC laboratory. Statham (now made by ITE-Gould) and Setra.
Both kinds were used in these tests.
The Setra Model 141 Accelerometer is a variable capacitance type Accelerometer.
It is excited with direct current and a built in oscillator converts the supply current to a 20 MHz internal operating frequency which is applied to two fixed insulated electrodes. A thin stiff metal disk mounted on flexures between the electrodes is deflected proportionally 4
to acceleration, and the change In capacitance is converted by built in circuitry to a direct current output.
The movable element is highly damped (0.7 of critical) by an air-flim damping mechanism.
The Setra Accelerometer has an output in the range of 100 mV/g.
The output was amplified by Burr-Brown amplifiers to give an output of about 2:5 V/g.
The 20 MHz carrier is present in the output at the low millivolt level.
amounting to a few percent of the full scale output. The amplifier output was therefore filtered, using the same set of 50 Hz low pass analog filters used with the DCDTs.
Statham Accelerometers are strain gage type accelerometers. Four resistances within the accelerometer are connected in a Wheatstone bridge, and changing acceleration changes the resistance of the strain gage elements resulting in a change In the output voltage.
The Statham Accelerometers were conditioned by the. Validyne equipment previously described (Section 2.3.3).
However, because the Statham is a low output device, relatively high amplification (400:1) was used.
AC conditioning was chosen, as in the case of the Wire Potentiometers.
for its superior interference rejection.
The Accelerometers were calibrated by placing them on a level surface in two positions. to obtain ig and -1g.
and on a vertical surface to obtain Og.
The frequency range of both accelerometers is down to 0.0 Hz and they also have very low response to transverse acceleration, so a horizontal orientation of the accelerometer is an excellent approximation of Og.
2.3.5 Rebar Strain Measurements Strain in the reinforcing bar was measured with Alitech weldable strain gages welded directly to the rebar. These gages were specified to be operational up to strain levels of 2%.
Strain measurement Is based on the principal that the resistance of the gage changes in direct proportion to the strain. The leads from the gage are brought outside the specimen to a terminal block mounted on the specimen as close as practical to the gage. From this point, another shielded cable connects the strain gage to a second terminal block on the back of the signal conditioner where the leads from the Strain Gage are placed in series with a 120 ohm 0.05% resistor across the excitation voltage forming a two-arm bridge.
Strain Is then read as a change in voltage at the midpoint of the bridge.
The Validyne unit was again' used to provide 3 kHz excitation voltage and demodulation.
The amplification was adjusted in the 100:1 range to provide 10 Volt DC output at approximately 30 mils/inch (3%) strain.
The output was filtered by 50. Hz low pass analog filters built into the Validyne unit.
5
Calibration was accomplished by shunting the strain gage with a 3317 ohm resistor and entering the calculated equivalent strain into the data acquisition system.
(The resistor used was a 3.32 K-ohm 1% resistor.
the actual resistance of which was determined by a highly accurate laboratory DVM).
2.4 Data Acquisition The Data Acquisition System contains a calibration program.
With all the instrumentation connected to its signal conditioning and to the Data Acquisition System. a channel is selected for calibration.
A measurement of a known value is made with the appropriate Instrument. and the known value Is entered on the Data Acquisition System terminal.
The terminal CRT then displays the voltage measured and the value entered In adjacent columns and simultaneously displays a graphical representation of each calibration point.
The graphic display provides a quick visual check for linearity and reproducibility.
When satisfactory calibration data have been obtained, they are entered In the Data Acquisition System which then computes the slope (units/volts) of a least-squares line for those calibration points. This slope is then the calibration value and is stored permanently in the calibration file.
The Data Acquisition System is a system that digitizes analog voltage signals in accordance with a predetermined schedule and at a selected frequency.
The paragraphs below describe the analog to digital (A/D) process and some general principles that apply to ensure acquisition of valid data.
In general the instruments (Accelerometers. DCDTs. Wirepots and Strain Gages) generate a voltage signal when subjected to motion compatible with their function. Accelerometers measure absolute accelerations on the moving wall: the Wirepots measure relative displacements between a fixed point and the moving wall; and the DCDTs measure relative displacements between two points on the wall across a bedjoint.
The Strain Gages measure elongation of themselves (by changing their resistance) normalized to a strain value over the fixed length of the Strain Gage. These are described in more detail in Section 2.3.
The voltage signals generated are usually not directly compatible with the analog to digital converter of a data acquisition system in that the signal strength is too low to be properly defined by the 12 bit A/D converter most commonly used.
Therefore, signal amplifiers are inserted Into the circuit to amplify the voltage signal to a level suitable for the A/D converter.
To do so one must anticipate what the maximum response (acceleration, displacement, strain. etc.) will be and set the amplification such that the anticipated maximum voltage signal equals the maximum voltage level the 12 bit A/D converter can handle.
The drawback of this system is that if the anticipated maximum is exceeded an overflow situation will be created in the A/D converter and the real maximum will not be properly recorded.
6
Another phenomenon is usually encountered in A/D conversions if some precautions are not taken.
This phenomenon is the high frequency contamination of the signal that is to be digitized.
The contamination may originate from various sources.
If such a signal is digitized *as is. these high frequency components will be disguised as low frequency components.
For example if a 100 Hz signal is digitized at the rate of 75 points/sec the 100 Hz signal will show up as a 25 Hz signal.
Similarly if the digitization is only at the rate of 60 points/sec the 100 Hz signal will show up as a 20 Hz signal.
This problem can be avoided by a sufficiently high digitization rate to define all the frequencies that are present in the system or by inserting analog fliters into the circuit prior to digitization and predefining the cutoff and rolloff frequencies of the filter. The former method is not feasible because of the enormous amount of data gathered and the limitation of the available digitization rate. Therefore, analog filters are commonly used. The cutoff frequency of the filter should be outside the frequency range of interest for the recorded data to avoid any attenuation of significant frequency components and the roll off point should be no higher than half the frequency of the digitization.
The digital record will then contain no allasing and can later be digitally filtered to contain only those frequencies that are of interest.
For this test program the cutoff frequency of the analog filters was selected to be 50 Hz and the rolloff frequency was set at 250 Hz.
This required a minimum digitization frequency of 500 points/sec.
The A/D converter which is an integral part of the Data Acquisition System is capable of digitizing at the rate of approximately 90.000 values/sec. The converter is connected to a high-speed scanner which can scan up to 64 channels (inputs) according to a schedule which is computer controlled.
The combined system can thus technically accommodate 64 channels of data at the rate of approximately 1,400 readings/sec./channel. However, to preserve the phase relationship between the first and last channels of a sampling (scanning) schedule (important in a dynamic test), the digitization rate should not exceed 500 points/sec/channel if all 64 channels are sampled.
This gives approximately a 2 to 1 ratio between the inactive and active periods of the A/D converter.
The A/D converter itself is a 12 bit converter which is preset to read voltages in the range of +10 volts.
The 12 bit resolution implies that the +10 volts range can be resolved into 4096 (2 to the 12th power) different digital values (2048 negative, 2047 positive and the zero value).
To fully utilize this range the signal amplifiers are used as explained above.
7
COMPUTECH Reference Frame Servovalve Spreader Top Actuator Beam Wirepots Masonry Wall specimen Reaction Frame Servovalve Bottom Actuator Footing' Spreader C D Beam FIGURE 2.1 Test Setup 8
______COMPUTECH CY ui CES 91-6-8
COMPUTECH secondary Primary ISondary eec E
e FIGURE 2.3.a Schematic Representation of an LVDT 604n
+5 Volts O
Output 0o 604n FIGURE 2.3.b Wire Potentiometer Connections 10
3 QA/QC PROCEDURES In this section the QA/QC procedures used through out the duration of the test program are described. The description addresses procurement of all documents, Construction of the test specimens, sampling of material for testing, testing of material samples and verification of functionality and calibration of Instrumentation.
3.1 Procurement of Documents All handling and processing of documentation Including software and calculations were performed in accordance with CES's Quality Assurance Manual. Revision 1. issued December 15. 1980.
The manual and the procedures therein have been approved by Bechtel auditors on this and several other projects.
3.2 Construction of Specimens On August 27, 1982 a supplement to the CES QA Manual was issued and transmitted to BPC. Los Angeles in a letter dated September 8, 1982.
The supplement, which was issued specifically for the San Onofre Masonry Test Project. is called 'Guidlines for inspection of Construction for Compliance with Quality Assurance Manual'. The Supplement addresses the construction of footings. test specimens and the procedure for sampling and testing for material properties.
The general guidelines outlined in the Supplement were strictly followed with continuous supervision of all construction by engineering personnel from CES.
The supervision included placement of all steel. sampling of materials for material testing and orientation and handling of strain gages. A record was made of all construction and material sampling dates and each sample was marked according-to a predetermined code to ensure that correct samples would be tested on the correct date.
3.3 Testing of Material Samples The testing of all mortar, grout and steel samples was performed by an approved testing laboratory. Testing Engineers. Inc.. Oakland California. The results of these tests were transmitted to CES and the results tabulated and filed.
The testing of the compressive prisms and block samples were performed at EERC under supervision of CES engineers. The results from these tests were tabulated and filed.
3.4 Instrumentation Prior to the selection of the various Instruments the functionality of each 11
was checked on an oscilloscope. The calibration process for each Instrument type is described in the first paragraphs of Section 2.4 of this report.
In addition. all the measured values (physical quantities vs. measured voltages) that constituted a single calibration value were tabulated in the daily test log for easy reference.
After welding each strain gage to the center rebar, the strain gages were tested by subjecting the rebar to tensile tests In several loading stages up to about half its yield.
Voltage readings were taken for all the gages at each loading stage. After verifying the linearity of the gages (those that were not were replaced) the rebar was raised to a vertical position and readied for construction.
After each test wall was in place on the "shake table" and the instruments mounted, each Instrument was zeroed (to give zero voltage reading in the initial wall position).
The strain gages were then calibrated in a similar manner to the other instruments by the data acquisition system by shunting the strain gage with a resistor and entering the calculated equivalent strain into the data acquisition system.
All the techniques used in calibrating and verifying the Instruments are described in more detail in the subsections of Section 2.3.
Between each test wall each instrument that experienced problems in the preceeding test was recalibrated and checked. Other instruments were spot checked at random.
12
4 TEST SPECIMENS In order to achieve the objective of the test program as presented in Section 1 of this report. the configurations of the chosen panels represented the governing masonry walls of the Fuel Storage Building and the Ventilation Equipment Building at San Onofre Unit 1. Due to their combinations of heights.
reinforcement patterns and location in the structure. the analysis results indicated that these wall configurations would exhibit the greatest seismic responses during a Design Basis Earthquake (DBE) event. While the test walls (lA. 18 and 1C) were meant to represent the Fuel Storage Building walls their response would also envelope the response of the Ventilation Equipment Building walls. This is due to the fact that the Ventilation Building walls have the same reinforcement ratios but are shorter In length. In addition, the Fuel Storage Building walls are all located in the second story of the building (twenty to thirty feet above grade) and will thus have amplified input motions. iThe Ventilation Equipment Building walls are founded on grade and therefore have a lower seismic Input.
41 Construction of the Test Specimens The test specimens were constructed by D A Sullivan Company. a masonry contractor with years of experience in constructing masonry test specimens for the different masonry test programs that have been conducted at the Earthquake Engineering Research Center (EERC).
Although the objective of the program did not necessitate close similarity between the test walls and the in situ walls, steps were taken to ensure that this similarity was as close as was reasonably possible.
In order to achieve similarity of construction materials. the original specification used in the construction of the in situ walls was used In the construction of the test specimens. This specification (BSO-112. January 11.
1965) includes information of all the construction materials used in the walls at the site.
The Implementation of the specification by the contractor was monitored by CES engineers and samples of all construction materials were taken and tested as further verification of the quality and similarity of the construction materials.
Construction of the test specimens took place in September 1982 and the walls were tested In May and June 1983.
The test specimens were therefore 8 - 9 months old at the time of testing. Refer to Sections 6 and 8 for detailed material properties.
4.2 Dimensions of Test Specimens Each test specimen was single wythe. constructed of 8 inch thick (nominal
= 7.625*) hollow concrete block (8' x 8' x 16" units) and a specified Grade 40 #7 vertical reinforcing bars and Grade 40 #5 horizontal reinforcing bars.
Each test specimen was approximately 8 feet long. This length of wall was selected for practical considerations of space. lifting capacity of the overhead 13
crane and the driving capacity of the actuators.
A lower bound on the wall length was set by the desire to have at least three vertical rebars in each test specimen.
With a 32-inch spacing of vertical rebar this required an eight-foot specimen length.
The specimens were approximately 24 feet high (36 block courses) with #7 reinforcing bars spaced vertically at 32 Inches and #5 bars spaced horizontally at 48 inches. All the Fuel Storage Building walls relevant to the test program have this same configuration. The Ventilation Equipment Building walls have the same reinforcing pattern but the walls are four feet (6 block courses) shorter.
In order to achieve the objective of the test program. the wall sections selected for testing were those that proved to be the most critical in the nonlinear analyses performed by CES. Figure 4.1 shows the wall configuration, the block layout and the reinforcment and grout patterns.
4.3 Boundary Conditions The base detail for each of the test specimens called for dowelling into a concrete base. using the same area of dowelled steel and the same embedment percentage as In the in situ walls. This assured the same base fixity conditions at the base of the test panels as are present in the In situ walls.
The site walls have a pin connection at their tops which is typically a ledger angle. The test specimen had connections at the top of the wall as shown in Figure 4.2.
The top actuator was attached to the steel member at the top of the panel via a pin connection.
Therefore, the top connection of the test panels was similar to the insitu walls.
4.4 Attachments The Fuel Storage Building above elevation +42 feet includes approximately 300 lineal feet of masonry walls. The items attached to the applicable masonry walls consist mostly of electrical conduit and minor items such as grounding cable, telephones. small diameter copper tubing and other similar minor items.
Due to their light weights all of the above items other than the electrical conduits were not considered relevant to the test program.
The small amount of electrical conduit attached to these walls is all surface mounted, with support spacing limited to eight feet.
The maximum weight of conduit tributary to any of these supports is approximately 200 pounds.
By comparison, the weight of each test specimen exceeds 11.000 pounds for an eight foot span, so that the maximum conduit weight tributary to the Type 1 wall does not exceed 2% of the wall weight.
In addition, the most heavily loaded conduit supports are found typically in the top or bottom third of the wall and/or near cross walls.
Therefore, given the sparsity of the conduit. Its location and weight. It was not deemed necessary to include it in the test program. Therefore the test specimens had no equipment attached to them.
14
COMPUTECH Bond Bea'm Reinforcing:
Vertical: 3 87 Grade 40 Aebars Horizontal: 6 #5 Grade 40 Top Bond Beam: 4 0s Grae 4o Dowels: 6 0s Grade 4o All horizontal reinforcing is 05 rebars except at the top Bond Seam
.haoed areas indicate grouted cells Figure 4.1 Fuel Storage Building Test Specimens -
Reinforcing Details 15
COMPUTECH Top of Wall
- 5 Grade 40 Rebar.
- 6 Grade 40 Rebars.
W10 Stiffened Spreader Beam (Strong-back).
C 0
3/4' 0 Bolt at 166 (avg.)
- 6 Grade 40 5'
Embedded.
~
~6 Bolts total.
Rebars.
FIGURE 4.2 Fuel Storage Building Test Specimens Connection Detail at Top of Specimens.
16
5 INPUT TIME HISTORIES The test input motions were selected by reviewing the analyses results obtained by CES (see References 3. 4 and 7) and identifying those motions that produced the highest analytical response levels in the subject walls. In the analysis. Taft 1952 applied simultaneously along the three principal building axes, produced maximum response in the subject walls. The duration of the test input motions was established with consideration of the nonlinear response of the walls.
All the time histories that were used in the testing of the wall panels were based on real recorded earthquakes.
Verification of similarity of input actuator motions to those of in-structure spectra was done through spectral comparison. The criterion for acceptability of the similarity of the motions was that the actuator motion response spectra were as close as possible within the physical capabilities of the actuators and their control system to the Instructure spectra over the frequency range of interest:
Le.. the frequency range from the uncracked to the fully yielded masonry walls.
The sections below describe the actions taken to select. modify and test the input time histories for the Fuel Storage Building test specimens.
5.1 Duration The duration of motion that was used in the test program was 30 seconds.
The factors that influenced the selection of the time history duration were the following:
- 1.
The design strong motion duration which is appropriate for the San Onofre site was documented in Attachment 6 to SCE's letter to the NRC dated August 9. 1982 regarding free field ground motion. Based on the data included in that report. It is concluded that a mean design duration of about ten seconds is considered appropriate since this duration will be used with ground motion parameters which are at least 84th percentile instrumental values.
Furthermore, It is concluded that the use of a twenty second duration would exceed the average maximum value of strong motion duration obtained from all sources in the literature and is very conservative. The 30 seconds duration that was selected for the testing of the walls is obviously conservative when compared to the values In the literature as summarized in Attachment 6 to SCE's August 9th letter.
- 2.
Results from the nonlinear analysis of the masonry walls indicated that the maximum response of key parameters. such as deflections and rebar strains. occurred within the 'first 20 seconds of the response.
The time histories *used In these analyses had a duration of 20 to 30 seconds. As stated above.
these time histories were based on real recorded earthquake motions in which the strong motion part was contained within 17
the first 20 seconds.
- 3.
During the past 10 years of shake table testing at the Earthquake Engineering Research Center (EERC) of the University of California. Berkeley. several earthquake motions have been developed and are kept on flie. Each record has the essential spectral characteristics of the recorded motion but is modified with a high pass filter to ensure that the physical capabilities of the actuators used to drive the shake table are not exceeded.
These records include El Centro. Taft. Olympia and Pacoima dam events.
These earthquake motions all have durations of 30 seconds. The EERC experience in using these records with all kinds of structures has been that they are of sufficient duration for nonlinear response.
5.2 Modifying the Time Histories The actuator system used in the test program consisted of two actuators oriented perpendicular to the test panel.
There was one actuator at the top and one at the bottom of each test panel. In this configuration the actuators subjected the wall to horizontal out-of-plane excitation.
The actuators were controlled through a displacement command signal, as opposed to a force command signal. For this reason, the displacement time histories of the selected earthquake motions were used as input commands to drive the actuators.
The input time histories were determined from a nonlinear analysis of the Fuel Storage Building.
In the analysis, acceleration time histories at the top of the fuel pool and at the roof levels were retained, modified and used as inputs to the tests. These input time histories included the instructure amplification as determined by the non-linear analysis. The analysis that resulted in the most critical wall response was for the Taft ground motion and therefore the response time histories for the Taft ground motion were used for the testing of the walls. The input motions were different for the two actuator levels.
The time histories retained from the non-Ilnear analysis were in the form of accelerations.
These acceleration time histories contained significant low frequency components which when converted to displacement commands for the actuators exceeded the displacement and velocity capacity of the actuators and the hydraulic system.
To ensure that the stroke limitations of +6 inches and the velocity limitations of 30 inches/sec were not exceeded the displacement commands were high pass filtered to eliminate the low frequency components from the signals.
For this purpose a time domain filtering with a filter having the rolloff frequency equal to 0.35 Hz and the cutoff frequency equal to 0.45 Hz was applied. With this operation the command signals were compatible with the capacity of the actuators and the hydraulic system without compromising the spectral match within the frequency range of the walls when they went from the uncracked state to the cracked and fully yielded state.
18
To verity that the spectral match was adequate the command signals were run through the actuators without the wall attached and data on the actuator stroke and accelerations were gathered. By analyzing the data and obtaining response spectra the input amplitude of the signals could be adjusted to ensure that the test response spectra enveloped the target response spectra (from the analysis) over the frequency range of interest (0.0 -
34.0 Hz.).
As a further assurance that the target spectra would be matched during the tests the test command signals were increased by 10% over the full range of frequencies. Figures 5.1 through 5.6 show the modified analytical test displacement command signals for the two actuators, the acceleration time histories inherent in these command signals and the test target response spectra.
The spectral plots include the response spectra required for the tests (with the 10% increase) and the target response spectra (from the analysis).
19
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6 TESTING OF THE FUEL STORAGE BUILDING WALL SPECIMENS This section discusses the type of tests performed on the specimens and provides details of the testing performed on each of the 3 specimens (1A. 18 and 10).
6.1 Tests Performed The testing performed on the specimens (IA.
1B and IC) consisted of material tests. damping tests (using free vibrations induced by pulling the walls back and releasing) and the full intensity dynamic test.
6.1.1 Material Property Tests Nine cylinder samples of mortar and nine cube samples of grout were sampled concurrent with the construction of each specimen. The samples were taken in groups of three, the first group from the bottom third of the wall. the second group from the center third of the wall and the third group from the top third of the wall.
One sample of grout and one sample of mortar from each group were then tested at the age of 7 days. a second sample from each group at the age of 28 days and the last samples from each group were to be tested within 48 hrs of the full intensity dynamic testing of each wall specimen. The testing of the last group of material samples did not in general meet the 48 hrs deadline. However. considering the age of the wall specimens at the time of their testing (8 - 9 months) this increased time between testing of the wall specimens and the material samples has negligible influence on the results. The tests were performed by Testing Engineers.
Inc. of Oakland. California and conformed to ASTM C91 and ASTM C109
- 75.
In addition to the grout and mortar samples, three samples of block were retained and three three-unit high prisms were constructed concurrent with each wall specimen. One prism and one block corresponded to each of the three groups of grout and mortar in terms of materials and locations within the wall. These samples were tested at the EERC under supervision of'engineers from CES and conformed to ASTM E 447-74 and ASTM C 140-75.
Two specimens of the #7 Grade 40 rebar were also sampled and tested, one sample for the strain gaged rebar in the center of the wall and one sample from one of the side rebars.
These tests conformed to ASTM A 370-75 and were performed by Testing Engineers. Inc. of Oakland. California.
6.1.2 Low Level Pull Back Tests Pull back testing was used to evaluate the damping corresponding to the uncracked and the cracked states of the test panel.
This involved 26
statically displacing the specimens, then releasing them suddenly and letting them vibrate freely while measuring the panel deflections and accelerations.
The damping was then determined by the logarithmic decrement method following standard procedure.
6.1.3 High Level Dynamic Response Tests The high level dynamic test involved subjecting the specimens to the full Intensity Input motion while measuring the out-of-plane deflections.
accelerations, wall curvature. faceshell strains, joint openings and steel strains.
The input command signals have been described in Section 5 and the instruments in Section 2 of this report.
The instrumentation on the Fuel Storage Building wall specimens consisted of 7 Accelerometers. 11 Wire Potentiometers. 22 DCDTs and 20 Strain Gages in addition to the stroke (displacement) and the load time histories of the two actuators. This is a total 64 channels of data which was the capacity of the Data Acquisition System.
The instrument layout is schematically shown in Figure 6.1 and the assignment of the instruments to the data acquisition channels is shown in Table 6.1. The data acquisition and the data reduction are discussed in Section 2.4 and Section 7 respectively.
27
Section 6.2 through Section 11 and Appendices A. B and C are proprietary to Southern California Edison Company.
28 125
12 REFERENCES
- 1.
Computech Engineering Services. Inc.. "San Onofre Nuclear Generating Station. Unit 1. Seismic Evaluation of Reinforced Concrete Masonry Walls.
Volume 1: Criteria'. forwarded by letter from K P Baskin to D M Crutchfield dated January 15. 1982.
- 2.
Computech Engineering Services, Inc.. *San Onofre Nuclear Generating Station. Unit 1. Seismic Evaluation of Reinforced Concrete Masonry Walls.
Volume 2: Analysis Methodology". forwarded by letter from K P Baskin to D M Crutchfield dated January 11.
1982.
- 3.
Computech Engineering Services. Inc.. *San Onotre Nuclear Generating Station. Unit 1. Seismic Evaluation of Reinforced Concrete Masonry Walls.
Volume 3: Masonry Wall Evaluationo. forwarded by letter from K P Baskin to D M Crutchfield dated January 11.
1982.
- 4.
Computech Engineering Services. Inc.. *San Onofre Nuclear Generating Station. Unit 1. Seismic Evaluation of Reinforced Concrete Masonry Walls.
Volume 4: Fuel Storage Building'. forwarded by letter from K P Baskin to D M Crutchfield dated April 30, 1982.
- 5.
NRC letter from W A Paulson to R Dietch dated February 17.
1982.
- 6.
NRC letter from D M Crutchfield to R Dietch dated April 29. 1982.
- 7.
Computech Engineering Services. Inc., "San Onofre Nuclear Generating Station Unit 1. Seismic Evalution of Reinforced Concrete Masonry Walls. Volume 5:
Fuel Storage Building Soil Backfill Condition Evaluation." forwarded by letter from K. P. Baskin to D. M. Crutchfield dated September 30. 1982.
- 8.
Clough. R. W. and Penzien. J.. 'Dynamics of Structures". McGraw Hill. 1975.
126
SAN ONOFRE NUCLEAR GENERATING STATION. UNIT 1 SEISMIC EVALUATION OF REINFORCED CONCRETE MASONRY WALLS APPENDIX A
MASONRY WALL TEST PROGRAM RESULTS FROM TESTING WALLS lA. 18 AND 10 Prepared For:
BECHTEL POWER CORPORATION Los Angeles. California Prepared By:
COMPUTECH ENGINEERING SERVICES.
INC.
Berkeley. California Report No. R557.09 February 1984
INFORMATION PRESENTED IN THIS REPORT IS PROPRIETARY TO SOUTHERN CALIFORNIA EDISON COMPANY
SAN ONOFRE NUCLEAR GENERATING STATION. UNIT 1 SEISMIC EVALUATION OF REINFORCED CONCRETE MASONRY WALLS APPENDIX B
MASONRY WALL TEST PROGRAM RESULTS FROM TESTING WALLS 1A.
11 AND 1C Prepared For:
BECHTEL POWER CORPORATION Los Angeles. California Prepared By:
COMPUTECH ENGINEERING SERVICES.
INC.
Berkeley. California Report No. R557.09 February 1984
INFORMATION PRESENTED IN THIS REPORT IS PROPRIETARY TO SOUTHERN CALIFORNIA EDISON COMPANY
SAN ONOFRE NUCLEAR GENERATING STATION. UNIT 1 SEISMIC EVALUATION OF REINFORCED CONCRETE MASONRY WALLS APPENDIX C
MASONRY WALL TEST PROGRAM RESULTS FROM TESTING WALLS 1A. 18 AND IC Prepared For:
BECHTEL POWER CORPORATION Los Angeles. California Prepared By:
COMPUTECH ENGINEERING SERVICES.
INC.
Berkeley. CalifornIa Report No. R557.09 February 1984
INFORMATION PRESENTED IN THIS REPORT IS PROPRIETARY TO SOUTHERN CALIFORNIA EDISON COMPANY