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Installation Manual
Models 4911A/4911
VW Rebar Strain Meters
No part of this instruction manual may be reproduced, by any means, without the written consent of Geokon, Inc.
The information contained herein is believed to be accurate and reliable. However, Geokon, Inc. assumes no responsibility for
errors, omissions or misinterpretation. The information herein is subject to change without notification.
Copyright © 1989, 1996, 2004, 2007,2008,2009,2010, 2012, 2013 Geokon, Inc.
(Doc Rev O 6/13)
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Related Manuals for Geokon 4911A
Summary of Contents for Geokon 4911A
- Page 1 VW Rebar Strain Meters No part of this instruction manual may be reproduced, by any means, without the written consent of Geokon, Inc. The information contained herein is believed to be accurate and reliable. However, Geokon, Inc. assumes no responsibility for errors, omissions or misinterpretation.
- Page 3 The buyer's sole remedy for any breach of this agreement by Geokon, Inc. or any breach of any warranty by Geokon, Inc. shall not exceed the purchase price paid by the purchaser to Geokon, Inc. for the unit or units, or equipment directly affected by such breach.
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Page 5: Table Of Contents
............................2 RELIMINARY ESTS 2.2. R ....................... 2 EBAR TRAIN ETER NSTALLATION 2.2.1. Model 4911A ............................2 2.2.2. Model 4911 "Sister Bar" ........................3 2.3. C ............................5 ABLE NSTALLATION 3. TAKING READINGS ............................5 3.1. O GK-403 R ...................... 5... - Page 6 LIST of FIGURES, TABLES and EQUATIONS Page 1 - M 4911A R ..................... 1 IGURE ODEL EBAR TRAIN ETER 2 - M 4911 R ......................1 IGURE ODEL EBAR TRAIN ETER 3 - M 4911A I ........................3 IGURE ODEL...
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Page 7: Introduction
Geokon. The Model 4911A Vibrating Wire Rebar Strain Meter consists of a short length of high strength steel welded between two 18" (457 mm) long sections of reinforcing bar. It is designed to be welded between sections of structural concrete reinforcing bar. -
Page 8: Installation
By pulling on the strain meter it should be possible to change the readout digits, causing them to rise as tension increases. Checks of electrical continuity can also be made using an ohmmeter. For the 4911A, resistance between the gage leads should be approximately 50 Ω, ±10 Ω, for the 4911, 50 Ω, ±10 Ω. -
Page 9: Model 4911 "Sister Bar
(installed after excavation) Rebar Strain Meters (2 places, opposite) Figure 3 - Model 4911A Installation 2.2.2. Model 4911 "Sister Bar" The "Sister Bar" is usually installed using standard iron tie wire. Normally ties near the ends and at the one third points are sufficient if the gage is being wired to a larger section of rebar or to horizontal bars. - Page 10 Instrument Cables Pile Rebar Strain Meters (2 or 3 places) Rebar Reinforcement or Pre-Stressing Cables Concrete Rebar Strain Meters (2 or 3 places) Rebar Strain Meters (2 or 3 places) Figure 4 - Model 4911 "Sister Bar" Installation Instrument Cables Reinforcing Rebar Instrument Cable or Strand...
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Page 11: Cable Installation
2.3. Cable Installation As noted in the installation sections, route the instrument cables along the structural rebar and tie off using nylon cable ties every 2-3 feet (1 meter) to secure. Outside of the instrumented structure, the cable should be protected from accidental damage caused by moving equipment or other construction activity. -
Page 12: Operation Of The Gk405 Readout Box
Use the POS (Position) button to select position B and the MODE button to select Dg (digits). Other functions can be selected as described in the GK404 Manual. The GK-404 will continue to take measurements and display the readings until the OFF button is pushed, or if enabled, when the automatic Power-Off timer shuts the GK-404 off. -
Page 13: Measuring Temperatures
°C automatically. 4. DATA REDUCTION 4.1. Strain Calculation The basic units utilized by Geokon for measurement and reduction of data from Vibrating Wire Rebar Strain Meters are "digits". Calculation of digits is based on the following equation; ... -
Page 14: Temperature Correction
4.2. Temperature Correction Rebar strain meters are usually embedded in concrete and strained by the concrete, the assumption being that the strain in the meter is equal to the strain in the concrete. When the temperature changes, the concrete expands and contracts at a rate slightly less than the rate of the steel of the vibrating wire. -
Page 15: Environmental Factors
4.3. Environmental Factors Since the purpose of the strain meter installation is to monitor site conditions, factors which may affect these conditions should be observed and recorded. Seemingly minor effects may have a real influence on the behavior of the structure being monitored and may give an early indication of potential problems. - Page 16 Figure 7 - Sample Model 4911 Calibration Sheet...
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Page 17: Troubleshooting
Symptom: Strain Meter Fails to Read Is the cable cut or crushed? This can be checked with an ohmmeter. For the 4911A, nominal resistance between the two gage leads (usually red and black leads) is 50Ω, ±5Ω, the same for the 4911,50Ω, ±5Ω. Remember to add cable resistance when checking (22 AWG stranded copper leads are approximately 14.7Ω/1000' or 48.5Ω/km, multiply by 2 for... -
Page 18: Appendix A - Specifications
Grade 60 Rebar and High Strength Steel Electrical Cable: 2 twisted pair (4 conductor) 22 AWG Foil shield, PVC jacket, nominal OD=6.3 mm (0.250") Table A-1 Model 4911A/4911 Strain Meter Specifications Notes: ¹ Consult the factory for other sizes available. A.2 Thermistor (see Appendix B also) Range: -80 to +150°... -
Page 19: Appendix B - Thermistor Temperature Derivation
APPENDIX B - THERMISTOR TEMPERATURE DERIVATION Thermistor Type: YSI 44005, Dale #1C3001-B3, Alpha #13A3001-B3 Resistance to Temperature Equation: − 273 2 A B LnR C LnR Equation B-1 Convert Thermistor Resistance to Temperature T = Temperature in °C. Where; LnR = Natural Log of Thermistor Resistance A = 1.4051 ×... -
Page 20: Appendix C - Deriving The Calibration Factor, C, From The Test Data
APPENDIX C – DERIVING THE CALIBRATION FACTOR, C, FROM THE TEST DATA The Model 4911A/4911 Strain Meters are calibrated by loading them in a testing machine hence the gage factor, C, must be determined after converting loads to strains. This is done as follows: The central section of the rebar strain meter, the unbonded length, (7.5"... - Page 21 Rebar Size Diameter 0.500 in. 0.196 in 2 0.248 in 2 1.27 cm 1.264 cm 2 1.60 cm 2 0.625 in. 0..3058 in 2 0.357 in 2 1.59 cm 1.973 cm 2 2.303 cm 2 0.750 in. 0.390 in 2 0.442 in 2 1.905 cm 2.516 cm 2...