Pre-stressing concrete with V-Rod CFRP FiberLoc

Transcription

1 Pre-stressing concrete with V-Rod CFRP FiberLoc 1

2 FiberLoc overview FiberLoc is a patented anchoring system specifically designed to be used with Pultrall s Carbon fiber composite tendons (CFRP) for pre-stressing concrete structures such as precast bridge decks and girders. Although pre-stressing CFRP may look similar to pre-stressing steel strand there are major differences and precautions that must be followed in order to have a safe and successful installation. The following guide was prepared with step by step instructions and photographs to help the user understand with ease. SAFETY DISCLAIMER Please be aware that the great tensile loads implied in prestressing precast concrete elements with FiberLoc may involve risks to the system users health and safety. It is the sole responsibility of the system user to determine the proper means to control/contain these risks. The following document outlines recommendations in controlling/containing those risks but Pultrall assumes no responsibility and no liability as to the appropriateness and effectiveness of the safety measures implemented by the FiberLoc users. 2

3 FiberLoc ANCHOR SYSTEM INSTALLATION GUIDE Inspection and safety precautions: Version 7.1 All components must be kept in a clean dry place to prevent rust. Prior to using the anchor system a visual inspection of all the components must be done to determine if any parts are in need of replacement. The copper sleeves are a one (1) time use item and must not be reused. The barrel and wedges are reusable items although they must be visually inspected. Immediately discard parts that show signs of impact dents, deformation, cracks or rust. They must not be reused. Furthermore, barrels and wedges must undergo a non-destructive Magnaflux dye inspection test (SPOTCHECK) after every 100 uses for the barrels and after 200 uses for the wedges. Any signs of cracks will render the components unfit for use. Immediately discard the components as they must not be reused. The wedges are sold as a matching set of 3 and must be used and identified as a set. They must not be mismatched with other wedges. All wedges (set) must be replaced by a new set even if only one of the wedges shows signs of damage. In the interest of safety, all components during and after loading including CFRP tendons must be adequately shrouded. Suitable constructed guards or restraints must be used as to prevent any flying components in the event of a failure. During and after stressing (loading), operators must not stand in the line of stressing or behind the jack. High pressure dry graphite lubricant must be used. (The following lubricants are recommended.) Crown Dry Graphite lubricant 8078 (manufactured by AERVOE Industries in.) CRC Dry Graphite lubricant (Manufactured by CRC) Sprayon LU 204 Dry film graphite lubricant (Manufactured by SPRAYON) Plastikote 281 Dry Graphite lube (Manufactured by Valspar Corporation) 3

4 NOTE: Any mishandling of the components or assembly instructions could compromise the integrity of the anchor system and lead to a premature failure of the anchor system or the CFRP bar and/or bodily injury. (Refer to the handling and installation precautions on page 28.) FiberLoc anchor system components: The FiberLoc anchor system is made up of four main components, namely a soft copper sleeve, three steel wedges, a steel barrel and a rubber o-ring (Figure 1). The tools needed to attach and remove the anchor from a CFRP bar include the hydraulic pre-seating device (Figure 4 and figure 5), hydraulic pump (Figure 5), pre-seating fitting (Figure 2) and a disassembly fitting. (Figure 3) Other system components include the guide tool (Figure 6) which is used to maintain an even spacing between the wedges and the reshaping tools (taper tool and reshaping die) which are used to reshape the copper sleeves (Figure 7). Figure 1 (FiberLoc system components) 4

5 Figure 2 (Pre-seating fitting) Figure 3 (Disassembly fitting) Figure 4 (Hydraulic pre-seating device) 5

6 Figure 5 (FiberLoc pre-seating device and pump) Figure 6 (Guide tool) Figure 7 (Copper sleeve reshaping tools) 6

7 Handling of copper sleeves The FiberLoc copper sleeves are manufactured with a special grade of copper that has been annealed in order to increase its malleability. Due to this malleability, special care must be taken during their handling as they are very soft and can deform quite easily. Copper sleeves can be reshaped in the event that they have been deformed during handling. This can easily be done by using the reshaping tools (taper tool and reshaping die). These tools are composed of 2 parts, a taper steel tool and a hinged reshaping die. To reshape the copper sleeve simply: 1. Pass the taper tool through the copper sleeve until the sleeve is positioned completely on the straight and parallel section of the steel tool.(figures 8,9 and 10) Figure 8 Figure 9 Figure 10 7

8 2. Insert the taper tool and copper sleeve in the reshaping die and close with slight pressure to reshape the copper sleeve. (Figures 11 and 12) Figure 11 Figure Open the die and remove the copper sleeve from the tapered tool. Important notice: Sleeves that too severely deformed or that taper tool does not enter at least one of the ends must be discarded. As seen in figure 13 (Sleeve on the left is too severely deformed, sleeve on right can be reshaped.) Figure 13 8

9 Cleaning of components 1. At every use, wedges, barrel and copper sleeve must be cleaned with new unused (nonrecycled) acetone in order to remove any traces of oils, grease or any other contaminants that might affect the proper function of the anchor system. We recommend the use of a polyethylene squirt bottle for the acetone as this will prevent any contamination of the acetone in the bottle. It is important to use clean gloves during the cleaning process. 2. Prior to cleaning the copper sleeve, blow clean compressed air on the inside of the sleeve to remove any foreign material or loose copper oxide that may have formed during the annealing process.(figure 14) Figure 14 (compressed air) 3. Clean the outside of the copper sleeve with acetone and a clean rag. (Figures 15 and 16) Figures 15 Figures 16 9

10 4. Then completely wet the inner surface of the sleeve by squirting acetone. (Figure 17) Figure For the other components squirt acetone on a clean rag and rub all surfaces. (Figures 18,19 and 20) Figure 18 10

11 Figure 19 Figure 20 11

12 Cleaning of CFRP tendon 1. Eliminate any foreign matter or contaminants by cleaning the non-sanded portion of the CFRP tendon that will receive the anchor. Use new non-recycled acetone and a clean lint free cloth (Figure 21 and 22). Care must be taken not to contaminate the cleaned components prior to pre-stressing. Figure 21 Figure 22 12

13 Lubrication of components Proper and sufficient lubrication of the barrels and wedges is a critical aspect that must never be overlooked. Failure in doing so will increase the risk of failure by slippage of the CFRP tendon from the FiberLoc anchor. Necessary measures must be taken as to not to contaminate the clean copper sleeves and CFRP tendon when spraying the lubricant. It is recommended that the lubrication process of the barrels and wedges be performed at a different area isolated from the cleaning process and the pre-stressing. Barrel 1. Vigorously shake the graphite lubricant can for one minute in order to properly disperse the graphite in the solvent. 2. Evenly spray a generous amount of lubricant inside the barrel while holding the barrel in the air and in a downward position. (Figure 23) 3. Do not spray the barrel on a flat surface as the blowback will prevent the lubricant from reaching the other end. (Figure 24) Figure 23 (Good method of spraying barrel) Figure 24 (Do not spray with barrel on a surface) 4. Let the lubricant dry. 13

14 5. Once all the solvent has evaporated apply a generous second coat, however this time spray from the other end of the barrel. (Figure 25) Figure Once the solvent has completely evaporated, inspect the inside of the barrel. The surface must be completely covered with lubricant. Re-spray if needed. 14

15 Wedges 1. Vigorously shake the graphite lubricant can for one minute in order to properly disperse the graphite in the solvent. 2. Separate the wedges and lay them on a flat surface with the outside side up. (figure 26) 3. Completely coat the outside of the wedges by applying 2 to 3 light coats of lubricant. (Figure 27) 4. Let the solvent evaporate completely between coats. This will prevent any lubricant run-off from reaching the inside section (contact area between the wedges and the copper sleeve). Do not coat the inside or the ends of the wedges. Figure 26 Figure Once the solvent has completely evaporated, inspect the surface for complete coverage. Reapply lubricant if needed. 15

16 FiberLoc Anchor assembly 1. With clean gloves, slip the copper sleeve onto the section of cleaned un-sanded CFRP tendon and position it at the intended anchor placement by leaving ¼ of an inch of the bar protruding. (Figure 28) Figure Carefully slip the barrel over the copper sleeve with the smallest opening first without touching the copper sleeve and lay it to rest on the CFRP tendon (Figure 29). (Touching the copper sleeve with the barrel will transfer lubricant from the barrel to the sleeve and thus contaminate the sleeve.) Figure 29 16

17 3. Slip the rubber O-ring past the copper sleeve (Figure 30). Figure Assemble the wedges around the copper sleeve by evenly spacing them from one another and centered on the copper sleeve. While holding the wedges firmly, slip the o- ring on the smallest end of the wedges and roll it all the way to the groove at the larger end (Figures 31 and 32). Figure 31 Figure 32 17

18 5. Once the o-ring is in place, verify that the wedges are evenly distributed around the copper sleeve and that they are positioned at the same distance lengthwise from one another. (Figure 33) Figure Slip the barrel over the wedge assembly. (Figure 34) Figure 34 18

19 7. Use the wedge guide tool (figure 35) to evenly distribute and position the wedges around the copper sleeve. This will also help to align the wedges lengthwise to ensure an even pressure distribution on the CFRP tendon. 8. Position the guide tool over the CFRP tendon and copper sleeve. The three blades of the guide tool must enter the spaces in between the wedges. (Figure 36) 9. Firmly push on the guide tool to insert the wedges while holding the barrel. (Figure 37) Figure 35 Figure36 Figure 37 19

20 Important notice: Misalignment of the wedges (uneven as per one another) as per Figure 38 will cause an unbalanced pressure distribution and can lead to premature failure of the CFRP tendon and/or other components. The wedges must be positioned evenly as per Figure 39 before and after applying the pre-seating load. Figure 38 (uneven wedge distribution) Figure 39 (good wedge distribution) 20

21 10. Position the anchor assembly in the hydraulic jack pre-seating device.(figure 40) Figure In order to prevent any undue damage to the end of the copper sleeve it is important to slip the pre-seating fitting over the copper sleeve and rod until it sits flat against the wedges. This way the wedges will be evenly seated in the barrel during the pre-seat loading. (Figure 41). Figure 41 21

22 Important notice: If for any reason the copper sleeve is damaged or crushed during the pre-seating (Figure 42) then it must discarded and replaced to ensure a proper pressure distribution of the wedges in the barrel. Figure Slowly extend the hydraulic jack with the pump while making sure the piston ram fits over the pre-seat fitting. (Figure 43). Once the ram is completely seated against the preseating fitting high pressure loading can begin.(figure 44) Figure 43 Figure 44 22

23 13. In order to properly seat the wedges in the barrel, a load of 74 kn or lbs of force is needed. To determine the hydraulic pressure needed to exert this force, the effective surface area of the hydraulic cylinder is needed. In this case the hydraulic cylinder used in the pre-seating device is either an Enerpac model RCH-123, Simplex RC123 or equivalent. The effective surface area of this size cylinder is 2.76 in². To determine the pressure (psi), the load is divided by the effective surface area (in²). Therefore lbs / 2.76 in² = 6000 psi. The hydraulic pressure to be used is 6000 psi. 14. Load the jack until the pressure gauge reads 6000 psi. 15. If the load decreases then bring it back to 6000 psi. Repeat as necessary until the load is stable at 6000 psi for at least 5 seconds. (Figure 45) Figure If an electric or gas hydraulic pump is used to pre-seat the anchor then a pressure relief valve must be used in order to maintain the 6000 psi load for at least 5 seconds. 23

24 17. Release the hydraulic pressure and remove the pre-seating device assembly. The FiberLoc anchor is now ready. (Figure 46) Figure 46 24

25 FiberLoc anchor disassembly: The hydraulic jack seating device is also used for the disassembly of the anchor system. 1. Cut the CFRP bar leaving 1 to 2 centimetres protruding from the anchor assembly (Figure 47). Figure Position the pre-seat fitting in the pre-seating device as per Figure 48 and 49 or directly on the anchor assembly as per Figure 50 and 51. Figure 48 Figure 49 25

26 3. Position the disassembly fitting at the opposite end (Figures 50 and 51). (The anchor assembly must face the opposite direction of the assembly procedure.) Figure 50 Figure Position the anchor assembly in the pre-seating device with the preset fitting end towards the hydraulic piston as per Figure 52. Figure 52 26

27 5. Slowly extend the hydraulic jack with the pump while guiding the preset fitting over the CFRP bar and into the barrel. By doing so, the hydraulic jack will push the wedges out of the barrel. (Figures 53 and 54) Figure 53 Figure Once the wedges release from the barrel remove the hydraulic pressure and manually disassemble the components. (Figure 55) Figure The components are ready to be reused after inspection and cleaning. 27

28 Pre-stressing with FiberLoc anchors Due to the fragile nature of carbon fiber, extra precautions must be taken when handling the CFRP bars. (see handling and installation precautions below) Handling and installation precautions Only FIBERLOC anchors must be used on the CFRP bar and installed as per the FIBERLOC ANCHOR SYSTEM INSTALLATION GUIDE. Any torsion of CFRP tendons must be avoided especially during twisted loading. Transfer boxes and harnesses are used during pre-stressing to eliminate any torsion induced by the steel strand. (See figure C) To prevent any damage to the CFRP, the transfer box must be placed and supported as to position the CFRP tendon level and centered with the through holes in the form work. (Figure A) The transfer box must remain free of debris or welds that could prevent the barrel end from resting flat against the transfer box and perpendicular to the CFRP (Figure B) Predetermining the proper position for the transfer boxes and harnesses prior to the set-up is essential in order to prevent the transfer boxes from exiting the harnesses during the bar loading and thus twisting the bar due to the elongation of the CFRP tendons. Safety pins are to be used on the opened end of the transfer boxes as to prevent the FIBERLOC anchor from escaping in case of a bar or anchor failure. (Figure A) Pre-stress jacks must not be used on the CFRP (Steel strand with standard pre-stress chucks are used with the hydraulic jack ) (Figure C) Harnesses must remain over the transfer boxes at all times during and after the tendon is loaded to the pre-stress level. (See pre-stress installations example Figure D) A load cell should be used at the dead end of at least one of the CFRP tendons to confirm the pressure readout from the pre-stress hydraulic jack. The elongation of the assembly should also be measured and noted. The load cell shall also be used to monitor the overnight loss of stress due to the relaxation of the CFRP tendon assembly and the concrete curing. The amount of relaxation may be compensated by increasing the level of stress during the initial jacking of the CFRP. 28

29 Figure A (harness removed for clarity) Figure B (barrel must rest flat at the ends of the transfer box) 29

30 Load each rod assembly according to CSA S6-06, ACI 440, ISIS design manual No. 5 prestressing Concrete Structures with FRP, or the recommendations of the design engineer. Concrete vibrators must not come in contact with the CFRP tendons when vibrating the concrete. Figure C Important notice Please keep in mind that FiberLoc was designed and sold with the intent of prestressing one section of slab or element at a time. Although pre-stressing numerous sections in series is a possibility, the lack of test results and knowledge in this matter leads us to remind you that it is not a recommended practice. Therefore at the present moment, pre-stressing in series is not recommended. 30

31 Figure D (Example of FiberLoc pre-stress installation) 31