Prestressed Post - tensioning Method
1 range
This process standard applies to the general industrial and civil construction site prestressed concrete post-tensioned hydraulic tensioning construction (not including components and block making).
2 construction preparation
2.1 Materials and main equipment
2.1.1 Prestressing tendons: The heat treatment of pre-stressed steel, steel wire, strand varieties, specifications, diameter, must meet the design requirements and national standards, should be factory quality certificate repeated test report. Cold-drawn Ⅰ, Ⅱ, Ⅲ grade steel should also be cold-drawn mechanical properties of the test report.
2.1.2 Prestressing tendons in the form of anchors, fixtures and connectors should be consistent with the design and application of technical requirements, should be factory certification, into the construction site should be "concrete construction and acceptance of the Code" (GB50204- 92) of the provisions of acceptance and assembly of the static load test.
2.1.3 grouting cement shall not be less than 425, ordinary Portland cement or according to the design requirements, should be a factory certificate and re-test report card.
2.1.4 The main machine has: hydraulic stretching machine, electric high-pressure pump, grouting equipment, test mode.
2.2 Operating conditions
2.2.1 The prestressing tensioning machine has been verified and documented. Check the tensioning equipment and equipment is normal and reliable, if found to have abnormal conditions, should be repaired before use. Grouting equipment ready.
2.2.2 The strength of the concrete structure (or block) must meet the design requirements, such as the design is not required, should not be less than 75% of the design strength. The size, appearance quality, reserved hole and embedded parts of the component (or block) shall be inspected and checked and qualified. The assembled block shall be assembled and checked.
2.2.3 anchor fixture, the connector should be ready, and after inspection and acceptance.
2.2.4 Prestressed tendons or prestressed steel wire bundles have been completed.
2.2.5 grouting with the cement slurry (or mortar) mix and the end of the concrete mix ratio has been experimentally determined.
2.2.6 tensioning site should be smooth, smooth, tension at both ends of the security measures.
2.2.7 has been technical to the end, and should be the prestressing tendons tension tonnage and the corresponding gauge pointer readings, steel calculated elongation value written on the card, and hung in a clear position, in order to observe the operation of the master.
3 operating process
3.1 Process flow:
Check the component (or block)
↓
Prestressed tendons produced → wear prestressed tendons
↓
Anchorage inspection → installation and tensioning equipment Tensioning equipment pre-inspection
↓
La Zhang
↓
Grouting → making cement slurry test block
↓
Lifting ← pressure cement slurry test block
In this case,
3.2 Check the components (or block): In particular, carefully check the tendons of the tunnel. The holes shall be of the correct size and position, smooth and smooth, without local bending. The embedded steel plate at the end of the tunnel shall be perpendicular to the axis of the tunnel. The grouting hole and vent shall meet the design requirements. Do not meet the requirements of the channel, to clean up or make good treatment.
3.3 wear prestressed tendons.
3.3.1 before wearing tendons, should check the steel (or beam) specifications, the total length is to meet the requirements.
3.3.2 when wearing tendons, with the prestressed bar bolts Ruibian screw should be good to protect the thread, so as not to damage. Steel bars or wire bundles shall be numbered in a sequence of steel bars or steel wires and shall be fitted with a piercing beam. First, the steel or beam piercing the lead from one end into the tunnel, at the other end of the piercing, and then gradually to the steel or steel wire bundle to the other side.
3.3.3 After putting on the steel bar, mark the beam number on the component so as to check it.
3.4 installation of anchorage and tensioning equipment: the installation of anchorage and tensioning equipment, the straight line of prestressed tendons, tension lines should be so that the action line and the center line of the hole in the process of tension with each other overlap; the curve of prestressing tendons, should So that the tension line of action and the center point of the end of the tunnel tangent coincides with each other.
3.5 Stretch:
3.5.1 Prestressing tendon tensioning procedures, design requirements should be carried out, if the design is not specified, you can take one of the following procedures:
3.5.1.1 0 → 105% σcon hold for 2min → σcon.
3.5.1.2 0 → 103% σcon
Σcon is the prestressing stress of prestressing tendon.
3.5.2 Prestressing tendon tension in the order should meet the design requirements, when no specific requirements of the design, can be taken in batches, phased symmetrical tension.
When using batch tension, should be calculated in batches of prestressed loss of tension, were added to the first tensioned prestressed tendons tension control stress value, or use the same tension by the root of the value of the reset complement.
3.5.3 single prestressed coarse steel (tensile machine tension screw rod end) tension, it should be a little afterburner, the pad position according to the design requirements to identify, and then according to the provisions of the tensioning process tension. Tension is completed, with the board tighten the nut, the steel anchorage, measured the actual elongation of steel, and make tensioning records.
3.5.4 prestressed steel wire towers with double-acting jacking taper anchor anchor when anchoring, should be the following requirements:
3.5.4.1 Pre-Pull: After pulling out the wire for a short length, check whether the length of each wire is the same. If there is any inconsistency, the wedge should be retreated and then tightened to tighten the wedge.
3.5.4.2 tension and pressure: pre-tension adjustment after the tension in accordance with the provisions of tensioning process. Tension is completed, measured wire elongation value, bitter and in line with the provisions, can be the top pressure anchor. Top pressure anchor must be shut off when the tank oil, to the small tank into the oil, so that small cylinder piston top anchor.
3.5.4.3 Checking: Jack is loaded into the unstretched end of the tension, tension to control stress, the top anchor. When both ends of the top tension is completed, should be measured steel wire slide into the anchor in the shrinkage of the amount of compliance requirements, if greater than the specified value, must be re-tensioning, back up losses.
3.5.4.4 The number of wire breaks and slippage shall not exceed 3% of the total number of wires of the same cross-section, and only one strand of steel wire shall be allowed. Such as more than the above requirements must be re-tensioned, then the wire should be pulled to the original tension tonnage, Laxong anchor, with a steel drill slot into the pad plate, jammed anchor, and then return to the cylinder, The anchor is pulled out and the entire anchor is removed. Respectively, to check whether the anchor ring was pumped into the groove, whether the fine tooth was flattened anchor, if such cases, to exchange anchor, re-tensioning, if the anchor ring, anchor is still intact, then as long as the top Pressure to increase the pressure when the top anchor.
3.6 Fill pre-stressed records.
3.7 Grouting:
3.7.1 grouting pore pressure water should be cleaned, and check the grouting holes, vent holes and prestressed tendons connected channels, otherwise, should be dealt with in advance.
3.7.2 prestressed tendons should be completed as soon as possible after the completion of tunnel grouting to reduce the pre-should be lost.
3.7.3 grouting pressure is generally 0.4 ~ 0.6MPa.
3.7.4 grouting sequence should be on the next after the upper hole to prevent leakage of slurry to block the lower hole to the exhaust vents emerge after the thick slurry, which blocked the exhaust hole, and then grouting to 0.6MPa, to maintain l ~ 2min , You can plug the grouting hole.
3.7.5 Make test block and pay attention to maintenance.
3.8 pouring end of concrete or end protective treatment, and pay attention to concrete curing;
4 quality standards
4.1 Warranty items:
4.1.1 The variety and quality of the prestressed tendons must meet the design requirements and the relevant standards.
Inspection methods: Check the factory quality certificate and test report card.
4.1.2 The mechanical properties of the cold-drawn reinforcement shall comply with the design requirements and construction specifications.
Inspection method: check the factory quality certificate, test report and cold-drawn record.
4.1.3 Prestressed tendons used in the anchorage, fixture and connector quality must meet the design requirements and construction specifications and special requirements.
Check the number: According to "Code for Construction and Acceptance of Concrete Structures" the sixth chapter 6.2.12 of the provisions of the sample.
Inspection method: Check the factory certificate, hardness, static load anchorage performance and appearance size inspection report of anchor, clamp and connector.
4.1.4 strength of concrete and block vertical seam concrete (mortar) strength, must meet the design requirements and construction specifications and requirements.
Test method: Check with the conditions of conservation of concrete (mortar) test block test report.
4.1.5 The anchorage stage The tension of the prestressed tendons at the tensioned end must be in accordance with the provisions of 6.3.9 of the Code of Concrete Construction.
Inspection method: check the application of prestressing records.
4.1.6 The strength of the cement slurry shall conform to the requirements of the design or construction specifications.
Test method: a comprehensive observation and inspection of cement slurry test block test report.
4.2 Basic Items:
4.2.1 The percentage of deviation between the actual prestressed value and the design specified value shall not exceed ± 5%.
Check the number: according to the number of different types of prestressed concrete projects, 10% of the sample, but not less than three kinds.
Inspection method: check the application of prestressing records.
4.2.2 Prestressed tendons (steel wire, strand or steel) the number of broken or slippage is strictly prohibited more than the same section of the structure of the total number of pre-stressed 3%, and a bunch of steel wire is not more than one.
Check the number: full inspection.
Inspection method: comprehensive observation and inspection of the application of prestressing records.
5 protection of finished products
5.1 Components shall not be twisted and damaged during lifting.
5.2 stacking site should be flat, solid, pad to be consistent from top to bottom.
6 should pay attention to quality problems
6.1 Prestressed tension end of the set should meet the design requirements, when no specific requirements of the design should meet the following requirements:
6.1.1 Prestressing tension in the process of core-pulling: When the prestressing tendon is longer than 24m, it should be tensioned at both ends. For straight-line prestressing tendons with a length of not more than 24m, La Zhang.
6.1.2 Prestressing tension when pre-embedded bellows hole: For prestressing tendons and straight-line prestressing tendons with length greater than 30m, it is advisable to stretch at both ends. For straight-line prestressing tendons up to 30m in length, One end of tension.
When more than one end of the same section of the tensile strength of the tendons, the tensioning side should be set at the two ends of the structure.
When both ends of a prestressed tendons stretch at the same time, it is appropriate to first anchor at one end, and then make up the tension at the other end after the anchor.
6.2 Over-lying pouring of the components, should be on the next level after the first layer of tension. In order to reduce the upper and lower layers due to friction caused by the loss of prestressing can be increased layer by layer tension. But the bottom tension should not be greater than the top tension of 5% (steel wire, strand, heat treatment steel) or 9% (cold drawn Ⅱ, Ⅲ, Ⅳ grade steel), and the maximum tensile stress: cold drawing Ⅱ, Ⅲ, Ⅳ Grade steel shall not exceed 90% of the yield strength, steel wire, strand shall not exceed 75% of the yield strength, heat treatment shall not exceed 70% of the standard strength. The deviation of the actual prestress value after tensioning shall not exceed 5% of the specified value.
6.3 exposed after the length of the prestressed anchor, not less than 30mm. Anchors should be protected with end-capped concrete, and if exposed for long periods of time, measures should be taken to prevent corrosion.
6.4 prestressed tendons after tension, the channel should be as soon as possible grouting. Multi-span continuous prestressing tendons connected with connectors should be filled with a span and then filled with a span, and should not be continuously grouted after completion of tensioning.
6.5 channel grouting should be used not less than 425 number of ordinary Portland cement mortar configuration; for large pore channels can be mortar grouting. Mortar and mortar strength, should meet the design requirements, and should not be less than 20N / mm2.
6.6 cement mortar water to cement ratio of 0.4 ~ 0.45, 3h after mixing the bleeding rate should be controlled at 2%, the maximum shall not exceed 3%, cement slurry can be mixed with non-corrosive effect of prestressed tendons admixture. Generally can be doped with 0.05% to 0.1% aluminum powder or 0.25% calcium lignosulfonate water reducing agent.
6.7 When cold-drawn coarse steel bars are used as prestressing tendons, the end-bar screws must be welded and then cold-drawn to allow the individual butt-welded joints to undergo a cold-drawing test.
7 Quality records
This process standard shall have the following quality records:
7.1 Concrete component, block tensile strength test pressure test report sheet.
7.2 pre-stressed tendons of the factory quality certificate or test report card.
7.3 Cold-drawn records of prestressing tendons.
Test report on mechanical properties of cold - drawn prestressed.
Test Report on Welded Joints of Cold - drawn Prestressed.
7.6 Certificate of prestressing tendons and connectors and inspection records.
7.7 Prestressed tensioning equipment Verification records.
7.8 Prestressing tensioning records.
7.9 pre-stressed channel grouting test block strength test report form and cement factory certificate.
Strength test report of concrete block and block standard.
7.11 Other relevant information on design requirements.
This process standard applies to the general industrial and civil construction site prestressed concrete post-tensioned hydraulic tensioning construction (not including components and block making).
2 construction preparation
2.1 Materials and main equipment
2.1.1 Prestressing tendons: The heat treatment of pre-stressed steel, steel wire, strand varieties, specifications, diameter, must meet the design requirements and national standards, should be factory quality certificate repeated test report. Cold-drawn Ⅰ, Ⅱ, Ⅲ grade steel should also be cold-drawn mechanical properties of the test report.
2.1.2 Prestressing tendons in the form of anchors, fixtures and connectors should be consistent with the design and application of technical requirements, should be factory certification, into the construction site should be "concrete construction and acceptance of the Code" (GB50204- 92) of the provisions of acceptance and assembly of the static load test.
2.1.3 grouting cement shall not be less than 425, ordinary Portland cement or according to the design requirements, should be a factory certificate and re-test report card.
2.1.4 The main machine has: hydraulic stretching machine, electric high-pressure pump, grouting equipment, test mode.
2.2 Operating conditions
2.2.1 The prestressing tensioning machine has been verified and documented. Check the tensioning equipment and equipment is normal and reliable, if found to have abnormal conditions, should be repaired before use. Grouting equipment ready.
2.2.2 The strength of the concrete structure (or block) must meet the design requirements, such as the design is not required, should not be less than 75% of the design strength. The size, appearance quality, reserved hole and embedded parts of the component (or block) shall be inspected and checked and qualified. The assembled block shall be assembled and checked.
2.2.3 anchor fixture, the connector should be ready, and after inspection and acceptance.
2.2.4 Prestressed tendons or prestressed steel wire bundles have been completed.
2.2.5 grouting with the cement slurry (or mortar) mix and the end of the concrete mix ratio has been experimentally determined.
2.2.6 tensioning site should be smooth, smooth, tension at both ends of the security measures.
2.2.7 has been technical to the end, and should be the prestressing tendons tension tonnage and the corresponding gauge pointer readings, steel calculated elongation value written on the card, and hung in a clear position, in order to observe the operation of the master.
3 operating process
3.1 Process flow:
Check the component (or block)
↓
Prestressed tendons produced → wear prestressed tendons
↓
Anchorage inspection → installation and tensioning equipment Tensioning equipment pre-inspection
↓
La Zhang
↓
Grouting → making cement slurry test block
↓
Lifting ← pressure cement slurry test block
In this case,
3.2 Check the components (or block): In particular, carefully check the tendons of the tunnel. The holes shall be of the correct size and position, smooth and smooth, without local bending. The embedded steel plate at the end of the tunnel shall be perpendicular to the axis of the tunnel. The grouting hole and vent shall meet the design requirements. Do not meet the requirements of the channel, to clean up or make good treatment.
3.3 wear prestressed tendons.
3.3.1 before wearing tendons, should check the steel (or beam) specifications, the total length is to meet the requirements.
3.3.2 when wearing tendons, with the prestressed bar bolts Ruibian screw should be good to protect the thread, so as not to damage. Steel bars or wire bundles shall be numbered in a sequence of steel bars or steel wires and shall be fitted with a piercing beam. First, the steel or beam piercing the lead from one end into the tunnel, at the other end of the piercing, and then gradually to the steel or steel wire bundle to the other side.
3.3.3 After putting on the steel bar, mark the beam number on the component so as to check it.
3.4 installation of anchorage and tensioning equipment: the installation of anchorage and tensioning equipment, the straight line of prestressed tendons, tension lines should be so that the action line and the center line of the hole in the process of tension with each other overlap; the curve of prestressing tendons, should So that the tension line of action and the center point of the end of the tunnel tangent coincides with each other.
3.5 Stretch:
3.5.1 Prestressing tendon tensioning procedures, design requirements should be carried out, if the design is not specified, you can take one of the following procedures:
3.5.1.1 0 → 105% σcon hold for 2min → σcon.
3.5.1.2 0 → 103% σcon
Σcon is the prestressing stress of prestressing tendon.
3.5.2 Prestressing tendon tension in the order should meet the design requirements, when no specific requirements of the design, can be taken in batches, phased symmetrical tension.
When using batch tension, should be calculated in batches of prestressed loss of tension, were added to the first tensioned prestressed tendons tension control stress value, or use the same tension by the root of the value of the reset complement.
3.5.3 single prestressed coarse steel (tensile machine tension screw rod end) tension, it should be a little afterburner, the pad position according to the design requirements to identify, and then according to the provisions of the tensioning process tension. Tension is completed, with the board tighten the nut, the steel anchorage, measured the actual elongation of steel, and make tensioning records.
3.5.4 prestressed steel wire towers with double-acting jacking taper anchor anchor when anchoring, should be the following requirements:
3.5.4.1 Pre-Pull: After pulling out the wire for a short length, check whether the length of each wire is the same. If there is any inconsistency, the wedge should be retreated and then tightened to tighten the wedge.
3.5.4.2 tension and pressure: pre-tension adjustment after the tension in accordance with the provisions of tensioning process. Tension is completed, measured wire elongation value, bitter and in line with the provisions, can be the top pressure anchor. Top pressure anchor must be shut off when the tank oil, to the small tank into the oil, so that small cylinder piston top anchor.
3.5.4.3 Checking: Jack is loaded into the unstretched end of the tension, tension to control stress, the top anchor. When both ends of the top tension is completed, should be measured steel wire slide into the anchor in the shrinkage of the amount of compliance requirements, if greater than the specified value, must be re-tensioning, back up losses.
3.5.4.4 The number of wire breaks and slippage shall not exceed 3% of the total number of wires of the same cross-section, and only one strand of steel wire shall be allowed. Such as more than the above requirements must be re-tensioned, then the wire should be pulled to the original tension tonnage, Laxong anchor, with a steel drill slot into the pad plate, jammed anchor, and then return to the cylinder, The anchor is pulled out and the entire anchor is removed. Respectively, to check whether the anchor ring was pumped into the groove, whether the fine tooth was flattened anchor, if such cases, to exchange anchor, re-tensioning, if the anchor ring, anchor is still intact, then as long as the top Pressure to increase the pressure when the top anchor.
3.6 Fill pre-stressed records.
3.7 Grouting:
3.7.1 grouting pore pressure water should be cleaned, and check the grouting holes, vent holes and prestressed tendons connected channels, otherwise, should be dealt with in advance.
3.7.2 prestressed tendons should be completed as soon as possible after the completion of tunnel grouting to reduce the pre-should be lost.
3.7.3 grouting pressure is generally 0.4 ~ 0.6MPa.
3.7.4 grouting sequence should be on the next after the upper hole to prevent leakage of slurry to block the lower hole to the exhaust vents emerge after the thick slurry, which blocked the exhaust hole, and then grouting to 0.6MPa, to maintain l ~ 2min , You can plug the grouting hole.
3.7.5 Make test block and pay attention to maintenance.
3.8 pouring end of concrete or end protective treatment, and pay attention to concrete curing;
4 quality standards
4.1 Warranty items:
4.1.1 The variety and quality of the prestressed tendons must meet the design requirements and the relevant standards.
Inspection methods: Check the factory quality certificate and test report card.
4.1.2 The mechanical properties of the cold-drawn reinforcement shall comply with the design requirements and construction specifications.
Inspection method: check the factory quality certificate, test report and cold-drawn record.
4.1.3 Prestressed tendons used in the anchorage, fixture and connector quality must meet the design requirements and construction specifications and special requirements.
Check the number: According to "Code for Construction and Acceptance of Concrete Structures" the sixth chapter 6.2.12 of the provisions of the sample.
Inspection method: Check the factory certificate, hardness, static load anchorage performance and appearance size inspection report of anchor, clamp and connector.
4.1.4 strength of concrete and block vertical seam concrete (mortar) strength, must meet the design requirements and construction specifications and requirements.
Test method: Check with the conditions of conservation of concrete (mortar) test block test report.
4.1.5 The anchorage stage The tension of the prestressed tendons at the tensioned end must be in accordance with the provisions of 6.3.9 of the Code of Concrete Construction.
Inspection method: check the application of prestressing records.
4.1.6 The strength of the cement slurry shall conform to the requirements of the design or construction specifications.
Test method: a comprehensive observation and inspection of cement slurry test block test report.
4.2 Basic Items:
4.2.1 The percentage of deviation between the actual prestressed value and the design specified value shall not exceed ± 5%.
Check the number: according to the number of different types of prestressed concrete projects, 10% of the sample, but not less than three kinds.
Inspection method: check the application of prestressing records.
4.2.2 Prestressed tendons (steel wire, strand or steel) the number of broken or slippage is strictly prohibited more than the same section of the structure of the total number of pre-stressed 3%, and a bunch of steel wire is not more than one.
Check the number: full inspection.
Inspection method: comprehensive observation and inspection of the application of prestressing records.
5 protection of finished products
5.1 Components shall not be twisted and damaged during lifting.
5.2 stacking site should be flat, solid, pad to be consistent from top to bottom.
6 should pay attention to quality problems
6.1 Prestressed tension end of the set should meet the design requirements, when no specific requirements of the design should meet the following requirements:
6.1.1 Prestressing tension in the process of core-pulling: When the prestressing tendon is longer than 24m, it should be tensioned at both ends. For straight-line prestressing tendons with a length of not more than 24m, La Zhang.
6.1.2 Prestressing tension when pre-embedded bellows hole: For prestressing tendons and straight-line prestressing tendons with length greater than 30m, it is advisable to stretch at both ends. For straight-line prestressing tendons up to 30m in length, One end of tension.
When more than one end of the same section of the tensile strength of the tendons, the tensioning side should be set at the two ends of the structure.
When both ends of a prestressed tendons stretch at the same time, it is appropriate to first anchor at one end, and then make up the tension at the other end after the anchor.
6.2 Over-lying pouring of the components, should be on the next level after the first layer of tension. In order to reduce the upper and lower layers due to friction caused by the loss of prestressing can be increased layer by layer tension. But the bottom tension should not be greater than the top tension of 5% (steel wire, strand, heat treatment steel) or 9% (cold drawn Ⅱ, Ⅲ, Ⅳ grade steel), and the maximum tensile stress: cold drawing Ⅱ, Ⅲ, Ⅳ Grade steel shall not exceed 90% of the yield strength, steel wire, strand shall not exceed 75% of the yield strength, heat treatment shall not exceed 70% of the standard strength. The deviation of the actual prestress value after tensioning shall not exceed 5% of the specified value.
6.3 exposed after the length of the prestressed anchor, not less than 30mm. Anchors should be protected with end-capped concrete, and if exposed for long periods of time, measures should be taken to prevent corrosion.
6.4 prestressed tendons after tension, the channel should be as soon as possible grouting. Multi-span continuous prestressing tendons connected with connectors should be filled with a span and then filled with a span, and should not be continuously grouted after completion of tensioning.
6.5 channel grouting should be used not less than 425 number of ordinary Portland cement mortar configuration; for large pore channels can be mortar grouting. Mortar and mortar strength, should meet the design requirements, and should not be less than 20N / mm2.
6.6 cement mortar water to cement ratio of 0.4 ~ 0.45, 3h after mixing the bleeding rate should be controlled at 2%, the maximum shall not exceed 3%, cement slurry can be mixed with non-corrosive effect of prestressed tendons admixture. Generally can be doped with 0.05% to 0.1% aluminum powder or 0.25% calcium lignosulfonate water reducing agent.
6.7 When cold-drawn coarse steel bars are used as prestressing tendons, the end-bar screws must be welded and then cold-drawn to allow the individual butt-welded joints to undergo a cold-drawing test.
7 Quality records
This process standard shall have the following quality records:
7.1 Concrete component, block tensile strength test pressure test report sheet.
7.2 pre-stressed tendons of the factory quality certificate or test report card.
7.3 Cold-drawn records of prestressing tendons.
Test report on mechanical properties of cold - drawn prestressed.
Test Report on Welded Joints of Cold - drawn Prestressed.
7.6 Certificate of prestressing tendons and connectors and inspection records.
7.7 Prestressed tensioning equipment Verification records.
7.8 Prestressing tensioning records.
7.9 pre-stressed channel grouting test block strength test report form and cement factory certificate.
Strength test report of concrete block and block standard.
7.11 Other relevant information on design requirements.
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