Prestressed tendons, pipes, anchor clamps and connectors for prestressed concrete

The focus of the acceptance is on the batch and inspection, checking, testing items and qualification standards

1. Types of prestressed tendons

【Formula】The silk thread is the same as the batch

The quality of the prestressed tendons used in the prestressed concrete structure shall comply with the provisions of the current national standards "steel wire for prestressed concrete" GB/T5223-2014, "steel strand for prestressed concrete" GB/T5224-2014, "unbonded prestressed steel strand" JG/T161-2016 and other specifications. Each batch of steel wire, steel strand and steel bar should be composed of products of the same grade, the same specification and the same production process.

2. Prestressed tendon approach inspection

【Formula】 The standard specification of the document package is repeated one by one

When the prestressed tendon enters the site, its quality certification documents, packaging, marks and specifications should be inspected, and the following provisions shall be met:

1) The weight of each batch of steel wire inspection shall not be greater than 60t, and the shape, size and surface quality of each batch of steel wire shall be inspected one by one. 3 reels were randomly inspected from the steel wires that passed the inspection, and samples were taken at either end of each steel wire for mechanical property tests and other tests. If there is a failure in the test result, the steel wire of the disc will be scrapped, and the sample of double the number of samples from the steel wire reel that has not been tested in the same batch shall be re-inspected, if there is still a disqualified, it shall be inspected one by one, and the qualified person shall receive.

2) The weight of each batch of steel strand inspection shall not be greater than 60t, the surface quality and external dimensions of each batch shall be inspected, and then any 3 reels shall be taken from each batch of steel strand, and a sample shall be intercepted from any end of the selected steel strand in each reel for mechanical property test and other tests. If there are less than 3 trays per batch, all should be inspected. If one of the test results is unqualified, the unqualified disc will be scrapped, and double the number of samples will be taken from the batch of untested steel strands for re-inspection of the unqualified item. If there is still one unqualified, the batch of steel strands should be inspected one by one, and the qualified person will receive it.

3) The weight of each batch of finished rolled threaded steel bars shall not be greater than 60t, and the surface quality shall be inspected one by one, and any 2 steel bars in each batch shall be selected for tensile test after the appearance inspection is qualified. If one of the test results fails, double the number of samples will be taken and the test will be repeated. If there is still one unqualified, the batch of reinforcement is unqualified.

3. Precautions for transportation, storage and construction operation of prestressed tendons

【Formula】Clean and avoid the winch warehouse and put 2

(4) The tendons must be kept clean. Mechanical damage and harmful rust should be avoided during storage, handling, and construction operations. If it is stored for a long time, regular visual inspections must be arranged.

The prestressed steel strand should be transported in a tray, and the diameter of the reel should not be less than 1.0m, and the steel strand stacked on the bottom steel strand should not exceed 4000kg when stored.

(5) The storage warehouse should be dry, moisture-proof, well-ventilated, and free of corrosive gases and media. When stored outdoors, it should not be stacked directly on the ground, and must be heightened, covered, corrosion-proof, rain-proof, and the time should not exceed 6 months.

4. The cutting length of the prestressed tendon is determined

【Formula】The top of the anchor of the hole seat is exposed and long, and the cold drawing elastic tension is reserved.

The cutting length of the prestressed tendon should be determined by calculation, and the length of the hole or pedestal of the structure, the length of the anchor (clamp), the length of the jack, the reserved amount of the pier head, the length of the cold tensile tendon, the elastic retraction value, the tensile length value and the exposed length and other factors should be considered in the calculation.

5. Production of prestressed tendons

【Formula】There are many cutting headsets

2) Prestressed tendons should be cut by grinding wheel saw or cutting machine, and arc cutting should not be used.

3) When the prestressed tendon is anchored by upsetting, the high-strength steel wire should be hydraulicly cold headed, the cold-drawn low-carbon steel wire can be cold-stamped and roughed, and the steel bar should be electrothermally upset, but the HRB500 grade steel bar should be electrothermally treated after upsetting. The upsetting and heat treatment of the end of the cold-drawn steel bar should be carried out before the cold drawing of the steel bar, otherwise the tension inspection should be carried out on the upsetting head one by one, and the control stress during the inspection should not be less than the control stress when the steel bar is cold drawn.

4) When the prestressed tendon is composed of multiple steel wires or steel strands, prestressed steel with equal strength should be used in the same bundle of prestressed steel bars. When braiding, it should be combed straight and not twisted one by one, tied firmly, every 1m, and should not be intertwined. The braided wires and strands should be stored according to the number. The distance between the fulcrum of the steel wire and the steel strand bundle shall not be greater than 3m, and the overhanging length of the end shall not be greater than 1.5m.

6. Pipes for prestressed rib holes

【Formula】Golden snail plastic wave bends the inner light, strong rigidity and force transmission without slurry leakage.

(1) In the post-tensioned bonded prestressed concrete structure, the pores of the prestressed tendons are generally composed of rigid or semi-rigid pipes poured in the concrete. For general projects, the steel pipe core pull, hose core pull or metal telescopic sleeve core pull can be used to reserve the hole. The pipe poured in concrete should have sufficient strength and rigidity, no slurry leakage, and be able to transmit the cohesion force as required.

(2) Commonly used pipes are metal spiral pipes or plastic (chemical building materials) corrugated pipes. The pipe should have a smooth inner wall and can be bent into the proper shape without curling or being flattened. The performance of the metal spiral pipe should comply with the provisions of the current national standard "Metal Corrugated Pipe for Prestressed Concrete" JG/T225-2020, and the physical energy of the plastic pipe should meet the provisions of the current industry standard "Plastic Bellows for Prestressed Concrete Bridge" JT/T529-2016.

7. Other requirements for pipe (hole) channel

【Formula】The ratio of steel polywall thickness to area

1) In some special parts of the bridge, when the design is not required, smooth steel pipe or high-density polyethylene pipe that meets the requirements can be used, and the pipe wall thickness shall not be less than 2mm.

2) The internal cross-sectional area of the pipeline should be at least 2.0 times the net cross-sectional area of the prestressed tendons. When this area is insufficient, it should be verified by test whether it can be carried out normal grouting operation. Pipes with extra-long steel bundles should also be tested to determine their area ratio.

8. Pipeline entry acceptance

【Formula】Check and check the batch

1) When the pipeline enters the site, the factory certificate and quality assurance certificate should be checked, and the category, model, specification and quantity should be checked, and the appearance quality inspection of the pipeline, radial stiffness and anti-leakage performance should be carried out. The inspection method should be carried out in accordance with the relevant norms and standards.

2) The pipeline is inspected in batches. Each batch of metal spiral pipe is composed of products made by the same manufacturer and the same batch of steel strips, with a cumulative production volume of half a year or 50,000m for a batch. Each batch of plastic pipes is composed of products with the same formula, the same process and the same equipment for stable and continuous production, and the quantity of each batch should not exceed 10,000m.

(3) When the metal pipe is stored outdoors, the time should not exceed 6 months.

9. Post-tensioned prestressed anchors and connectors are classified according to the anchoring method

【口诀】握铸夹子

Anchors and connectors can be divided into clip type (single-hole and multi-hole clamp anchorage), support type (upsetting anchorage, nut anchorage), grip type (extrusion anchorage, embossed anchorage) and combined type (hot-cast anchorage, cold-cast anchorage) according to different anchoring methods.

10. Basic requirements for anchors, clamps and connectors

【Formula】Stain and rust are cracked and cracked by a single root, and the anchoring force is suitable for low grading

(1) The surface of anchors, clamps, connectors and anchor pads for prestressed tendons should be free of dirt, rust, mechanical damage and cracks.

(3) Prestressed anchors, clamps and connectors shall have reliable anchoring performance, sufficient bearing capacity and good applicability, and shall comply with the provisions of the current national standard "Anchors, Fixtures and Connectors for Prestressed Tendons" GB/T14370-2015 and "Technical Regulations for the Application of Anchors, Fixtures and Connectors for Prestressed Tendons" JGJ85-2010.

(4) Anchors (or connectors) suitable for high-strength prestressed tendons can also be used for low-strength prestressed tendons, and anchors (or connectors) that can only be applied to low-strength prestressed tendons, shall not be used for high-strength prestressed tendons.

(5) The anchor should meet the requirements of graded tensioning, supplementary tensioning and relaxing prestress. The anchor anchor anchoring multiple prestressed tendons should have the possibility of single tensioning in addition to the performance of the whole bundle of tensioning.

(6) The connector used for the post-tensioning method must meet the performance requirements of the anchor.

11. Anchor backing plate requirements

【Formula】Steel cast horn tendon vertical irrigation

(7) When the anchor backing plate under the anchor requires the use of horn pipe, the horn pipe should be made of steel or cast iron. The anchor backing plate should be provided with sufficient spiral reinforcement or mesh distribution reinforcement.

(8) The anchor backing plate and the prestressed tendon (or hole) should be perpendicular to each other in the anchoring area and its vicinity. Grouting holes should be set on the anchor backing plate of post-tensioning members.

12. Anchors, fixtures and connectors are required to enter the site for acceptance

【Formula】Batch checking, multiple, qualified

(1) When the anchors, fixtures and connectors enter the site for acceptance, the anchoring performance, category, model, specification and quantity shall be checked according to the factory certificate and quality certificate, and the appearance inspection, hardness inspection and static load anchorage performance test shall be carried out after confirmation.

(2) The acceptance should be carried out in batches, and when the batches are divided, the products produced under the same material and the same production process conditions can be listed as the same batch. Anchors and clips should be accepted with no more than 1,000 sets. Each acceptance batch of connectors should not exceed 500 sets.

1) Visual inspection:

10% and no less than 10 sets of anchors (clips or connectors) are selected from each batch for appearance quality and dimensional inspection. There shall be no cracks on the surface of all samples, and the dimensional deviation shall not exceed the allowable deviation of the size specified in the product standard and design drawings. When there is a set of unqualified, take double the number of wrong tools to redo the inspection, if there is still a set of non-conformity, then check one set by one, and only those who pass can be used.

2) Hardness test:

5% and no less than 5 sets of anchors (clips or connectors) are selected from each batch for hardness testing. Do hardness test for parts with hardness requirements, and extract at least 5 pieces from each set of clamp pieces for porous clamp anchors, and test 3 points for each part, and its hardness should be within the range of product design requirements. When a part is unqualified, it should be redone with double the number of parts, and when there is still a piece of unqualified, the batch of products should be checked one by one, and the qualified ones can be used.

(3) Static load anchorage performance test: For important projects such as bridges and extra-large bridges, anchors with incomplete quality certification data, incorrect or doubtful quality, 6 sets of anchors (clips or connectors) are extracted in the same batch that have passed the appearance and hardness inspection to form 3 prestressed tendon anchor assemblies, and the static load anchorage performance test is carried out by a professional testing institution with corresponding qualifications. If there is a test piece that does not meet the requirements, the test should be redone with double the number of anchors (fixtures or connectors), if there is still a test piece that does not meet the requirements, the batch of products will be regarded as unqualified products.

For the acceptance of anchors (clips or connectors) used for small and medium-sized bridges, the static load anchorage performance can be provided by the anchor manufacturer test report.

Yesterday 速记口诀

1. The compressive strength of concrete

15 statistical standard deviations, ten groups of unknown methods

2. High-strength concrete admixture

Cinder silica boiling powder

3. Concrete construction

Metering, stirring, transportation and watering

4. Raw material measurement

The measuring instrument is checked regularly, and the bone water is added at one time.

5. Concrete mixing

The uniform color does not leave the secretion, and the collapse 2 sticky protection when mixing

6. Concrete transportation

It can tolerate and protect the prohibition of collapse and mixing/condensation leakage and absorption, and the prohibition of collapse and mixing.

7. Inspection before pouring concrete

Molded base embedded rib joint

8. Concrete pouring

The amount of pump is continuous in the same section, and the dispersion of vibration is delayed

9. Concrete curing

Vacuum thin plastic film, covered with sprinkling culture. 5. Keep warm and strong

Three days ago, shorthand mantra 4/8

1. Design and verification of templates, brackets and arches

The knot is rigid and stable, the pre-arching force of the load, the rod base is set with a symbol, and the rigidity is checked and the anti-tilt is checked

2. Construction design basis

Knot across the load place to prepare

3. Construction design content

The general situation is based on the book materials, and the safety system is required to be dismantled

4. Load combination when designing templates, brackets and arches

12 self-weight, 5 side pressure, 3 walks, 4 vibrations, 6 tilting, wind and snow heat preservation 7 water, rigid and strong static movement.

5. The deformation value of the formwork, bracket and arch

Lu Lu 4 Bai Yin 25, 500 hoops 1.5.

6. The construction precamber of the formwork, bracket and arch should be considered

Bullet non-bullet pre-sinking

7. Production and installation of brackets and arches

The pressure base is forbidden to bubble and frozen, the column is in the middle of the hole, the support is not altogether, and the pressure frame is inspected in multiple layers.

8. Template production and installation

Cooperate with the pier platform tilt and check the special argument

9. Regulations on the installation of inflatable capsule core molds

When checking for leaks and stabilizing voltage

10. Provisions for the removal of formwork, brackets and arches

非不损，承加重，芯内不塌缝。

11. Regulations on the unloading of the arch of the mortar masonry and concrete block arch bridge

Pulp 80, small finish, solid arch protection, large empty arch horizontal

12. The principle of circular dismantling of formwork, bracket and arch

Split longitudinal and horizontal

Seven days ago, shorthand mantra 4/4

1. The production temperature of modified asphalt mixture

The thickness of the sticky gas is high

2. Modified asphalt mixture mixing equipment and time limit

Intermittent dust is added, and storage and leakage are checked

3. Modified asphalt mixture paver and paving parameters

The track is paved with temperature speed and flat

4. Requirements for compaction molding of modified asphalt mixture

The principle of pressure temperature vibrating steel machine cannot be prevented

Two weeks agoShorthand mantra 3/28

1. Common retaining wall construction methods in urban road and bridge engineering

Cast-in-place masonry reinforcement

2. Divide according to the structural form and structural characteristics of the retaining wall

Heavy arm (wall) column bar bars

3. Structural characteristics of gravity retaining wall

Self-stabilizing pouring masonry construction province

4. Balanced retaining wall composition

Upper and lower platforms

5. Structural characteristics of balanced retaining wall

The filling is steep and steep, reducing the height of the wall and digging the foundation

6. Structural characteristics of reinforced concrete cantilever retaining wall

The fill is not high

7. Reinforced concrete buttress retaining wall composition

Bottom support

8. Structural characteristics of reinforced concrete buttress retaining wall

The filling and ribbing force is good

9. It is composed of a column-plate retaining wall with a loading plate

Base pillar block pulling

10. Structural characteristics of column-plate retaining wall with unloading plate

Fill the soil less digging and pre-assemble

11. Structural characteristics of anchor retaining wall

Bolt ribs are pre-assembled

12. a column plate pull block

It is composed of a self-supporting (tail rod type) retaining wall

13. Provincial soft pre-spelling soil block

Structural characteristics of tail rod retaining wall

14. Structural characteristics of reinforced soil retaining wall

The geotechnical neatness is soft and the price is beautiful

15. Retaining wall construction requirements

The foundation is changed to view the water filtration seam

16. The appearance and size of the retaining wall structure bearing earth pressure

The main fovea is raised and is quietly centered