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Among some of the issues in the construction of prestressed should be noted

2014-10-14 09:04:47

In the use of prestressed, it should pay attention to the following conditions in order to ensure the safety of both sides.

(A) cutting tendons, should adopt the wheel saws, arc cutting shall not be used;

(2) strand compiled bundle, should straighten out by the root, tied into bundles, not disorder. Fixed end of the extruded strand anchorage or embossed type anchor, should advance with the pressure plate and spiral ribs are assembled;

(3) prestressing equipment and instrumentation equipment used should have regular maintenance and calibration;

(4) pre-tensioning the tendons, should provide concrete strength pressure test reports. When the compressive strength of concrete to meet the design requirements, the design strength of not less than 75 percent grade, before prestressing;

(5) pre-tensioning the tendons, bearing plate surface should be cleaned and checked the quality of concrete bearing plate behind. Such as where there are empty concrete phenomenon, should be repaired with epoxy mortar in tension before;

(6) When the installation of prestressed anchor plate to deal with positive clips should not matter, and the chip position should be uniform: it may not matter too heavy beat films clip to clip rabbit knock the bad;

(7) large tonnage official tensioning tendons before, should be tested in conjunction with professional tension. Confirm tensioning process is reasonable, Tensile Value is normal, there is no harmful after cracks appeared before the bulk tension. When necessary, the actual determination of pore friction losses. Tendons shall not be used for curve single small jack tensioning; avoid unnecessary loss of prestress. In tension, the operator must stand safety zone, good protective measures, attention to the operator and non-standing tension when tension tendons good front;

(8) tendons in tension, you should start with a zero load to measure the tensile elongation values ​​starting point of beginning, and then loaded to the desired grade tensile force;

(9) tensioning tendons management, to take stress control, elongation checked. Tolerance and calculated actual elongation elongation values ​​of -5% to +10%. If more than this value, should be suspended tension; after take measures to adjust before continuing tension; elongation values ​​as small, ultra-tensioned measures can be taken, but not greater than 0.8fptk Tension limit value; multi-wave curve tendons in order to improve the tensile stress at the support, reducing post-tensioned prestressed tensile stress under the mouth, can be taken over Zhang back loose technologies;

(10) pore filling requirements dense grout intensity level should be less than C30. Before filling pores should be moist, clean, grout should be carried out slowly and evenly, without interruption, and should exhaust fluent. In case of clogged pores, filling the mouth must be replaced, but you must first poured into the slurry discharge, in order to avoid the presence of gas poured into the grout between the two. In the filled pores and closed vent, the pressure should continue to 0.5-0.6Mpa, later closed filling holes. Vertical channels of grouting pressure shall be determined in accordance with the height of grouting; additional anchorage, please visit Global anchor net.

(11) multi-span continuous prestressed tendons of pore filling with connectors should be tensioned END across a cross-reperfusion, not all the time in the cross-grouting post-tensioning is completed;

(12) After anchoring tendons exposed length, not less than 30mm, prestressed concrete application of capping protection. When exposed to be a long-term measures should be taken to prevent corrosion; when there is rust Strand, set anchor holder section and the outer end of the strand rust and dirt cleaned rabbit in the installation and tensioning when rust, dirt fill clip red tank and cause slippery silk;

(13) tools for three-in clip, clip work for two, the two can not be mixed. Can not work as a tool to anchor the anchor can not be reused;

(14) prestressed to keep, without the use of rust, water and other debris contamination. Work to remove the box clip foam can be used, but the longer prestressed beams shall be repeated when tensioning the anchor, apply a small amount of lubricant is recommended (eg, anchor spiritual retreat) in the anchor plate tapered bore, both conducive to work clip anchor follow-up and return times and it helps anchor the anchor; tool clip before the outer surface of the cone hole and anchor plates coated surface using a lubricant, and often remove surface debris clips, can retire anchor flexible, but the tooth surface cracking or clip should be replaced when damaged, can not re-use;

(15) Tension should have security measures can not stand the tension jack man;

(16) supporting the use of anchoring system should not be mixed with other systems. As do static load test, use of organic solvents (such as gasoline) to clean clip and anchor plate bore rust oil wipe clean, otherwise it will affect the anchorage performance;

(17) prestressed construction by professional construction team to carry out, and construction personnel should undergo professional training certificates.

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