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Prestressed tensioning of prestressed concrete steel strands can improve the bearing capacity of bridges or components. This article will specifically introduce the tensioning process of prestressed concrete steel strands.
Prestressed tensioning of prestressed concrete steel strands must be carried out in strict accordance with the steel strand tensioning procedure in the design drawing to ensure that the elongation value error during the tensioning process is within 6%. The following is the specific tensioning process of prestressed concrete steel strands.
1. Check the concrete strength of the tension beam section, and when it reaches more than 90% of the design strength, it can be tensioned.
2. Press air into the hole to remove debris in the hole.
3. Remove the concrete on the anchor pad and correct the orifice.
4. Steel strands for prestressed concrete are bundled in pairs.
5. Double control is adopted during tensioning, that is, stress control is the main method. The elongation is used as verification. The actual elongation value is compared with the theoretical elongation value, and the error should be within 6%, such as the actual elongation value and the theoretical elongation. If the value error exceeds 6%, the tension should be stopped, the cause should be found out, and then the tension should be carried out.
6. During the tensioning operation, the readings of the oil pressure gauges at all levels of tensioning tonnage should be found according to the jack calibration curve, and the card should be filled in to make an obvious mark on the spot for use during tensioning.
7. Move the jack and the oil pump to the tension end of the beam body, and scrub the jack chuck clean, and spare the vulnerable parts of the tensioning machine before the tensioning construction. In order to reduce the friction loss, both ends are simultaneously symmetrically tensioned.
8. Before the tensioning construction, start the oil pump to drain the air in the jack and the tubing and check whether the tensioning equipment is leaking at the same time. When both ends are stretched at the same time, pair the radios to communicate with each other to report the pressure gauge reading and elongation to ensure that the oil pressure rises at the same speed, and pay close attention to the wire breakage and make a record.
9. During the tensioning process, the relevant tensioning record form should be filled out carefully for inspection.
10. The tensioning equipment, tools, and instruments are used and managed by special personnel to prevent the oil gauge of the jack from being lost or damaged. The calibration period of the tensioning equipment is half a year. If an abnormal situation occurs during construction, the equipment needs to be re-calibrated.
11. During tension, the oil pressure is increased in sequence according to the six-level loading process, and the classification methods are 15%, 30%, 50%, 80%, 100%, 102% (103%), and the elongation value must be measured for each level of loading. , And check the deviation between the elongation value and the calculated value at any time. The actual tensile elongation value is equal to 0~initial stress elongation value + initial stress~control stress elongation value. 0~initial stress elongation value is not suitable for direct measurement. It is calculated by theory, that is, the initial stress elongation value is ~2 times The initial stress of the prestressed concrete steel strand is regarded as the 0~initial stress elongation value. A steel ruler is used to measure the elongation value, and a steel tape measure is prohibited. The initial stress value of the steel strand for prestressed concrete tension is 15% of the design control stress. After being loaded step by step, it reaches 102% (103%) of the design stress, and then the load is held for 2 minutes. If the value of the hydraulic gauge drops during construction, the pressure The meter reading makes up 100% of the tensile force and then anchors it.
12. After the tensioning is completed, the anchor shall be sealed with dry cement paste mixed with epoxy resin or water glass, so as to press the grout as soon as possible. The pre-stressed concrete strand at the anchor mouth is cut with a grinding wheel saw, and electric welding is strictly prohibited to prevent stress loss under the anchor after the pre-stressed concrete strand is heated. The pre-stressed concrete steel strand at the anchor mouth is left 6~10cm out of the anchor.
If we want to stretch the prestressed concrete strand, the above steps must be strictly followed to prevent the loss of the performance of the prestressed concrete steel strand. If after reading the above, you still don't know much about the tension of prestressed concrete steel strands, you can contact us for more detailed solutions.
As a professional manufacturer of prestressed concrete products, we have always been committed to providing customers with safe and high-quality products. We have accumulated rich manufacturing experience and established a complete quality management system, which can strictly control the quality of products. We can also provide customers with thoughtful service and effective solutions. If you want to buy our prestressed concrete steel strands, please contact us immediately!