Stretching operation procedure

 Problems    |      2018-10-19
1. Tensioning sequence of steel strand bundles:
When the concrete strength reaches 85% of the designed value, the tensile strength begins to stretch. According to the principle that the tensile strength is close to the neutral axis steel strand first, the prestressed reinforcement must be braided before binding to prevent it from crossing and twisting.
Tensioning sequence of a single strand:
0 -- 10 percent amorphous con -- 100 percent amorphous con (2 min load anchorage)
2. Open the b-way globe valve (return valve) according to the oil pump instructions, and then start the oil pump motor when the a-way globe valve is closed. Provide oil to the tensioning cylinder for pre-tensioning.
3. When the oil meter reaches the reading required for initial stress (10% accepcon), the oil is postponed to feed, and the elongation value is taken as the elongation value for the initial stress of the steel strand.
4. Continue to advance slowly. When the tensile force reaches the control stress, the oil supply to road A can be stopped and maintained for two minutes.
5. Oil valve is rotated, and at the same time, the pressure of stop valve (oil return valve) is gently returned. At this point, the tension cycle is completed. Remove the jack and mark the length of the strand after the anchor so as to observe the phenomenon of sliding anchor.