How to deal with the fracture or slip of prestressed tendons during tensioning?

In the process of tensioning, if the prestressed tendon breaks or slips, the treatment method is as follows:

Specific methods:

In the process of tensioning, the wire breakage and slippage of prestressed tendons should be avoided, and it is not necessary to deal with them within the scope permitted by the specification. If the quantity exceeds the control quantity listed in the specification, it should be replaced in principle. If it can't be replaced, remedial measures can be taken under allowable conditions, such as increasing the prestress value of other tendons, but it must meet the requirements of limit States in each stage of design.

Brief introduction of tension:

Prestressed tensioning is to apply tension in the member in advance, so that the prestressed tensioning member bears compressive stress, and then produces certain deformation to cope with the load on the structure itself, including self-weight, wind load, snow load, earthquake load and so on. Generally, steel strand, jack, anchor plate and clip are used for tensioning.

Main impacts:

When one end is tensioned, if the tensioned end is called end A and the fixed end is called end B, then when the tensioned end is pulled from initial stress 0 to tensile force 100%, the elongation will gradually affect the end B with the increase of stress, and the total elongation is 100.

When the two-end tensioning process is adopted, due to the change of tensioning form, the form of end B is changed from fixed end to tensioning end, and the midpoint between end A and end B is called C. Then, tensioning ends A and B are respectively tensioned from initial stress 0 to 100% stress, and the extended influence range is affected from end A to end C and end B respectively.

Pre-stressed tensioning preparation:

1, preparation before prestressed construction

Tension grouting equipment in place: two sets of YT-V CNC intelligent tensioning equipment produced by Hebei Yitie Electromechanical Technology Co., Ltd. are used for prestress tensioning equipment, and the supporting jack is 150t2. The equipment matching calibration work has been completed, and the anchorage of tensioning equipment matching tools is the same anchorage and the matching products of the same manufacturer.

2, prestressed tensioning and grouting design and specification requirements

By mainly controlling the tensile stress and checking it with the actual elongation value, the tension of each grade can be accurately controlled, and the corresponding elongation can be measured and recorded. The difference between the actual elongation value and the theoretical value should be controlled within 6%, otherwise, the tensioning should be suspended until the reason is found out and adjusted.

3, steel strand processing and installation

After the concrete strength of this project reaches 100% of the design strength, the steel strand bundle will penetrate into the tunnel (to prevent the steel strand from rusting due to premature penetration). Before penetration, the steel strand bundles will be numbered and braided to prevent the steel strands from intertwining in the tunnel. Before threading, the steel strand will be treated as a side, and the end will be wrapped with plastic tape to prevent the corrugated pipe from being damaged and blocked.