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prestressing equipment

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Jacks are essential tools in prestressing operations and are used to apply tension to strands within tendons. There are two main types of jacks:

A. Mono-Strand Jack

A mono-strand jack is primarily used in building construction, where tendons typically consist of a small number of strands (usually 3 to 4). This type of jack is designed to stress each strand individually, ensuring precise control over the tensioning process. Since buildings generally have shorter tendons compared to bridges, stressing strands one by one is a practical and efficient approach in this context.




B. Multi strands jack: In bridge construction, where tendons contain a significantly larger number of strands, using a mono-strand jack would be impractical. Stressing strands one by one in such cases would not only be time-consuming but also increase the risk of strand entrapment. Therefore, multi-strand jacks are used to simultaneously stress all the strands within a tendon in a single operation, improving efficiency and ensuring uniform prestressing.
         Jack calibration: Jacks must undergo periodic calibration to ensure accurate force application during the stressing process. This is critical because the pressure reading displayed on the jack's built-in gauge often differs from the actual applied force. Calibration helps determine a correction factor, which is then used to adjust the readings and ensure the correct prestressing force is applied. Regular calibration enhances the precision and safety of the prestressing operation.




C. Master gauge: A master gauge is an external pressure gauge attached to jacks to provide an accurate and reliable reading of the jack's pressure. Since the built-in gauges on jacks may not always be precise, the master gauge serves as a reference for calibration and verification. Like jacks, master gauges must also be periodically calibrated to maintain accuracy and ensure that the correct prestressing force is applied during the operation.













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