Introduction
Prestressed concrete is a widely used construction technique that enhances the strength and durability of structures by applying compressive stresses before external loads are introduced. A critical component in this process is the multi-strand jack and multi-strand anchorage system, which ensures efficient force transfer.
In this guide, we’ll walk you through the step-by-step process of applying prestressed multi-strand jacks for tensioning multi-strand anchorages, while incorporating high-ranking SEO keywords to help professionals find this resource easily.
Step-by-Step Guide to Applying Multi-strand Jacks for Anchorage Tensioning
1. Preparation & Safety Checks
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Inspect the multi-strand jack and anchorage system for damage.
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Ensure all strands (PT tendons) are properly aligned in the duct.
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Verify that the anchor wedges are clean and free from debris.
2. Installing the Multi-strand Jack
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Position the multi-strand hydraulic jack over the strands.
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Secure the jack to the bearing plate and ensure proper seating.
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Connect the hydraulic pump and perform a pressure test to check for leaks.
3. Applying Prestressing Force
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Gradually increase hydraulic pressure to tension the strands.
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Monitor the elongation and pressure gauge readings to ensure accuracy.
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Refer to PTI guidelines for acceptable tolerances in force application.
4. Locking the Strands in the Anchorage
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Once the desired force is achieved, release hydraulic pressure slowly.
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The anchor wedges will grip the strands, maintaining the prestressing force.
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Trim excess strands and apply corrosion protection if required.
5. Post-Tensioning Verification
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Measure final elongation and compare it with theoretical calculations.
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Use load cells or strain gauges for force verification if necessary.
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Document all readings for quality assurance.
Why Proper Tensioning Matters
Improper tensioning can lead to:
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Loss of prestress force (leading to structural weakness)
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Strand slippage (causing anchorage failure)
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Uneven load distribution (increasing cracking risk)
For best practices, consult ACI 423.7-14 on post-tensioning systems.
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