HiSCS site team has initiated the stressing works of PT tendons in the slabs-bridges of the new office complex in Maroussi area, Athens-Greece, named “THE GRID”.
The stressing procedure of tendons is a critical step in post-tensioning, as it determines the final level of compression that is applied to the slab, creating internal forces that counteract tensile stresses, which helps to reduce cracking and control deformation. It is a critical action that directly impacts the performance, safety, and durability of the structure. Properly stressed tendons ensure that the slab can handle the loads it will encounter throughout its lifespan, maintain its shape under stress, and resist cracking—all factors that lead to a longer-lasting and more efficient structure.
In this project, stressing is implemented gradually in all 20 slab-bridges, consisting of 7 up to 40 nos. of PT tendons. Each tendon consists of a stressing (live) end and dead end (onion type embedded in the concrete), having 4 or 5 wire strands of 15.7mm nominal diameter.
As per the design, a stressing force of about 193KN/strand up to 221KN/strand will be applied. In total, more than 2680 stressing operations will take place, using a mono-strand jack.
The stressing process follows the below basic steps:
- Study of PT design data, pressure-force calculation based on jack calibration report.
- Check-availability of equipment (jack, pump and calibrated gauge).
- Visual inspection of stressing anchorage, strands overlength and cleaning if necessary.
- Installation of anchor heads and wedges (has preceded).
- Safety measures and notification of works (warning signs and no-go area marking off).
- Initial stressing to eliminate slack, marking on the strands.
- Stressing in phases (50-100bars) up to the final stressing force. In each phase the apparent elongation of jack piston is recorded.
- Recording of the actual elongation on the strand.
- Calculation of the total elongation, excluding losses (i.e., wedges drawn-in etc.) and issuance of stressing protocols.
