Experiences in assessment, replacement and repair of external tendons

The paper presents experiences with damages that occurred when using external tendons. Reason for these damages could be both technical deficiencies of a tendon system (system = components, design, corrosion protection, installation, stressing etc.) or simply human mistakes. Damages often could occur at deviators and anchorages, since forces are transferred to the structure there and the tendon is loaded in transverse direction. Damages will be presented, explained (why it is a damage), which measure had been taken and of course also advice for the future (lessons learned). The damages occurred on site or during testing of external tendon systems. Hence, the paper shall help the reader/attendant to understand sensitivity of external tendons. Furthermore, to these damages experiences with replacement (mainly cutting of the old tendon) of external tendons with flexible filler mass are shared. “Experience” focusses mainly on the de‐installation, re‐installation, grouting and stressing process. Topics that will be covered are:

‐ Improper design and/or installation of deviators and subsequent damages to the tendon sheath

‐ Torsional strand failure due to improper deviation at stressing anchor

‐ Limitations of the tendon path

‐ Deficient encapsulation of the prestressing steel

‐ Tendon force measurement options