Serviceability Response of Rehabilitated Unbonded Post-tensioned Indeterminate I-Beams Consisting UHSSCC

The ultra-high strength self-compacting concrete, UHSSCC is the new generation type of concrete with a compressive strength higher than ۸۰MPa. The application of this type of concrete on the serviceability state in CFRP strengthened unbonded post-tensioned indeterminate I-beam is monitored and the results are compared theoretically using different standards. For this aim, full scale I-beam of ۹m length was cast, by UHSSCC. During the beam service load test, the stress and strain of materials, and also deflection and crack widths were monitored at different locations using different types of sensors. Based on the experimental measurements and observations, the beam serviceability response was compared theoretically by different methods. As the considerations prepared in the standards do not cover strengthening of such members with unbonded tendons, and also no trace of deflection prediction for such continuous member, one can find in the open literature. It is therefore, this investigation was planned. A comparison between theoretical and monitored results was performed for serviceability response and it was found that although, the stress of materials are well within the standards limitations for crack widths of ۰.۱ and ۰.۲ mm of bonded tendon, but the full service load is reached at a higher load, while the flexural crack, experience a width of ۰.۳ mm. It is also apparent that the loads corresponding to the conventional suggested deflection limits will cause to exceed serviceability state of strengthened unbonded beam, and new limitations are introduced for crack widths of ۰.۱, ۰.۲ and ۰.۳ mm to predict service deflection of beams.

Keywords:

Serviceability , Unbonded post-tensioned , Continuous beams , UHSSCC , Monitored