Long-Term Bending Creep Behavior of Thin-Walled CFRP Tendon Pretensioned Spun Concrete Poles
3. Experimental Specimens and Bending Test Setup
|Pole No.||Initial CFRP prestress (MPa)||Bending test||Cracking moment (kNm)||Creep moment (kNm)||Failure moment (kNm)||Time to failure||Midspan deflection at failure (mm)||Δεc,max (‰)||ΔεCFRP, max (‰)||Failure mode|
|7||1600||quasi-static||2.58||n.a.||5.76||1 h||66.4||−5.37||10.55||HPSC crushing|
|8||1600||quasi-static||2.41||n.a.||5.53||1 h||70.6||−5.90||11.33||HPSC crushing|
|14||1600||creep||n.a.||4.07||4.07||16.54 y||68.6 *||−6.84 *||9.27 *||bond|
4. Results and Discussion
4.1. Short-Term Bending Behavior
4.2. Long-Term Bending Behavior Outdoors
- The short-term bending behavior of CFRP prestressed HPSC poles is bilinear with considerable rotation capacity at failure. The moment vs. curvature behavior and the failure moment for HPSC crushing can be modeled by a simple cross-sectional analysis following the beam theory of hybrid prestressed cross-sections.
- The long-term bending serviceability of CFRP prestressed HPSC poles is satisfactory for realistic service moments, represented by the lowest loaded pole, No. 12, in the test series presented. Long-term curvatures and deflections stabilize after six months of sustained loading. Furthermore, pole specimens under realistic long-term service moments showed crack patterns that were stable over time and minimal slippage of the tendons with respect to the pole’s end faces. The latter proves the successful and durable anchorage of the Al2O3 sand-coated CFRP prestressing tendons of this study in thin-walled precast concrete members under realistic long-term service loads.
- Pole No. 14, which was loaded with twice the maximum long-term service moment, failed after 16.5 years, due to bond failure of the highest loaded CFRP tendon. The debonding of the Al2O3 sand coating from the CFRP tendon surface could be clearly observed.
- The long-term evolution of curvatures due to bending creep of the poles could be modeled analytically with reasonable accuracy using a simple, direct analysis based on the assumption that HPSC creep governs the strain and stress redistribution over the cross-section with time.
Conflicts of Interest
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Terrasi, G.P.; Meier, U.; Affolter, C. Long-Term Bending Creep Behavior of Thin-Walled CFRP Tendon Pretensioned Spun Concrete Poles. Polymers 2014, 6, 2065-2081. https://doi.org/10.3390/polym6072065
Terrasi GP, Meier U, Affolter C. Long-Term Bending Creep Behavior of Thin-Walled CFRP Tendon Pretensioned Spun Concrete Poles. Polymers. 2014; 6(7):2065-2081. https://doi.org/10.3390/polym6072065Chicago/Turabian Style
Terrasi, Giovanni P., Urs Meier, and Christian Affolter. 2014. "Long-Term Bending Creep Behavior of Thin-Walled CFRP Tendon Pretensioned Spun Concrete Poles" Polymers 6, no. 7: 2065-2081. https://doi.org/10.3390/polym6072065