Unal, Gonca. Simplified prediction equation for ultimate stress in beams prestressed with hybrid tendons. Retrieved from https://doi.org/doi:10.7282/T3NP23G5
DescriptionThe use of unbonded tendons is getting more widespread in post-tensioning industry; especially in rehabilitation and strengthening of existing damaged concrete members. The prediction of the stress at ultimate in unbonded tendon is important in calculating the capacity of structural members. This thesis presents a simplified prediction equation for concrete beams prestressed with hybrid (a combination of bonded and unbonded) tendons. The proposed equation is based on the Generalized Incremental Analysis (GIA) which uses the trussed-beam model developed by Ozkul et al. (2008) and Nassif et al. (2003). The main objective of this research is to develop a simple, but accurate design equation for the prediction of the stress at ultimate in unbonded tendon. Most important parameters such as loading type, effective prestress of unbonded tendon, concrete strength, area of steel reinforcement and span-to-depth ratio are taken into consideration. The equation is applicable to beams prestressed with unbonded or hybrid, FRP or steel, external or internal tendons. For the validation of the proposed simplified equation, test results available in the literature (199 beams) are collected. The results show that the proposed simplified equation exhibited very good accuracy for the calculation of stress at ultimate in unbonded tendon. The simplified equation is easy to use, accurate and applicable to any material type and combination of tendons.