A Comparitive Study on the Ultimate Tendon Stress of Unbonded Tendon According to Various Codes

규격별 비부착 긴장재의 극한응력식에 대한 비교 연구

The unbonded prestressed concrete(PSC) members exhibit very different structural behavior from that of bonded PSC members because of having different tendon stress increment. Recently, AASHTO changed the provision of ultimate tendon stress with unbonded tendons, because some researches tried to improve the provision of ultimate tendon stress with unbonded tendons. The purpose of the present study is to compare various Codes with the ultimate failure stresses of prestressing(PS) steels for the unbonded PSC members. To this end, Some national Codes have been collected and analyzed. A series of major influencing variables have been included in the analysis. It was found that the span-depth ratio, neutral axis depth-effective depth ratio, concrete compressive strength, effective prestress, and prestressing steel ratio have great influence on the ultimate failure stress of PS steel in unbonded PSC members. The Comparison indicates that existing formulas including ACI and domestic Code's equations shows some unwarranties. The present study allows more realistic analysis and design of prestressed concrete structures with internal unbonded tendons.