The effects of tendon bond lenght of prestressed ground anchors to the stability of anchored retaining systems

Abstract

Prestressed ground anchors are mainly used for reinforcing lateral earth support systems. Prestressed ground anchorage technology has become popular just after they were first used in 1930s and today anchored systems are designed offering economical solutions to both temporary and permanent stability problems.Tendon steel of a prestressed anchor is the prestressing element and it consists of grouted and ungrouted parts. Grouted part is the tendon bond length that transmits the applied tensile load to the ground and ungrouted part is the free tendon length that transfers the resisting force from the bond length to the facing. In this thesis, pull-out tests and an analysis of field tests using slope stability technique were performed. The effect of tendon bond length to the factor of safeties of anchored retaining systems was analyzed in both field tests and stability analysis. According to the pull-out tests, anchors that did not satisfy the acceptance criteria had much longer or shorter tendon bond length values than the design bond length. In the literature research, a designed tendon bond length value was obtained for prestressed ground anchors. Even though tendon bond lengths shorter than the design value reduce the factor of safety, the result of the conducted analysis and software computations indicate that also an increase in bonded length causes a reduction in the factor of safety.