Shear resistance of concrete girders prestressed with unbonded tendons.

摘要

External post-tensioning and reduction of bonded reinforcement in concrete girders eliminate the need for concrete clear cover. Application of high-performance concrete with enhanced strength and ductility allows further reduction of the sectional thicknesses to bare minimums. This optimization, however, necessitates accurate assessment of the state of stress in concrete girders.; This thesis presents a truss model describing the shear-resistance mechanisms of externally prestressed girders without longitudinal bonded reinforcement. The model shows arching and spreading of compressive stresses. As such, it considers shear failure due to both web compression and diagonal tension. The study consisted of a large-scale experiment and nonlinear finite element analysis of the shear-critical behaviour of an externally prestressed girder. Experimental study agreed with the proposed truss model. Finite element modelling procedure must be refined. The proposed model facilitates the synthesis of a shear-design method for consistent dimensioning of concrete and steel reinforcement in externally prestressed girders.