In prestressed concrete structures, the evaluation of the safety level is generally carried out by separating the bending moment\r\nstrength and the shear force capacity. Actually interaction between bending moment (M) and shear force (V) can have significant\r\nconsequences on evaluations in service life, especially when the ultimate limit state (ULS) is considered. In this paper, the M-V\r\ninteraction is addressed for prestressed concrete girders, in the cases of both bonded and unbonded prestressing tendons. It can\r\nbe demonstrated, by drawing the interaction domains (M-V), that a significant reduction of the safety level has to be considered\r\nwhen shear force is evaluated together with bendingmoment on the ULS of the cross-section, especially for external prestressing in\r\nconcrete T-shaped or box sections of bridge girders. Interaction domains allow designers to evaluate and optimize reinforcement\r\nratios, geometric properties of the beam, and effects of shear on the ultimate state. An analytical model, based on the stress field\r\ntheory, is developed and proposed in this paper.Anumerical example is developed and interaction domains are given for an example\r\nof a box section with variation in reinforcement ratio and tendon slope. A validation of the presentedmodel is given, by comparing\r\nexperimental data in the literature with results found using the proposed analytical approach.
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