针对悬浇预应力混凝土箱梁桥合龙段底板在合龙索张拉过程中经常发生分层破坏的现象，介绍了混凝土多种破坏准则，并从理论上指出最大拉应力准则不适用于箱梁桥合龙段的底板抗裂设计，而应该采用双向应力状态下的混凝土强度破坏准则。选取多座典型破坏桥梁与未发生破坏桥梁为研究对象，建立了桥梁结构的三维实体有限元模型，得出合龙段底板预应力管道之间的竖向应力与纵向应力，进而利用不同混凝土破坏准则分别对典型桥梁的应力状态及安全性做了预测，并与桥梁实测结果进行了对比，证明了理论分析的正确性。研究结论可为同类桥梁的抗裂设计提供参考。

According to the phenomenon of laminating crack while tensioning the pre-stressed cables at bottom slab in closure segment for prestressed concrete continuous box girder bridges constructed by hanging basket, different failure criterions of concrete are introduced in this paper. It indicates from theory that the failure criteria under biaxial stress is more applicable to anti-crack design than the maximum tensile stress criterion for closure segment of box girder bridges. Based on 8 typical bridges that selected as the research objects, the FEM (finite element method)models are established and the transverse and vertical stress between pre-stressed tendons at bottom slab in closure segment are obtained; the stress state and security of bottom slab under different failure criteria are forecasted and compared with field test data. Finally, the theoretical analysis is proved. The conclusions can be regarded as reference for the anti-crack design of similar bridges.