无粘结预应力筋极限应力计算方法

Calculation Method of Ultimate Stress of Unbonded Prestressed

建立了基于增量变形的适用于无粘结预应力混凝土梁受力全过程的数值分析方法,可用来分析正常使用状态及承载能力极限状态下,无粘结预应力筋应力的变化情况。本文的方法能够模拟混凝土梁开裂引起的结构刚度变化情况,利用本文所建立的分析方法,研究了不同加载方式、跨高比、预应力筋线形对无粘结预应力筋应力增量的影响。与现有理论计算方法及试验结论的对比结果表明基于增量变形的数值方法略大于理论计算结果,并准确反映了无粘结预应力筋的应力增量与关键截面变形值接近直线关系这一结构机理,说明利用基于增量变形的数值方法可对无粘结预应力筋的应力变化、无粘结预应力混凝土梁的抗弯强度进行较合理而精确的评估。

The numerical analysis method for the whole process ofthe unbonded prestressed concrete beams based on incrementaldeformation is established, which can be used to analyze thestress state of the unbonded prestressed tendons under the normalstate of use and the limit of the carrying capacity. The method ofthis paper can simulate the change of structural stiffness causedby cracking of concrete beams. By using the analysis method es-tablished in this paper, the effects of different loading modes,span ratio and prestressing tendons on stress increment of un-bonded prestressed tendons are studied. The results show that thenumerical method based on incremental deformation is slightlylarger than the theoretical results and accurately reflects thestraight line relationship between the stress increment of unbond-ed prestressed tendon and the critical section deformation vale. The numerical results show that the stress - strain of unbond-ed prestressed tendons and the flexural strength of unbonded prestressed concrete beams can be evaluated reasonably and accu-rately by numerical method based on incremental deformation.