腐蚀钢绞线预应力混凝土梁受弯承载力评估

Evaluation on flexural strength of prestressed concrete beams with corroded steel strands

考虑腐蚀引起钢筋名义概率强度的降低,采用实用概率极限状态设计表达式中的抗力项进行预应力混凝土梁受弯承载力计算,可以获得基于材料强度平均值、标准值、设计值共3级可靠度水平的受弯承载力评估结果。基于试验结果统计,建立了随腐蚀率变化的腐蚀钢绞线名义抗拉强度与名义条件屈服抗拉强度的平均值、标准值以及设计值计算模型。分析表明:受拉钢绞线的计算极限状态(即条件屈服状态)名义应力低于实际极限状态(即极限受拉状态)名义应力,而其他钢筋的计算极限状态名义应力与实际极限状态名义应力相互吻合。最后结合算例阐述了上述方法的具体应用。

Based on the mean value,characteristic value and design value of material strength respectively,the flexural strength with three-level reliability degree of prestressed concrete beams can be evaluated using the resistance term of the applied probabilistic limit state design equation and considering the reduction of the nominal probabilistic strength of steel bars due to corrosion.Based on the statistical study of the test results,a computing model that could predict the mean value,characteristic value and design value of the nominal tensile strength and nominal constrained yield strength of corroded steel strands considering corrosion rate was developed.Analysis results show that the nominal stress at nominal ultimate state（i.e.the constrained yielding state） of steel strands is generally lower than that at actual ultimate state（i.e.the ultimate tensile state）.While for other types of steel bars,the nominal stresses match well at the two ultimate states.At last,the application of the proposed method is demonstrated with an example.