公路早期部分预应力混凝土T梁腐蚀疲劳性能试验分析

Analysis of corrosion⁃fatigue behavior of the early partially prestressed concrete highway T⁃shaped girders

我国早期建造、处于腐蚀环境的在役公路预应力混凝土T梁桥面临严峻的腐蚀疲劳问题.为探讨此类桥梁的腐蚀疲劳性能,基于上世纪80年代公路部分预应力混凝土T梁标准图设计试验模型,开展特定钢绞线锈蚀率(设计锈蚀率为10%)下不同疲劳荷载幅值的部分预应力混凝土T梁模型的弯曲疲劳试验,获得模型梁在循环荷载作用下的跨中挠度、梁底纵向钢筋和受压区混凝土应变、竖向裂缝宽度等的发展规律及疲劳寿命.试验结果表明:在钢绞线腐蚀较为严重时,模型梁的弯曲疲劳破坏特征为受腐蚀钢绞线发生无征兆的断丝破坏,且受压区混凝土未出现被压碎现象,破坏模式为脆性破坏;在钢绞线锈蚀率基本相同时,模型梁的受弯性能随着疲劳荷载幅值的增大而显著下降,且其疲劳寿命也随着疲劳荷载幅值的增大而急剧下降.基于应力-寿命(S-N)理论,提出钢绞线锈蚀后的部分预应力混凝土T梁的疲劳寿命预测公式,可用于初步评估钢绞线锈蚀后的部分预应力混凝土T梁的疲劳寿命.

The prestressed concrete T⁃shaped girder highway bridges built early in corrosive environ⁃ment and still in service now is facing severe corrosion⁃fatigue problem.To study the corrosion⁃fatigue behavior of such bridges,several test models were designed based on the standard drawings of partially prestressed concrete highway T⁃shaped girders in the 1980s.The bending fatigue tests of partially prestressed concrete T⁃shaped girder models with specific steel strand corrosion rate(design corrosion rate is 10%)under different fatigue load amplitudes were carried out,and the development of the midspan deflections,normal strains of both longitudinal reinforcements and concrete in the compres⁃sion zone,and vertical crack width,as well as the fatigue lives were obtained.The experimental results show that the bending fatigue failure of each test model is characterized by asymptomatic wire breakage of the corroded steel strands and no crushing damage of concrete in the compression zone,and the failure mode is typical brittle;the bending performance of each test model significantly decrea⁃ses with the increase of fatigue load amplitude,and its fatigue life also rapidly decreases with the increase of fatigue load amplitude.Based on the stress⁃life(S⁃N)theory,a fatigue life prediction formula for partially prestressed concrete T⁃shaped girders with corroded steel strands is proposed,and it can be used to initially evaluate the fatigue life of partially prestressed concrete T⁃shaped girders with corroded steel strands.