On the basis of the real time measurement system for fatigue tests of conventional strain gauges,the fatigue tests and corrosion fatigue tests of 19 PC specimen beams of the heavy-haul railway were made.The development of fatigue failure patterns and the law of strains changing with the number of repeated loading of the PC beams were studied.The sectional strain distribution and neutral axis variations of PC beams in the process of fatigue loading were emphatically analyzed.The results show as follows:After multiple cycles of repeated fatigue loading,under the action of the upper limit of static fatigue loads,concrete in the compression zone of PC beams remains in the stage of elasticity,stresses are related to strains linearly and the fatigue deformation modulus E is attenuated continuously by three stages; for non-corrosion PC beams,the larger the amplitude of fatigue loading,the more obvious the neutral axis variations which move straight up; for fatigue loading of the medium amplitude,a long stable period,occurs with the neutral axis positions,occupying about 75％ ～85％ of the whole fatigue life;no matter what value the upper limit of fatigue loads is,the height of concrete in the compression zone remains basically unchanged when common reinforcements at the beam bottoms are damaged by fatigue on condition that the lower limit of fatigue loads is the same; unlike non-corrosion beams that experience three main stages,the cross-sectional neutral axis of corrosion beams remains largely unchanged under repeated fatigue loading.The results are of good reference to nonlinear analysis on a complete process of fatigue damaging in PC beams of heavy-haul railways.%基于传统应变片的疲劳试验实时测试系统,通过19片重载铁路预应力混凝土梁的疲劳和腐蚀疲劳试验,研究预应力混凝土梁疲劳破坏形态以及混凝土应变随重复荷载次数的变化规律,对预应力混凝土梁在疲劳加载过程中截面的应变分布与中和轴变化情况进行重点分析.结果表明,经过多次重复荷载作用后,预应力混凝土梁在疲劳上限静载作用下受压区混凝土仍处于弹性阶段,其应力-应变呈线性关系,但是混凝土疲劳变形模量在不断衰减,大致呈现三阶段衰减特征.对于非锈蚀预应力混凝土梁,疲劳幅值越大,中和轴变化越明显,呈直线式上移；中等幅值下,中和轴位置出现明显长稳定期约占整个疲劳寿命的75％～85％；疲劳下限荷载相同的梁,无论上限值多大,发生梁底普通钢筋疲劳断裂时对应的受压区混凝土高度基本相同.对于锈蚀预应力混凝土梁,疲劳反复荷载作用下构件的中性轴位置基本保持不变,不像非锈蚀试件那样呈现出明显的“三阶段”变化过程.本文的研究结果对疲劳重复荷载作用下重载铁路预应力混凝土梁疲劳损伤全过程非线性分析具有参考价值.
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