冻融与疲劳荷载交替作用下预应力混凝土梁损伤研究

通过12根预应力混凝土梁的冻融和疲劳交替试验,探索疲劳荷载上限、混凝土强度等级、预应力度及冻融疲劳交替次数比对试件外观形态、疲劳加载时的挠度及混凝土动弹性模量变化规律的影响;利用极差分析方法研究预应力度、疲劳荷载上限和冻融疲劳交替次数比对动弹性模量衰减速率的影响。试验结果表明,施加预应力和提高混凝土强度可以有效改善试件的抗冻性能;冻融作用增大了疲劳加载时试件的挠度增加率,促进了试件刚度的衰减;疲劳荷载上限始终是影响动弹性模量衰减的控制因素,随着试验的进行预应力度和冻融疲劳交替次数比对试件动弹模量的影响逐渐增加。

STUDY ON DAMAGE OF PRE-STRESSED CONCRETE BEAMS IN THE ALTERNATIVE ACTION OF FREEZE-THAWING AND FATIGUE LOAD

Based on the freeze-thawing and fatigue alternate experiment of twelve prestressed concrete beams,the effects of fatigue load limit,strength grade of concrete,prestress degree and freeze-thaw fatigue alternating frequency ratio on the variation of specimens appearance,deflection under fatigue load and concrete dynamic elastic modulus of specimens were studied.The effects of prestress degree,fatigue load limit and freeze-thaw fatigue alternating frequency ratio on the attenuation rate of dynamic modulus of elasticity were also studied by using the range analysis method.Test results show that applying prestress and improving the strength of concrete can effectively improve the frost resistance of concrete;freeze-thawing can promote the increment of mid-span deflection and attenuate the stiffness of specimens under fatigue load.The fatigue load limit is always the control factor which affect the dynamic modulus of elasticity attenuation,and the influence of factors that prestress degree and freeze-thaw fatigue alternating frequency ratio gradually go strong with the experiment on the damage of specimens.