RC空心板梁疲劳刚度退化规律试验研究

Experimental Research on Fatigue Stiffness Degeneration Regularity of RC Hollow Slab Beam

桥梁结构刚度随损伤发展会逐渐发生不可逆的退化,刚度退化与疲劳损伤之间有一定的内在关联,通过疲劳试验研究了刚度退化的规律和计算方法。疲劳试验发现钢筋混凝土空心板梁的刚度呈现出明显的三阶段退化规律:在0~0.15Nf阶段,梁的挠度增长非常明显,甚至可以达到疲劳破坏时总挠度的40%,但挠度增长速率逐渐变小;在0.15Nf^0.90Nf阶段,梁的挠度增长速率逐渐变小直至接近某一较小的常数;在0.90Nf^Nf阶段,梁的挠度增长速率逐渐变大,开始进入脆性疲劳断裂阶段,试验梁很快疲劳破坏。刚度退化曲线符合S形形态。根据刚度退化规律对试验数据进行拟合,得到可用于计算钢筋混凝土空心板梁刚度退化程度的公式,该公式与5根试验梁的试验结果吻合度较好,能够实现对刚度退化的定量描述。

Bridge structural stiffness will degenerate irreversible along with the damage progress,and a certain inherent relevance exists between stiffness degeneration and fatigue damage. The stiffness degeneration regularity and its calculation method are researched based on a series of fatigue experiments. According to the experimental resultal,it is found that reinforced concrete beam＇s stiffness degeneration presents a 3-stage regularity very obviously：（ 1） during the stage of 0- 0. 15 Nf,beam＇s deflection increased very obviously so far as to achieved 40% total deflection of fatigue failure,but its increasing rate lessened gradually;（ 2）during the stage of 0. 15Nf- 0. 9Nf,the deflection increasing rate diminished gradually to a certain constant;（ 3） during the stage of 0.9Nf- Nf,the deflection increasing rate largened gradually,the test beam turned into brittle fatigue fracture period and then destroyed rapidly. The stiffness degeneration curve accords with S style. Based on the stiffness degeneration regularity and experimental data fitting result,the calculation formula of reinforced concrete hollow slab beams＇ stiffness degeneration degree is obtained. The computed value of the formula agrees well with 5 test beams＇ experimental results,it can quantitatively describe reinforced concrete beams＇ stiffness degeneration.