基于裂缝参数的钢筋混凝土预裂梁刚度试验研究

Experimental study on stiffness of reinforced concrete pre-cracked beams based on crack parameters

为研究钢筋混凝土简支梁桥跨中开裂后的刚度特性,开展不同裂缝名义损伤比下跨中预裂梁的力学试验。试件为现浇钢筋混凝土预裂梁,考虑了跨中3种不同长度a(a=8、18和26 mm)的预制裂缝。试验研究8 m标准跨径混凝土简支梁不同荷载级别下跨中预裂梁抗弯刚度折减系数k随裂缝名义损伤比λ和裂缝张开度w的演化规律。研究表明,不同试验工况下,k均随λ和w的增加而降低,且k的降低幅度在裂缝长度小于钢筋保护层时变化较小,在裂缝长度接近钢筋高度时快速降低,而在高于钢筋位置后则降幅减缓。在此基础上,提出跨中开裂钢筋混凝土简支梁桥抗弯刚度折减系数的计算公式。研究结果为该类梁桥跨中开裂后刚度性能的准确预测与评估提供了依据。

To research the stiffness characteristics of simply-supported reinforced concrete bridges after cracking in the mid-span, mechanical tests of pre-cracked in the mid-span beams with different nominal damage ratios were carried out. The specimens were cast-in-situ reinforced concrete pre-cracking beams. In the specimens, three different lengths(a=8、18 and 26 mm) of cracks in the mid-span were considered respectively. The evolutions of stiffness reduction coefficient k with nominal damage ratio λ and crack opening w under load of the 8 m standard span reinforced concrete pre-cracked beams were studied through experiments. It was showed that under different test conditions, k decreased with the increase of λ and w. The pre-cracked specimens’k decreased little when the crack length was less than the thickness of the protective layer of reinforcement, decreased rapidly when the crack length was near the height of reinforcement. However, the decreased speed appears to fall back when the crack length was higher than the height of the reinforcement. On this basis, a formula for calculating the stiffness reduction coefficient of simply-supported reinforced concrete bridges after cracking in the mid-span was proposed. The effort of this paper could provide a basic for the accurately predicting and evaluating the stiffness characteristics of simply-supported reinforced concrete bridges after cracking.