Abstract: To research the mechanical mechanism of simply-supported reinforced concrete bridges after transverse cracking under vehicle static load, three kinds of transverse cracks with width of 1 mm and length of l=8, 18 and 26 mm were prefabricated respectively in the mid-span and 1/4 of the left and right sides of the cast-in-place reinforced concrete pre-cracked test beam. The simulation test of the reinforced concrete beams with 3 nominal damage ratios (0.053, 0.120 and 0.173) was carried out under vehicle static load. Compared with the integrated beam, the deflection u, the stiffness reduction coefficient η, the crack width w under load, the concrete stress σc in horizontal direction, the reinforcing steel stress σs, and the bonding stress σb between steel bars and concrete near the transverse crack of the pre-cracked test beam were analyzed through the experiment. The stress distribution characteristics of the concrete near the transverse crack of the pre-cracked test beam were studied, and the evolution law of relative deformation and bonding stress between steel bar and concrete at different cracking positions under vehicle static load was revealed. The research shows that the longer the crack length l is, the larger the deflection ucb, the steel stress σs and the concrete stress σc in horizontal direction near crack tip of the pre-cracked test beam under the same loading condition. When l is smaller than the reinforcement cover, the increase of ucb and σs is small; when l is equal to the height of the steel bar center line, ucb and σs increase rapidly; when l exceeds the height of the steel bar center line, ucb and σs decrease slightly. In the mid-span pre-cracked test beam, the bonding stress σb and the relative deformation Δw of the steel bar and concrete near the crack show obvious nonlinear law, while in the 1/4 pre-cracked test beam, σb and Δw satisfy the linear law.

Key words: bridge engineering, reinforced concrete beam, pre-cracked beam, integrated beam, crack, static load test

摘要： 为研究车辆静载下钢筋混凝土简支梁桥横向开裂后的力学机理，分别在现浇钢筋混凝土试验梁的跨中和左右侧1/4处，预制了宽度为1mm，3种裂缝长度l= 8、18和26 mm的横向裂缝，开展了3个裂缝名义损伤比λ=0.053、0.120和0.173的钢筋混凝土预裂梁及未经预裂处理的完整梁车辆静载模拟试验；对比分析了预裂试验梁横向裂缝附近的挠度u、刚度折减系数η、承载时裂缝宽度w，及裂缝附近水平方向混凝土应力σc、钢筋应力σs，和二者间的黏结应力σb等性能指标；研究了预裂试验梁裂缝附近混凝土的应力分布特征，揭示了车辆静载下不同开裂部位钢筋与混凝土间相对变形与黏结应力的演化规律。研究表明：裂缝长度l越长，相同加载工况下预裂试验梁的挠度ucb、钢筋应力σs以及裂缝附近水平方向混凝土应力σc也越大；当l小于钢筋保护层时，ucb和σs增幅较小，当l等于钢筋中线高度时，ucb和σs快速增大；当l超过钢筋中线高度后，ucb和σs小幅回落；跨中预裂试验梁中，裂缝附近钢筋与混凝土的黏结应力σb及相对变形Δw呈现明显的非线性规律，而1/4处预裂试验梁中，σb及Δw则满足线性规律。

关键词: 桥梁工程, 钢筋混凝土梁, 预裂梁, 完整梁, 裂缝, 静载试验