危旧预应力混凝土箱梁承载性能足尺试验

EXPERIMENTAL STUDY ON BEARING CAPACITY OF DANGEROUS AND/OR OLD PRE-STRESSED CONCRETE BOX GIRDERS

为获得危旧混凝土桥梁的真实承载性能,通过对足尺危旧预应力混凝土小箱梁进行抗弯和抗剪承载性能试验,研究危旧预应力混凝土小箱梁受力退化行为。通过足尺危旧预制箱梁残余承载能力试验,量测分析了试验梁的荷载、挠度、应变、裂缝宽度等,对危旧小箱梁的残余抗弯、抗剪极限承载能力及刚度进行了分析,得出危旧预制箱梁抗弯、抗剪受力性能及破坏机理。将足尺试验结果与承载力计算值以及公路I级设计内力值进行比较,分析危旧混凝土小箱梁的实际承载性能。引入损伤折减系数,建立危旧混凝土箱梁极限承载力计算公式。试验结果表明:结构损伤降低了箱梁的承载性能,试验梁在未开裂阶段的挠度不满足公路桥规对活载刚度的验算要求,抗弯足尺试验得到的抗弯承载力与抗弯承载力计算结果基本相同,比主梁设计内力弯矩值高70%;抗剪足尺试验结果比主梁设计内力剪力值分别高32%和37%;引入损伤折减系数后的抗弯、抗剪承载力计算公式可以较准确的评估危旧混凝土小箱梁的承载能力,可为我国大量现役混凝土小箱梁的评估与维护提供参考。

In order to obtain the true bearing capacity of dangerous and old pre-stressed concrete box girder bridges,experiments on flexural and shear bearing capacity of full-scale dangerous and old pre-stressed concrete small box girders are conducted to study the mechanical degradation behavior of dangerous and old pre-stressed concrete box girders.Through the residual bearing capacity test of the full-scale prefabricated box girder,the load,deflection,strain and crack width of the test girders are measured and analyzed.The residual bending and shear ultimate capacity and stiffness of the small box girders are analyzed.The bending and shear behavior and failure mechanism of precast box girders in danger are obtained.The comparisons between the results of full-scale test and the calculated value of bearing capacity and also the design value of the internal force of I-Class highway are operated to analyze the actual performance of the small box girder made of dilapidated concrete.The damage reduction coefficient is introduced to establish the formula of ultimate bearing capacity of the girder.The test results stated that the structural damage affected the bearing performance of this box girder.The deflection of the test girder in the uncracked stage did not meet the proof stiffness requirements under the variable load of highway bridge.The calculated results of the flexural bearing capacity are basically identified with the result from full scale flexural test,which is 70% higher than the design bending moment by the internal force of the main girder.The results of full-scale shear tests are respectively 32% and 37% higher than the internal shear design values of the girder.The formulas with damage reduction coefficient for calculating the bending and shearing capacity of the concrete box girders is applicable to evaluate the bearing capacity of the dilapidated concrete girders with more accurate results,which can provide a reference for the evaluation and maintenance of massive existing small concrete box girders in China.