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摘要: 为了将结构的动力参数应用于在役RC梁桥的实际承载能力评估, 根据四片钢筋混凝土简支T梁静、动力损伤试验成果, 应用非线性回归方法, 得到不同配筋率下表征T梁刚度比和频率比关系的曲线族方程, 建立了钢筋混凝土单梁结构动力特性与承载力之间的关系。基于实测基频和裂缝特征将整桥的动力特性分解为单梁的动力特性, 应用钢筋混凝土单梁模型试验研究成果, 对RC梁桥结构性能进行评估。本文建立的动力法评估模型为: 结构基频和裂缝特征→刚度→名义配筋率→单梁抗弯能力。通过对某座实际RC梁桥的动力法评定得到了单梁的变形控制弯矩、裂缝控制弯矩、强度控制弯矩, 评定结果与静载试验结果一致。可见, 以实测基频和裂缝特征可预测出RC简支梁桥的实际承载力, 精度满足实际应用要求。Abstract: Dynamic parameters were used to evaluate the loading capability of existing RC girder bridge. According to the experimental results of damnification test on four pieces of RC simple T-beam and applying nonlinear regression analysis method, some equations expressing the relation of the stiffness ratio and frequency ratio of T-beam were obtained, a relation of the structural dynamic characteristic and bearing capacity of RC single beam was proposed. Based on the measured basic frequency and crack characteristic, the dynamic characteristic of the whole bridge was divided into the dynamic properties of single beams. So the model of dynamic assessment was expressed, structural basic frequency and crack characteristic→rigidity→nominal ratio of reinforcement→resistance to bending of single beam. In the dynamic assessment of a actual RC simple bridge, the deflection-controlling bending moment, crackcontrolling bending moment and intensity-controlling bending moment of single beam are obtained, the evaluation result of vibration method is accurate and accordant to static test result, which indicates that the frequency and crack characteristic can be used to forecast the loading capability of existing RC girder bridge. 3 tabs, 9 figs, 9 refs.
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Key words:
- bridge engineering /
- RC bridge /
- bearing capacity /
- vibration testing /
- evaluation method
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表 1 混凝土取芯试件抗压强度
Table 1. Compressive strength of concrete core sample
测点 直径d/mm 长度l/mm d·l-1 抗压力/kN 换算标准抗压强度/MPa 1# 99.4 136.5 0.728 300 39.61 2# 99.5 134.5 0.740 219 29.76 3# 99.5 78.0 1.276 290 34.35 
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表 2 理论与实测基频
Table 2. Theoretical basic frequencies and test basic frequencies
项目 频率/Hz 一阶 二阶 三阶 理论值 5.577 12.699 18.043 实测值 5.860 12.700 20.510
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表 3 动力法预测结果
Table 3. Predictive result by dynamic method
梁号 1#粱 2#梁 3#梁 预测承载力 EIsi/(kN·m2) 1 333 366.695 1 658 686.975 2 043 595.638 μnom 0.046 0.058 0.071 Mδ/(kN·m) 1 947.059 2 542.300 3 305.770 Mf/(kN·m) 1 119.369 1 392.477 1 715.611 Mu(kN·m) 1 689.145 2 188.942 2 818.618 荷载效应 Mr/(kN·m) 53.38 33.67 29.45 Mq/(kN·m) 466.1 413.2 358.5 Mg/(kN·m) 318.7 318.7 318.7 Mj/(kN·m) 1 110.0 1 052.0 925.6 注：Mr、Mq、Mg分别为人群荷载、汽车荷载、恒载在梁跨中引起的弯矩值，Mj为组合后最不利内力值。
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