高速铁路桥梁正加速研究应用机制砂混凝土,为探究规范中徐变模型对机制砂高强混凝土的适应性,开展8组机制砂高强混凝土徐变试验,并收集了相关试验17组,分析实测徐变系数与国内外规范模型预测值的吻合程度。研究发现:我国公路桥梁规范模...高速铁路桥梁正加速研究应用机制砂混凝土,为探究规范中徐变模型对机制砂高强混凝土的适应性,开展8组机制砂高强混凝土徐变试验,并收集了相关试验17组,分析实测徐变系数与国内外规范模型预测值的吻合程度。研究发现:我国公路桥梁规范模型(JTG 3362—2018)与机制砂高强混凝土试验的吻合度较低,比实测数据普遍高估50%以上,而fib Model Code 2010(fib MC 2010)和AASHTO 2017(SECTION 5(SI))模型的吻合度高于JTG 3362—2018模型。根据既有试验数据贫乏的特点,通过迭代法建立多系数连乘的徐变系数模型,该模型对湿度35%≤RH≤80%、fcu,28≤81 MPa、石粉含量w≤15%的机制砂高强混凝土徐变系数预测较好,预测误差不大于50%和20%的数据呈现频率分别为0.87和0.61,高于fib MC 2010和AASHTO 2017模型的0.78~0.79和0.29~0.41。拟合模型可为机制砂高强混凝土桥梁的徐变计算提供参考。展开更多
The structural health status of Hunan Road Bridge during its two-year service period from April 2015 to April 2017 was studied based on monitored data.The Hunan Road Bridge is the widest concrete self-anchored suspens...The structural health status of Hunan Road Bridge during its two-year service period from April 2015 to April 2017 was studied based on monitored data.The Hunan Road Bridge is the widest concrete self-anchored suspension bridge in China at present.Its structural changes and safety were evaluated using the health monitoring data,which included deformations,detailed stresses,and vibration characteristics.The influences of the single and dual effects comprising the ambient temperature changes and concrete shrinkage and creep(S&C)were analyzed based on the measured data.The ANSYS beam finite element model was established and validated by the measured bridge completion state.The comparative analyses of the prediction results of long-term concrete S&C effects were conducted using CEB-FIP 90 and B3 prediction models.The age-adjusted effective modulus method was adopted to simulate the aging behavior of concrete.Prestress relaxation was considered in the stepwise calculation.The results show that the transverse deviations of the towers are noteworthy.The spatial effect of the extra-wide girder is significant,as the compressive stress variations at the girder were uneven along the transverse direction.General increase and decrease in the girder compressive stresses were caused by seasonal ambient warming and cooling,respectively.The temperature gradient effects in the main girder were significant.Comparisons with the measured data showed that more accurate prediction results were obtained with the B3 prediction model,which can consider the concrete material parameters,than with the CEB-FIP 90 model.Significant deflection of the midspan girder in the middle region will be caused by the deviations of the cable anchoring positions at the girder ends and tower tops toward the midspan due to concrete S&C.The increase in the compressive stresses at the top plate and decrease in the stresses at the bottom plate at the middle midspan will be significant.The pre-deviations of the towers toward the sidespan and pre-lift of the midspan girder can reduce the adverse influences of concrete S&C on the structural health of the self-anchored suspension bridge with extra-wide concrete girder.展开更多
The calculation model for the relaxation loss of concrete mentioned in the Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTG D62—2004) was modified according to experime...The calculation model for the relaxation loss of concrete mentioned in the Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTG D62—2004) was modified according to experimental data. Time-varying relaxation loss was considered in the new model. Moreover, prestressed reinforcement with varying lengths(caused by the shrinkage and creep of concrete) might influence the final values and the time-varying function of the forecast relaxation loss. Hence, the effects of concrete shrinkage and creep were considered when calculating prestress loss, which reflected the coupling relation between these effects and relaxation loss in concrete. Hence, the forecast relaxation loss of prestressed reinforcement under the effects of different initial stress levels at any time point can be calculated using the modified model. To simplify the calculation, the integral expression of the model can be changed into an algebraic equation. The accuracy of the result is related to the division of the periods within the ending time of deriving the final value of the relaxation loss of prestressed reinforcement. When the time division is reasonable, result accuracy is high. The modified model works excellently according to the comparison of the test results. The calculation result of the modified model mainly reflects the prestress loss values of prestressed reinforcement at each time point, which confirms that adopting the finding in practical applications is reasonable.展开更多
文摘高速铁路桥梁正加速研究应用机制砂混凝土,为探究规范中徐变模型对机制砂高强混凝土的适应性,开展8组机制砂高强混凝土徐变试验,并收集了相关试验17组,分析实测徐变系数与国内外规范模型预测值的吻合程度。研究发现:我国公路桥梁规范模型(JTG 3362—2018)与机制砂高强混凝土试验的吻合度较低,比实测数据普遍高估50%以上,而fib Model Code 2010(fib MC 2010)和AASHTO 2017(SECTION 5(SI))模型的吻合度高于JTG 3362—2018模型。根据既有试验数据贫乏的特点,通过迭代法建立多系数连乘的徐变系数模型,该模型对湿度35%≤RH≤80%、fcu,28≤81 MPa、石粉含量w≤15%的机制砂高强混凝土徐变系数预测较好,预测误差不大于50%和20%的数据呈现频率分别为0.87和0.61,高于fib MC 2010和AASHTO 2017模型的0.78~0.79和0.29~0.41。拟合模型可为机制砂高强混凝土桥梁的徐变计算提供参考。
基金Project(201606090050)supported by China Scholarship CouncilProject(51278104)supported by the National Natural Science Foundation of China+2 种基金Project(2011Y03)supported by Jiangsu Province Transportation Scientific Research Programs,ChinaProject(20133204120015)supported by the Research Fund for the Doctoral Program of Higher Education of ChinaProject(12KJB560003)supported by Jiangsu Province Universities Natural Science Foundation,China
文摘The structural health status of Hunan Road Bridge during its two-year service period from April 2015 to April 2017 was studied based on monitored data.The Hunan Road Bridge is the widest concrete self-anchored suspension bridge in China at present.Its structural changes and safety were evaluated using the health monitoring data,which included deformations,detailed stresses,and vibration characteristics.The influences of the single and dual effects comprising the ambient temperature changes and concrete shrinkage and creep(S&C)were analyzed based on the measured data.The ANSYS beam finite element model was established and validated by the measured bridge completion state.The comparative analyses of the prediction results of long-term concrete S&C effects were conducted using CEB-FIP 90 and B3 prediction models.The age-adjusted effective modulus method was adopted to simulate the aging behavior of concrete.Prestress relaxation was considered in the stepwise calculation.The results show that the transverse deviations of the towers are noteworthy.The spatial effect of the extra-wide girder is significant,as the compressive stress variations at the girder were uneven along the transverse direction.General increase and decrease in the girder compressive stresses were caused by seasonal ambient warming and cooling,respectively.The temperature gradient effects in the main girder were significant.Comparisons with the measured data showed that more accurate prediction results were obtained with the B3 prediction model,which can consider the concrete material parameters,than with the CEB-FIP 90 model.Significant deflection of the midspan girder in the middle region will be caused by the deviations of the cable anchoring positions at the girder ends and tower tops toward the midspan due to concrete S&C.The increase in the compressive stresses at the top plate and decrease in the stresses at the bottom plate at the middle midspan will be significant.The pre-deviations of the towers toward the sidespan and pre-lift of the midspan girder can reduce the adverse influences of concrete S&C on the structural health of the self-anchored suspension bridge with extra-wide concrete girder.
基金Project(51551801)supported by the National Natural Science Foundation of ChinaProject(14JJ4062)supported by the Natural Science Foundation of Hunan Province,China
文摘The calculation model for the relaxation loss of concrete mentioned in the Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTG D62—2004) was modified according to experimental data. Time-varying relaxation loss was considered in the new model. Moreover, prestressed reinforcement with varying lengths(caused by the shrinkage and creep of concrete) might influence the final values and the time-varying function of the forecast relaxation loss. Hence, the effects of concrete shrinkage and creep were considered when calculating prestress loss, which reflected the coupling relation between these effects and relaxation loss in concrete. Hence, the forecast relaxation loss of prestressed reinforcement under the effects of different initial stress levels at any time point can be calculated using the modified model. To simplify the calculation, the integral expression of the model can be changed into an algebraic equation. The accuracy of the result is related to the division of the periods within the ending time of deriving the final value of the relaxation loss of prestressed reinforcement. When the time division is reasonable, result accuracy is high. The modified model works excellently according to the comparison of the test results. The calculation result of the modified model mainly reflects the prestress loss values of prestressed reinforcement at each time point, which confirms that adopting the finding in practical applications is reasonable.
