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The extreme temperature differences in fiat steel box girder of a cable-stayed bridge were studied.Firstly,by using the long-term measurement data collected by the structural health monitoring system installed on the Runyang Cable-stayed Bridge,the daily variations as well as seasonal ones of measured temperature differences in the box girder cross-section area were summarized.The probability distribution models of temperature differences were further established and the extreme temperature differences were estimated with a return period of 100 years.Finally,the temperature difference models in cross-section area were proposed for bridge thermal design.The results show that horizontal temperature differences in top plate and vertical temperature differences between top plate and bottom plate are considerable.All the positive and negative temperature differences can be described by the weighted sum of two Weibull distributions.The maximum positive and negative horizontal temperature differences in top plate are 10.30 ℃ and -13.80 ℃,respectively.And the maximum positive and negative vertical temperature differences between top plate and bottom plate are 17.30 ℃ and-3.70 ℃,respectively.For bridge thermal design,there are two vertical temperature difference models between top plate and bottom plate,and six horizontal temperature difference models in top plate. 相似文献
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Damage alarming and safety evaluation using long-term monitoring data is an area of significant research activity for long-span bridges. In order to extend the research in this field, the damage alarming technique for bridge expansion joints based on long-term monitoring data was developed. The effects of environmental factors on the expansion joint displacement were analyzed. Multiple linear regression models were obtained to describe the correlation between displacements and the dominant environmental factors. The damage alarming index was defined based on the multiple regression models. At last, the X-bar control chart was utilized to detect the abnormal change of the displacements. Analysis results reveal that temperature and traffic condition are the dominant environmental factors to influence the displacement. When the confidence level of X-bar control chart is set to be 0.003, the false-positive indications of damage can be avoided. The damage sensitivity analysis shows that the proper X-bar control chart can detect 0.1 cm damage-induced change of the expansion joint displacement. It is reasonably believed that the proposed technique is robust against false-positive indication of damage and suitable to alarm the possible future damage of the expansion joints. 相似文献
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高耸高层钢结构焊缝在风和地震作用下的疲劳裂纹萌生和扩展是一种危及结构安全甚至引起结构倒塌的钢结构重要破坏形式,已经引起国际土木工程领域的关心和重视.高耸高层钢结构焊缝多轴高周弹性应力疲劳和多轴低周塑性应变疲劳劣化机理和寿命预测的研究现状是:1)焊缝应力和应变演化过程分析;2)焊缝疲劳损伤表征;3)焊缝疲劳寿命预测与设计方法.在此基础上指出未来的主要研究方向,包括:1)焊缝多尺度应力和应变状态模拟方法;2)焊接残余应力场的产生机理、分布模式和松弛规律;3)焊缝等效疲劳损伤参量的数力学表征;4)焊缝疲劳劣化机理;5)焊缝疲劳寿命预测方法.研究结果可为高耸高层钢结构焊缝疲劳劣化机理与寿命预测研究提供参考. 相似文献
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大跨斜拉桥扁平钢箱梁的多尺度损伤分析研究 总被引:1,自引:0,他引:1
以润扬大桥斜拉桥为分析对象,提出了扁平钢箱梁结构的多尺度损伤分析方法。采用子结构方法将钢箱梁结构全尺度动力响应和细节尺度构件损伤相互衔接实现多尺度损伤分析。在此基础上对模态曲率、模态应变能、模态柔度和斜拉索索力指标的损伤识别效果进行了比较研究。分析结果表明:(1)无噪声情况下,除了模态柔度指标不能够正确识别钢箱梁腹板损伤以外,各损伤指标均能正确识别其余所有损伤工况。(2)对大多数情况,柔度指标的抗噪性最好,曲率指标和应变能指标次之,索力指标最差;(3)应变能指标和柔度指标在钢箱梁结构损伤定位上具有一定的互补性。 相似文献
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摘 要:通过钢梁损伤试验,验证基于小波包能量谱的结构损伤预警方法在实际结构上应用的有效性。对钢梁进行完好工况和三个损伤工况的动力响应测试,对得到的响应进行小波包分解,考察损伤前后各个特征频带的能量变化。试验结果显示,损伤预警指标ERV和ERVD能够对三种损伤工况做出有效预警;同一工况的多次测试得到的损伤预警指标ERVD虽有变化但变化不大。基于小波包能量谱的结构损伤预警指标对结构损伤具有敏感性、对测试噪声具有鲁棒性,可以用于实际结构损伤预警。 相似文献
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大跨维修机库动力特性复杂,针对该类结构的减震研究则刚刚起步。本文结合大跨机库的地震响应特点,采用布置柱间消能支撑来进行机库结构地震响应的被动控制。结合减震结构优化模型特点与主要优化算法的数学原理,选取模式搜索算法作为结构减震装置参数优化分析工具,通过目标函数程序的编制实现了模式搜索算法在结构被动控制系统参数优化分析中的应用。最后针对机库基底剪力设置了适应度函数,进行了机库结构柱间耗能支撑阻尼系数的优化分析,并给出了机库减震效果随减震装置参数的变化规律。分析表明,模式搜索算法以及相应的优化程序可以有效地实现机库结构减震参数优化分析。 相似文献
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为揭示非平稳随机脉动风的时频特性,基于小波变换原理推导了时变功率谱的时间、频率和幅值与小波变换系数的关系,建立了非平稳随机脉动风时变功率谱估计的小波函数加权和法,并采用模拟非平稳脉动风和实测台风过程对理论推导结果进行了验证。研究结果表明:非平稳随机过程在某一时刻的不同尺度小波变换系数是一个以此非平稳随机过程的调制函数与小波函数的乘积为调制函数的非平稳随机过程的傅里叶变换,非平稳随机过程的时变功率谱等于不同尺度和不同时移的小波函数模平方的加权和,小波函数加权和法计算的非平稳随机脉动风的时变功率谱与理论结果具有良好的一致性。小波函数加权和法可有效地估计非平稳随机脉动风的时变功率谱,估计的时变功率谱可为进一步理解强(台)风的随机脉动特性奠定基础。 相似文献
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