桥梁模态频率与运营环境作用的相关性
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摘要
桥梁模态频率随运营环境作用的变化规律是结构健康监测的研究主题之一.根据东海大桥6 a监测数据的周期变化特性,识别了运营条件下主梁竖弯、侧弯、扭转基频变化的影响因素,采用偏相关系数和周期平均法对比了各因素的影响程度.研究发现,东海大桥的模态频率存在1 a、1周、1 d、12.42 h等变化周期,与结构温度、交通荷载、风荷载、海面高度等的变化周期相吻合;结构温度和交通荷载是引起该桥频率变化的最主要因素,它们在各周期上的相对影响大小不同;周期平均法可有效分离监测数据中的年、周、天周期成分,揭示不同运营环境作用与频率变化的相关性.研究结果有助于加深对桥梁运营期频率变化的理解,从而更准确地评估结构性能.
In the vibration based structural health monitoring(VBSHM) field,the modal frequency of a structure is commonly used as an indicator for the global health condition of the structure. However,field measurements have shown that the modal frequency of a bridge varies with structural anomalies and the operational and environmental actions,e. g.,temperature and traffic loading. Moreover,the latter variation usually exceeds the frequency shifts induced by the small and medium structural anomalies. To highlight the anomaly-induced frequency changes,the variability of modal frequencies of bridges with the operational and environmental actions must be investigated,and then,the action-induced frequency variations need to be eliminated. According to the periodic characteristics of the six-year monitoring data of the Donghai Bridge,this research identified the main actions that affected the modal frequencies of the first vertical/lateral bending modes and torsional mode of the girder of this bridge,and further,it compared the relative contributions of actions to the variability of frequencies through the partial correlation coefficients and the proposed cyclic averaging method. The results show that the modal frequencies of the Donghai Bridge vary at cycles as 1 a,1 week,1 d,and 12. 42 h,which coincide with the inherent predominant cycles of structural temperature,traffic loading,wind loading,and sea levels,respectively. Structural temperature and traffic loading are the most influential factors for the frequency variation,and their relative importance is different for each individual cycle. The results also show that the cyclic averaging method can effectively separate the components in periods of 1 a,1 week,and 1 d and can disclose the inherent correlation between actions and modal frequencies. This study helps in enhancing the understanding of the frequency variability for operational bridges and may lead to a more reliable evaluation of structural performance.
In the vibration based structural health monitoring(VBSHM) field,the modal frequency of a structure is commonly used as an indicator for the global health condition of the structure. However,field measurements have shown that the modal frequency of a bridge varies with structural anomalies and the operational and environmental actions,e. g.,temperature and traffic loading. Moreover,the latter variation usually exceeds the frequency shifts induced by the small and medium structural anomalies. To highlight the anomaly-induced frequency changes,the variability of modal frequencies of bridges with the operational and environmental actions must be investigated,and then,the action-induced frequency variations need to be eliminated. According to the periodic characteristics of the six-year monitoring data of the Donghai Bridge,this research identified the main actions that affected the modal frequencies of the first vertical/lateral bending modes and torsional mode of the girder of this bridge,and further,it compared the relative contributions of actions to the variability of frequencies through the partial correlation coefficients and the proposed cyclic averaging method. The results show that the modal frequencies of the Donghai Bridge vary at cycles as 1 a,1 week,1 d,and 12. 42 h,which coincide with the inherent predominant cycles of structural temperature,traffic loading,wind loading,and sea levels,respectively. Structural temperature and traffic loading are the most influential factors for the frequency variation,and their relative importance is different for each individual cycle. The results also show that the cyclic averaging method can effectively separate the components in periods of 1 a,1 week,and 1 d and can disclose the inherent correlation between actions and modal frequencies. This study helps in enhancing the understanding of the frequency variability for operational bridges and may lead to a more reliable evaluation of structural performance.
引文
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[5]Gentile C,Saisi A.Operational modal testing of historic structures at different levels of excitation.Constr Build Mater,2013,48:1273
[6]Xu Y L,Xia Y.Structural Health Monitoring of Long-Span Suspension Bridges.Abingdon:Spon Press,2011
[7]Ding Y L,Li A Q.Temperature-induced variations of measured modal frequencies of steel box girder for a long-span suspension bridge.Int J Steel Struct,2011,11(2):145
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[9]Zhou H F,Ni Y Q,Ko J M.Eliminating temperature effect in vibration-based structural damage detection.J Eng Mech,2011,137(12):785
[10]Xia Y,Chen B,Weng S,et al.Temperature effect on vibration properties of civil structures:a literature review and case studies.J Civil Struct Health Moni,2012,2(1):29
[11]Mosavi A A,Seracino R,Rizkalla S.Effect of temperature on daily modal variability of a steel-concrete composite bridge.J Bridge Eng,2012,17(6):979
[12]He X F.Vibration-Based Damage Identification and Health Monitoring of Civil Structures[Dissertation].San Diego:University of California,2008
[13]Peeters B,De Roeck G.One-year monitoring of the Z24--Bridge:environmental effects versus damage events.Earthquake Eng Struct Dyn,2001,30:149
[14]Moser P,Moaveni B.Environmental effects on the identified natural frequencies of the Dowling Hall Footbridge.Mech Syst Signal Process,2011,25(7):2336
[15]Wattana K,Nishio M.Traffic volume estimation in a cable-stayed bridge using dynamic responses acquired in the structural health monitoring.Struct Control Health Monit,2017,24(4):e1890
[16]Magalhaes F,Cunha A.Automated identification of the modal parameters of a cable-stayed bridge:influence of the wind conditions.Smart Struct Syst,2016,17(3):431
[17]Cross E J,Koo K Y,Brownjohn J M W,et al.Long-term monitoring and data analysis of the Tamar Bridge.Mech Syst Signal Process,2013,35(1-2):16
[18]Sun L M,Zhou Y,Xie D Q.Periodic characteristics of environmental effects on modal frequencies of a cable-stayed bridge.J Tongji Univ Nat Sci,2015,43(10):1454(孙利民,周毅,谢大圻.环境因素对斜拉桥模态频率影响的周期特性.同济大学学报(自然科学版),2015,43(10):1454)
[19]He X Q,Liu W Q.Applied Regression Analysis.3rd Ed.Beijing:China Renmin University Press,2011(何晓群,刘文卿.应用回归分析.3版.北京:中国人民大学出版社,2011)
[2]Ralbovsky M,Deix S,Flesch R.Frequency changes in frequencybased damage identification.Struct Infrastruct Eng,2010,6(5):611
[3]Yu Y G,Zong Z H,Chen B C,et al.Effects of environmental temperature on modal frequency of continuous rigid frame bridge.J Vib Meas Diagn,2014,34(1):69(余印根,宗周红,陈宝春,等.环境温度对连续刚构桥模态频率的影响.振动、测试与诊断,2014,34(1):69)
[4]Magalh2es F,Cunha A,Caetano E.Vibration based structural health monitoring of an arch bridge:from automated OMA to damage detection.Mech Syst Signal Process,2012,28:212
[5]Gentile C,Saisi A.Operational modal testing of historic structures at different levels of excitation.Constr Build Mater,2013,48:1273
[6]Xu Y L,Xia Y.Structural Health Monitoring of Long-Span Suspension Bridges.Abingdon:Spon Press,2011
[7]Ding Y L,Li A Q.Temperature-induced variations of measured modal frequencies of steel box girder for a long-span suspension bridge.Int J Steel Struct,2011,11(2):145
[8]Li S L,Li H,Ou J P,et al.Identification of modal parameters of bridges considering temperature and wind effects.China Civil Eng J,2009,42(4):100(李顺龙,李惠,欧进萍,等.考虑温度和风速影响的桥梁结构模态参数分析.土木工程学报,2009,42(4):100)
[9]Zhou H F,Ni Y Q,Ko J M.Eliminating temperature effect in vibration-based structural damage detection.J Eng Mech,2011,137(12):785
[10]Xia Y,Chen B,Weng S,et al.Temperature effect on vibration properties of civil structures:a literature review and case studies.J Civil Struct Health Moni,2012,2(1):29
[11]Mosavi A A,Seracino R,Rizkalla S.Effect of temperature on daily modal variability of a steel-concrete composite bridge.J Bridge Eng,2012,17(6):979
[12]He X F.Vibration-Based Damage Identification and Health Monitoring of Civil Structures[Dissertation].San Diego:University of California,2008
[13]Peeters B,De Roeck G.One-year monitoring of the Z24--Bridge:environmental effects versus damage events.Earthquake Eng Struct Dyn,2001,30:149
[14]Moser P,Moaveni B.Environmental effects on the identified natural frequencies of the Dowling Hall Footbridge.Mech Syst Signal Process,2011,25(7):2336
[15]Wattana K,Nishio M.Traffic volume estimation in a cable-stayed bridge using dynamic responses acquired in the structural health monitoring.Struct Control Health Monit,2017,24(4):e1890
[16]Magalhaes F,Cunha A.Automated identification of the modal parameters of a cable-stayed bridge:influence of the wind conditions.Smart Struct Syst,2016,17(3):431
[17]Cross E J,Koo K Y,Brownjohn J M W,et al.Long-term monitoring and data analysis of the Tamar Bridge.Mech Syst Signal Process,2013,35(1-2):16
[18]Sun L M,Zhou Y,Xie D Q.Periodic characteristics of environmental effects on modal frequencies of a cable-stayed bridge.J Tongji Univ Nat Sci,2015,43(10):1454(孙利民,周毅,谢大圻.环境因素对斜拉桥模态频率影响的周期特性.同济大学学报(自然科学版),2015,43(10):1454)
[19]He X Q,Liu W Q.Applied Regression Analysis.3rd Ed.Beijing:China Renmin University Press,2011(何晓群,刘文卿.应用回归分析.3版.北京:中国人民大学出版社,2011)