考虑双非线性影响的大跨度上承式钢拱桥地震响应研究
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摘要
以研究上承式大跨度钢拱桥的非线性地震响应和损伤机理为目的,应用考虑双非线性以及地震过程中轴力变化影响的计算方法,对跨度为200 m的两铰拱桥和无铰拱桥设计方案进行了计算,分析了结构在强地震荷载作用下地震响应和损伤程度,比较了计算方法、输入地震波以及结构设计条件对地震响应计算结果的影响。结果表明,上承式钢拱桥具有较好的结构抗震性能,在强地震荷载作用下损伤程度不显著;钢拱桥在地震荷载作用下无卓越的振动振型,地震响应计算需考虑多个振型的影响;当拱肋轴力达到屈服轴力的20%-30%时,弹塑性地震响应计算不宜忽略轴力变化的影响。几何非线性对拱肋的弯矩地震响应有较明显的影响;柔性的两铰拱桥由于自振周期长,受到的地震荷载比对应的无铰拱略小,损伤程度也相对较轻些;无铰拱桥在拱脚截面位置容易发生地震损伤,设计时应确保拱脚截面在屈服以后不发生局部失稳。
Based on elasto-plastic large displacement analysis and considering the effects of changing axial force,the dynamic response and damage mechanism of long span steel deck arch bridge under strong earthquake was studied.Taking two deck arch bridge models-the one is of two-hinged connections and the other of two fixed connections-with span length of 200m as examples,the dynamic response and plastic damage under strong earthquake waves of the two bridges were calculated.The effects of different analysis procedure,earthquake wave records and design conditions on earthquake response and damage of the bridge were studied.The results show that steel deck arch bridges have preferable seismic resistant ability and may yield only limited damage under strong earthquake motion;it is necessary to consider the effect of multiple modes on earthquake response,because of nonexistence of dominant mode in response;and the effect of changing axial force on elasto-plastic response of bridge should not be ignored when it exceeds 20-30% of yield axial force.Geometric nonlinearity is of remarkable effect on moment response of arch rib.By comparing the response of hinged and fixed arch bridge,the hinged arch bridge bears smaller earthquake load than the fixed arch bridge,because the structure is more flexible and has longer natural period than the fixed bridge.In addition,fixed arch bridge is prone to be damaged at arch base cross-section,and it is suggested that preventive measures against local buckling should be taken to keep its load-carrying capability after yield.
Based on elasto-plastic large displacement analysis and considering the effects of changing axial force,the dynamic response and damage mechanism of long span steel deck arch bridge under strong earthquake was studied.Taking two deck arch bridge models-the one is of two-hinged connections and the other of two fixed connections-with span length of 200m as examples,the dynamic response and plastic damage under strong earthquake waves of the two bridges were calculated.The effects of different analysis procedure,earthquake wave records and design conditions on earthquake response and damage of the bridge were studied.The results show that steel deck arch bridges have preferable seismic resistant ability and may yield only limited damage under strong earthquake motion;it is necessary to consider the effect of multiple modes on earthquake response,because of nonexistence of dominant mode in response;and the effect of changing axial force on elasto-plastic response of bridge should not be ignored when it exceeds 20-30% of yield axial force.Geometric nonlinearity is of remarkable effect on moment response of arch rib.By comparing the response of hinged and fixed arch bridge,the hinged arch bridge bears smaller earthquake load than the fixed arch bridge,because the structure is more flexible and has longer natural period than the fixed bridge.In addition,fixed arch bridge is prone to be damaged at arch base cross-section,and it is suggested that preventive measures against local buckling should be taken to keep its load-carrying capability after yield.
引文
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[8]台湾交通部「公路桥梁耐震设计规范」,2000.
[2]Nonaka T,Usami T,Yoshino H,et al.Elastic-plastic behaviorand improvement of seismic performance for upper-deck typesteel arch bridges[J].Journal of Structural Mechanics andEarthquake Engineering,JSCE,2003,(731):31-49.
[3]Morishita K,Inoue K,Kawashima K,et al.,Experimentalverification on the effectiveness of damper braces for reducingresponse of a steel model bridge[J].Journal of Structural Me-chanics and Earthquake Engineering,2004,(766):277-290.
[4]Sakai J,Kawashima K.Seismic response of a reinforced con-crete arch bridge taking account of axial force and moment in-teraction[J].Journal of Structural Mechanics and EarthquakeEngineering,2003(724):69-81.
[5]Usami T,Ge H,Hioki K,et al,Seismic performance upgra-ding of steel arch bridges using structural control dampers a-gainst transverse directional earthquake motions[J].Journal ofStructural Mechanics and Earthquake Engineering,2004,(766):245-261.
[6]AASHTO LRFD Bridge Design Specifications[S],SI Units 3rdEdition,1996.
[7]台湾交通部「公路桥梁设计规范」,2001.
[8]台湾交通部「公路桥梁耐震设计规范」,2000.
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