强倾弱弯梁桥设计准则研究

多起梁桥倾覆事故显示，主梁发生横向倾覆而未发生强度破坏，说明独柱墩梁桥的抗倾覆承载力和抗弯承载力不匹配。为避免超载作用下梁桥发生非延性的倾覆破坏，提出了强倾弱弯设计准则，并推导了强倾弱弯的计算公式。以跨径分布、箱梁线重度和支座分布等为参数，给出了三跨连续梁超载系数的快速计算公式。进一步以江苏无锡312高架桥、哈尔滨三环路鸿福路段高架桥和湖州104高架桥为例，进行强倾弱弯设计准则分析和初步验证。结果表明：①车道荷载横向偏载、纵向满布是连续梁桥抗倾覆最不利的活载布置方案；②传统独柱墩梁桥难以满足强倾弱弯设计准则，无法保证强度破坏发生在倾覆破坏之前；③忽略支座尺寸、大转动效应以及桥梁实际抗弯承载力与设计抗弯承载力的差异，抗倾覆稳定系数应大于2.88才能实现强倾弱弯，而不是2018版《公路钢筋混凝土及预应力混凝土桥涵设计规范》中规定的2.5。

Strong Overturning-weak Bending Design Criterion for Girder Bridges

Single-column girder bridges frequently exhibit the characteristic of transverse overturning instead of strength failure in accidents,which shows that their anti-overturning stability does not match their strength.To prevent the non-ductile overturning failure of a structure under the influence of an undetermined overload,a design criterion for strong overturning-weak bending is proposed,and the calculation formula for this criterion is derived.Based on the span and support configurations and the linear gravity distribution of the box girder,a fast calculation formula for the overload coefficient of a three-span continuous beam is proposed.The proposed design criterion was verified by evaluating the stability of Wuxi 312and Harbin Hongfu viaducts,and Huzhou 104viaduct.The research results show:①the most unfavorable live load configuration for anti-overturning stability in continuous beam bridges is for the lane load to be applied over all spans in the longitudinal direction,and close to the edge of the roadway in the transverse direction;②the traditional single-column girder bridge is unable to meet the proposed design criterion,as strength failure occurs before overturning;and③without considering the bearing width,non-linear large rotation of the girder,and the difference between the actual strength and the design strength in calculation,the anti-overturning stability coefficient must be greater than 2.88to meet the proposed design criterion,rather than 2.5,as defined by“Code of Design for Reinforced and Prestressed Concrete Highway Bridges.”