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强震区桥梁抗震挡块强度退化模型及其应用

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钢筋混凝土抗震挡块作为强震区桥梁的重要受力构件,强震下往往率先发生严重破坏,而现行规范中尚未明确给出挡块的抗震设计方法及其分析模型.为此,在揭示钢筋混凝土抗震挡块斜截面破坏机理的基础上,基于刚体转动平衡方程推导了考虑混凝土残余抗拉强度和钢筋变形协调性的3类挡块强度计算公式,并通过能量等效原理建立了挡块强度双折线退化模型.以九度区一座近断层的中小跨径梁桥为例,通过剪切铰模型模拟挡块强度双折线退化,进而探讨挡块承载力下降对桥梁下部结构地震需求的影响.研究结果表明:所提抗震挡块强度计算公式及其强度退化模型能够较为精确地预测挡块的力学特征(计算平均误差小于5％),采用剪切铰模型能够合理地模拟挡块在强震下的损伤行为;强震作用下,不考虑抗震挡块碰撞效应的影响将低估桥梁下部结构的地震需求,会导致不安全的设计结果;而仅考虑挡块刚性碰撞(不考虑挡块承载力下降)则会高估桥梁下部结构的地震需求,容易造成不必要的浪费;抗震挡块不仅起到限制主梁横向位移的作用,而且挡块的损伤一定程度上起到消耗上部结构地震力的作用;考虑所提挡块强度退化后,能准确反映主梁与挡块之间的碰撞力对桥梁下部结构地震需求的影响.所提的挡块强度退化模型及其模拟方法可为九度区中小跨径梁桥的抗震设计提出借鉴.
Strength Degradation Model for Seismic Retaining Blocks on Bridges in High-intensity Earthquake Regions
As important load-bearing members on bridges in high-intensity earthquake regions,reinforced concrete seismic retaining blocks are often the first to be severely damaged during an earthquake.However,neither a seismic design method nor an associated analysis model for such blocks has been provided in the current code.Therefore,the damage mechanism of the diagonal section of a reinforced concrete seismic retaining block was employed to derive the strength formulas for three types of blocks considering the residual tensile strength of concrete and the coordination of steel deformation.Based on the rigid body rotation equation of equilibrium,a double-line degradation model of block strength was subsequently established using the energy equivalence principle.Taking a medium-span girder bridge near a fault in the ninth-degree earthquake intensity region as an example,the double-line degradation of block strength was simulated using a shear hinge model to explore the influence of block bearing capacity on the seismic demand applied to the bridge piers.The results show that the proposed block strength formula and strength degradation model can accurately predict the mechanical characteristics of the block(with an average error of less than 5％)and that the shear hinge model can reasonably simulate its damage behavior.On the one hand,failing to consider the influence of the block collision effect under intense earthquakes will underestimate the seismic demand on the piers,leading to an unsafe design.On the other hand,considering the rigid block collision without accounting for the decrease in block bearing capacity will overestimate the seismic demand on the pier,resulting in unnecessary waste.Indeed,the results indicate that the influence of the retaining block is not restricted to its limitation of the lateral displacement of the bridge beam;damage to the block also consumes the seismic forces generated in the superstructure to a certain extent.Therefore,the proposed strength degradation model should be applied to determine the influence of the collision force between the bridge beam and block on the seismic demand applied to the bridge piers.In summary,the proposed retaining block strength degradation model and simulation method can be used for the seismic design of medium-span girder bridges in ninth-degree earthquake intensity regions.

bridge engineeringstrength degradation modelshear failure mechanismanti-seismic retaining blocksliding effect of laminated bearingsninth-degree intensity region

韦旺、邵长江、袁得铮、王春阳、李贞新、庄卫林、OKOYA ONOUNGOUA F F

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西南交通大学土木工程学院,四川成都 610031

陆地交通地质灾害防治技术国家工程研究中心,四川成都 610031

中交公路规划设计院有限公司,北京 100088

桥梁工程 强度退化模型 剪切破坏机理 抗震挡块 板式橡胶支座滑动效应 九度区

国家自然科学基金项目国家自然科学基金项目

5197858151178395

2024

10.19721/j.cnki.1001-7372.2024.07.015

中国公路学报
中国公路学会

中国公路学报

CSTPCD北大核心
影响因子：1.607
ISSN：1001-7372
年,卷(期)：2024.37(7)
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