货车撞击双柱式RC桥墩的损伤机理与计算方法

Damage Mechanism and Calculation Method for Double-column RC Bridge Piers Subjected to Truck Impact

为了明确货车撞击双柱式RC桥墩的损伤机理和破坏模式,为桥墩抗撞设计提供计算方法,利用显式动力分析软件LS-DYNA建立货车撞击双柱式RC桥墩的精细化有限元模型,采用框架墩简化质量模型替代整桥模型,引入三脉冲荷载简化模型作为加载机制,并对有限元模型和数值算法的有效性进行验证。对双柱式RC桥墩进行荷载-结构响应分析,考虑货车车型、车重、车速和桥墩尺寸等因素的影响,获取了桥墩在货车撞击下的受损破坏全过程,揭示了从弯曲裂缝产生、弯剪裂缝发展到剪切破坏的详细演进路径。明确了货车撞击双柱式RC桥墩的损伤机理,桥墩动力响应受到应力波传播和惯性作用双重影响,受撞桥墩截面最大剪力和弯矩出现在撞击荷载达到峰值时刻前后。分析了不同工况下桥墩破坏模式和截面内力响应,将双柱式RC桥墩受撞破坏模式分为弯曲破坏、剪切破坏和完全坍塌3种基本类型。提出了货车撞击双柱式RC桥墩动态抗剪承载力计算方法、桥墩截面动态剪力和动态弯矩的计算方法,结果表明:桥墩动态抗剪承载力与混凝土抗拉强度成正比,并与桥墩截面直径平方成正比。受撞桥墩截面内力计算值与有限元仿真值整体拟合度达到95%以上,所提方法可用于双柱式RC桥墩的抗撞击设计计算。

To study the damage mechanism and damage mode of double-column RC piers impacted by trucks,and to provide computational methods for the design of piers to resist collision,the power analysis software LS-DYNA was used to establish a refined finite element model of doublecolumn RC piers impacted by trucks.Additionally,a simplified mass model of frame piers is used to replace the entire bridge model,a simplified model of the three-impulse load is introduced as a loading mechanism,and the finite element model and numerical algorithms are validated.The effectiveness of the finite element model and numerical algorithm is verified.The load-structure response analysis of double-column RC piers is performed by taking into account(among others)the influence of the truck model,vehicle weight,vehicular speed,and pier size.The entire process of damage and destruction of the piers under the impact of trucks is obtained,and the detailed evolution paths from the generation of bending cracks and the development of bendingshear cracks to shear destruction are revealed.The damage mechanism of double-column RC abutment impacted by trucks is clarified,and the dynamic response of the abutment is affected by both the stress wave propagation and inertia,and the maximum shear force and bending moment of the impacted abutment cross-section appear before and after the moment when the impact load reaches the peak value.Under different working conditions,the damage mode of the pier and the internal force response of the cross-section were analyzed,and the damage mode of the doublecolumn RC pier was divided into three basic types:bending damage,shear damage,and complete collapse.The results obtained using the proposed truck impact double-column RC abutment dynamic shear capacity calculation method,and dynamic shear force and dynamic bending moment calculation method of the abutment cross-section show that the dynamic shear capacity of the abutment and the tensile strength of the concrete are directly proportional to the squared diameter of the abutment cross-section.The overall fit between the calculated internal force and the finite element simulation values in the cross-sections of the impacted piers is more than 95%,which can be used for the impact-resistant design calculation of double-column RC piers.