摘要
以某大型深水桥梁的群桩基础为对象,建立考虑动水效应和桩-土相互作用的非线性计算模型,以近、远场强震记录为输入,分析了不同水深下群桩基础的动力响应及损伤特性。可发现,近场地震下群桩基础的动力响应均大于远场,弯矩、剪力、位移的最大增幅分别出现在冲刷线以下不同深度处,轴力的最大增幅则出现在桩顶处,弯矩、剪力、位移和轴力的最大增幅分别为150.6%、227.2%、333.4%和64.2%。近场地震下,墩底、桩顶是主要易损部位,当PGA=0.38g和0.6g时,桩顶损伤指数分别为0.19和0.40,损伤水平及范围随地震动强度增加而增大,随水深增加而略有增大;远场地震下,群桩基础主要处于弹性状态。由于桩周土的约束作用,一定深度的土层交界处也可能出现桩基损伤,且损伤程度会随地震动强度的增加而增大,并向两端扩散。对比表明,近场地震下深水群桩基础的动力响应及损伤均明显大于远场,表明脉冲型近断层地震动具有更高的变形和耗能需求,应在深水桥梁的抗震设计尤其是基础延性设计中予以重视。
Taking the group-piles foundation of a large deep-water bridge as a study object,its nonlinear calculation model considering hydrodynamic effect and pile-soil interaction was built. The strong near-fault and far-field earthquake records were taken as inputs,the dynamic response and damage characteristics of the foundation under different water depths were analyzed. The results show that the dynamic responses of the foundation under near-fault earthquakes are larger than those under far-field earthquakes; the maximum increments of shear force,moment,and displacement appear at different depths beneath the erosion line,while those of axial force appear at the pile top,the maximum increments of moment,shear force,displacement and axial force are 150. 6%,227. 2%,333. 4% and 64.2%,respectively; under near-fault earthquakes,the pier bottom and pile top are main vulnerable positions,the damage indexes of the pile top are 0. 19 and 0. 40,respectively under peak ground accelerations( PGAs) of 0. 38 g and 0. 6 g; the damage level and range increase with increase in earthquake intensity,and increase slightly with increase in water depth;under far-field earthquakes,the group-piles foundation is mainly in elastic state,due to the constraint effect of soil around piles,structural damage may occur at some junctions of soil layers with a certain depth,the damage level increases with increase in earthquake intensity and spreads to both ends. Comparisons show that the dynamic responses and structural damage of the foundation under near-fault earthquakes are significantly greater than those under far-field earthquakes; the impulse type near-fault earthquakes have higher deformation and energy-dissipation demands,more attentions should be paid to the aseismic design of deep-water bridges,especially,the ductility design of their foundations.
出处
《振动与冲击》
EI
CSCD
北大核心
2017年第24期13-22,共10页
Journal of Vibration and Shock
基金
国家自然科学基金(51378050)
高等学校学科创新引智计划(111计划)(B13002)
中国铁路总公司重大课题(2013G002-A-3)
中央高校基本科研业务费(2016JBM044)
关键词
深水桥梁群桩基础
非线性模型
动水效应
桩-土相互作用
动力时程分析
地震损伤特性
近、远场地震
group-piles foundation of a deep-water bridge
nonlinear model
hydrodynamic effect
pile-soil interaction
dynamic time history analysis
seismic damage characteristic
near-fault and far-field earthquake
