摘要
为研究基坑开挖对邻近建筑物上部结构的内力及重力二阶效应的影响,通过有限元法建立基坑-土体-建筑物整体三维模型,研究条形基础、箱型基础及桩基础的多层框架建筑物在与基坑不同距离条件下,其总沉降量、差异沉降量及角变量的变化规律;然后通过SAP2000有限元研究由于基坑开挖引起邻近结构物支座变位导致内力及重力二阶效应的影响规律。结果表明:相对于条形基础及桩基础,基坑开挖对邻近的箱型基础建筑物影响最大;本算例条件下,基坑开挖对邻近多层框架的影响总体上而言相对较小,条形基础、桩基础或箱型基础的多层框架结构受邻近基坑开挖导致的内力变化值在11%以内;重力二阶效应(P-Δ)随着结构层高的增加而增加,12层框架结构P-Δ效应最大(7.5%),构件的承载力能满足开挖后的验算要求,总体可控;但由于随着结构层数的增加,邻近结构物的P-Δ效应及内力变化趋势将会增加,因此对于高层或者超高层,需要进行专门计算研究以确定总体承载力的变化情况,根据承载力的变化情况有效控制基坑变形。
To have a better understanding on impact of deep foundation excavation on the internal force and the gravity second-order effect of the superstructure of adjacent buildings,the author developed an overall"pit-soil-building"numerical model with geotechnical finite element software PLAXIS88 to study the change rules of the total settlement,differential settlement and angles the of multi-story framed buildings on the shallow strip foundation,the box foundation and the pile foundation respectively at different distances from the foundation excavations.Then,the rules of impact on the internal force and the gravity second-order effect resulted from base displacement of the neighboring buildings caused by the foundation excavation was further studied through SAP2000 finite element method.The results show that the foundation excavation impacts the neighboring buildings on the box foundation heavier than it impacts those on the shallow strip and the pile foundations.This case study indicates that the impact of foundation excavation is generally and relatively small on multi-story frames of the neighboring buildings.Specifically,the variations of the internal force of the multi-story frame structures of the buildings on strip,pile or box foundation caused by the foundation excavation are all within 11%.When a building has more stories the gravity second-order effect(P-Δ)increases and the building of 12 stories has the largest P-Δeffect(7.5%).Further,the impact is under control,for the bearing capacity of the building components can meet the requirement for a nearby foundation excavation according to calculation.However,with the increase of the number of stories,the P-Δeffect of adjacent structures and the change trend of internal forces will increase.Therefore,for high-rise or super-high-rise buildings,special calculation and research are needed to determine the change of overall bearing capacity and effectively control the deformation of foundation pit according to the change of bearing capacity.
作者
徐建宁
XU Jianning(China Railway First Group Co.,Ltd.,Xi’an 710054)
出处
《土工基础》
2019年第6期668-673,678,共7页
Soil Engineering and Foundation
关键词
深基坑
建筑物
有限元分析
结构内力
重力二阶效应
Deep Foundation Excavations
Buildings
Finite Element Analysis
Structural Internal Force
Gravity Second-Order Rffect
