道路配套工程施工对运营地铁车站的影响分析

运营地铁保护区内施工要求高,地铁车站上方覆土浅,卸载对既有结构的影响明显。文章以上跨地铁的市政配套工程为例,通过有限元分析和抗浮验算,研究施工对既有地铁结构变形、抗浮稳定安全系数的影响。由计算结果可知,开挖卸载对结构竖向变形影响明显,压顶梁拆除对地铁结构抗浮稳定影响满足规范要求。数值模拟数据与监测数据对比,模拟结果与实际情况相吻合,可为类似工程提供一定的参考。

施工阶段墩梁固结处应力监测与分析

以某(96+96)m T形刚构桥为研究对象,通过Midas/FEA软件建立了三维有限元模型,结合现场应力监测值,对其施工过程中墩梁固结处的应力变化规律进行了研究分析.结果表明:随着悬臂施工阶段的进行,零号块顶板、腹板和底板均表现出受压的状态,压应力呈增大趋势,且在最大悬臂阶段达到了最大值;通过横向和竖向预应力的张拉,减小了零号块的主拉应力.

新建地铁车站深基坑紧贴既有地铁站变形分析

以新建北京地铁10号线二期宋家庄站和7号线双井站为例,对新建地铁车站深基坑紧贴既有地铁车站特级风险采用FLAC3D和Midas-GTS两种有限元软件进行分析,并结合10号线二期宋家庄站现场变形监测结果对比研究,总结降水、基坑开挖等不同阶段引起既有车站的水平、竖向变形规律,并提出风险预警及施工加固措施.

Finite element model updating of existing steel bridge based on structural health monitoring

Based on the physical meaning of sensitivity,a new finite element(FE) model updating method was proposed. In this method,a three-dimensional FE model of the Nanjing Yangtze River Bridge(NYRB) with ANSYS program was established and updated by modifying some design parameters. To further validate the updated FE model,the analytical stress-time histories responses of main members induced by a moving train were compared with the measured ones. The results show that the relative error of maximum stress is 2.49% and the minimum relative coefficient of analytical stress-time histories responses is 0.793. The updated model has a good agreement between the calculated data and the tested data,and provides a current baseline FE model for long-term health monitoring and condition assessment of the NYRB. At the same time,the model is validated by stress-time histories responses to be feasible and practical for railway steel bridge model updating.

Seismic Deformation and Seismic Resistance Analysis of Shapai Roller Compacted Concrete Arch Dam Based on Field Monitoring and Dynamic Finite Element Method

Shapai Roller Compacted Concrete(RCC) Arch Dam is the highest RCC arch dam of the 20th century in the world with a maximum height of 132m,and it is the only concrete arch dam near the epicentre of Wenchuan earthquake on May 12th,2008.The seismic damage to the dam and the resistance of the dam has drawn great attention.This paper analyzed the response and resistance of the dam to the seismic wave using numerical simulations with comparison to the monitored data.The field investigation after the earthquake and analysis of insitu data record showed that there was only little variation in the opening size at the dam and foundation interface,transverse joints and inducing joints before and after the earthquake.The overall stability of the dam abutment resistance body was quite good except a little relaxation was observed.The results of the dynamic finite element method(FEM) showed that the sizes of the openings obtained from the numerical modeling are comparable with the monitored values,and the change of the opening size is in millimeter range.This study revealed that Shapai arch dam exhibited high seismic resistance and overload capacity in the Wenchuan earthquake event.The comparison of the monitored and simulated results showed that the numerical method applied in this paper well simulated the seismic response of the dam.The method could be useful in the future application on the safety evaluation of RCC dams.

Cross spectral energy method for damage assessment of the cable-stayed bridge under operational conditions

The new cross spectral energy method(CSEM)is proposed for maintaining cable-stayed bridge safe-ty by the measurable output-only vibration response.Damage assessment of real structures is limited by aseries of problems such as unknown ambient excitation forces,errors introduced by system identification,incomplete dynamic measurements,etc.Thus the methodology based on cross spectral energy of eachsubstructure member is derived to meet these challenges.The novel damage index does not require anymodal or parameter identification technology.It can be calculated directly from vibration test data.In or-der to evaluate the efficiency of the presented methodology,a three dimensional(3D)actual cable-stayedbridge model with one or more damaged positions under operational conditions was studied.In order totestify the reliability of damage detection method,the response data was polluted by the random noise.Itis proved that the proposed method can successfully localize all damage cases even in noisy data.Withthe help of examples,the CSEM can potentially be applied as a nondestructive evaluation technique(NDT)for on-line health monitoring of cable-stayed bridges with minimum disruption of its operations.

Experimental and finite element analyses on the corrosion of underground pipelines

Underground pipelines, on which a city relies for survival and development, have become an important part of lifeline engineering. Underground pipelines are utilized for conveying liquid, gas or loose solid, pipeline leakage and damage occasionally resulting from corrosion. Corrosion monitoring of underground pipelines is aimed at ensuring their normal operation and preventing loss of life and property. In this paper, a new method to monitor corrosion of pipelines has been proposed to solve the mentioned problem. Under the influence of internal pressure and corrosion, the pipeline wall becomes thinner and the circumferential deformation increases. The method is to indirectly investigate pipeline corrosion by monitoring the circumferential deformation. Numerical simulation confirms that the circumferential strain curve of the pipeline wall measured by using the proposed method to describe the corrosion is feasible. The proposed method provides a new way for real-time and long-term monitoring and management of underground pipelines.