基于碳化理论的钢筋混凝土桥梁正常使用极限状态耐久性评估方法研究

钢筋混凝土结构耐久性问题是一个十分重要而亟待解决的问题。对钢筋混凝土结构耐久性的研究十分必要和迫切。首先根据现有碳化深度预测模型,以混凝土保护层厚度为结构抗力,以混凝土碳化深度值为荷载效应,建立钢筋混凝土桥梁正常使用极限状态的状态方程,由此得到钢筋混凝土桥梁结构耐久性的概率评价模型。然后结合实例对某一钢筋混凝土桥梁进行了耐久性及参数敏感性分析。实例说明了本文方法的有效性。

海洋双井口吸力桩井口间距设计方法

海洋双井口吸力桩作为一种海上钻井结构,其井筒对称分布于桩体中轴线两侧。在钻完井及后续测试作业中,由于一侧井口承载较大的载荷,导致对吸力桩基础产生偏心载荷作用,影响结构稳定性。基于目标靶区土质情况及井口载荷,对外径为2~4 m的双井口吸力桩井口间距进行了设计分析。通过倾覆失稳理论,考虑了小位移失稳和大位移倾覆两种失稳模式,分析了环境载荷对结构稳定性的影响,并根据API相关规范选取了环境参数和安全系数。通过参数敏感性分析,确定了桩体高度、贯入深度和井口间距对倾覆性能的影响,并推荐了设计井间距为3.5 m,以确保结构的稳定性和防止井口设备互相干涉。

Parametric analysis on buffeting performance of a long-span high-speed railway suspension bridge

The buffeting performance of kilometer-level high-speed railway suspension bridges has a great impact on the smooth operation of high-speed trains.To investigate the buffeting performance of the structure significantly different from traditional suspension bridges,the first long-span high-speed railway suspension bridge,Wufengshan Yangtze River Bridge(WYRB),is taken as a numerical example to demonstrate the effects of structural parameters and wind field parameters on the buffeting responses.Based on the design information,the spatial finite element model(FEM)of WYRB is established before testing its accuracy.The fluctuating wind fields are simulated via both classical and stochastic wave based spectral representation method(SRM).Finite element method is further taken to analyze the parametric sensitivity on wind induced buffeting responses in time domain.The results show that the vertical displacement is more sensitive to the changing dead load than the lateral and torsional ones.The larger stiffness of the main girder and the lower sag-to-span ratio are both helpful to reduce the buffeting responses.Wind spectrum and coherence function are key influencing factors to the responses so setting proper wind field parameters are essential in the wind-resistant design stage.The analytical results can provide references for wind resistance analysis and selection of structural and fluctuating wind field parameters for similar long-span high-speed railway suspension bridges.

Structural-acoustic coupling characteristics of honeycomb sandwich plate based on parameter sensitivity analysis

The structural-acoustic coupling model for isotropic thin elastic plate was extended to honeycomb sandwich plate(HSP) by applying Green function method.Then an equivalent circuit model of the weakly-strongly coupled system was proposed.Based on that,the estimation formulae of the coupled eigenfrequency were derived.The accuracy of the theoretical predictions was checked against experimental data,with good agreement achieved.Finally,the effects of HSP design parameters on the system coupling degree,the acoustic cavity eigenfrequency,and sound pressure response were analyzed.The results show that mechanical and acoustical characteristics of HSP can be improved by increasing the thickness of face sheet and reducing the mass density of material.

Sensitivity analysis for parameters of a monitoring system for steep slopes of open-pit mines

Monitoring the stability of steep slopes of open-pit mines is a major issue relating to production safety in mines.In order to determine the technical parameters of a new type of supervising system applied in monitoring steep slopes of open-pit mines,the MSARMA method was used to establish analytical models for the monitoring system,given various parameter settings based on the description of mechanical monitoring principles.We used this sensitivity analysis to conclude that the setting of the most sensitive location of a mechanical monitoring system should be within a range of 1/5～1/2 of the lower part in a vertical direction of steep slopes,with a rational and feasible range of the dip angle setting between 0°～20°.Given the analytical results of our on-site experiments,we have shown that the parameters determined reflect the stability of steep slopes accurately and effectively.These conclusions provide a basis for the application of a new type of steep slope stability monitoring technology in open-pit mines.

Influences of the Suspension Parameters on the Vehicle Suspension Performance for a Terrain Vehicle

This paper describes an effective methodology for evaluation of the suspension parameters intended to be used for a terrain vehicle. The objective of this approach is to make quick analyses of the sensitivity of the vehicle suspension parameters. For the purpose of developing such a methodology, a mathematical modeling of a quarter vehicles suspension system is developed. Sensitive analysis of the suspension parameters is performed by employing the standard deviation of the vehicle body acceleration, dynamic tire load, and suspension travel. Sensitivity analysis results have shown that the spring stiffness, damping coefficient, tire stiffness and sprung mass have substantial influence on the ride comfort and road holding, while un-sprung mass on the other side has much lower impact in performance of the vehicle suspension system.

Sensitivity Analysis of Geological Parameters Influencing a Solute Transport from a Deep Repository of Spent Nuclear Fuel

When evaluating Nuclear Waste DGR Safety, it is necessary to confirm its safety in a long run and above all its safety towards the biosphere which is more precisely that the biosphere will not be in any hazard caused by radioactive substances, With the aid of geologists, a model of a hypothetical area was elaborated and described with the use of geological and hydrogeological parameters. The volume of isotopes released out of the massif at the borderline of the near/far field from the DGR was determined. The paper results showed that ground water flow and transport of substances within the area were first to be determined. The Flow123D SW was used for the determination. The resulting outcome represents a determination of transported substances concentration depending on time. The disadvantage of the model is the fact that all the input parameters were set deterministically. The problem is solved by using the sensitivity analysis （changing the input parameters） or using the Monte Carlo Method. The major results are： calculations of the radionuclide concentrations in the elements depending on time and determination of parameters that have the biggest impact on the sensitivity of the whole model.