Highway Planning and Design in the Qinghai–Tibet Plateau of China: A Cost–Safety Balance Perspective

Engineering designs for mountainous highways emphasize compliance checking to ensure safety. However, relying solely on compliance checking may lead designers to minimize costs at the expense of high risk indicators, since the overall risk level of the highway design is unknown to the designers. This paper describes a method for the simultaneous consideration of traffic safety risks and the associated cost burden related to the appropriate planning and design of a mountainous highway. The method can be carried out in four steps: First, the highway design is represented by a new parametric framework to extract the key design variables that affect not only the life-cycle cost but also the operational safety. Second, the relationship between the life-cycle cost and the operational safety risk factors is established in the cost-estimation functions. Third, a fault tree analysis (FTA) is introduced to identify the traffic risk factors from the design variables. The safety performance of the design solutions is also assessed by the generalized linear-regression model. Fourth, a theory of acceptable risk analysis is introduced to the traffic safety assessment, and a computing algorithm is proposed to solve for a cost-efficient optimal solution within the range of acceptable risk, in order to help decision-makers. This approach was applied and examined in the Sichuan–Tibet Highway engineering project, which is located in a complex area with a large elevation gradient and a wide range of mountains. The experimental results show that the proposed approach significantly improved both the safety and cost performance of the project in the study area.

Effect of sinusoidal waveform and frequency on space charge characteristics of polyimide

The charge phenomena under sine and half‐wave sine voltages within the frequency range of 500 Hz are studied here.Based on the pulsed electro‐acoustic method,the traditional circuit design under high-frequency voltages is first analysed.It is found that the selection of a 186 pF protection capacitor and a 333 kΩprotection resistor can ensure that the actual voltage applied to the sample is consistent with the expected input.Based on this design,experimental results show that the polarity of the charge accumulated in the depth of the sample is determined by that of the upper electrode.Comparison results under special voltages with different amplitudes and frequencies indicate that the amount of accumulated charge under sine voltages are larger than those under positive and negative half-wave sine and DC conditions,and the samples under lower-frequency conditions show more charge accumulation.The maximum electric field strengths appear at 90 and 270 degrees of the sine voltage with a frequency of 10 Hz,and their values are 68.55 and 81.82 kV/mm,respectively.Therefore,the charge characteristics are easily affected by the voltage’s waveform and frequency parameters.The results obtained here can provide guidance for the application of insulating materials under special voltage environments.