公路平曲线半径的可靠性设计

为了解决现行路线设计规范在平曲线半径设计时采用定值型设计车速法存在的问题,提出了转弯半径的可靠性设计方法．以现行公路工程结构可靠度设计统一标准为依据,对平曲线半径的可靠度进行了定义,以车辆转弯时的横向滑移失稳现象为约束条件,建立了转弯半径的功能函数,推导了转弯半径可靠性计算的数学模型．对于可靠度及可靠指标数学模型的求解,提出可根据具体条件选用解析法或蒙特卡洛法计算．结合工程案例,用自编程序示范了平曲线半径的可靠性设计方法,结合公众心理承受度,推荐了平曲线半径可靠性设计的目标可靠度及可靠指标,并计算了现行路线设计规范的隐含可靠度．算例及对规范隐含可靠度的分析结果表明,按设计车速法设计弯道半径,即使能满足现行有关规范和指南的验算要求,但未必能满足可靠性设计的要求．在平曲线半径设计中推行可靠度设计方法可提高道路安全性．

Reliability design method for horizontal curve radius of highway alignment

To solve the problems in design speed method for calculation of horizontal curve radius in the current specification, reliability design method is presented. Based on Unified Standard for Reliability Design of Highway Engineering Structures, the reliability of curve radius was defined. With lateral slide of vehicle traveling around horizontal curve as constraints, the performance function of curve radius was established and models for calculation of its reliability and reliable indicator were deduced. For solution of the models, analytical methods and Monte Carlo method were recommended. With self developed program, a case study was conducted to illustrate the reliability design method in calculating curve radius of an accident prone highway. Based on psychological investigation, target reliability, reliable indicator, and minimum curve radiuses were recommended for design of curve radius of various grades of two lane highway. Hidden reliability of the current specification was calculated. The case study and the hidden reliability analysis together shows that even if the design result with design speed method satisfy requirement of the specification, it maybe not reach the standard of reliability design method. Therefore, Reliability design method for horizonal curve radius of highway alignment is helpful for safety improvement.