基于逆可靠度的单轨梁容许应力计算方法

单轨梁是一种兼具承重和导向功能的新型轨道结构,其目标可靠度与应用于常规铁路不同,沿袭铁路规范的安全系数进行设计存在不合理之处。为此,提出一种基于抛物线拟合原理的逆可靠度计算方法,并基于该方法进行了单轨梁设计安全系数的校核。首先,对现行铁路规范中的设计目标可靠度进行了校核,随后基于极限状态铁路规范校核了跨座式单轨梁的设计目标可靠度,并结合基于抛物线拟合原理的逆可靠度求解方法,反解了一级安全水平对应的单轨规范荷载组合I对应的容许应力提高系数为1.05。同时,随着活载效应占比的减少,容许应力提高系数的增幅不超过0.01。最后,比较了不同设计参数均值、标准差的变化对单轨梁可靠度的影响,其中抗力均值、抗力和汽车荷载的变异系数对可靠度的控制能力较强,证明这两者是控制单轨梁设计的主要参数。

A Calculation Method for Allowable Stress of Monorail Beam Based on Inverse Reliability

Monorail beam is a new type of track structure with both bearing and guide functions. Its target reliability is inconsistent with that of conventional railways and it is unreasonable to design following the safety coefficient of the allowable railway code. A method for calculating inverse reliability based on parabolic fitting principle is proposed. Based on this method, the safety factor of monorail beam design is checked. First of all, The design objective reliability in current railway codes is checked. Then, based on the limit state railway code, the design objective reliability of monorail beams is verified. Combining with the inverse reliability solution method based on parabolic fitting principle, the allowable stress enhancement factor under load combination I is calculated to be 1.05. At the same time, with the decrease of the proportion of live load effect, the increase of the allowable stress enhancement factor is not more than 0.01. Finally, the effects of mean and standard deviation changes of different design parameters on reliability are compared. The mean resistance and the resistance and variation coefficient of automobile load have strong control effect on reliability, which proves that they are the main control factors in the design of monorail beam.