基于MCMC-CCRAA的大跨径斜拉桥施工风险预警模型

A Construction Risk Early Warning Model of Long-span Cable-stayed Bridge Based on MCMC-CCRAA

为预防桥梁施工过程中安全事故的发生,完善施工风险预警机制,提升施工风险评估的可靠性,结合大跨径斜拉桥施工风险特点,提出了基于MCMC法与CCRAA法的大跨径斜拉桥施工风险预警模型。依据施工工序,对大跨径斜拉桥施工过程进行风险源识别,建立了施工风险层次评价体系。由于大跨径斜拉桥施工风险分析的信息较少,为最大限度地利用已有信息,采用MCMC方法中的Gibbs抽样,通过数值模拟直接从后验分布中生成参数向量的仿真样本,并针对这些仿真样本进行了统计推断,求解了复杂后验分布高维积分,进而得到了一级风险源的施工风险概率。运用CCRAA法首先确定风险基值,计算了相对海明距离,按比例对各一级风险源的风险值进行了补偿,得到风险区间后再进行风险聚合,求得二级风险源的施工风险概率,避免了聚合风险出现极值或者对风险概率产生依赖。基于以上两种方法,并结合大跨径斜拉桥施工实际,构建了施工风险概率区间,进而建立了大跨径斜拉桥施工风险预警模型,并实施了施工风险二次评估,以确保桥梁施工安全。通过工程实例分析表明:该预警模型对大跨径斜拉桥实际施工风险能做到有效评估,对于保证桥梁施工安全具有一定的实用价值。

In order to prevent the occurrence of safety accident during bridge construction,improve the construction risk early warning mechanism and the reliability of construction risk assessment,a construction risk early warning model for long-span cable-stayed bridge based on MCMC and CCRAA is put forward combining with the construction risk characteristics of long-span cable stayed bridge. Based on construction procedure,the risk sources in the construction process of long-span cable-stayed bridge are identified and the construction risk level evaluation system is established. Due to the less information for construction risk analysis of the bridge,in order to maximize the usage of existing information,Gibbs sampling method in the MCMC method is used,the simulation samples of the parameter vectors are generated directly from the posterior distribution by numerical simulation. Through statistical inference of the simulation samples,the high dimensional integral of complex posterior distribution is calculated,and the construction risk probability of the first level risk source is obtained. The base value of risk is determined before using CCRAA method,the relative Hamming distance is calculated and the risk value of each first level risk source is compensated inproportion. The risk aggregation is conducted after getting the risk interval,and the construction risk probability of the second level risk source is obtained,thus the extreme value of risk aggregation or the dependence of risk probability is avoided. Based on the above 2 methods,combining with the construction practice of the bridge,the construction risk probability interval is constructed,the construction risk early warning model for the bridge is established,and the second assessment of construction risk is conducted to ensure the safety of bridge construction. The analysis of engineering example shows that this early warning model can effectively evaluate the actual construction risks of long-span cable-stayed bridges,and has certain practical value to ensure the construction safety of the bridge.