既有结构时变可靠度分析的数学方法

发布时间：2018-06-23 00:58

本文选题：既有结构 + 可靠度　；参考：《清华大学》2015年硕士论文

【摘要】：既有结构在服役过程中,碰撞损伤、介质侵蚀等原因会导致结构承载能力的降低,从而对其正常服役带来安全隐患。可靠度分析以概率统计为基础,着眼于结构在服役过程中的承载能力及荷载的不确定性,是结构安全评价的重要手段。对结构进行可靠度分析,可以得到定量的安全评估结果,进而为结构设计和服役期内的维护措施优化提供重要依据。选取合适的承载能力衰减以及荷载过程模型是结构可靠度分析的基础。在现有的可靠度研究中,概率模型选取往往基于很多假设;这些假设在简化问题的同时也带来了可靠度评估结果与真实情况的差异。本研究主要讨论劣化结构时变可靠度分析中的模型改进,具体内容有:(1)考虑荷载随机过程的相关性对结构时变可靠度的影响,指出:若不考虑荷载过程相关性,会低估结构的可靠度;并且,荷载过程相关性越大,低估的效果越明显。(2)研究了荷载的统计参数(均值、标准差)的时变特性对结构可靠度的影响,并提出了可靠度计算的显式公式。算例表明:车载随机过程参数对结构可靠度的影响显著。在20年的评估期内,均值每年增加1.1%或标准差每年增加1.3%,都会造成结构的失效概率增大两倍。(3)以风荷载为例,研究了荷载发生频率的时变特性对结构可靠度的影响,并给出了可靠度计算的显式公式。(4)研究了既有劣化桥梁的服役历史对结构后续服役期内的可靠度的更新效果,指出:当车载历史中包含超载现象或桥梁承载能力明显劣化时,更新后的可靠度更能反映既有桥梁真实的可靠度水平,而不考虑车载历史则会明显低估桥梁的可靠度水平。(5)研究了既有劣化桥梁的服役历史对结构当前时刻初评承载能力的更新作用,并给出了显式计算公式。分析表明,车载大小和承载能力衰减程度对可靠度的更新效果有显著影响。当车载历史中包含超载现象或桥梁承载能力明显劣化时,更新后的可靠度更能反映既有桥梁真实的可靠度水平,而不考虑车载历史则会明显低估桥梁的可靠度水平。
[Abstract]:During the service of the existing structure, the damage of collision and the erosion of the medium will lead to the decrease of the bearing capacity of the structure, which will bring the hidden danger to the normal service of the existing structure. Reliability analysis, based on probability and statistics, focuses on the bearing capacity and the uncertainty of load in the course of service, which is an important means of structural safety evaluation. By analyzing the reliability of the structure, the quantitative safety evaluation results can be obtained, which can provide an important basis for the structural design and the optimization of maintenance measures during the service period. The selection of appropriate load capacity attenuation and load process model is the basis of structural reliability analysis. In the existing reliability studies, the selection of probabilistic models is often based on many assumptions, which simplify the problem and lead to the difference between the reliability evaluation results and the real situation. The main contents of this study are as follows: (1) considering the influence of the random process of load on the time-varying reliability of the structure, it is pointed out that if the correlation of load process is not considered, The reliability of the structure is underestimated, and the greater the correlation of the load process, the more obvious the effect of underestimation. (2) the influence of the time-varying characteristics of the statistical parameters (mean, standard deviation) of the load on the reliability of the structure is studied. An explicit formula for reliability calculation is presented. An example shows that the parameters of the vehicle random process have a significant effect on the reliability of the structure. During the 20-year evaluation period, the average value increases by 1.1% per year or the standard deviation increases by 1.3% per year, which results in a double failure probability of the structure. (3) taking the wind load as an example, the influence of the time-varying characteristics of the frequency of the load on the reliability of the structure is studied. The explicit formula of reliability calculation is given. (4) the renewal effect of the service history of the existing degraded bridge on the reliability during the subsequent service period of the structure is studied. It is pointed out that when the overloading phenomenon is included in the vehicular history or the bearing capacity of the bridge is obviously degraded, The updated reliability can better reflect the true reliability level of the existing bridges. The reliability level of the bridge is obviously underestimated without considering the history of the vehicle. (5) the renewal of the service history of the existing degraded bridge to the initial assessment of the bearing capacity at the present moment of the structure is studied, and the explicit calculation formula is given. The analysis shows that the vehicle size and the attenuation degree of the bearing capacity have a significant influence on the reliability renewal effect. When the overloading phenomenon is included in the vehicle history or the bearing capacity of the bridge is obviously degraded, the updated reliability can better reflect the true reliability level of the existing bridge, but the reliability level of the bridge will be obviously underestimated without considering the vehicular history.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU311.2

【参考文献】