钢板组合梁温度作用的极值统计模型

Extreme value statistical model of temperature action of steel plate composite girder

为建立桥梁温度作用的实用统计模型,梳理了代表值的统计计算方法.以钢板组合梁有效温度为例,利用试验测试、数值模拟和气象相关性公式计算3种方式得到温度作用样本,采用区组模型和超阈值模型推算了代表值,分析了样本和统计模型的适用性.结果表明:试验测试样本最直接有效,但样本量较小导致推算结果偏小;数值模拟和气象相关性公式计算利用历史气象数据得到数十年的丰富样本,推算结果更准确;数值模拟适用性更广泛,气象相关性公式计算仅适用于影响因素较简单的温度作用;选择合适的区组间隔可保证极值的独立性,提高区组模型的准确性;桥梁温度极值成串出现概率较高,应用超阈值模型需对样本除串;温度规律性变化拟合时需关注短时波动,避免高估随机部分离散性;试验地区组合梁100 a重现期的最高和最低有效温度分别为46.69和-21.04℃,有必要细化规范温度分区或绘制等温线图.

To establish a practical statistical model for bridge temperature action, the statistical calculation methods for representative values were reviewed. Taking the effective temperature of a steel plate composite girder as an example, temperature action samples were obtained by experimental tests, numerical simulation and meteorological correlation calculation. Representative values were calculated using the block maximum model(BM) and the peaks-over-threshold model(POT). The applicability of different samples and statistical models was analyzed. The results show that the test samples are the most direct and effective, but small size leads to smaller representatives. Numerical simulation and meteorological correlation formula calculation use historical meteorological data to obtain rich samples over decades, so representative values are more accurate. Numerical simulation is more widely applicable, while correlation formulae are suitable for temperature actions influenced by simple factors. Selecting appropriate interval to ensure the independence of extremes improves the accuracy of BM. The probability of bridge temperature extremes in series is high, and methods should be taken to reduce correlations of samples for POT. Attention should be taken to the short-term fluctuation when fitting the regular part of temperature actions, so as to avoid overestimating the discreteness of random parts. The maximum and minimum effective temperatures corresponding to 100 a return period of the composite girder are 46.69 and-21.04 ℃ in the test area, respectively. It is necessary to refine temperature zoning or drawing isotherm maps in the specification.