ANALYSIS OF GLOBAL RELIABILITY AND SENSITIVITY OF STRUCTURES BASED ON MLS-SVM
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摘要: 作为一种有效的代理模型,支持向量机(SVM)以统计学习中的结构风险最小化原则为基本原理,在具有隐式极限状态函数的结构可靠度分析中得到了广泛的应用。然而,传统的支持向量机在核函数的选择、全局基本变量空间建模、计算效率等方面还存在许多不足。针对这些不足,该文提出一种新的基于移动最小二乘(MLS)技术的支持向量机模型(MLS-SVM),可以在全局基本变量空间中具备自适应能力。该文将MLS-SVM应用于复杂结构的整体可靠度和全局灵敏度分析,并将该模型与基于再生核函数的支持向量机(RPK-SVM)及基于最小二乘的支持向量机(LS-SVM)进行比较分析,结果表明:该文提出的模型相较其他两种模型具有更高的精度和计算效率。Abstract: As one of efficient surrogate models, the support vector machine (SVM), which is based on the principle of structural risk minimization in statistical learning, has been widely used in structural reliability analysis with implicit limit state functions. However, the traditional support vector machines still have many shortcomings, such as the selection of kernel function, global basic variable space modeling, computational efficiency, etc. In order to overcome these shortcomings, this paper proposes a new support vector machine model based on moving least squares (MLS) technology named MLS-SVM. With this model, the training sample sets can be adaptive in the global basic variable space. Then this model is applied to global reliability and sensitivity analysis of reinforced concrete (RC) frame structures, and then is compared with the support vector machines based on the regenerative kernel function (RK-SVM) and the least square technique (LS-SVM). It is shown by the numerical results that, compared with the two comparative models, the MLS-SVM model has higher accuracy and better computational efficiency.
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表 1 结构不确定性因素
Table 1. Structural uncertainty factors
不确定性来源 随机变量 平均值 变异系数 相关性系数 分布类型 C30 混凝土 ${X_1}( { {f_{\rm c0,core} } })$ 28.99 N/mm2 0.20 0.3 对数正态 ${X_2}( { {f_{\rm cu,core} } } )$ 17.91 N/mm2 0.20 0.3 ${X_3}( { {\varepsilon _{\rm c0,core} } } )$ 0.0023 0.20 0.3 ${X_4}( { {\varepsilon _{\rm cu,core} } } )$ 0.0143 0.20 0.3 ${X_5}( { {f_{\rm c0,cover }} } )$ 25.57 N/mm2 0.20 0.3 ${X_6}( { {\varepsilon _{\rm cu,cover} } } )$ 0.0040 0.20 0.3 C35 混凝土 ${X_1}( { {f_{\rm c0,core} } })$ 32.57 N/mm2 0.20 0.3 对数正态 ${X_2}( { {f_{\rm cu,core} } } )$ 20.76 N/mm2 0.20 0.3 ${X_3}( { {\varepsilon _{\rm c0,core} } } )$ 0.0022 0.20 0.3 ${X_4}( { {\varepsilon _{\rm cu,core} } })$ 0.0124 0.20 0.3 ${X_5}( { {f_{\rm c0,cover} } } )$ 29.76 N/mm2 0.20 0.3 ${X_6}( { {\varepsilon _{\rm cu,cover} } })$ 0.0040 0.20 0.3 HRB335 钢筋/(N/mm2) ${X_7}( { {f_{\rm y} }})$ 378 0.10 0.4 对数正态 ${X_8}( { {E_0} } )$ 200000 0.05 0.4 恒荷载/kN/m3) ${X_9}( \gamma )$ 26.50 0.10 − 正态 活荷载/(kN/m) ${X_{10} }( q )$ 0.98 0.45 − Gamma 表 2 总水平地震作用及统计信息
Table 2. General earthquake level and statistical information
结构类型 标准值 平均值 变异系数 分布类型 F3 487.67 548.01 0.3 极值Ⅰ型 F6 506.85 665.81 F9 613.28 727.79 表 3 考虑水平地震作用变异性的结构整体可靠度指标
Table 3. The global reliability index of the structure considering the variability of horizontal earthquake action
可靠度指标 变异系数 0.2 0.4 0.6 0.8 1.0 Kriging F3 0.7527 0.5154 0.4190 0.3327 0.3021 F6 0.5225 0.4227 0.4061 0.3166 0.2434 F9 0.6417 0.4609 0.3825 0.2883 0.2848 SVR(RBF) F3 0.8141 0.5747 0.4228 0.4106 0.3758 F6 0.5569 0.4689 0.4154 0.3311 0.2502 F9 0.6888 0.5200 0.4346 0.4003 0.3876 SVR(RPK) F3 0.7910 0.5666 0.4507 0.4105 0.3569 F6 0.5576 0.4552 0.4150 0.3276 0.2582 F9 0.8343 0.6302 0.5390 0.5301 0.5111 MLS-SVM F3 0.7501 0.5135 0.4278 0.3540 0.2970 F6 0.5429 0.4420 0.4007 0.3205 0.2460 F9 0.6125 0.4564 0.35686 0.31469 0.2881 FORM F3 0.7763 0.5037 0.4048 0.3644 0.3144 F6 0.5145 0.4529 0.3933 0.3042 0.2400 F9 0.6571 0.4755 0.4029 0.3221 0.2753 表 4 结构全局灵敏度指标
Table 4. Structural global sensitivity index
随机变量 变量编号 $ {S_i} $(F3) ${{S}_i^{\rm T}}$(F3) $ {S_i} $(F6) ${{S}_i^{\rm T}}$(F6) ${S_i}$(F9) ${{S}_i^{\rm T}}$(F9) $钢筋屈服强度{f_{\rm y}}$ 1 0.648700 0.667500 0.693500 0.70350 0.713100 0.72000 $约束混凝土极限应力{f_{\rm cu,core} }$ 2 0.003650 0.004840 0.005238 0.00374 0.000380 0.00420 $无约束混凝土峰值应力{f_{\rm c0,cover} }$ 3 0.005449 0.008500 0.008173 0.00880 0.005750 0.04576 $约束混凝土峰值应变{\varepsilon _{\rm c0,core} }$ 4 0.002653 0.004345 0.003200 0.00536 0.002490 0.00560 $约束混凝土极限应变 {\varepsilon _{\rm cu,core} }$ 5 0.005102 0.007121 0.004279 0.00580 0.003600 0.00739 $无约束混凝土极限应变{\varepsilon _{\rm cu,cover} }$ 6 0.000040 0.001440 0.000154 0.00238 0.000319 0.00291 $约束混凝土峰值应力 {f_{\rm c0,core} }$ 7 0.243000 0.253400 0.230700 0.24000 0.254000 0.27400 钢筋弹性模量E0 8 0.000259 0.002295 0.000058 0.00191 0.000390 0.00241 混凝土容重γ 9 0.042550 0.042950 0.045540 0.04286 0.023080 0.01529 楼面活荷载q 10 0.000008 0.003500 0.000136 0.00245 0.000030 0.00259 -
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