基于OpenSees的场地条件对RC框架结构易损性影响初探

Analysis of the influence of site conditions on the fragility of RC frame structures based on OpenSees program

目前对于结构易损性的研究主要倾向于考虑结构模型的多样化、精细化,而忽略或者简化场地土层条件的影响。基于OpenSees平台建立基岩和土层上两跨两层、两跨六层的RC框架结构的简化模型,选取54条峰值加速度大于0.8m/s^(2)地震动记录作为输入,通过数值模拟得到结构的易损性曲线。通过易损性曲线对比分析,结果显示:1)轻微破坏性能水准下,不同场地条件及结构层数工况得到的易损性曲线基本一致;2)除轻微破坏外各破坏性能水准下,土层的存在明显降低了结构破坏的概率;3)不严重破坏性能水准下,场地条件为基岩时,层数越高,越易破坏;场地条件为土层时,层数越低,越易破坏;4)严重破坏性能水准下,土层场地上结构未发生严重破坏;基岩场地的结构在输入峰值加速度大于0.4g时出现严重破坏,且六层结构的易损性曲线略高于两层结构。

The current research on fragility mainly considers the diversity,and precisely simulation of performance of structural components,but ignoring or simplifying the effect of site conditions.Using OpenSees program,simplified models of two-span,two-story and two-span,six-stories RC frame structures sitting on bedrock or soil sites are built.Collecting 54 ground-motion records which peak ground-motion acceleration exceeds 0.8 m/s^(2),numerical simulations are carried out by seismically loading,and that fragility curves are obtained and comparatively analyzed.The analytical results indicate that:1)the fragility curves obtained for different site conditions and different numbers of stories are basically staying consistent when RC structure experiences light damage levels;2)the presence of soil site tends to reduce the probability of structural damage for various damage performance levels except slight damage;3)for structures in less severe damage level,the possibility of damage of the six-story structure on rock site is higher than that of two-story structure,while such tendency remains opposite for soil site condition;4)under severe damage performance level,structures on soil site are not severely damaged;while structures on rock site are severely damaged when input peak ground-motion acceleration is greater than 0.4g,and the fragility curve of the six-story structure remains higher than that of the two-story structure.