磚牆造成之軟弱層及短柱效應之研究

Abstract

本文藉由預先裝置在結構物上之強震儀在經歷過地震後所收錄的加速度歷時資料，利用系統識別的方法，對兩棟建築物識別其基本振動週期，然後以Membrane模擬磚牆，藉由磚牆彈性模數E值的調整，使系統識別與分析模式之振動週期趨於一致，以建立較符合實際結構行為之分析模式，再對該建築物做動力歷時分析，探討軟弱層及短柱效應。研究結果顯示，一樓形成軟層的結果，一樓的角柱部分將承受很大的柱軸力，而彎矩和剪力的大小則和地震特性有關，在相同的地震力作用下，軟層現象將會使一樓柱承受更大的彎矩和剪力。矮牆的加入造成部分短柱，研究顯示這些短柱在相同的地震力下，將承受比原先設計還大的剪力，因而有可能發生剪力破壞。

This research calibrates the natural frequency and period of building by system identification utilizing the acceleration time history, which were collected from seismometers installed on building during earthquake. The brick wall was simulated by membrane element in the analytic model. By the adjust of the Yong’s modulus of the brick wall to match the natural frequency of the analytical model and calibrated from system identification, a better estimative analysis model can be obtained. The effect of soft story and short columns were investigated by analyzing the analytical model subjected to time history analysis. The results show that the columns in the corner of ground story bear extremely large axial force under the condition that the ground story becomes a soft story. The frequency content of the earthquake can have a significant influence on the moment and shear force of columns. For the same earthquake force act on the building with soft story, the moment and shear force of columns are larger than those building without soft story. Half story height walls create short columns. The results show that short columns have larger shear force than these long columns.