鋼筋混凝土結構物排除軟弱層之簡易設計方法

Abstract

歷年勘災經驗顯示，許多於地震中發生嚴重倒塌之建築物，係由於其在一樓多為公共開放空間，使用上為求寬敞明亮，常有牆體打通及樓層挑高之情形；二樓以上在使用上則常為私密住宅，具有大量之隔間牆及隔戶牆。上述情形造成一樓之柱牆量明顯低於其上樓層，建築物因而在一樓形成軟弱底層，倒塌風險大大提高。 為使人民之居住安全有所改善，建築物中具有軟弱層之特性者，應對於柱牆量明顯不足之樓層進行補強，提升樓層抵抗側力之強度與勁度，進而排除軟弱層破壞之不利因子。根據初步評估之概念，建築物的耐震能力係由豎向構材所貢獻，因此進行補強設計之關鍵即在於對豎向構材抗側力特性的了解。現有初評方法多以校舍為背景發展而來，但考量校舍與住宅具有不同之結構特性，其認定之豎向構材與耐震能力的關係，可能不適用於住宅。因此為使本研究能適用於各類建築物，將藉由臺灣RC建築物資料庫進行大量統計，得到各類豎向構材之尺寸，而後利用側力位移曲線分析求得各類豎向構材之平均單位面積抗側力強度與強度參與係數，以此建立出樓層剪力強度與勁度的評估公式，最後提出適用於RC建築物的排除軟弱層簡易補強設計方法。本研究並利用提出的樓層剪力強度評估公式對資料庫中之建築物進行耐震能力初步評估的應用，並與現有方法進行比較。

The experience of seismic reconnaissance shows that many buildings severely collapsed in the earthquake due to the walls removed and the story height increased on the first story for the purpose of spaciousness and brightness. Besides, the second and upper stories were often used to be private residence with large numbers of partition walls. The above situation caused the areas of columns and walls of the first story to be significantly lower than the upper stories, and the building thus formed a soft story on the ground floor, with the risk of collapse greatly increased. In order to improve the safety of people's living, the soft story with obviously insufficient vertical members in the building should be retrofitted to improve the lateral strength and stiffness, so that the deficiency of the soft story can be eliminated. According to the concept of the seismic preliminary evaluation method, the seismic capacity of the building is contributed by the vertical members, so the key to the retrofit design lies in the understanding of the lateral force characteristics of the vertical members. The existing methods of preliminary evaluation are mostly based on school buildings. However, considering the different structural characteristics of school buildings and residential buildings, the relationship between the vertical members and the seismic capacity may not be applicable to residential buildings. Therefore, in order to make this study applicable to various types of buildings, a large number of statistics will be carried out based on Taiwan's RC building database to acquire the dimensions of various types of vertical members. Then the lateral force displacement curve analysis will be used to obtain the average lateral strength per unit area and strength participation coefficient for the vertical members. And the evaluation formula of the story shear strength and stiffness is established. Finally, a simple retrofit design method to eliminate the deficiency of the soft story for the RC buildings is proposed. This study also uses the proposed evaluation formula of the story shear strength to apply the seismic preliminary evaluation to the buildings in the database and the comparison with the existing methods will be carried out.