- 學位論文
非韌性鋼筋混凝土短柱之耐震側力位移曲線研究
Lateral Load Deflection Curves of Reinforced Concrete Columns with Non-Ductile Detailing
摘要
921集集大地震中為數不少的鋼筋混凝土建築嚴重受損甚至倒塌，並造成重大之損失。倒塌之鋼筋混凝土建築物大多都因為柱之垂直承載力喪失所致。從受損的柱發現多數為非韌性配筋，亦即柱箍筋間距過大或不具備耐震135度彎鉤，而使得這些柱可能無法具備良好的消能與變形能力。且鋼筋混凝土建築物常爲了通風、冷氣裝設、門窗等，易使柱形成短柱。造成柱的破壞模式可能由撓曲破壞變為撓剪破壞，使柱的韌性無法充分發揮，將導致建築物產生非預期性倒塌的危險。 本研究依實際比例製作六座鋼筋混凝土柱試體，分別變化主筋量、箍筋間距、箍筋型式與承載軸力，採取雙曲率變形與固定軸力的形式，進行靜態反覆載重試驗，以瞭解非韌性配筋鋼筋混凝土短柱受撓剪破壞之行為，以及撓剪破壞後柱之崩塌行為。實驗結果顯示承載軸力之增加會降低柱桿件之位移能力，而箍筋比之增加會提高柱之位移能力，再者增加主筋量可以延緩撓剪破壞後柱之崩塌時間。 在分析方面，本研究係將目前既有之側力位移曲線預測方法與實驗結果進行比對，以確認各方法在本研究試體之適用性。結果顯示國家地震工程研究中心校舍結構耐震評估與補強技術手冊之預測，最為接近實驗之結果。但是在低主筋量柱之軸力破壞點位移預測上則高估許多。
並列摘要
During the 1999 Chi-Chi earthquake in Taiwan, a large number of old buildings suffered from severe damage or complete failure, and there were thousands of casualties and a great loss of property. A large majority of building collapse resulted from the loss of vertical-load carrying capacities of columns. Most of the damaged columns were found with non-ductile detailing, such as widely spaced hoops with 90 degree end hooks. These columns are known to have poor seismic performance in terms of ductility and energy dissipation capacity. Due to the architecture needs, such as: door, window, etc, the columns are constraint or so called short column. This changes the failure mode from flexural failure to flexural shear failure. There are several important variables which can affect the strength and behavior of columns, such as longitudinal reinforcement ratio, axial load and hoop detailing. Totally, six full scale specimens were tested under cyclic lateral load with double curvature and constant axial load until failure to observe the behavior of flexural shear and axial failure of columns. Test results show that under different magnitude of axial load, the collapse behavior is different in sense that higher axial load can accelerate the failure process. Columns with larger transverse reinforcement ratio can sustain higher lateral displacement capability, and larger longitudinal reinforcement ratio can enhance the ductility by extending the flexural shear displacement to axial displacement. The experimentally observed behavior is compared with predicted behavior based on several available analytical models. The Technology Handbook for Seismic Evaluation and Retrofit of School Buildings of NCREE assessment model provides the closest estimations with the experimental results, but with light longitudinal reinforcement columns seem to overestimate the axial failure displacements.