非韌性鋼筋混凝土短柱受撓剪破壞之耐震行為研究

Study on the Seismic Performance Curves of Non-Ductile Reinforced Concrete Short Columns Failed in Flexural Shear Failure

錢宗國(Tsung-Kuo Chien)

指導教授 ： 黃世建

國立臺灣大學/工學院/土木工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.00686

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。因此，本研究依實際比例製作六座鋼筋混凝土柱試體，分別變化箍筋間距、箍筋型式與承載軸力，採取雙曲率變形與固定軸力之方式，進行靜態反覆載重試驗，以瞭解非韌性配筋鋼筋混凝土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。另外，當試體在剪力破壞後，側力強度即開始迅速衰減，隨即喪失軸向承載能力，軸力破壞點側位移與撓剪破壞點側位移相當接近。
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ASCE 41 update之預測，最為接近實驗之結果。Elwood and Moehle、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與郭武威之預測模型，在軸力破壞點之位移預測上高估許多。

關鍵字

鋼筋混凝土 ； 柱 ； 撓剪破壞 ； 雙曲率變形 ； 地震

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. There are several important variables which can affect the strength and behavior of columns, such as axial load and hoop detailing. Therefore, six full scale specimens with light transverse reinforcement were tested quasistatically 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. On the other hand, after shear failure, the lateral load resisting capacity of columns reduced significantly, leading to total lost of vertical-load carrying capacity. The flexural shear failure displacement is close to axial failure displacement.
The experimentally observed behavior is compared with predicted behavior based on several available analytical models. The ASCE/SEI 41-06 update assessment model provides the most closest estimations with the experimental results. Meanwhile, the models from Elwood and Moehle, Technology Handbook for Seismic Evaluation and Retrofit of School Buildings of NCREE, and Kuo et al. seem to overestimate the axial failure displacements.

並列關鍵字

column ； double curvature ； flexural shear failure ； reinforced concrete ； seismic

參考文獻

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[4] Elwood, K. and Moehle, J., “Axial Capacity Model for Shear-Damaged Columns,” ACI Structural Journal, Vol. 102, No. 4, pp 578-587, 2005.