鋼筋混凝土柱耐震補強與圍束效應之實驗研究

Abstract

鋼筋混凝土柱構件為一般結構中相當重要的構件，在地震力作用下，柱構件應有一定的變形能力並且確保軸向以及側向承載能力皆能維持，因此柱構件的剪力容量要足夠並且受良好的圍束作用，而橫向鋼筋是影響耐震行為的重要存在，提供剪力強度的同時也可以在配置條件合格的前提下，提供圍束效果。 針對橫向鋼筋配置量不足，會導致剪力破壞的既有柱構件或是震後有損壞需要緊急補強的既有柱構件，本研究提出了一種可以快速安裝於既有柱體外部的「外部圍束」補強方法，除了可以提供剪力強度之外，透過對其施加橫向預力，可以提供主動圍束的效益。本研究設計四座利用外部圍束補強柱內部無配置橫向鋼筋的柱構件(高長比=4)，透過不同的設計參數，包括:外部圍束橫向螺桿施加預力大小、配置間距以及試體施加軸力，觀察此種補強方法的適用性以及利用此種補強方法的柱構件的行為。 針對新建結構，承錨結構工業技師事務所的莊國榮技師開發了一種新型態的繫筋「90-180度繫筋」，利用此新工法，可以改善施工性，並且透過同時圍束繫筋兩端的閉合箍筋和縱向鋼筋，進而提高圍束效果。 本研究利用試驗方法，針對兩個試驗主題，分別於國家地震工程研究中心進行鋼筋混凝土柱之行為試驗，實驗配置為雙曲率，以觀察柱構件於真實結構中之耐震行為表現。試驗結果顯示，利用外部圍束補強的柱構件，可以提高柱構件的剪力容量，避免脆性剪力破壞的發生；而使用90-180度繫筋的試體，透過圍束效果的改善，可以使柱構件有良好的耐震行為，為未來可以廣泛於業界推廣的新工法。

The reinforced concrete columns are important members of structures. Under the attack of earthquake, columns should have deformability and ensure that both axial and lateral bearing capacity can be maintained. Therefore, the shear capacity of columns should be high enough, and the confinement of columns should also be under good condition. Transverse reinforcement is an important resistance that affects the seismic behavior. Transverse reinforcement can provide the confining effect and the shear strength. For existing columns that are susceptible to shear failure due to insufficient transverse reinforcement or require emergent retrofit after the earthquake, this study proposes a retrofitting measure using the 'external hoop.' External hoop can be quickly installed outside the existing column. In addition to providing shear strength, this method can provide the active confinement by applying lateral prestress to the external hoops. In this study, four columns (height-to-depth ratio of 4) without internal transverse reinforcement are retrofitted with external hoops. Test parameters include the lateral prestress level, the spacing of the external hoops and the applied axial force. Therefore, we can observe the applicability of this retrofit method and the behavior of columns using this retrofit method. For new structures, this study proposes a new type of tie '90-180 degree tie.' Using this new construction method, the constructability and the confinement effect can be improved. These two test programs were carried out in NCREE. The column specimens were tested under double curvature with high axial loads to observe the seismic behavior of columns of real structures. The test results show that columns retrofitted with external hoops can have higher shear capacity to avoid the occurrence of brittle shear failure. The columns using the 90-180 degree tie can improve the confining effect and enhance the seismic behavior. It is proved to be a new construction method that can be widely promoted in the industry in the near future.