碳纖維補強清水磚牆加載實驗及水平-位移關係計算

Experimental Study and Load-Displacement Calculation of URM Wall Strengthened with CFRP under In-Plane Loading

磚牆貼附碳纖維補強工法具有自重輕與保持原有建築風貌之優點，因此近年來碳纖維貼附補強逐漸被應用於歷史建築物清水磚牆，但有關其補強行為之研究仍相當有限，而有關補強後牆體之耐力估算，亦有待更深入探討。
本研究之主要目的在透過實驗探討單面貼附碳纖維補強之清水磚牆在水平返復加載下之結構行為及破壞機制，並提出其水平加載-位移關係計算方法以為實務應用。針對此探討，本文製做5道磚牆試體進行面內水平返復加載實驗。試體包括無裂損牆體補強以及裂損牆體修復補強兩種，碳纖維貼附於牆體對角線及牆體邊緣。實驗結果顯示補強牆體之極限加載發生於磚牆產生剪力破壞時，而碳纖維補強層則因容許變位較佳而未有裂損。整體而言，在牆體破壞後，碳纖維受拉變形，對牆體造成束制效應，此效應有助於減緩牆體開裂後之強度衰減。震前與震後補強牆體在韌性與加載過程之能量消耗能力方面均較未補牆體顯著提升。
對於碳纖維補強牆體之加載-位移關係計算方面，本文納入epoxy之剪應變以及碳纖維受拉變形對牆體造成之束制效應。經由計算及實驗比較，本文之推估曲線與實驗曲線趨勢變化相近，牆體在極限水平耐力與實驗之差值比在15%以內。

Recently, CFRP (carbon fiber reinforced polymers) due to its light weight and good for keeping the architectural scenery has become a strengthening technique commonly adopted for historic masonry buildings. However, behavior studies of CFRP strengthened wall are still limited, especial the evaluation of wall strength after strengthening.
This paper is aimed to investigate the structural behavior and damage mode of strengthened masonry wall. The load-displacement relationship that is useful in practice is established. In this study, five masonry wall specimens were manufactured and subjected to in-plane horizontal cyclic loading. The specimens include four URM walls and one post-damaged wall. All the specimens were CFRP strengthened on the diagonal and wall edge. Test results showed the ultimate strength reached as the shear damage of wall occurred. However, at this stage, the CFRP laminate damage is not observed due to it’s better allowable strain. It is also found that, after wall cracked, the CFRP laminate provided confined force to the specimen. This effect was helpful to retard the decrease of resistant capacity. In general, the tests indicated that both URM wall and post-damage wall obtain a significant improvement of the in-plane shear capacity, ductility, and energy-absorption after strengthened with CFRP.
For the evaluation of load-displacement relationship of CFRP strengthened wall, the shear strain of epoxy and the confined effect provided by carbon fiber is counted. The comparisons show the calculated and test curves have similar variation trend and curve shape. The ultimate load difference between evaluation and experiment is less than 15%.