A Study on Reinforcement Detailing and Retrofitting Effect of RC Squat Walls

台灣在經歷九二一大地震的摧殘後，為數不少的鋼筋混凝土建築物嚴重損壞或是倒塌，其中校舍內之低矮型建築物受損尤其嚴重，仔細檢視此類建築物毀損照片後，可以發現低矮型建築物大都缺少牆體的配置，或是於牆體有開門開窗之現象，造成抵抗地震力之側向強度嚴重不足。因此對於地震發生頻繁的台灣，如何提升既有建物之耐震能力成了重要的課題。 剪力牆由於具有極高之勁度，若增設於一耐震構架中可大幅提升整體結構系統之勁度及抗側力強度，因此對於耐震能力的提升是相當有效的。雖然剪力牆於提升耐震能力上是一個不錯的方法，但其傳力機制及破壞行為仍需進一步釐清；此外，於低矮型剪力牆內水平與垂直剪力筋分別扮演之角色及其重要性，也希望能有更清楚的瞭解；而在剪力牆補強工法之應用上，植筋鑽孔的數目與其補強效果之相關性仍待探討。本研究共製作六座低矮型剪力牆試體，其中四座為新建一體澆置，剩下兩座為補強方式施作之試體，旨在進行剪力牆牆體鋼筋配置及補強效果之探討。 由試驗結果可以發現牆體不論是減少水平或是垂直剪力筋，其強度差異並不大；以溫度鋼筋配置之12公分厚鋼筋混凝土牆，不因鋼筋量較少導致迅速破壞，反而也能發展一定之側向強度；至於使用大號數鋼筋進行單排植筋則同樣能發展出理想之強度，惟需注意植筋之伸展長度及搭接長度。 分析的部分則是以ACI規範與本研究建議之公式分別於對角剪力破壞及界面滑移破壞進行預測，由分析結果顯示，Paulay and Priestly建議之界面剪力摩擦公式對於低矮型剪力牆產生滑移破壞之預測較為準確，軟化壓拉桿模型在對角剪力破壞之預測上優於ACI的剪力強度公式。During the 921 earthquake in Taiwan, many reinforced concrete buildings were damaged or collapsed especially for low-rise school buildings. Due to the lacking of walls or the walls with too many openings, insufficient lateral load capacity was found for those damaged buildings. Therefore, how to enhance the capacity of seismic resistance in existing buildings is an important issue. Because of its large lateral stiffness and strength, shear wall can increase the lateral resistance of structural system easily. Although installing the shear wall is an effective method to enhance the capability of seismic resistance, the force transfer mechanisms and failure modes need to be further studied. In addition, the role of shear reinforcement in the squat wall also needs to be clearly defined. Furthermore, to reduce the number of reinforcement planting for the retrofitting method using shear wall is of interest. This research included a testing of six specimens of squat shear wall. Four specimens were made by simultating new construction; the other two specimens were the RC frames retrofitted with RC walls. By testing these specimens, the role of shear reinforcement and the retrofitting effect of RC squat walls can be investigated. According to test results, the lateral strength of shear wall is remained the same regardless of the amount of horizontal or vertical shear reinforcement in the wall. In addition, the specimen with 12 cm RC wall detailed using the shrinkage and temperature reinforcement can develop a sufficiently large lateral strength. The retrofitting method by planting the large size of shear reinforcement can develop the targeted strength. However, the length of lap splice of these planted shear reinforcement should be carefully designed. Strength evaluation of diagonal shear failure and sliding failure was also performed in this study. The analytic result shows the SST model is better than the ACI code in predicting diagonal shear strength of squat RC wall. In predicting the interface shear strength, the formula which suggested by Paulay and Priestly shows better performance the ACI code method