A Project Case Study of Retrofitted Concrete Columns Using Ultra-High Performance Concrete: The Historical Site of Forest of Steles at the Great South Gate in Taiwan

The Forest of Steles at the Great South Gate is the first stele forest in Taiwan, with seven of the steles being first-class historical monuments. The building is a one-story RC structure composed of columns and rectangular beams. On September 18, 2022, a 6.8 magnitude earthquake occurred in Taiwan, causing significant cracks in the columns. Upon investigation, it was found that most of the cracks occurred at both ends of the columns. It was determined that the cause of the cracks was insufficient flexural capacity at the ends of the columns. In this project, the current capacity curve of the building was analyzed using the Taiwan Earthquake Assessment for Structures by Pushover Analysis (TEASPA3.0). The result showed that the Capacity to Demand Ratio (CDR) of the building was only 0.633, indicating the need for seismic retrofitting of the building. The retrofitting analysis was based on TEASPA3.0 and combined with the UHPC auxiliary analysis program developed by National Cheng Kung University to obtain the capacity curve after retrofitting. The CDR of the building after retrofitting was 1.104. Compared with traditional concrete, Ultra-High Performance Concrete (UHPC) has a flexural strength that is more than five times higher. Its mechanical properties can effectively reduce the strengthened section compared with the traditional methods, thus maintaining the original size of the column. This method is the first practical application of seismic retrofitting with UHPC in Taiwan.