Ultimate Load Capacity of Washed Bottom Ash Concrete Filled in Perforated Built-up Cold-formed Steel ColumnFadhluhartini Muftah, Mohd Syahrul Hisyam Mohd Sani and Md Rabiul AlamE3S Web Conf., 659 (2025) 04001DOI: https://doi.org/10.1051/e3sconf/202565904001