Prediction of prestress-force in prestressed concrete beams using natural frequency and machine learning - Tran, Quoc-Tien; Tran, Manh-Hung; Nguyen, Tran-Minh-Quan; Bui, Ngoc-Tuan-Hung; Nguyen, Huu-Thinh; Chiem, Hong-Huan; Nguyen, Chi-Khai; Pham, Minh-Nhan; Khanh, Le; Ho, Duc-Duy (VNUHCM Journal of Engineering and Technology, 2024)