Theoretical study on the nonlinear performance of single-box multi-cell composite box-girder with corrugated steel webs under pure torsion

Composite box-girders with corrugated steel webs (CBGCSWs) have become attractive structures in bridge engineering. However, wide single-box multi-cell CBGCSWs (SBMC-CBGCSWs) under heavy eccentric load may suffer sudden failures, because of the sharp decrease in torsional stiffness induced by the thin corrugated steel webs (CSWs). Thus, the accurate prediction of their entire torsional performance becomes necessary to avoid failure or damage. In this study, a theoretical model based on rotating-angle theory is proposed for SBMC-CBGCSW with prestressing under torsion. This model primarily incorporates the influence of prestressing on concrete element and proposes new average stress-strain relationships for prestressed concrete strut. Furthermore, a rational shear strain relationship between inner and outside CSWs is employed to better calculate the torsional contribution of inner CSWs. The proposed model is validated by experimental and numerical results taken from the companion paper, and the comparison between this proposed model and other models proves its superiority in predicting cracking and ultimate stages of SBMC-CBGCSW with prestressing. In addition, it is found that neglecting the initial state of concrete element caused by prestressing will result in underestimation of cracking and ultimate torques, and meanwhile the shear strain relationship between inner and outside CSWs adopted in this model can predict the torsional behavior of inner CSWs more accurately and reasonably. (C) 2020 Elsevier Ltd. All rights reserved.