Bond-slip effect in novel steel box-concrete composite structures part Ⅱ: Long-term loading

Abstract

Considering bond-slip effect, the structural response of steel box-concrete composite beams (SBCCB) subjected to short-term load has been investigated utilizing theoretical analysis, numerical simulation, and loading test in PartⅠof this study. In PartⅡof this study, the effect of shrinkage and creep of concrete core will be quantitatively studied to investigate the long-term response of SBCCB. For analyzing long-term structural performance, equivalent elastic modulus method is introduced to deduce the theoretical formulas of deflection and stress. Besides, the long-term deflection and stress considering bond-slip effect are also derived. In addition, finite element models are constructed to further validate the accuracy of theoretical solutions. Creep coefficient and shrinkage strain determined according to six kinds of specifications are compared. Then, comparative analysis of long-term stress and deflection, as well as the comparison of numerical and theoretical results, are performed. Research findings show that the proposed formulas are applicable for predicting long-term response of SBCCB. Meanwhile, the additional stress and deflection induced by creep and shrinkage of concrete core in SBCCB are not neglectable and should attract enough attention. Increment ratios corresponding to additional deflection and stress are 20%-25% and 8–10%, respectively. Combined with PartⅠof this study which focuses on short-term performance, the research findings in Part Ⅱ can further improve the long-term design methodology of practical SBCCB.