عنوان مقاله [English]
The balanced cantilever construction of pre-stressed concrete box-girder bridges has been recognized as one of the most efficient methods of bridge construction. This method has great advantages over other methods, especially in urban areas where traffic may be interrupted, or over deep valleys or waterways where formwork could be expensive and hazardous. Time-dependent deformation of materials has adverse effects on balanced cantilever bridges. The time-dependent concrete creep and shrinkage effects on segmental bridges are more critical than other types of concrete bridges. An increase in time-dependent deformation of concrete leads to the reduction of pre-stressing force of cables and affecting the service ability of the balanced cantilever bridges. The combined effects of creep and shrinkage of concrete and relaxation of pre-stressing tendons cause gradual changes in the internal forces and deflections of span. Despite a wide range of applications of balanced cantilever light-weight concrete bridges with longer spans, there is no sufficient knowledge about the time-dependent behavior of light-weight concrete. In this study, time-dependent analyses of balanced cantilever light-weight concrete bridges are carried out by considering the creep and shrinkage of light-weight concrete and relaxation of pre-stressing cables. Stolma bridge field experimental results are used to verify the analysis method. ABAQUS software capabilities are utilized to consider the step-by-step construction procedure, so the suitable simulation of the bridge lifetime is achieved. The numerical study is performed for one, three, five and thirty years after the completion of construction procedure. A parametric study is conducted based on three types of concrete LC60, LC40, and LC25 as well as two types of behavior of steel, normal relaxation and low (TRB) relaxation. The results demonstrate that time-dependent deformations have considerable effect on lifetime behavior of light-weight concrete bridge. Most of the time-dependent deformation happened in early years after the completion of construction procedure of the bridge. The parametric study showed the identical
results of contribution of creep, shrinkage and relaxation effects on the deflection of the middle span for different types of concrete. The effect of relaxation on the deflection of the middle span is negligible for relaxation cables.