Evaluation of creep effects on the time-dependent deflections and stresses in prestressed concrete bridges

Abstract

In this paper, time-dependent deflections, stresses and internal forces in prestressed concrete box-girder bridges due to creep of concrete are investigated. Simple equations, correlated with a step-by-step numerical simulation analysis, are developed to calculate long-term behavior of segmentally erected prestressed concrete box-girder bridges built by the balanced-cantilever method. Three-dimensional finite-element models of the mentioned bridges, including effects of the load history, material nonlinearity, creep and aging of concrete, were developed using ABAQUS software. The three-dimensional shell elements are used for modeling box-girder walls, while Rebar elements are used for modeling prestressing tendons. The step-by-step procedure allows the simulation of the construction stages, effects of time-dependent deformations of materials and changes in the bridges' structural system. Different examples of bridges, built by the balanced-cantilever method, are studied over a 30-year duration. Practical equations are modified to calculate time-dependent deflections and redistribution of internal stresses and forces in bridges constructed by the balanced-cantilever method, and good agreements between the results of the proposed method and numerical analysis are found. Significant time-dependent effects on bridge deflections and redistribution of internal forces and stresses are observed.

Keywords:

• Creep
• Segmental bridges
• Box-girder
• Prestress
• Long-term deformations
• Creep analysis
• Balanced-cantilever construction
• Redistribution of stresses