Abstract
The early cracking of concrete beam bridges remains a concern in civil engineering. An analytical model considering the combined effect of thermo-hydro-mechanical processes forms the basis for assessing the cracking risk of girders during construction. Based on the equivalent hydration theory, the temperature and moisture conduction processes and the evolution of the mechanical properties of concrete were modeled as a function of the equivalent age. A coupling model for the temperature and moisture fields was established, and a theoretical framework for analyzing the thermo-hydro-mechanical combined effect was presented. Based on this, a numerical analysis method was proposed and implemented into ABAQUS; the results were validated with some typical tests. Finally, a long-span prestressed concrete (PC) box girder bridge with balanced cantilever construction was taken as an example, and the causes of web cracking and its impact degree were analyzed. The results show that the rate of moisture conduction is significantly lower than the rate of temperature conduction; even for thin-walled components, there exists a significant humidity gradient on the surface layer. The humidity-induced shrinkage and restraint of the precast members are the main causes of web cracking.
Highlights
During the setting and hardening period, concrete is subjected to the combined effect of hydration heat, ambient temperature and humidity, shrinkage and creep, and selfweight, that is, the combined effect of thermo-hydro-mechanical processes [1,2]. is leads to elastic and inelastic deformations
When the damage due to the combined effect of thermohydro-mechanical processes accumulates to a certain extent, early-age cracks are induced in the concrete. e early-age cracking of concrete bridges is a universal phenomenon
A long-span prestressed concrete (PC) box girder bridge with balanced cantilever construction was taken as an example, and the causes of web cracking and its impact degree were analyzed
Summary
During the setting and hardening period, concrete is subjected to the combined effect of hydration heat, ambient temperature and humidity, shrinkage and creep, and selfweight, that is, the combined effect of thermo-hydro-mechanical processes [1 ,2]. is leads to elastic and inelastic deformations. Erefore, it is necessary to establish a suitable method to analyze the combined effect of the thermo-hydro-mechanical processes. Cervera et al [13, 14] formulated a coupled thermo-chemo-mechanical model for the behavior of concrete at early ages, but the effect of the relative humidity is not considered. Lackner and Mang [15] proposed a chemo-mechanical model for early-age cracking of concrete in which the effect of relative humidity is neglected. To accurately analyze the thermo-hydromechanical combined effect in the construction process of concrete bridges, the temperature and moisture conduction processes and the evolution of the mechanical properties of concrete were modeled as a function of the equivalent age based on the equivalent hydration theory. A long-span prestressed concrete (PC) box girder bridge with balanced cantilever construction was taken as an example, and the causes of web cracking and its impact degree were analyzed
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