Long-Term Behavior of a Composite Prestressed Concrete Railway Bridge: Part II--Constitutive Law and Analysis

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Title: Long-Term Behavior of a Composite Prestressed Concrete Railway Bridge: Part II--Constitutive Law and Analysis

Author(s): J. C. Chern, Y. G. Wu, Y. W. Chan, and T. Y. Chou

Publication: Special Publication

Volume: 129

Issue:

Appears on pages(s): 115-142

Keywords: cracking (fracturing); creep properties; diffusion; strains; prestressed concrete; railroad bridges; shrinkage; stress relaxation; General

Date: 12/1/1991

Abstract:
Continuing the study of long-term behavior of a U-type composite prestressed concrete bridge, this paper presents a constitutive law for structural analysis and a nonlinear diffusion theory for the understanding of internal humidity distribution in a structure. The constitutive law was formulated based on a new rheological concrete element, which is a series coupling of a generalized Kalvin chain unit, a cracking unit, and a unit representing thermal strain or shrinkage. The previously obtained exponential algorithm for cracking, treated as strain softening, is combined with the exponential algorithm for generalized Kelvin chain element. The nonlinear diffusion theory, which considers both the pore humidity and aging effects on the diffusivity, was found to give very good fit to the distribution of internal humidity of concrete. The material parameters needed for the constitutive law and diffusion theory were identified. The numerical results using finite element method show the history of the prestress transfer between a young bridge deck and more matured girders. The calculated strains based on the presented method were found to be in good agreement with field measured data.