Description of Concrete Creep under Time-Varying Stress Using Parallel Creep Curve

Abstract

An incremental format of creep model was presented to take account of the development of concrete creep due to loading at different ages. The formulation was attained by introducing a horizontal parallel assumption of creep curves and combining it with the vertical parallel creep curve of the rate of creep method to remedy the disadvantage of the rate of creep method that significantly underestimates the amount of creep strain, regardless of its simple format. Two creep curves were combined by introducing an ageing parameter whose value was obtained from two sets of time-dependent laboratory experiments on cylindrical specimens. The presented creep description takes the advantage that a single creep curve due to the initial loading describes the entire development of creep under the persistent change of creep-causing stress. Further, the creep formulation takes advantage of being consistent with the incremental format of age-dependent constitutive formulation. The performance of the presented creep equation was investigated with time-dependent laboratory experiments on cylindrical specimens and compared with the performances of four existing creep models.

Rate-Type Age-Dependent Constitutive Formulation of Concrete Loaded at an Early Age

“…PCM was recently presented to account for the creep behaviors under a time-varying stress-history [27]. The creep model was formulated by combining the creep curve of the rate of the creep method (RCM) with that of EMM to account for the effects of age on creep upon loading.…”

“…Several methods have been presented to depict the development of creep strain under time history loading, including the effective modulus method (EMM) [13], rate of creep method (RCM) [26], and the ageing coefficient method (ACM) [10]. Recently, the parallel creep method (PCM) [27] was presented to account for the creep behaviors under a time-varying stress-history by combining the creep curve of RCM with that of EMM to account for the effects of age on creep upon loading. Three creep models, namely EMM, ACM, and PCM, are employed in this paper to define the creep terms in the constitutive formulation, where two types of creep functions including those with and without consideration of the elastic modulus development are accounted for in each creep model.…”

Modified PCI Multipliers for Time‐Dependent Deformation of PSC Bridges

“…On the contrary, after the girder erection, a considerable amount of immediate deflection and long-term deflection due to dead loads such as topping and common duct partially offset the camber. Advances in Civil Engineering 10 …”

“…Until recently, many researchers have proposed various methods to predict the long-term behavior of PSC bridges [6][7][8][9][10][11]. However, the reliability of such predictions has not been sufficiently verified, and these methods are difficult and complicated for designers to understand and use.…”

Modeling of microstructural effects on the creep of hardened cement paste using an experimentally informed lattice model

“…As a result, the evaluation of the integral requires an extensive memory capacity and a progressively increasing number of calculations for each time step (Bažant, 1988; Di Luzio, Cedolin, & Beltrami, 2020). In the literature, several simplified and approximate methods for the calculation of creep strain have also been adopted, such as the aging coefficient method (Bažant, 1972; Granata, Margiotta, & Arici, 2013) and the parallel creep method (Park, Lee, & Lee, 2016). In addition, it is suggested in Bažant (1988) that the computational cost can be substantially reduced if the integral‐type constitutive equations are replaced by the differential‐type laws.…”