Abstract
Pipe cooling is one of the most important measures of mass concrete temperature control, but pipe cooling has its advantages and disadvantages. Inappropriate pipe-cooling water temperature may result in excessive stress and crack. Considering the fact that concrete is a type of three-phase composite material and the sizes of cooling pipe and aggregate are basically on the same scale, the mesoscopic heterogeneity of concrete may have a great effect on the stress field surrounding the pipe. This article computes the pipe cooling–induced stress and damage and analyzes the differences between the homogeneous model and heterogeneous model based on mesoscopic mechanics. In this study, both linear elastic analysis and nonlinear damage analysis are performed; elastic modulus and creep are used as a function of concrete age; and several factors such as temperature difference, multistep cooling mode, and earlier cooling are also studied. The research results show that due to the mesoscopic heterogeneity characteristics of concrete, there is a great deal of difference between homogeneous model and heterogeneous model; pipe cooling can lead to large residual stress around the aggregate and produce a large range of damage, and previous homogeneous model indeed underestimates the effect of cooling-induced stress; using multistep cooling and early cooling mode can reduce this damage; the cooling-induced damage has significant influence on the anti-crack performance of concrete. In the final, based on the research results, the temperature difference between the concrete and pipe water of the second-phase cooling was recommended to be controlled at approximately 5°C.
Highlights
Artificial cooling of concrete by embedded pipe was first tested on the Owyhee Arch Dam Project in the United States.[1]
In this article, considering concrete as a multiphase composite material and visco-elastic material, the authors use mesoscopic mechanics and the coupled creep–damage model to investigate the CPWTD problem of the secondphase cooling, calculate the temperature field and the stress field at mesoscale, analyze a variety of CPWTDs effect and the cooling damage evolution process, and evaluate the cooling-induced stress and damage effects on concrete anti-crack performance by numerical simulation
The mesoscopic heterogeneity characteristic of concrete has an obvious influence on the damage of the concrete near the cooling pipe
Summary
Artificial cooling of concrete by embedded pipe was first tested on the Owyhee Arch Dam Project in the United States.[1]. In this article, considering concrete as a multiphase composite material and visco-elastic material, the authors use mesoscopic mechanics and the coupled creep–damage model to investigate the CPWTD problem of the secondphase cooling, calculate the temperature field and the stress field at mesoscale, analyze a variety of CPWTDs effect and the cooling damage evolution process, and evaluate the cooling-induced stress and damage effects on concrete anti-crack performance by numerical simulation Because both the modulus of elasticity and unit creep of concrete vary with time, the incremental method is used, and the time t is divided into a series of time increments Dt1, Dt2,., Dtn. The strain increment of concrete under complex stress includes the elastic strain increment, creep strain increment, temperature strain increment, and autogenous shrinkage strain increment; the total strain increment can be decomposed as follows fDeng = ÈDeenÉ + ÈDecnÉ + ÈDeTn É + ÈDesnÉ ð1Þ where fDeeng is the instantaneous elastic strain increment, fDecng is the creep strain increment, fDeTn g is the thermal strain increment, and fDesng is the autogenous shrinkage strain increment. Substituting fDsfn g into equations (2), (9), (11), and (14), the following equations can be obtained ð1
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