Research on the spatial shrinkage history model of concrete based on temperature history factor
[Objective]The current cracking risk assessment of mass concrete in engineering focuses on temperature stress and assumes that the overall concrete is uniformly shrinking.However,due to the influence of the non-uniform temperature field of mass concrete on its shrinkage development,the shrinkage development and distribution within is not uniform,leading to an un-derestimation of the risk of cracking.In order to better estimate and predict the risk of cracking,[Methods]the distributed opti-cal fiber is utilized to measure the temperature and deformation history of mass concrete in an arch bridge foundation.Based on this,the temperature history factor is proposed,and the calculation model of in-plane mass concrete shrinkage considering tem-perature history factor is established.Then,the difference in maximum tensile stress development between this shrinkage model and the uniform shrinkage model adopted by existing specification is analyzed through finite element calculation.[Results]The measured result indicate that the temperature of the core foundation exhibits elevated levels,while the shrinkage progresses rapid-ly during the initial phase,achieving 80%of its ultimate value within a span of 3.4 days.However,the final shrinkage value is relatively low at only 330 με.On the contrary,the temperature is lower and the shrinkage development is slower at the edge of the foundation,taking 13.3 days to reach 80%but result ing in a higher final shrinkage value of 470 με.The result of the finite element calculation indicate that,despite the low initial maximum tensile stress under differential contraction conditions,there is a subsequent increase in the final maximum tensile stress by 26.8%from 5.85 MPa to 7.42 MPa,when compared to uniform contraction conditions.[Conclusion]The findings indicate that the disparity in temperature history between the internal and ex-ternal regions of mass concrete significantly influences the progression of shrinkage.In the initial stage,the shrinkage of center undergoes rapid development with a significant shrinkage value,while the shrinkage of exterior progresses at a slower pace with a smaller shrinkage value.This differential growth mitigates the tensile stress induced by temperature gradients and consequently leads to an overestimation of early cracking risk.Subsequently,the shrinkage development of the central concrete stagnates,while the external concrete shrinkage continues to develop and gradually exceeds the center,thereby exacerbating tensile stress induced by temperature gradients and leading to an underestimation of subsequent cracking risks.
mass concreteconcrete shrinkagenumerical modelcracking risktemperature stressinfluence factor
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