粗骨料超高性能混凝土高温热工参数细观模拟与离散性分析OA北大核心CSTPCD

The thermal parameters of coarse aggregate ultra-high performance concrete(CA-UHPC)at high temperatures are critical for the fire resistance design of such structures,with the discreteness of these properties being a key factor in the variability of component-level fire resistance.To investigate the patterns and discretenessin CA-UHPC's thermal properties under high temperatures,a mesoscale geometric model incorporating random distributions of steel fibers and aggregates was developed,using a porosity random field to represent mortar heterogeneity.This led to a model considering both inclusions and mortar randomness.High-temperature thermal properties of the matrix were linked to porosity,assigning appropriate thermal properties to each component,thus creating a dual-random mesoscopic heat transfer model.The finite element method was then used to compute the thermal properties of CA-UHPC at high temperatures,examining the impact of variations in component properties on thermal properties'values and variability.Findings indicate that the dual-random mesoscopic model more accurately reflects CA-UHPC's heterogeneity and the dispersion of macroscopic thermal properties caused by mortar heterogeneity.When the content of each phase component is consistent,the spatial random distribution of both inclusions and mortar porosity significantly affects CA-UHPC's macroscopic thermal conductivity,with less impact on macroscopic density and specific heat.Employing a random method that accounts for the randomness in the content of each phase component in sample blocks allows for a reasonable simulation of the dispersion in macroscopic density and specific heat of CA-UHPC blocks.