含粗骨料的钢管超高性能混凝土高温劣化机理与细观数值模拟方法

含粗骨料的钢管超高性能混凝土（CA-UHPCFST）承载力高、造价较低、避免超高性能混凝土高温易爆裂难题，是一种具有广泛应用前景的高性能结构形式。而材料/结构的高温劣化是结构抗火设计的核心问题。本项目拟从材料和构件两个层面对其高温劣化机理与细观数值模拟方法进行深入研究，具体包括：1）对高温作用下含粗骨料的超高性能混凝土（CA-UHPC）的宏观热力学性能进行研究，提出高温热工参数和力学参数的取值方法；2）对不同高温条件和荷载作用后的CA-UHPC孔隙结构和微观形貌等进行试验，研究宏观热力学参数与细观结构演化之间的关系规律，揭示其高温劣化机理；3）建立CA-UHPC的双随机细观数值模型和CA-UHPCFST的宏-细观组合热力耦合数值模型；4）基于高温试验研究和宏-细观数值模拟，揭示不同温度条件下钢管对CA-UHPC的约束效应及其高温失效机理。研究成果将为该结构的防火设计和可靠度分析奠定基础。

The ultra-high performance concrete-filled steel tube with coarse aggregates (CA-UHPCFST) possess the characteristics of high bearing capacity, low cost and explosive spalling prevention of UHPC. It is a kind of high performance structure with strong potential in application. However, the core issue of the structural design of fire resistance is the degradation of material/structure at elevated temperatures. The microscopic deterioration mechanism and numerical simulation method of CA-UHPC and CA-UHPCFST are to be intensively studied in the project. The research objectives are: (1) The investigation of thermal and mechanical properties of CA-UHPC at elevated temperatures; (2) The pore structure and micro topography of CA-UHPC under the coupled effect of elevated temperature and loading; (3) Establishment of the double-random numerical model of porosity and aggregates of CA-UHPC, and the coupled thermal-mechanical and macroscopic-microcosmic model of CA-UHPCFST; (4) The confinement effect and failure mechanism of CA-UHPCFST at elevated temperatures based on high temperature experiments and macro-mesoscopic numerical simulations. The research aims at improving the design of fire resistance and reliability analysis for the CA-UHPCFST structures.