Concrete at high temperatures: hygro-thermo-mechanical degradation of concrete

[摘要] The main aim of the presented work is the development of a reliable and coherent solution approach to investigate thermo-hygro-mechanical behaviour of concrete, especially under severe heating conditions. The work focuses on the development and extension of an existing analytical, numerical and constitutive model developed at the University of Glasgow. This is then used as a predictive modelling tool to investigate the response of concrete structures subject to combined thermo-mechanical loads. The thesis focuses initially on the coupled heat and mass transport model. A novel alternative formulation for sorption isotherms, that is applicable to both normal and high strength concrete, is developed. Furthermore, the effect of the slip flow effect is included and several state equations, including relative permeability and saturation vapour pressure, are adopted. Additionally, the effect of polypropylene fibres as a spalling prevention technique is modelled via a modification of the intrinsic permeability formulation. The transport model is further coupled with a damage-based mechanical model for concrete.The fully coupled thermo-hygro-mechanical model is presented through validation and verification problems and case studies. The model is implemented in a finite element formulation and behaves in a robust manner. The predictions of moisture state for the benchmark problems of drying and heating compare well with experimental results. Classical behaviour associated with heated concrete, such as moisture clog, gas pressure build-up, etc. are all captured by the presented model. The thesis concludes by considering the analysis of prestressed concrete pressure vessel.

[发布机构] University:University of Glasgow;Department:School of Engineering

[关键词] high temperatures, explosive spalling, fire conditions, coupled processes, polypropylene fibres, high-strength concrete,