Model-Based Assessment of Long-Term Serviceability and Fire Resistance for Underground Reinforced Concrete Ducts

Abstract

The collapse simulation of underground reinforced concrete (RC) ducts surrounded by soil foundations in a fire is conducted using multi-scale finite element analysis. The underground RC ducts are found to be deteriorated by both long-term soil subsidence and creep and shrinkage of concrete. The long-term shear crack risk is clarified by site inspection of some underground RC ducts. To conduct the structural risk assessment, the multi-scale simulation is applied and its performance upgraded to 1000°C. The release of chemically bound water from hardened cement paste is developed in the scheme of micropore structural modelling. It is linked with the mesoscale thermodynamics of vapour and the mechanics of the solid skeleton, and its fracture is integrated with the macroscopic cracked concrete constitutive models. This framework is upgraded to include the spalling of concrete cover in the event of a fire, and the exposure of reinforcing bars to high temperatures during a fire is reproduced. As the moisture dynamics inside the micropores of concrete can be used to determine the creep and shrinkage of concrete, long-term RC deformation can also be consistently taken into account for its normal use.

Keywords:

• multi-scale modelling
• fire
• dehydration
• underground RC duct
• failure mode shift

Disclosure statement

No potential conflict of interest was reported by the authors.