10.19: The steel and fibre‐reinforced concrete circular hollow section composite column exposed to fire

Abstract

The recent development in technology of production and transport of the steel fibre-reinforced concrete enables its utilization in composite steel-concrete structures. This work is focused on development of mechanical behaviour and design model of circular hollow section (CHS) composite steel and fibre-concrete (SFRC) column at elevated temperature. Research includes two levels accuracy/complexity, allowing simplified or advanced approach to design following the coming changes in European standard for composite member design in fire (EN1994-1-2:2005) [1]. Experimental studies of the project include mechanical tests of heated fibre-concrete samples in tension and compression, thermal behaviour under uniform and nonuniform loading of stubs of CHS and tests of full scale SFRC CHS columns in steady-state and transient-state regimes. Developing advanced finite element method (FEM) simulation of global mechanical behaviour of SFRC CHS columns is a multi-levelled composite mechanical and thermo-model and provide numerous numerical experiments. Together with standard steel material model in fire, FEM model of mechanical behaviour of fibre-reinforce concrete at elevated temperature is prepared. Validated simplified and advanced thermal model of SFRC CHS at elevated temperature gives temperature fields and moisture distribution inside section which depends on direction, heat flux, sizes and gives possibility to model different fire cases of full-scale columns in bending and buckling at elevated temperature. Prepared analytical and simplified FEM mechanical model of column is taking in account degradation of mechanical properties, analytical models of transfer of heat inside column section and provides simplified solutions for designers.