TY - JOUR A1 - Correia, A.M. A1 - Rodrigues, J.P.C. A1 - Korzen, Manfred T1 - Experimental research on the load-bearing capacity of partially encased steel columns under fire conditons N2 - The composite steel and concrete columns are known to have enhanced fire behaviour when compared with bare steel columns. However there are still aspects that must be clarified, as the influence of the building surrounding structure on the fire resistance of the columns. In this paper, the results of fire resistance tests on partially encased steel columns carried out with two different experimental systems are compared. In one of the experimental systems, the building surrounding structure is materialised by a steel restraining frame, and in the other is performed by the so-called substructuring method. Due to the concept of hybrid substructuring, the entire building is decomposed in two parts: one is represented by the building element under test, whereas the remaining building is simulated numerically in a computer. The main conclusion drawn from this work was that the surrounding structure has a major influence in the development of axial forces in the test columns. Moreover, it was observed that the higher the non-dimensional axial restraint ratio the lower the critical time of the columns. KW - Fire resistance KW - Thermal restraint KW - Composite steel-concrete columns KW - Substructuring method KW - Restraining frame PY - 2012 DO - https://doi.org/10.1260/2040-2317.3.1.81 SN - 2040-2317 VL - 3 IS - 1 SP - 81 EP - 94 PB - Multi-Science Publ. Co. CY - Brentwood AN - OPUS4-25632 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hauswaldt, Sebastian A1 - Korzen, Manfred A1 - Hartmann, S. ED - Fontana, M. ED - Frangi, A. ED - Knobloch, M. T1 - A continuum-mechanical model for FE-simulations of steel constructions in fire N2 - This paper presents a thermoviscoplastic constitutive model within the framework of continuum mechanics for the description of the behavior of structural steel subjected to fire loading. The model is represented through a set of ordinary differential equations and belongs to the class of so-called unified theories which do not separate plastic and creep strains. The material parameters are identified for the structural steel S 235 on the basis of tension and compression tests at constant temperature with varying strain rates and verified against transient creep test with varying temperature. For effective numerical simulations with the finite element program ABAQUS the model is prepared with a stress algorithm and consistent tangent operator. The simulations are compared with experimental data of fire resistance tests on columns. T2 - SIF 2012 - 7th International conference on structures in fire CY - Zurich, Switzerland DA - 06.06.2012 KW - Constitutive equation KW - Viscoplasticity KW - Endochronic plasticity KW - UMAT KW - Finite element method KW - Fire resistance PY - 2012 DO - https://doi.org/10.3929/ethz-a-007050197 SP - 439 EP - 448 CY - Zurich, Switzerland AN - OPUS4-26108 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -