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Keywords: fire analysis, FEM, reinforced concrete structures, fracture, damage, civil engineering practice.

Summary

Concrete behaviour at high temperatures represents a complex phenomenon that in general case requires a coupled hygro-thermo-chemo-mechanical model. An example of an advanced hygro-thermo-mechanical model is presented by Gawin [1]. This paper presents a modification of the combined fracture-plastic model developed by the authors and initially presented in Cervenka [2,3].

The extended model is applied for the analysis of structures subjected to fire, where the material properties of concrete as well as the properties of the reinforcement are strongly dependent on temperature. The objective was to develop a model that can be applied to large-scale analyses of engineering problems at a reasonable computational cost.

A staggered solution scheme is adopted. This means that the analysis consists of two steps. First, a transport analysis is executed to compute hygro-thermal conditions within the structure. These are then utilised in a subsequent usual static analysis. The two step approach significantly simplifies the analysis and the incurred inaccuracy typically remains at an acceptable level.

The presented work is an extension of a previously published thermally dependent model by Cervenka [4]. The paper presents new results and an application to a real tunnel scenario. The temperature distribution inside a heated structure is calculated by a separate non-linear transient thermal analysis. The obtained temperature fields are then applied in a mechanical analysis, which takes into account the thermally induced strains as well as the material degradation induced by high temperatures.

The model was developed during the European research project UPTUN GRID-CT-2002-00766. The model behaviour is tested on a few sample analyses such as uni-axial tensile and compression tests as well as test on the experimental data of a real scale fire experiment of a tunnel suspended ceiling.

The temperature dependent mechanical model is implemented in the program ATENA [5]. This program was also used to analyse the examples presented in this paper.

References

1: Gawin D., Pesavento F., Schrefler B.A., "Modelling of hygro-thermal behaviour of concrete at high temperature with thermo-mechanical and mechanical material degradation", CMAME, 192, 1731-1771, 2003. doi:10.1016/S0045-7825(03)00200-7
2: Cervenka J., Cervenka V., Eligehausen R, "Fracture-Plastic Material Model for Concrete, Application to Analysis of Powder Actuated Anchors", FRAMCOS 3, 1107-1116, 1998.
3: Cervenka J., Papanikolaou V.K., "Three dimensional combined fracture-plastic material model for concrete", Int. J. Plasticity, doi:10.1016/j.ijplas.2008.01.004, 2008. doi:10.1016/j.ijplas.2008.01.004
4: Cervenka J., Surovec J., Kabele P., "Modelling of reinforced concrete structures subjected to fire", Proc. EuroC-2006, ISBN 0415397499, 515-522, 2006.
5: ATENA Program Documentation, Cervenka Consulting, Prague, Czech Republic, 2005.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 88 PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping and M. Papadrakakis Paper 226 Modelling of Concrete Fracture and Damage Due to High Temperatures J. Cervenka¹, L. Jendele¹ and J. Surovec² ¹Cervenka Consulting, Prague, Czech Republic ²Faculty of Civil Engineering, Czech Technical University, Prague, Czech Republic doi:10.4203/ccp.88.226 purchase the full-text of this paper Full Bibliographic Reference for this paper J. Cervenka, L. Jendele, J. Surovec, "Modelling of Concrete Fracture and Damage Due to High Temperatures", in B.H.V. Topping, M. Papadrakakis, (Editors), "Proceedings of the Ninth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 226, 2008. doi:10.4203/ccp.88.226 Keywords: fire analysis, FEM, reinforced concrete structures, fracture, damage, civil engineering practice. Summary Concrete behaviour at high temperatures represents a complex phenomenon that in general case requires a coupled hygro-thermo-chemo-mechanical model. An example of an advanced hygro-thermo-mechanical model is presented by Gawin [1]. This paper presents a modification of the combined fracture-plastic model developed by the authors and initially presented in Cervenka [2,3]. The extended model is applied for the analysis of structures subjected to fire, where the material properties of concrete as well as the properties of the reinforcement are strongly dependent on temperature. The objective was to develop a model that can be applied to large-scale analyses of engineering problems at a reasonable computational cost. A staggered solution scheme is adopted. This means that the analysis consists of two steps. First, a transport analysis is executed to compute hygro-thermal conditions within the structure. These are then utilised in a subsequent usual static analysis. The two step approach significantly simplifies the analysis and the incurred inaccuracy typically remains at an acceptable level. The presented work is an extension of a previously published thermally dependent model by Cervenka [4]. The paper presents new results and an application to a real tunnel scenario. The temperature distribution inside a heated structure is calculated by a separate non-linear transient thermal analysis. The obtained temperature fields are then applied in a mechanical analysis, which takes into account the thermally induced strains as well as the material degradation induced by high temperatures. The model was developed during the European research project UPTUN GRID-CT-2002-00766. The model behaviour is tested on a few sample analyses such as uni-axial tensile and compression tests as well as test on the experimental data of a real scale fire experiment of a tunnel suspended ceiling. The temperature dependent mechanical model is implemented in the program ATENA [5]. This program was also used to analyse the examples presented in this paper. References 1 Gawin D., Pesavento F., Schrefler B.A., "Modelling of hygro-thermal behaviour of concrete at high temperature with thermo-mechanical and mechanical material degradation", CMAME, 192, 1731-1771, 2003. doi:10.1016/S0045-7825(03)00200-7 2 Cervenka J., Cervenka V., Eligehausen R, "Fracture-Plastic Material Model for Concrete, Application to Analysis of Powder Actuated Anchors", FRAMCOS 3, 1107-1116, 1998. 3 Cervenka J., Papanikolaou V.K., "Three dimensional combined fracture-plastic material model for concrete", Int. J. Plasticity, doi:10.1016/j.ijplas.2008.01.004, 2008. doi:10.1016/j.ijplas.2008.01.004 4 Cervenka J., Surovec J., Kabele P., "Modelling of reinforced concrete structures subjected to fire", Proc. EuroC-2006, ISBN 0415397499, 515-522, 2006. 5 ATENA Program Documentation, Cervenka Consulting, Prague, Czech Republic, 2005. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £145 +P&P)
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