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Projects / Programmes source: ARIS

Explosive spalling and resistance of reinforced concrete structures under severe conditions in fire

Research activity

Code Science Field Subfield
2.01.03  Engineering sciences and technologies  Civil engineering  Constructions in civil engineering 

Code Science Field
T230  Technological sciences  Building construction 

Code Science Field
2.01  Engineering and Technology  Civil engineering 
Keywords
natural disasters, fire resistance, spalling of concrete, reinforced and prestressed concrete structures
Evaluation (rules)
source: COBISS
Researchers (10)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  33102  PhD Urška Bajc  Civil engineering  Junior researcher  2014  21 
2.  20157  PhD Bojan Čas  Civil engineering  Researcher  2011 - 2014  152 
3.  33293  PhD Jerneja Češarek Kolšek  Civil engineering  Researcher  2012 - 2013  67 
4.  25423  PhD Tomaž Hozjan  Civil engineering  Researcher  2011 - 2014  301 
5.  30509  PhD Anka Ilc  Mechanics  Researcher  2012  13 
6.  21368  PhD Peter Kante  Civil engineering  Researcher  2011 - 2014  47 
7.  14507  PhD Igor Planinc  Civil engineering  Researcher  2011 - 2014  379 
8.  28380  PhD Urban Rodman  Civil engineering  Researcher  2011 - 2012  23 
9.  02189  PhD Miran Saje  Civil engineering  Head  2011 - 2014  484 
10.  27673  PhD Eva Zupan  Mechanics  Researcher  2011  56 
Organisations (3)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0792  University of Ljubljana, Faculty of Civil and Geodetic Engineering  Ljubljana  1626981  26,390 
2.  7002  Družba za avtoceste v Republiki Sloveniji d.d. (Slovene)  Celje  5814251 
3.  7947  ELEA iC design and consulting d.o.o.  Ljubljana  5522749  166 
Abstract
Explosive spalling of concrete is a violent phenomenon in all kinds of reinforced concrete structures. Recent catastrophic fires in tunnels of Mont Blanc, Tauern and St. Gothard are some examples of the impact of such unpredictable natural disasters and especially the explosive spalling of concrete structures to the safety of people, as well as the ecological degradation of the environment. That is why it is of an utmost importance to understand this phenomenon and its influence to the safety of buildings. As reported by many researchers, the understanding of the phenomenon of explosive spalling of concrete during fire is still humble. In the scientific literature, two main hypotheses explaining spalling can be found: it occurs due to increased pore pressures or due to a restrained thermal dilatation. The enhanced capability of computers now encourages the development of sophisticated mathematical models. Most authors are working on the chemical, hydrological, thermal and mechanical background to explain the phenomenon of explosive spalling, while only a minority is studying the structural effects on reinforced concrete structures. Modelling can be divided into two separate phases. In the first phase, combustion and heat transfer with convection and radiation during fire is modelled to determine the time and space distribution of the temperature in the fire compartment. Based on the first phase, the impact of fire on concrete structure is determined in the second phase. However, the second phase is also very demanding, as the concrete is porous composite material, where the pores are filled with liquid water, vapour and dry air. The second phase thus needs to be modelled as a coupled thermal, hydrological, chemical and mechanical process, as a necessary basis for the assessment of exposure to explosive spalling. Note that the mathematical models for spalling have not yet been developed in sufficient detail. We wish to introduce a new two-phase numerical model for the fire analysis of all kinds of reinforced concrete structures subject to explosive spalling. In the first phase we will, considering different fire scenarios, using available research and commercial computer programs, determine the time and space distribution of the temperature in the fire compartment. We will focus on the second phase, where we wish to extend the existing coupled model of heat and moisture transfer to geometrically non-linear reinforced and prestressed concrete structures. On the basis of the proposed scenario of spalling of concrete, we will determine the behaviour of reinforced concrete structures as the chemical, hydrological, thermal and mechanical coupled problem. We will assess the complexity of the numerical model and the relationship between the essential material and geometric parameters that influence the onset of explosive spalling of concrete during fire. Our model will hopefully provide better understanding of the evolution and the process of explosive spalling of concrete and necessary structural measures to prevent or reduce these effects. The model will serve for the evaluation of the adequacy of various simplified models for fire safety of structures that are now in use in the European technical regulations. We will be able to plan the fire safety and the price adequacy for several extremely important engineering facilities to be built in Republic of Slovenia.
Significance for science
The development and improvement of numerical methods for the fire analysis of reinforced concrete structures and the related phenomenon of explosive spalling is a subject of extensive research, which is easily confirmed by a number of recent papers. The newly started international research projects with similar goals are also indicative that the research in the area of concrete spalling is necessary. With the proposed model, we intend to achieve a better understanding of the evolution and process of explosive spalling of concrete in reinforced concrete structures and to propose the necessary structural measures to prevent or reduce the effects of explosive spalling on concrete structures, while allowing us to determine the starting point for designing more specific and targeted experiments to further and deepen understanding of this phenomenon. The developed numerical model for analyzing the effect of spalling of concrete on the safety of all types of reinforced concrete structures will also be able to evaluate the adequacy of various simplified models of the fire safety of structures that are now in use in the European technical regulations (CEN EN 1992-1-2:2005).
Significance for the country
As it is pointed out in the Resolution for the national development and research programme 2006–2013, it is a priority to use research resources to assist Slovenian economy. Since this is one of the main goals of the proposed research, we feel that this condition is fully satisfied. The Republic of Slovenia is planning a re-assessment of fire safety in tunnels at highways, the construction of the railway network with tunnels and the re-construction of the thermal power plant Šoštanj as well of the nuclear power plant Krško. With the numerical model in hand, we will be able to design the fire safety more reliably and economically. One of the parallel goals of this project is to enhance the knowledge of engineering students and engineers in practice of fire phenomena, in particular about the fire resistance of structures. The project enables the strengthening of the international ties with other similar institutions in Europe and it enables increasing flow of knowledge, expertises and competences into industrial enterprises.
Most important scientific results Annual report 2011, 2012, 2013, final report, complete report on dLib.si
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