Projects / Programmes
January 1, 2015
- December 31, 2018
| Code |
Science |
Field |
Subfield |
| 2.01.00 |
Engineering sciences and technologies |
Civil engineering |
|
| 2.05.00 |
Engineering sciences and technologies |
Mechanics |
|
| Code |
Science |
Field |
| T230 |
Technological sciences |
Building construction |
| Code |
Science |
Field |
| 2.01 |
Engineering and Technology |
Civil engineering |
Geometrically exact beams; composite beams; concrete structures; effect of fire on structures; effect of wind on structures; reliability of structures; technology problems in concrete and timber; numerical formulations; statistical methods; dynaimics; high temperatures; ultrasonics
Researchers (19)
Organisations (1)
Abstract
The programme consists of the development of theoretical concepts and new numerical tools as well as their adaptation to solving particular problems in structural engineering. The tools to be investigated include: static and dynamic numerical formulations for the analysis of geometrically exact spatial frames; non-linear numerical formulations of composite spatial beams; numerical formulations for the spatial structures subject to fire;
numeric formulations of moister, vapour, air and temperature transfer in porous media;
numerical formulations for the stress and strain evolution in hardening concrete; formulations to identify the burja wind statistical parameters; and the development of ultrasonics methods in determining characteristics of hardening concrete/asphalt. The tools will be applied in various structural engineering problems like: the behaviour of spatial concrete and steel frames in fire; the application of external steel plates in reinforcing existent bridge constructions; dynamic and static analysis of electric transmission lines including the simulation of the erection process and sleet loads; bearing capacity and ductility of the fibre-reinforced concrete; the effect of fire followed by an explosion on steel structures; searching for a controlled heating of an optimal concrete hardening; performing systematic reliability studies of reinforced concrete frames with stochastic fire load parameters.
Significance for science
• The achievements of the research group regarding new numerical formulations of geometrically exact beams are now very well recognized and well cited in international community. There are 6 formulations of ours. The first one (Jelenić & Saje 1995) uses PVW in conjunction with the variation of rotational vector interpolation; the second one makes only bending strains with respect to the fixed coordinate system to be interpolated (Zupan & Saje 2003); the third one is a pure strain-based formulation using the collocation method where the consistency condition is satisfied in a strong way (Zupan & Saje 2003); the fourth formulation is the collocation-quaternion-based one, where the displacements and quaternions are interpolated (Zupan E., Zupan & Saje 2009); the fifth formulation is the strain-based but specific in having constant strain interpolation (Češarek, Zupan & Saje 2012); the sixth formulation again employs quaternions, yet this time they are combined with the PVW (E. Zupan, Saje & Zupan 2013). Some of the above formulations are also extended to dynamics (2012-2013) and/or non-linear materials like steel, concrete and reinforced concrete.
•The majority of citations of the present research programme come from our research in composite structures. For example, in their paper on composite structures, some Chinese authors cited 5 our papers (from 26 references given there); in another paper by the USA authors, the ratio is 7/34. There are 9 papers in which we propose the foundations of the geometrically and materially linear and non-linear theories of layered structures, where tangent slip as well as normal uplift are considered and presented in Steel & Compos. Struct. 2004, Comput. & Struct. 2004, 2011, 2013, J. Struct. Eng. 2007, Struct. Eng. & Mech. 2006, 2010, and Eng. Struct. 2010. The theories have extensively been applied in stability analyses of composite columns at room temperature and in fire. Some studies were focused also on stability of partially delaminated spatial beams. The results of such analyses were presented in the subsequent 9 journal papers. One of the papers, namely “The influence of boundary conditions and axial deformability on buckling behaviour of two-layer composite columns with interlayer slip” (Schnabl & Planinc, Eng. Struct. 2010) was commented by the anonymous reviewer as "The reviewer would like to remark that this paper is the best he has reviewed since long time, and of great importance for researchers working in the field of composite structural members with interlayer slip".
• The fire analysis has become very popular recently. During the last 10 years or so we have proposed various numerical formulations for estimating behaviour of concrete, steel and timber structures in fire. We have developed some sophisticated numerical tools for thermal and mechanical analyses, and performed parametric analyses to assess and understand the response of particular structures in fire. The transport of moisture, vapour and air in concrete (or timber) during fire is modelled as a coupled non-stationary process. The temperature and pressure fields were taken as applied internal loads in the subsequent mechanical calculations. The mechanical model assumes the geometrically non-linear beam where the criterion of the local critical state and the subsequent strain localization are described in the paper “On strain softening in finite element analysis of RC planar frames subjected to fire” (Markovič, Saje, Planinc & Bratina, Eng. Struct. 2012).
• One of our best achievements is the invention of the ultrasonic apparatus in conjunction with the artificial neuron networks for predicting concrete strength and the onset of concrete hardening, presented in seven papers in top journals. We only mention one of them, “Prediction of concrete strength using ultrasonic pulse velocity and artificial neural networks” (Trtnik, Kavčič & Turk, Ultrasonics 2009).
Significance for the country
Many commercial computer programmes for the structural analysis are available and one may get an impression that further new software in engineering mechanics would be superfluous. Life does not prove that. A part of the problem seems to be an insufficient theoretical knowledge that engineers presently have, which is probably due to inappropriate university curricula in Slovenia. The limited possibilities of solving practical problems, if using commercial programmes, appear when non-linear analyses of structures subject to non-standard loads (like collision of two structures, the response to an earthquake or wind, structural behaviour in fire, effects of fluids on structures) must be performed, or searching for the reasons for collapse and identifying non-linear parameters of a structure, is carried out. These examples require accurate and reliable numerical formulations adapted to the speciality of the problem, and the use of the non-commercial programmes gets sense. This is exactly the case here, where slip and localization issues in fire analyses must be well accounted for. One particularly important type of structure that is vulnerable to fire is the highway tunnel structure, where the prediction of its mechanical safety to fire must be highly accurate and strictly conservative.
• Concrete plays a very important role in construction engineering. Here the technology of placing large concrete volumes (like in concrete water dams or bridge column foundations) or of prefabricated concrete elements must be designed such to increase the quality of the product and the decrease of its price. Such a technology requires the knowledge of the behaviour of concrete during early hardening stage. The ultrasonic methods of measuring being a part of the programme definitely help to meet these goals.
• In terms of the relative forest cover, Slovenia is one of the first countries in the European Union. It is almost unbelievable that the use of timber in construction is relatively limited. In the view of sustainable development which has to be one of the Slovenian priorities, the use of timber as a structural material is important. The results of this research will increase the added value to the timber as building material. At the moment the timber obtained from Slovenian forests are exported into other countries where are properly graded and labelled and imported back to Slovenia as a graded and labelled structural timber at a considerably higher price. We strongly believe that Slovenian industry should be capable to perform grading and labelling of its own and if necessary imported timber. Therefore, the activities of the group regarding the timber strength grading have a very important economical impact.
Most important scientific results
Annual report
2015,
2016,
2017,
final report
Most important socioeconomically and culturally relevant results
Annual report
2015,
2016,
2017,
final report
