Advanced numerical analysis as a tool for the research and design of unconventional steel structures
Event details
| Date | 21.10.2016 |
| Hour | 12:15 › 13:15 |
| Speaker | Prof. Dr Charis J. Gantes, Institute of Steel Structures – School of Civil Engineering – National Technical University of Athens, Greece |
| Location | |
| Category | Conferences - Seminars |
Abstract : Numerical calculation of the ultimate strength of unconventional steel structures by means of the nonlinear finite element method will be presented. In modern codes checks in the ultimate limit state are commonly carried out by comparing action effects obtained from linear elastic analyses with corresponding resistances given from formulas that account indirectly for geometric and material nonlinearity as well as imperfections. Thus, prediction of collapse, which is a strongly nonlinear phenomenon, is possible by performing linear analyses, using simple software that is readily available and sufficiently reliable for ordinary structural systems. Alternatively, prediction of ultimate strength via nonlinear numerical analyses is also permitted by modern codes. This method is recommended for complex structural systems or members with unusual shapes and irregular cross-sections, as such cases are not covered by available buckling curves and interaction equations. This can only be accomplished successfully if engineers posses the necessary theoretical background, so that that they can set-up realistic numerical models, select appropriate solution algorithms and parameters and are able to interpret correctly the results.
Along these lines, in the first part of the present lecture fundamental concepts of nonlinear structural behavior will be briefly reviewed. Numerical tools for understanding the behavior, predicting all possible failure modes and evaluating the ultimate capacity of steel structures using commercially available software will then be presented. Failure dominated by either material yielding or instability will be addressed, as well as interaction of failure modes. Steps of the proposed methodology include setting up an appropriate finite element model, obtaining critical buckling modes from linearized buckling analysis (LBA), and then using a linear combination of these modes as imperfection pattern for a geometrically and material nonlinear imperfection analysis (GMNIA). Equilibrium paths accompanied by snapshots of deformation and stress distribution at characteristic points will be highlighted as a powerful tool for evaluating the results of the GMNI analysis, identifying the dominant failure modes and thus proposing appropriate strengthening measures, if needed.
In the second part of the presentation applications of this approach in research activities will be described, including (i) strengthening of the manhole at the base of wind turbine towers to avoid local buckling, (ii) formulating design rules for laced and battened built-up members used in long-span and/or large height steel hangars and bridges, (iii) studying the buckling behavior of large-diameter industrial steel chimneys.
In the third and final part applications of the above approach in actual engineering projects will be briefly mentioned, including (i) the suspended roof covering the archaeological site of Aristotle’s Lyceum in Athens, (ii) the evaluation of consequences of potential landslides and fault activation on the buried pipeline Kipoi-Alexandroupolis-Komotini, (iii) the steel structures providing temporary support for the deep excavations of Thessaloniki Metro, (iv) the steel structures supporting the cladding of Oval Tower in Limassol.
Bio :
Prof. Charis Gantes, born in Athens, Greece, in 1962, attended the German High school of Athens (Dörpfeld Gymnasium), and then obtained a Civil Engineering Diploma from the National Technical University of Athens (NTUA) in 1985, and a Master’s (1988) and Ph.D. (1991) from the Massachusetts Institute of Technology (MIT). Since 1994 he is faculty member in the Institute of Steel Structures at NTUA, where he is teaching steel structures, structural stability and tension structures.
His current research activity is in the area of structural behavior, analysis and design under extreme loads, including seismic, wind and blast, leading structures to nonlinear response, with emphasis on steel structures. He is author of one book in English, on deployable structures, and three books in Greek, on design of unconventional steel structures, structural stability and tension structures. He is also author of 10 book chapters, 81 peer-reviewed journal papers and 150 conference papers. His research work has received more than 950 citations, excluding self-citations and citations by co-authors. He is Editor-in-Chief of the Journal of the International Association for Shell and Spatial Structures (IASS). He is Member of CEN Project Team SC3/T1 of Part 1-1 of Eurocode 3, which is part of the development of the second generation of Structural Eurocodes.
In addition, he is active in structural design and consulting, having participated in design projects of the steel roofs of three major Greek football stadiums, structures for the 2004 Athens Olympic Games, buried pipelines transporting oil and natural gas, underground structures including tunnels and stations for the Athens subway, transmission towers, guyed towers, wind turbine towers, port, marine, energy and industrial facilities projects, as well as the seismic design of the steel gates for the New Panama Canal.
Practical information
- General public
- Free
Organizer
- Prof. Dr Brice Lecampion & Prof. Dr Katrin Beyer
Contact
- Prof. Dr Dimitrios Lignos