Reliability of structures exposed to traffic loads and environmental loading
Civil engineering structures are subjected to various actions, like traffic loads or climatic actions. The extreme values of these actions are of utmost importance, as they govern the design or the re-assessment of these structures. Moreover, in Eurocode 1, the actions to take into account for the assessment of civil engineering structures (wind, snow, traffic, ..) have been chosen with extrapolation of measured values, for a given value of the return period. So, some questions remain: are these extrapolated values still valid? Are the extrapolation methods that have been used suitable?
The objective is to investigate extreme traffic loads applied on medium and long span bridges over long time periods, and to assess the extreme load effects by extrapolation, taking into account updated heavy vehicle weight distributions; this methodology will also be applied to the natural loading (wind and waves) applied on on-shore and off-shore wind turbines, and the induced load effects and stress cycles useful for damage assessment; the safety margins and reliability indexes (linked to the probability of failure) of these structures (bridges and wind turbines) may then be assessed for extreme load effects and fatigue limit states.
The findings from ESR2's project (long-term monitoring through fibre optics) will be used to extrapolate extreme effects through real measurements. Links to ESR4's project (determination of critical zones to monitor in order to assess the structures) exist, in order to choose accurate locations to assess the extreme effects and fatigue of structures, and to adapt the traditional methods of assessment. Afterwards advanced probabilistic methods and reliability theory tools will be implemented to examine the residual lifetime of existing structures, within the required level of safety, and the real safety level of new structures according to the up-dated actions.
The work will begin with a literature review of the existing mathematical statistical methods that could be used for dealing with this problem. In particular, this literature review will include the PhD work (download) done on a close subject, in the same laboratory.
Then, on real measures of actions (traffic and wind), methods for assessment of extreme values will be applied. The induced reactions by this extreme actions on the structures (bridges or wind turbines) will then be compared to the measured reactions.
By comparison with existing design standards (Eurocodes in Europe, but also standards from the USA or India), conclusions on the load models currently in use can be drawn.
More precisely: The goal of this PhD work is to determinate and to compare the various mathematical statistical methods making it possible to assess the extreme values of anthropic and natural actions, and to determinate if those are suitable for the assessment of extreme actions on structures. In order to achieve that, the focus will be on traffic loads (weigh-in-motion data, gathered on French weigh-in-motion stations over long periods of time) and wind actions (measured in Danemark, by COWI). The considered structures are bridges and wind turbines.
- Identification of best long-term measurements (traffic loads effects, environmental effects).
- Identification and comparison of extrapolation methods for these effects (same behaviour for the structures).
- Comparison with extreme effects obtained through numerical simulation.
- Assessment of uncertainty of the extrapolated extreme value.
- Assessment of divergence between extrapolated extreme value (thus while assuming same linear elastic behaviour) and extreme effects with real behaviour of the structure.
- Conclusions on best methods to obtain extreme effects, anthropic or natural, on structures, conclusions on design of structures.
- The results will methodologies for best assessment of extreme actions on structures and assessment of extreme effects on structures.
- Scientific publications in journals and conferences with domains applied mathematics and civil engineering.
- Technical background for ongoing works in the writing of national and international (European) guides and standards on vulnerability of civil engineering structures to extreme (weather) effects and the mitigation of the damage.
- Zhou X.Y.
Statistical analysis of traffic loads and thier effects on bridges
PhD thesis, 2013
- OBrien E.J., Schmidt F., Hajializadeh D., Zhou X.Y., Enright B., Caprani C.C., Wilson S., Sheils E.
A Review of Probabilistic Methods of Assessment of Load Effects in Bridges Structural Safety, 53, 44-56, 2015
- EN 1991, Eurocode 1: Actions on structures
- Nesterova M., Schmidt F., Brühwiler E., Soize C.
Generalized Pareto Distribution for reliability of bridges exposed to fatigue
IABMAS 2018, 9th International Conference on Bridge Maintenance, Safety and Management, Melbourne, Australia, 9-13 July 2018
Green open access with a 12 months embargo. Download the abstract here
- Nesterova M., Schmidt F., Soize C., Siegert D.
Extreme effects on bridges caused by traffic and wind
CFM 2017, Congrès Français de Mécanique 2017, Lille, France, 28 August - 01 September 2017
- Sawicki B., Brühwiler E., Nesterova M.
Fatigue safety verification of a steel railway bridge using short term monitoring data
IALCCE 2018, The Sixth International Symposium on Life-Cycle Civil Engineering, Ghent, Belgium, 28-31 October 2018
- Nesterova M., Schmidt F., Soize C.
Extreme Values analysis for the combination of traffic and environmental actions on cable-state bridges with orthotropic deck
Submitted to Bridge Structures Journal (2018)
ESR 6: Mariia Nesterova (Ifsttar)
Local academic supervisor: Dr Franziska Schmidt (Ifsttar)
Industrial co-supervisor: COWI
PhD director: Prof. Christian Soize (Paris Est University)