Reliability of structures exposed to traffic loads and environmental loading

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 of ESR2 (long-term monitoring through fibre optics) will be used to extrapolate extreme effects through real measurements. Links to ESR4 (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.

Host institution

IFSTTAR - Marne-la-Vallée, France

ESR6

Mariia Nesterova

Local academic supervisor

Dr Franziska Schmidt (IFSTTAR)
franziska.schmidt(at)ifsttar.fr
Tel: +33 (0)1 81 66 83 44  

Industrial co-supervisor

Prof. Henrik Niedermayer (COWI)
hkn(at)cowi.dk
Tel: +45 56 40 21 35  

PhD enrolment

Paris Est University (Graduate school: MSTIC)
PhD Director: Prof. Christian Soize

Start date: 1st November 2016
Duration: 36 months

Synopsis

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? 

Objectives

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 done on a close subject, in the same laboratory  https://tel.archives-ouvertes.fr/tel-00862408/document
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.

Tasks and methodology

  • 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.

Results

The results will methodologies for best assessment of extreme actions on structures and assessment of extreme effects on structures.

Dissemination

  • 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.

Secondments

  • EPFL (Lausanne, Switzerland)
    August & September 2017
  • AAU (Aalborg, Denmark)
    November, December 2019 & January 2019

Research field

Applied mathematics, civil engineering.

Keywords

Extreme actions, extreme value theory, bridges, wind turbines, traffic loads, wind loads.

Key publications

  • PhD work on extreme effects of traffoc loads on bridges: https://tel.archives-ouvertes.fr/tel-00862408/document
  • Eugene J. OBrien, Franziska Schmidt, Donya Hajializadeh, Xiao Yi Zhou, Bernard Enright, Colin C. Caprani, S. Wilson, Emma Sheils 2015, A Review of Probabilistic Methods of Assessment of Load Effects in Bridges, Structural Safety, 53, 44-56
  • EN 1991, Eurocode 1: Actions on structures