Civil Engineering Research Seminar: Risk assessment of steel bridges under the influence of changing environmental conditions

When?

Thursday 14 June 2012, 13:00 to 14:00

Where?

40 AA 03

Open to:

Students, Staff

Speaker:

Alexandros Kallias

Admission price:

No charge

Abstract:

Corrosion is a commonly observed deterioration mechanism in metallic bridges, resulting in loss of material with time, which may lead to impaired performance and premature in-service failures. A number of factors are known to influence the initiation and subsequent rate of corrosion in metallic bridges, including climatic parameters such as relative humidity and temperature, atmospheric pollutants (e.g. SO2) and high airborne salinity. On the other hand, pier scour in bridges over water is a leading cause of catastrophic bridge failures and it is characterised by the absence of warning signs (i.e. sudden failure).

Alterations of the exposure conditions, for instance due to climate change or/and adoption of government policies related to the levels of atmospheric pollutants, are likely to influence the long-term corrosion rates and scour performance of metallic bridges.

Both deterioration processes (corrosion and scour) are associated with large uncertainties due to the variability in the factors which determine the exposure conditions. Reliability analysis is considered as a suitable means of dealing with these uncertainties, since the influence of changing environmental conditions on the long-term structural bridge performance can be quantified on a rational basis.  

This study presents a methodology, based on reliability analysis, for the time-dependent risk assessment of corroding metallic railway bridges, considering the impact of long-term changes in climatic and atmospheric pollutant variables. The evolution of variables related to the deterioration process (e.g. climatic parameters, atmospheric pollutants, etc) and bridge resistance variables are treated as random using suitable distributions. The time evolution of the probability of failure of the bridge is quantified through Monte Carlo simulation and this is then extended into risk by considering the consequences of bridge failure. The procedure is demonstrated through a case study using a steel railway bridge. Results are presented for the moment-capacity and scour limit states of the bridge, considering a number of emission scenarios based on UKCP09 climate projections and assumed changes in the concentrations of atmospheric pollutants.

Bio: BEng, MSc in Structural Engineering and PhD from the University of Surrey. Alexandros works as a research fellow with Dr. B. Imam, on the long-term performance assessment of metallic railway bridges.