Rust i stålkonstruksjoner i bygg

Mohammad Ali Mahdavipour fra Fakultet for teknologi og realfag ved UiA disputerer for ph.d.-graden med avhandlingen «Failure prediction of steel components under the coupled effect of excessive plastic deformations and pitting corrosion» mandag 23 mai 2022.

Han har fulgt doktorgradsprogrammet ved Fakultet for teknologi og realfag ved UiA, med spesialisering i ingeniørvitenskap, forskningsområde bygg.

Slik oppsummerer Mohammad Ali Mahdavipour selv avhandlingen:

Failure prediction of steel components under the coupled effect of excessive plastic deformations and pitting corrosion

Nowadays, modern computers have made advanced computational resources accessible to analysts engaged in the field of structural engineering.

Through these advancements, the role of numerical modeling has increasingly become more significant in both research and engineering projects.

In addition, improved testing facilities and measuring instruments like digital image correlation (DIC) have made material testing more informative than before, and engineers can calibrate more complicated material models to simulate complex phenomena such as plasticity and fracture.

Testing and modeling

All developed testing and numerical modeling techniques come together to form a numerical failure assessment framework for steel structures.

Due to the distinct advantages of numerical modeling over full-scale testing, this framework is well-developed in many applications (e.g., elastic analyses).

However, in many other applications, numerous involved phenomena and their interactions with each other, as well as additional factors (e.g., corrosion), call for more development both in material testing and numerical techniques to customize the framework to better suit the final application.

An alternative approach

This thesis has focused on the failure assessment of steel components under the coupled effect of extensive plasticity and pitting corrosion. A framework was developed based on experimental material calibration and stochastic numerical modeling approaches.

To establish the assessment framework, this thesis has investigated material scale by proposing and validating an alternative approach to calibrate ductile fracture criterion based on the DIC technique.

The proposed method makes calibration feasible for welding and heat-affected zones and mitigates the inaccuracies typically associated with the common calibration process.

Corrosion uncertainties

In addition, the failure of practical steel members with pitting corrosion under excessive plastic deformations was predicted on the component scale by considering the pitting corrosion uncertainties. For this purpose, the corrosion uncertainties were explicitly involved in developing the concept of fracture-based fragility curves at the component level.

In this connection, a mesh carving technique with distinct features was introduced and validated to implement the random pitting morphologies into numerical models.

The proposed fragility curves resulting from the failure assessment framework can address the effect of pitting corrosion in terms of the probability of failure, which is an important parameter for the risk-based corrosion management in steel structures located in corrosive environments.

Furthermore, the localized material behavior due to pitting corrosion was efficiently linked to component scales.

For this purpose, relevant challenges and proper solutions were discussed in terms of applying the micromechanics-based modeling to a large-scale and complicated geometry, e.g., a steel beam-to-column joint.

In this connection, two-level numerical modeling was proposed as a solution to reduce the complexity of the problem for a practical structural application.

A development path

In general, this thesis provides a developmental path from a material to a component scale to establish a failure assessment framework and to push different aspects of it towards the final application that is predicting the effect of pitting corrosion in steel structures under extreme loads.

Based on the outcomes of such a framework, decision-makers can utilize risk management methods and assess the most critical scenarios in terms of principal criteria, e.g., health and safety, economy, and environment, and accordingly update protection and retrofit plans to extend the lifetime of steel structures.

Opponent ex auditorio:

Disputasleder inviterer til spørsmål ex auditorio i innledningen i disputasen. Tidsfrist for å stille spørsmål er senest i løpet av pausen mellom opponentene. Den som stiller spørsmål bør ha lest avhandlingen. Kontaktpersonens e-post er tilgjengelig i chat-funksjonen under disputasen, og spørsmål ex auditorio kan sendes til Kristine Evensen Reinfjord på e-post kristine.reinfjord@uia.no

Disputasfakta:

Prøveforelesning og disputas finner sted i Auditorium C2 40, Campus Grimstad og digitalt i konferanseprogrammet Zoom (lenke under).

Disputasen blir ledet av visedekan Rein Terje Thorstensen, Fakultet for teknologi og realfag, Universitetet i Agder.

Prøveforelesning mandag 23 mai kl 10:15

Disputas mandag 23 mai kl 12:15

 

Oppgitt emne for prøveforelesning: «Design of steel structures in a sustainable future»

Tittel på avhandling: «Failure prediction of steel components under the coupled effect of excessive plastic deformations and pitting corrosion»

Søk etter avhandlingen i AURA - Agder University Research Archive, som er et digitalt arkiv for vitenskapelige artikler, avhandlinger og masteroppgaver fra ansatte og studenter ved Universitetet i Agder. AURA blir jevnlig oppdatert.

Avhandlingen er tilgjengelig her:

https://uia.brage.unit.no/uia-xmlui/handle/11250/2994239

Hvis lenken ikke virker kan du lese avhandlingen som pdf:

PHD_Thesis_Mohammad_Ali_Mahdavipour_print

 

Kandidaten: Mohammad Ali Mahdavipour (1986, Shahrbabak, Iran) B.Sc. Civil Engineering, Yazd University (2010) M.Sc. Structural Engineering (Amirkabir University of Technology (2013).

Opponenter:

Førsteopponent: Professor Arild Holm Clausen, NTNU - Norges teknisk-naturvitenskapelige universitet

Annenopponent: Head of Sub-Department, Dr.-Ing. Till Clausmeyer, Technische Universität Dortmund, Tyskland

Bedømmelseskomitéen er ledet av førsteamanuensis Martin Choux, Universitetet i Agder

Veiledere i doktorgradsarbeidet var førsteamanuensis Dmitry Vysochinskiy, Universitetet i Agder (hovedveileder) og førsteamanuensis Zhiyu Jiang, Universitetet i Agder (medveileder)