Johan Maljaars

Research area

Many existing structures such as bridges and wind turbines should be safe in use, meaning that degradation should remain within allowable limits and that structures have the possibility to redistribute forces in case of a local failure or overload. Monitoring of structures may aid in assessing the current state of the structure. The trick is to combine monitoring data with physical based models to predict the safety and the end of life.

My research expertise and interests are in fatigue and fracture, structural performance, and fire resistance of steel and aluminium structures. I work on the development and improvement of response and degradation models and on enriching these models with data from monitoring and measurement campaigns.

In application areas such as bridges, wind turbines and offshore structures, I aim to enhance a longer and safe use of these structures as compared to the current state-of-the-art. In this respect, my research objectives closely fit with the TNO goals set in the roadmaps of infrastructures, off shore, and energy.

Recent results

My PhD students and I have established a reliability framework for fatigue of bridges, which allows to determine the safety margins for fatigue failure of any bridge. We used it in deriving the safety factors that all structural engineers in Europe apply in the design of new and in the assessment of existing infrastructures. The framework also allows to quantify the updated safety by using results from periodic or unique inspections.

I have developed software that accurately mimics the load effect induced by the crossing of vehicles over a bridge. This software is applied in the assessment of large bridges in The Netherlands, and it is used to develop a new, simplified load model that structural engineers can use to design or asses structures, with substantial improvement of the accuracy as compared to the current state-of-the-art.

Further, I have developed numerical tools that allow for determining the influence of the material alloy on the deformation capacity of joints. More specific, we are able to accurately predict the onset and development of buckling and crack forming.

PhD supervision

• Fatigue assessment of welds with large imperfections in existing bridges (3 PhD-s) (Funding source Ministry of Economic Affairs, Rijkswaterstaat and ProRail. In collaboration with M2i)
• Crack growth rate and critical defect of squat defects in rails (1PhD) (Funding source Ministry of Economic Affairs and ProRail. In collaboration with M2i)
• Multi-scale modelling of sandwich panels exposed to fire (1PhD) (Funding source CRC)
• AI aided visual inspection of steel bridges (1 PhD) (Funding source EASI)

Top publications

• Maljaars J., M. Euler, "Fatigue SN curves of bolts and bolted connections for application in civil engineering structures", International Journal of Fatigue, 151 (2021): 106355.
• Maljaars J. “Evaluation of traffic load models for fatigue verification of European road bridges”, Engineering Structures 225 (2020); 111326.
• Maljaars J., D. Leonetti, C. Maas, “Fatigue life prediction of hot riveted double covered butt joints”, International Journal of Fatigue, 124, 99-112, 2019
• Maljaars J., E. Bonet, R.J.M. Pijpers, “Fatigue resistance of the deck plate in steel orthotropic deck structures”, Engineering Fracture Mechanics, 201, 214-228, 2018
• Leonetti D., J. Maljaars, H.H. Snijder, “Fitting fatigue test data with a novel S-N curve using frequentist and Bayesian inference”, International Journal of Fatigue , 105, 128-143, 2017