Fabian and Jaakko Ahvenainen Foundation grants awarded for 2022

Fatigue test and performance evaluation of welded joint of bridge weathering steel  

My research aims at developing evaluation methods to predict the fatigue life of details in steel bridges, including parent material and welded joints, based on the concept of theory of critical distance and the application of surface roughness measurement. In addition, calibrated fatigue load model with bridge weigh-in-motion data is also included. This will contribute to a more effective bridge design in terms of fatigue aspects.

Structural behavior of steel-concrete composite beams with expansion joints in the concrete slab
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In my master’s thesis I investigated the structural effects of concrete parapets on the overall strength of bridge structures. In this study the effect of the concrete parapets was examined on steel-concrete composite beams with expansion joints in the concrete slab. Based on experimental test and Finite Elemental Analysis, an increase of load-bearing capacity in the system was observed, which represented the effect of concrete parapets on the overall strength of bridge structures.

Behavior of structural members in sway-sensitive frames of reinforced concrete
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Eurocode 2 allows design of slender reinforced concrete columns using the general method. However, currently standard does not provide explicit limits for controlling the second order effect in design. In the study, experimental results of reinforced concrete columns were compared against commercial FEM-program and programmed solver program. As both the experimental and calculated results matched, thesis aimed to derive a suitable limit for a critical load factor of sidesway portal cast-in-situ reinforced concrete frames using the approximate flexural stiffness described in Eurocode 2 and flexural stiffness obtained by the general method.

Strength enhancement in cold-formed rectangular tubular sections made of high-strength steel
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Conventional tensile tests were carried out on cold-formed tubular sections made of S700MLH and S355J2/S420MHto determine material mechanical properties and to study the strength enhancement due to cold forming technique. Additionally, Digital Image Correlation method was utilized to support the results measured by traditional testing method and to demonstrate the benefits of DIC technique. Based on the stress-strain curves obtained from testing, the material model is proposed.

Finite element analysis of prestressed concrete slabs under impact loading
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The main goal of my master’s thesis was to investigate the ultimate perforation capacities of prestressed concrete slabs under impact by precast wall elements, which may occur on construction sites. Finite element models were developed for this investigation. The thesis also included the validation and assessment of the missile residual velocities, impacting the reinforced and prestressed slabs. The calibration of the velocities was achieved by introducing new threshold parameters to control the element deletion algorithm used in the user-modified concrete damage plasticity material model.