Ivan Tomasi

This paper is intended to study the fatigue behaviour of low-carbon steel DD11 with the combined effect of pre-strain and notch geometry, which are important in components working under cyclic loading in service. To this end, experimental fatigue tests were performed on specimens with different configurations: (i) specimens pre-strained to 24% (beyond the tensile strength point), (ii) specimens combining pre-strain and notch effects, and (iii) double-notched specimens, which feature a higher stress concentration factor. The experiments were complemented by numerical simulations and analytical formulations, and fracture surfaces were examined to support the interpretation of the results. The main results show that the applied pre-strain (24%) reduces the fatigue limit by 8.5% when compared to the un-notched case. However, when pre-strain and notch effects are combined, no significant additional influence on the fatigue limit is observed. In the double-notched configuration, a higher stress concentration factor is found compared to previous studies by the authors, leading to a reduction in the fatigue limit, with localised plasticisation similar to that observed in the compared scenario.

Tower cranes are highly vulnerable to seismic excitation owing to their slender geometry and pronounced dynamic behaviour. Although carbon fibre reinforced polymer (CFRP) materials offer significant lightweight potential, and damping devices are widely adopted for seismic protection, their combined application to tower cranes has received limited attention. This study numerically investigates the seismic response of a rearing jib tower crane equipped with a CFRP jib and base joint dampers. A finite element model was developed and analysed under four critical operating configurations through static structural, modal and response spectrum analyses in accordance with the Italian Building Code (NTC 2018). The performance of the CFRP solution was compared with that of a conventional steel crane, while two damper configurations with different stiffness values were also assessed. The proposed lightweight design reduced the total crane mass by 34% and the jib weight by 77%. Compared with the steel configuration, the CFRP solution decreased static displacements by 38–56% and equivalent stresses by 22–44%. Under seismic loading, the adoption of joint dampers reduced the maximum equivalent stress by up to 35%, while increasing structural displacements by 5–19% because of the lower support stiffness. The results demonstrate that combining CFRP lightweight design with seismic damping devices effectively improves the earthquake performance of tower cranes while maintaining structural safety.

This research study investigates the use of composite materials to reduce the weight of heavy industrial vehicle chassis. A new Carbon Fibre Reinforced Polymer (CFRP) crossmember was developed to replicate the mechanical performance of the traditional steel component while achieving substantial weight reduction. A multi-step approach was adopted: analytical and finite-element analyses were performed on single crossmembers to assess bending and torsional stiffness. The CFRP design achieved increases of 6.8% in torsional stiffness and 5.0% in bending stiffness, with a 68.1% weight reduction. After confirming stiffness equivalence, full chassis simulations were carried out to evaluate global performance. The steel model reproduced experimental results with a relative error of 1.13%, while the CFRP configuration enhanced overall torsional stiffness by 7.8%. Extending these results to all crossmembers, the initial cost increase of the CFRP solution could be recovered within about 2 years for the diesel scenario and 3.5 years for the electric one. Environmental benefits were also quantified, with annual CO₂ reductions of 708.4 kg and 298.6 kg, and cost savings of up to 463.3 EUR/year and 299.8 EUR/year, respectively.

Structural applications commonly adopt low-carbon steels, with the fatigue concept being one of the primary causes of failure. In this research, the aim was to study the fatigue behaviour of DD11 low-carbon steel, considering also specific conditions, like the effect of pre-deformation and influence of stress intensity factor. After determining the geometry and performing static tests to extrapolate the mechanical properties of the material, the fatigue behaviour of the base material was analysed, following the actual standards. Then, two conditions, a pre-strain equal to 11% and a notch, simulated with a hole and without pre-deformation, were studied. The results showed an absence of influence on the fatigue limit for the material with a pre-strain effect, and regarding the notching tests conducted, there was a low sensitivity to fatigue of the material.

This study investigates the dynamic behavior of an articulated boom offshore crane under various load application laws. The following steps were taken to perform numerical simulations using the finite-element method (FEM): Definition of the model’s geometry, materials, and boundary conditions. The modal analyses reveal significant resonance frequencies in the direction of load application (payload). The crane’s displacement, velocity, and acceleration responses are closely related to load application laws, specifically the time required to reach the structure’s full payload (epsilon). It is highly correlated with the dynamic factor (maximum acceleration multiplied by payload), which has a wide range of effects on the structure, including the effects of overstress, overturning, buckling, and so on. The main findings reveal a very strong exponential correlation, allowing the dynamic effect to be estimated as a function of epsilon time. This is a useful tool for increasing the safety and reliability of offshore lifting operations.

The aim of this research is to define a design approach for implementing composite materials in a component of an industrial vehicle, having weight reduction as the primary goal. Through the schematisation of the problem and analytical analysis, the definition of a new geometry, a material and production process, and numerical simulations and experimental studies to test the new solution, an optimization process of the chosen geometry is proposed. After the definition of the process, an applicative example is presented, analysing a front underrun protection device in two different solutions: one made of glass-fibre-reinforced polymer and the other of carbon-fibre-reinforced polymer. An economic comparison has also been conducted between the new configurations and the traditional steel version, showing a weight reduction of approximately 55% for the carbon-fibre-reinforced polymer solution and around 18% for the glass-fibre-reinforced polymer solution. These weight reductions are achievable through a reinvestment that can be amortized in less than five years, thanks to fuel consumption savings.

The present research describes a design of an overhead crane using different materials with a prestress method, which corresponds to an external compression force with the aim of reducing the displacement of the beam due to the external load. This study concerns a bridge crane with a span length of 10 m, with a payload equal to 20,000 N and an estimated fatigue life of 50,000 cycles. Three different materials are studied: steel S355JR, aluminium alloy 6061-T6 and carbon fibre-reinforced polymer (CFRP). These materials are analysed with and without the contribution of the prestress method. In reference to the prestressed steel solution (which has a weight equal to 79% of the non-prestressed configuration), this study designed an aluminium solution that is 50.7% of the weight of the steel one and a composite solution that is always 20.3% of the steel configuration. In combining the methods, i.e., the materials and prestress, compared to the non-prestressed steel solution with a weight evaluated to be 758 kg, the weight of the aluminium configuration is equal to 40% of the traditional one, and the composite value is reduced to 16%, with a weight of 121 kg.