Plastic waste management has received significant attention in recent decades due to the urgent global environmental crisis caused by plastic pollution. The versatile and durable nature of plastic has led to its widespread usage across various sectors. However, its nonbiodegradable nature contributes to unsustainable production practices, leading to extensive landfill usage and posing threats to marine ecosystems and the food chain. To address these environmental concerns, numerous challenges have been recently addressed through investigating alternative approaches for disposing of plastic waste, with the construction sector emerging as a promising option. Incorporating plastic waste materials into concrete not only offers economic benefits but also provides a valid alternative to conventional disposal methods. This paper presents the results of different experimental studies, some of them available in the literature and others new, discussing the feasibility of integrating plastic waste into concrete and its impact on mechanical properties. The influence of different sizes, natures, treatments, and percentages of plastic waste in the concrete mixtures is dealt with in order to provide further data for helping to understand the nonunivocal results in the literature, under the conviction that only further observations can help to understand the mechanics of concrete with plastic aggregates. The experimental investigation highlighted that one parameter that is better than others and can be considered to compare different experimental investigations is the variation in weight (due to the effective volume of plastics in the mix), determining a sort of increasing of porosity that degrades the mechanical characteristics. However, this seems inconsistent in some cases. Therefore, the need for further research is highlighted to refine production methods and optimize mix designs.

The aim of the paper is to provide practical guidelines for the design of welded joints of steel truss for encased composite steel–concrete beams. The results of experimental tests are presented and interpreted. The steel truss is made of a steel plate acting as the bottom chord, made of S355 structural steel, coupled with steel rebars which form the upper chord, and steel inclined web rebars (V-reverse) welded to the two chord elements, both of them made of steel B450C. Butt welded joints of web bar to bottom steel plate and fillet welding joints of inclined web bars to top chord bars were tested, as they are different from the ones which are normally used due to the coupling of different steel types and complex geometry. For the prediction of strength of fillet welding joints, two analytical expressions are derived: the first is based on a local failure criterion and the second on a limit domain of the welding section. Comparison with experimental data proves the equivalence and reliability of the proposed indications. Guidelines for choosing the effective dimensions of the fillet weld able to ensure a required strength are provided. For validation of the suggested guidelines, a high precision digital scanner is used to determine the geometrical characteristics of the fillet weld.

A model for the design of shear-flexure critical reinforced concrete elements strengthened with fiber-reinforced polymer (FRP) sheets and plates is presented. The model is based on the stress field approach and the equilibrium method and accounts for the different failure modes of FRP, focusing on the debonding of the FRP from the concrete surface. The efficiency of the model in the strength assessment of beams reinforced with FRP by the prediction of the shear-flexure capacity is checked by corroborating the results of several experimental tests found in the literature. Moreover, the presented model’s capacity to reproduce experimental behavior is compared with the formulations suggested by some codes. Finally, to demonstrate the model’s flexibility in evaluating the resistance domain for reinforced concrete beams strengthened with FRP and to investigate the influence of the shear-bending moment interaction, resistance domains with different arrangements of FRP reinforcement are presented.

The hybrid steel trussed concrete beams examined in the present study are comprised of two principal components, i.e., a steel joist with inclined rebars, realized in industry, which is welded to a smooth steel plate and then embedded within the concrete cast in situ. The paper presents first the state of the art on laboratory tests and analytical modeling of the steel-to-concrete stress transfer mechanism investigated by push-out tests. Next, the most relevant scientific contributions currently available in the technical literature regarding experimental investigation on actual shear behavior are summarized and discussed. Lastly codes and analytical models are reviewed.