The strut-type hybrid system can be made in different geometric shapes, which are affected by: the number and arrangement of struts, the shape and position of the cable in relation to the girder, and the size and shape of the cross-section of the girder. When choosing a system, all the listed parameters can vary geometrically, which has consequences on the behaviour of the girder when carrying the load by directly affecting the change in the stiffness of the system. In addition to the geometric parameters, the stiffness of the hybrid system is affected by variations in the properties of the incorporated materials and their mutual relations. In this paper, based on a detailed parametric analysis, the principles of design, the choice of materialisation, and the possibility of further optimisation of the persistent-type hybrid systems are given, with the aim of additionally increasing the load capacity and reducing the deformability. The results of this research are presented in the form of general expressions and diagrams, which can be applied with sufficient accuracy in practice when choosing the form and materialisation of the hybrid system, as well as the possibility of further optimisation of the system by applying pre-stressing. Using the example of external pre-stressing of a glued laminated timber girder, with the assumption of ensuring the lateral stability of the system, the results of the analysis of the behaviour of such a system under load in real conditions, i.e. the influence of the environment and changes in material properties, are given.

Plastic waste is a significant environmental and ecological problem that requires urgent action. Indeed, plastic waste pollutes our oceans, rivers, and lakes, harming aquatic life and marine ecosystems. Plastic debris also poses a threat to terrestrial wildlife, as animals can mistake plastic for food or become entangled in it, leading to injury or death. In addition, plastic production requires fossil fuels, leading to greenhouse gas emissions contributing to climate change. That is why recycling plastic waste is an important step towards reducing the environmental impact of plastic and creating a more sustainable future. The present work is part of this approach, and it aims to investigate the effects of the size of the plastic fibers and their percentages on the performances of Hot Mix Asphalt (HMA) in road pavement. Marshall Tests were carried out on the reference asphalt (without adding plastic) and the asphalt containing plastic waste in order to highlight the effect of these additives on the mechanical performance of asphalt mixtures. It has been found that the addition of PET plastic waste considerably improves the mechanical properties of the HMA. The findings revealed that additives composed of plastic fibres of size ranging between 0.125 and 1.25 mm give the best results in terms of Marshall’s Stability and Flow, by acting as reinforcement to the bitumen-aggregate mixtures. Furthermore, the optimum plastic content was found to be about 3.75% by weight of bitumen. It can be noted that the proposed solution fits very well with sustainable development.

During a seismic impact, the main emphasis is placed on the damage to bridge piers, which were isolated from the horizontal earthquake detector. Accordingly, when calculating the bridges, the reaction spectra obtained from the horizontal earthquake detector are used both for the piers and for the superstructure. The issue of seismic resistance of bridges is very important, especially for superstructures with long spans. It is necessary to construct dynamic curves of seismic resistance for superstructures of a specific system. The article deals with composite steel and concrete continuous span superstructure with a scheme L=3x63.0 m, on which we performed seven real earthquake records for all three categories of soil using the direct dynamic method and built the reference response spectra. Based on the obtained response spectrum and the methodology provided by different normative documents, the calculation of the selected superstructure was carried out, and the force values were determined. Discussion: On the basis of the results obtained with the reference response spectra and the curves given in the normative documentation, graphs were drawn, and composite steel and concrete continuous span superstructure with a scheme L=3x63.0 m of the vertical response spectra was determined.