Volume 67 (2021): Issue 4 (December 2021)

The built environment, through the consumption of energy from non-renewable sources and the associated CO₂ emissions, as well as through the production of waste throughout its life cycle and the effects of soil and water degradation, contributes significantly not only to the phenomenon of climate change, but also to the irreversible degradation of the natural environment. The concept of regenerative design provides a framework for a holistic approach to these issues in order to identify the most effective remedies, proposing the restoration and regeneration of the global socio-ecological environment through a system of engineering practices suitable to the specific context. The defining aspects of the regeneration applied in the buildings sector refer to the architecture and inserting in the natural environment ensuring a healthy and well-being indoor environment, reducing to zero the consumption of energy from non-renewable sources and promoting renewable energy sources, minimizing carbon footprint by rational use of materials and waste management throughout the life cycle.

In the execution of the foundation layers and the road base it is necessary to reduce the costs of their construction by using local materials (ballast or crushed stone). In some cases, the physical-mechanical characteristics of the local materials do not satisfy the conditions for dimensioning the road structure. Therefore, to improve these characteristics, they are stabilized with hydraulic binders (fly ash or various mixtures based on lime and cement). By using hydraulic binders, the aim is to obtain a speed in execution, to increase the physico-chemical and mechanical characteristics of the local aggregates and implicitly to reduce the overall costs of the work (Zarojanu, 1976).

The unprecedented scale of road network development programs in our country requires the consumption of materials (natural aggregates, binders), often non-renewable and expensive, which are difficult to secure from traditional sources. Alternative solutions for the replacement of natural aggregates, binders, as viable alternatives to classical technologies, the adoption and continuous development of recycling technologies are concerns of researchers, designers and road builders. So, the stabilized mixtures successfully form the sub-grade layers of the rigid road structures or both the sub-grade layers and the base layers of the semi-rigid structures (Zarojanu, 1976).

Compared to traditional, untreated, thick foundations, the stabilized foundations, consisting of a series of thinner layers (assizes), with considerably increased rigidity, ensure a more judicious distribution of traffic loads for lower overall thicknesses of the road structure (Boboc, 1995).

The paper shows the influence of some design parameters on the general stability of a single-track railway bridge, having the structure made of circular steel arches with rigid vertical hangers.

The following structural parameters were considered in this analysis: closed bridge with an upper winding made of horizontal members without links (diagonals) between them; closed bridge, with upper winding made of horizontal elements and ties made in the form of cross diagonals; static scheme of the arch in the transverse direction – hinged, fixed or portal frame. The analysis carried out is based on the normative SR EN 1993-2:2007. Eurocode 3: Design of steel structures. Part 2: Steel Bridges (EC3-2). The results obtained can be useful in the design of the arches structures for the field of bridges or other types of metal structures.

The comparative analysis on the workability of storable mixtures is intended, through the mathematical interpretation of the results, to improve the solutions for repairing local degradations by using storable mixtures.

The test of workability of the storable mixture at various bedding temperatures, but also during the storage period of the storable mixture came as a need to establish other tests to determine the physical-mechanical characteristics in addition to the attempt to establish the apparent density imposed by NE 025-2003 (NE 025-2003; Bambang, 2005).

The laboratory tests aimed to highlight the interaction between the complex mechanical behavior of storable asphalt mixtures and the variability of the factors acting on a road structure, the results being interpreted using the mathematical analysis software "Curve Expert Professional".

A current global effort is being made in order to find solutions that will limit global warming. The building sector is responsible for the highest share of total energy consumption, which requires the continuous development of strategies to increase buildings energy efficiency. Considering the high share of emissions generated by buildings, improving buildings energy performance can significantly slow down global warming.

A key point in developing strategies to reduce energy consumption and making more accurate forecasts of the evolution of global warming is to determine the actual energy consumption generated by the use of buildings, which in some cases may differ from the theoretical one. In order to determine the actual energy consumption, with high accuracy, determinations in situ of the thermal resistance of the building elements that form the envelope, are essential.

The article presents the main methods for determining the thermal resistance of building elements in situ, factors influencing the accuracy of the results, and recommendations for the use of methods to reduce the risk of errors.

The practical applicability of non-isothermal and inhomogenous air jets determined researchers concerned with their study to analyze from a mathematical and experimental point of view the technical elements related to this phenomena. The identified aspects were likely to generate the circumstances for the practical improvement of the systems that involve the presence of the nonisothermal and inhomogenous air jets, the researches highlighting different methods for determining the relevant technical parameters from this perspective.

Seismic activity in the last two decades validate the urgent improvement requirement of the ductile seismic design concept for the MR RC frame structures. This necesity of improvement comes from the unfavorable recorded seismic response of the MR RC frame structures required to on-site seismic actions. The same observations and conclusions (regarding the soft storey (Ground Floor (GF) or Current Floor (CF)) mechanism development and the seismic energy dissipation process in the RC columns marginal zones) were registered in the analytical research and the experimental studies on seismic platforms. The fragile rupture mechanism of the vertical structural elements produces the segmentation of the superstructure into rigid and fragile segment portions. In these conditions, the fundamental seismic response mechanisms and the seismic design elements of the MR RC frame structures found in current practice and considered in actual seismic design standards are specified through comparative methods. In the final chapter of the current theoretical research study, it were specified the main conclusions and immediate improvement necessity of the ductile seismic design concept for MR RC frame system.

Moment Resisting (MR) Reinforced Concrete (RC) frame system presented in the current seismic design standards and required to on-site seismic action develops the soft storey mechanisms. In practice, the idealized and theorized ductile seismic response specified in the seismic design standards for this structural system type does not occur. In these conditions, the current research study presents a logical scheme regarding the development method of the MR RC frame system. The main element of the logic scheme is the seismic response of the RC frame systems designed only for gravity loads. In correspondence with the structural deficiency sources, several aspects regarding the seismic design method were established, followed by the improvement of the ductile design concept. Also, a couple of solutions regarding plastic hinges control and plastic hinges concentration in the marginal zones of the RC beams are presented. These solutions are directed to existing MR RC frame structures and new MR RC frame systems designed in accordance with the current seismic standards.

This paper discusses the factors that can lead to the degradation of masonry structures and provides an overview of the existing techniques for their rehabilitation and consolidation. The degradation of masonry is often related to negative actions of the environment, such as water penetration, freeze-thaw cycles, chemical attacks, and exposure to pollutants. These factors can lead to the appearance of cracks, scaling, erosion, and other types of deterioration of masonry. To preserve masonry structures, frequent monitoring and repairs (locally), preferably immediately after any degradation, are the most important measures. When degradation occurs, prompt action is necessary to prevent further deterioration and to apply appropriate rehabilitation and consolidation methods. Rehabilitating a construction involves replacing or restoring degraded elements to restore functionality to the pre-degradation level and to improve the overall performance of the structure. In contrast, consolidation focuses on strengthening an existing structure by adding new structural elements or by applying specific consolidation techniques with the aim of achieving increased structural capacity. These processes are often interconnected and part of a larger process of restoring or maintaining buildings or structures. Regarding traditional solutions for consolidating masonry elements and structures, these consist of repairing or rebuilding affected areas with classic materials, such as simple or reinforced mortars, welded meshes, dowels, steel bars and profiles. Traditional masonry repair works include filling cracks by injection, partial disassembly of walls followed by reconstruction, dismantling of mortar joints followed by deep filling, stitching of cracks with steel dowels, and reinforcing and facing with mesh or mortar. These techniques are applied according to the degree and type of degradation of the existing structure, as well as local and environmental conditions, with the aim of ensuring efficient and durable consolidation of the structure. The informed decision on the rehabilitation or consolidation solution used and how it is to be applied is usually made after extensive studies and consultations to achieve the best possible result. Generally, masonry structures are considered very resistant and durable, due to their history of over 6000 years. However, proper care and attention to detail are crucial to prevent degradation and to maintain masonry structures in good condition.