Local buckling in metal sections is such a threat that Eurocode 3 imposes a passage through the classification of the section before any verification of the resistance of the structural elements. This characterization process is not necessary for flexural design (all sections are class 1). While in compression, their areas have different strength classes, several of which are class 4. This work focuses on studying merchant profiles subject to the risk of local buckling in compression. The neglected (ineffective) part of their sections is supposed to be damaged, which allowed us to associate this local instability with the damage parameter. There, it was necessary to appeal to the damage mechanic notions to formulate the evolution of the local instability of the thin wall of a metallic section. This simplifying approach is proposed to directly obtain the effective characteristics of the normalized areas via a damage parameter (Dc) without resorting to the classification of the sections and the effective calculation. The results obtained led us to propose two empirical and predictive models of the damage parameter associated with local buckling. The latter was validated by an analytical calculation and subjected to a statistical analysis of their accuracy.

It has become vital to look for alternatives to the non-renewable natural resources utilized in the building industry due to the vast and quick expansion in that sector in order to safeguard such resources from waste. Recycling varied concrete debris from demolished concrete buildings to substitute natural gravel in the production of various concrete mix types is one way to do this. In this study, the physico-mechanical characteristics of steel fiber-reinforced self-compacting concrete made of quartz gravel were examined. The percentages of recycled gravel used to replace the quartz gravel were 25, 50, and 75%, respectively. According to the findings, up to 75% of the quartz gravel may be replaced with recycled gravel. The correlation between the concrete's ultrasonic speed and mechanical strength was strong and promising.

The exploitation of solar energy has become a major concern, especially since our country holds a significant solar potential during the year. We can use concentrated solar energy to produce electricity or heat. This contribution consists, from simulations, in the parametric analysis of the operation of a solar concentration thermal installation, highlighting the direction of the variation of the thermal efficiency as a function of the low pressure for a machine working according to the ideal cycle of RANKINE.

Distributed database systems are increasingly becoming the dominant tools for data management. However, in these systems, the sites are remote and exchange a huge amount of data, which leads to bottlenecks as well as large disk accesses in data transfers that may be irrelevant. Query processing optimization techniques are an important concern for system administrators to improve the performance of distributed database systems (DDBS). Vertical fragmentation is a suitable solution but its complication lies in the large number of alternatives to obtain an optimal solution. This paper provides a new approach better suited to the problem of vertical fragmentation by the K-means classification algorithm but with our new adequate distance. To validate our approach, we compared our solution first with a vertical fragmentation algorithm called VFAR and second with the same k-means algorithm with the hamming distance.