Sidi Mohammed El-Amine Bourdim

The dynamic response of extended structures, particularly on heterogeneous soils, is strongly influenced by the spatial variability of seismic ground motion (SVGM), yet most existing coherency models either neglect site effects or rely on a single parameter. This study integrates two key site proxies—the fundamental soil frequency (f0) and the average shear wave velocity in the top 30 m (Vs30)—to evaluate their combined influence on lagged coherency using seismic data from 15 earthquake events recorded by a nine-station array in Chlef City, Algeria. The effect of f0 is first assessed observationally for three components (EW, NS, and vertical), followed by nonlinear regression to develop a Vs30-based coherency model. Results indicate that lagged coherency increases with higher f0 and Vs30 (stiffer soils) and decreases with increasing frequency and separation distance, with both parameters providing complementary insight into site effects. The vertical component generally exhibits higher coherency than horizontal components, emphasizing the importance of three-dimensional ground motion. Overall, the proposed framework improves the representation of the site effects in coherency modeling and offers a more realistic basis for the seismic analysis and design of extended structures subjected to spatially variable ground motions.

The present work aims to assess the large-scale seismic vulnerability of a set of 55 reinforced concrete educational establishments of different typologies (approximately 516 constructions) located within the urban perimeter of the city of Mostaganem. Among them, 328 buildings were constructed in accordance with the Algerian seismic regulation (built after 1980), while 188 constructions were built without a seismic design code (built before < 1980). This classification corresponds to the application/creation of this regulation following a major earthquake in Chlef (El Asnam) in 1980. Using the RISK-UE lm1 method, the vulnerability index was assessed based on a visual inspection for each building using an on-site inventory form to determine the general sources of seismic vulnerability. This strategy allows the prioritization of constructions according to their typologies, considering the structural system of the building and modifying factors, such as code level, maintenance condition, number of floors, plan and elevation irregularities, soil morphology, etc. The application of this methodology generated several seismic scenarios expressing the probable damage to the constructions, and the following results were suggested: The first two seismic scenarios have no damage corresponding to intensities I = 5; 6. The third scenario is characterized by low to negligible damage corresponding to intensity I = 7. Moderate damage was observed for the fourth seismic scenario (I = 8), while the fifth scenario generated by seismic intensity I = 9 presents moderate to heavy damage. The sixth scenario, with intensity I = 10, exhibits a relatively heavy damage balance. Starting from intensity I = 11, the damage becomes heavy to very heavy for the seventh scenario. Finally, the eighth scenario describes total destruction of the constructions. The results obtained from the application of this methodology on the educational buildings have been integrated into a Geographic Information System (GIS) environment to better understand the seismic behavior of the structures and to estimate the magnitude of seismic risk. This facilitates simulation and enables efforts to be made to take concrete preventive measures to strengthen existing educational buildings, thus reducing the negative impact of future earthquakes.

The direct modeling of masonry infill walls on many buildings, based on damage recorded by various past earthquakes, has become increasingly necessary in order to identify the seismic behavior of these elements, which constitute an important part of reinforced concrete buildings. In this paper, several 3D models were analyzed by the nonlinear static (pushover) method, when ignoring, and when considering, masonry infill walls. The finite element software SAP analyzed the proposed models. These models represent low and mid-rise reinforced concrete buildings infilled with double-leaf hollow bricks. The properties of materials used in Algeria, either in the frame elements or the infill elements, were used. The results obtained were compared according to two parameters, the natural time period of the building and the pushover curve, by varying the values of the dead load and the concrete compressive strength. The results were discussed according to the suggested parameters. The results showed that indirect modeling of such walls, either by taking assumptions embedded in the seismic behavior factor or by means of the macro-modal, can lead to a poor appreciation of the seismic behavior of such buildings. Consequently, direct modeling of walls by the infill of the real void showed acceptable results to some extent. This contributes greatly towards understanding the seismic behavior of this type of building.

Existing seismic vulnerability has become a topical of actuality, concerning both new and old buildings. Several techniques have been used to allow structures to better resist seismic events. In recent years, these have been so-called intelligent materials such as shape memory alloys (SMAs) due to their superelasticity and their ease in returning to their initial state after deformation, which can reach 10%. In the present article, nickel–titanium SMA is considered in a minaret of an old church transformed into a mosque to control the seismic response in terms of displacements, stresses and accelerations. The assessment of the seismic behavior was performed based on a modal and then transient analysis with Ansys software. The main objective was to determine the effectiveness of the addition of shape memory alloys by varying their number.

The traditional optimization methods are effective when dealing with small-scale problems. However, for large-scale problems, these methods fail to obtain optimal solutions, and after a long operation, several solutions are obtained. New methods, known as metaheuristics, have provided new implementations to be used in many applications. They have enabled the resolution of many complex industrial and technical problems. They have the merits of avoiding local optima and finding optimal solutions, due to their ease of understanding, flexibility, adaptation simplicity, and ability to get out of local optima traps. This article aims to model a 2D metal frame gantry with two spans and two levels already optimized by ROBOT Millennium software in order to show the effect of structural optimization in the pre-design phase and of obtaining its non-linear behavior by the pushover method. Three optimal dimensional configurations of this gantry were taken into account and the best was chosen, one which satisfied an adequate behavior in the non-linear domain while respecting the CM66 and Eurocode3 regulations.