Volume 16 (2021): Edizione 4 (December 2021)

Reliability analysis and stone columns techniques are widely used, with an increasing trend, in different geotechnical engineering problems. Design methods of stone columns is still based on deterministic approach, in spite some degree of uncertainties is associated with soil and stone column parameters. In the present work, reliability analysis of bearing capacity of stone columns is examined; using three methods of reliability analysis, First Order Second Moment FOSM, Point Estimate Method PEM, and Monte Carlo simulations MCs. Parametric analysis using all variables involved in stone columns design has been conducted. Distributions of random variables involved in stone columns design are considered either as normal or lognormal. The random variables correlation effect is examined. The study has allowed to evaluate parameter uncertainty effect on reliability index of stone columns, and has permitted to figure out reduced set of parameters that must be considered as random in reliability analysis of stone columns beside sensitivity analysis.

The dynamic analysis of structures under seismic ground motions is a major issue in earthquake engineering. The seismic ground motions observed at the surface are variables in space and time. The main causes of this variability come from seismic waves propagation between the source and the site, and in particular the local geological site conditions. For this purpose, it is essential to consider all these factors of the spatial variability of seismic ground motion when representing seismic loading to be applied to any structure. Given the scarcity of real seismic records, many researchers suggest the use of artificial or synthetic seismic motions. The main objective of this study is the simulation of spatially variable artificial seismic motions by considering all fact of factors of the seismic spatial variability, especially site local conditions. In this sense, a simulation technique of spatially variable seismic motions is developed using the spectral representation method. By adopting the unconditional simulation approach, the target seismic motion in bedrock is defined by the Clough-Penzien spectral model and a specified coherency loss model. Then, the simulated ground motions in the bedrock are projected on the surface by considering amplification site effect. The results showed that the simulated artificial seismic motions are strongly conditioned by the local site conditions.

This paper focuses on the field of mechanical vibrations experimental analysis in hand arm vibrations (HAVs) for people who by the nature of their job are subject to the mechanical vibrations.

Nitrate is the most common form of nitrogen in water. The presence of nitrates in drinking water can harm human health, this is why the maximum concentration of nitrates in potable water is imposed by law. The main treatment technologies used for treating this kind of water are reverse osmosis, ion exchangers, electrodialysis and biological denitrification. The goal of this paper is to determine the efficiency of biofilters in reducing the ammonium concentrations in water, depending on the carrier/filtration media used in the biofilters, the C:N:P ratio used and contact time between water and the attached biomass. The paper is based on the result obtained during experimental tests in which the concentration of nitrates in the raw water was 150 mg/l.

In this article, we present a method to obtain equations of non-degenerate conics in an initial Cartesian frame (xOy), starting from their canonical expressions in another Cartesian frame (x′′Cy′′).