Abdelhamid Guettala

Finite Element Analysis of Stress Concentrations in Isotropic and Composite Plates with Elliptical Holes

Panels and shells with variously shaped cutout are often used in both modern and classical aerospace, mechanical and civil engineering structures. The understanding of the effects of cutout on the load bearing capacity and stress concentration of such plates/shells is very important in designing of structures. Finite element investigation is undertaken to study the stress analysis of plates with central elliptical holes. In this study, the stress concentration factors (SCF) in cross-and-angle-ply composite plates as well as in isotropic plates subjected to uniaxial loading is studied. The main objective of this study is to demonstrate the accuracy of present element for stress analysis of plates with central cutout. The varying parameters, such as cutout shape (circular or elliptical), hole sizes (a/b) or cutout orientations, which affect the stress distributions and SCF in the perforated plates, are considered. The numerical results obtained by the present element are compared favorably with the analytic findings published in literature, which demonstrates the accuracy of the present element.

Study of the combined effect of different types of sand on the characteristics of high performance self-compacting concrete

Abstract The characteristics of self-compacting concrete at high performance (SCCHP) made with different types of sand were investigated. Three types of sands were used separately and in binary combinations: river sand (RS), dune sand (DS) and crushed sand (CS). The introduction of CS and DS aims to valorize the by-products of crushing and local materials for the formulation of the SCCHP. Different compositions containing RS, CS, DS and their binary mixtures were experimentally studied. First we started by the measurement of loose compactness’s of different combinations of aggregates and concretes. Thereafter, the SCCHPs were characterized by different test methods such as (slump flow test, L-box test and sieve stability test). Finally, the SCCHPs are subjected to mechanical testing. The obtained results proved that the binary combinations of different sands have a positive effect on the compactness. However, they do not give the best results in rheological and mechanical characteristics of the SCCHP. The results obtained by studying SCCHPs formulated by the addition of CS to the RS with moderate contents (≤40%), and by the addition of DS to the RS at low contents (≤20%) were very interesting from an economic, environmental or technological point of view.

The Effect of Alkali Silica Gel Formation from Alkali Silica Reaction in Mesoscopic Scale

In this article we treat a pathological problem for a better understanding of the phenomena of ASR; the modeling of ASR has been represented in a relative element of volume (REV) in mesoscopic scale. The method used to estimate the formation of ASG is the kinematic estimation of the ASR where it generates in the end an expansion, thus modeling leads to a better range of understanding of the rheological behavior of a concrete with ASR.The numerical model adopted to validate the effect of the expansion of alkali silica gel in terms of strain/stress is a phenomenological one, where it gives sustainable results with the rheological models.