Journal of Building Materials and Structures

Seismic analysis of Souk Tlata dam behaviour using finite element simulation

2022-05-15T13:51:42+00:00

In this study, earthquake resistance of Souk Tlata earth dam was examined. It corresponds to a preliminary investigation of the behaviour of the dam under earthquake loading with a dominant frequency close to the fundamental frequency of the dam. The dam was modeled with plane-strain finite elements using Plaxis-2D program. The behaviour of both the fill and core of the dam is described using the simple non associated Mohr-Coulomb criterion. The development of the safety factors as a function of the displacement of the dam crest dam reveals that the static stability of the dam under conditions of drawdown is not assured. Dynamic analyses are conducted under a real earthquake motion, which corresponds to the main shock of May 21, 2003 in Algeria. The results show that the seismic loading, with peak acceleration exceeding 0.10g, induces significant settlement at the crest of the dam and substantial displacement in the upper part of the rip-rap in the upstream side.

Static and dynamic behaviors of laminated composite plates resting on elastic foundation

2022-05-15T13:51:38+00:00

This present study consists to analyze the mechanical buckling and the free vibration stabilities of antisymmetric cross-ply and angle-ply laminated composite plates using a refined high order shear deformation theory of four variables against five in other high order theories. Among the advantages of this new theory it takes into consideration the shearing effect in the calculation of deformation without the need for shear correction factors and giving rise to a variation of the shear stresses along the thickness and satisfying the zero shear stresses condition in faces of the plate. The laminate resting on the Pasternak elastic foundation, including a shear layer and Winkler spring, are considered. The equations of the motion are derived from Hamilton’s principal. The closed form solution of simply supported rectangular plates has been obtained by using the Navier method. In addition, the effects of various parameters of the laminated composite plate on static buckling and dynamic are presented.

Free vibrational analysis of composite beams reinforced with randomly aligned and oriented carbon nanotubes, resting on an elastic foundation

2022-05-15T13:51:33+00:00

The main interest of this paperwork is to examinate the dynamic behavior (free vibrational response) of carbon nanotubes (CNT) composite beams standing on an elastic foundation of Winkler-Pasternak’s. The affected beam consists of a polymer matrix reinforced with single-wall carbon nanotubes (SWCNT’s), in which, a large number of CNT’s reinforcement of infinite length are distributed in a linear elastic polymer matrix. In this study the CNT’s are considered either aligned or randomly oriented on the matrix.

A refined high-order beam theory (RBT) is adopted in the present analysis using a new shape function. The refined beam theory which is summarized by differentiating the displacement along the beam transverse section into shear and bending components, initially the material properties of the composite beam (CNTRC) are estimated using the Mori-Tanaka’s method. The beam is considered simply supported on the edge-lines. NAVIER’s solutions are proposed to solve the boundary conditions problems. Since there are no results to compare with in the literature; the results in this study are compared with a free vibrational analysis of an isotropic beam. Several aspects such as the length/thickness ratio, volume fraction of nanotubes, and vibrational modes are carried out in the parametric study.

Valorization of dune sand of Djelfa (Algeria) treated by hydraulic binders in pavement foundations

2022-05-23T10:43:50+00:00

The purpose of this work is the study and the valorization of sand dune which is found in abundance in the region of Djelfa (Algeria); for use in pavement foundations. For this investigation a method of formulation has been proposed, which based on the stabilization of this local material using a mixture of two hydraulic binders. Various mixtures were subjected to classification tests, tests grain size distributions, tests of compaction with modified Proctor, shear strength, tests of bearing pressure (CBR unsoaked and soaked), compressive strength and tensile strength. The results obtained have shown that some mixtures are of high mechanical characteristics and could be then used in road foundations.

Basalt Powder Waste Application as Affordable Concrete Admixture

2022-05-15T13:51:24+00:00

Different weather conditions, like temperature and humidity influence on the performance of concrete structures to which they are normally subjected, especially at earlier stage of their service life. One of practical measures has been the regulation of the setting time of fresh concrete. Some admixtures are used in concrete to regulate the setting time and therefore increase structures performance under given situation. Almost all admixtures used in Rwanda are being imported from outside the country and this is one of factors affecting the construction cost. A big quantity of basalt powder at different sites in the country is left without being used and has been negatively impacting the environment. This study aimed at analyzing the potentials of basalt powder waste used in concrete as admixtures in different percentages, e.g. 0%, 5%, 10%, 15% and 20%. Different investigations on concrete incorporating basalt powder as admixture, such as the setting time, workability and compression tests were conducted. The results showed that the gradual incorporation of basalt powder waste as admixture up to 20%, accelerated the setting time more than 13 times, but decreased the compressive strength of concrete by around 24.5%, with comparison to normal concrete strength. The application of basalt waste in concrete would contribute not only to the reduction of environmental pollution but also to the provision of more affordable admixtures for mortar and concrete.

Hydration Behaviour and Characteristics of Binary Blended Metakaolin Cement Pastes

2022-05-15T13:51:20+00:00

Cement production consume large amount of energy to form clinker and carbon dioxide (CO₂) emitted into the atmosphere causing global warming. To mitigate this challenge, the use of Metakaolin (MK) as supplementary cementitious material cannot be over emphasized. This study evaluated the use of Metakaolin (MK) on hydration development of MK--PC blended cements and strength of Mortars. The MK with a Blaine fineness of 7883 cm²/g was used to replace Portland Cement (PC) at a level of 0, 5, 10, 15, 20, 25 and 30 % by mass of PC at a constant w/b ratio of 0.50 to prepare blended cements. Hydration development of blended cement and compressive strength of Mortars were investigated using chemically bond water and free-lime contents and strength tests respectively. X – Ray diffraction (XRD) and scanning electron Microscopy (SEM) techniques were also utilised in the analysis of Pozzolanic reaction and hydration products. Test results indicates that Water of consistency, setting times for the mixes increased with increase in MK contents, influence of MK on the chemically bond water and free Lime contents of the blended cements were due to its filler and dilution effects and Pozzolanic reaction. The cumulative non-evaporable water and free-lime contents increased by partial replacement of PC with MK due to PC hydration and Pozzolanic reaction. The tested Mortar prepared with blended cements with 30 % PC replacement with MK shows a retardation of strength development with a low value at early ages (7 days) and increased in growth at later ages (28 days). The compressive strength of tested mortar for 90 days curing age for the blended mortar is 31 N/mm² close to that of control Mortar (35 N/mm²). The results obtained from XRD and SEM analysis indicated increase in Calcium Hydroxide (CH) consumption and Calcium Silicate hydrate (C-S-H) formation in blended cement pastes with curing time. The PC replacement with MK induced changes in Microstructures of blended cement paste and chemical composition of hydration products. These results are potentials for modelling the behaviour of MK-PC blended cements.