Université Mouloud Mammeri de Tizi Ouzou (UMMTO): Research Review of Sciences and Technologies
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Stochastic Stability Analysis of Columns with Randomly Elastic Joint Ends and Two-Dimensional Random Material Properties Using Monte Carlo Simulation
Full text linkThis paper develops a Monte Carlo simulation (MCs) to analyze the stochastic stability of a pin-ended column with elastic rotational springs at both ends. The randomness of input factors is considered, including the rotational stiffness of elastic couplings at both ends of the column as random variables following a normal distribution and the elastic modulus of the column as a two-dimensional (2D), stationary, homogeneous Gaussian random field. The spectral representation method is applied to represent the 2D random field and generate realizations of the elastic modulus. The influence of random factors such as the standard deviation of the 2D random field, the standard deviation of normal random variables, and correlation distance in each direction on the coefficient of variation (COV) of the critical load is analyzed in detail in this study. The results indicate a strong correlation between the COV of the critical load and both the standard deviation of the 2D random field and the correlation distance. The COV increases significantly with increasing standard deviation, particularly for larger correlation lengths. However, the influence of the variability of rotational stiffness is relatively minor, especially at larger correlation distances
Sustainable Concrete Innovation: Crumb Rubber as a Partial Fine Aggregate Replacement
Full text linkThe exponential growth of the automobile industry contributes a significant accumulation of waste tires, presenting a substantial environmental challenge due to their non-biodegradable nature. This study investigates the potential of using crumb rubber produced from waste tires as a partial replacement for natural fine aggregates of concrete, aiming to enhance the material's properties while mitigating environmental impact. The mechanical and durability characteristics of concrete introducing 5%, 10%, and 15% crumb rubber were determined through various tests, including compressive strength, stress-strain behavior, and impact resistance. Results indicate that while there is a slight decrease in compressive strength with increased rubber content, the post-cracking behavior and impact resistance improve significantly, with energy absorption capacities increasing by 75%, 125%, and 158.4% for 5%, 10%, and 15% replacements, respectively. Additionally, durability tests reveal that rubberized concrete shows reduced chloride ion penetration and improved resistance to acid attack, with 30% reduction in chloride penetration at 15% rubber content. The findings suggest that incorporating crumb rubber can enhance the ductility and durability of concrete, making it a viable and sustainable alternative in construction, particularly in applications such as road pavements where impact resistance is crucial. This study contributes to the ongoing research on sustainable construction materials and emphasizes the importance of recycling waste materials to reduce environmental impact
Effect of Waste Plastic and Fiber Modification on Asphalt Mixture Properties
Full text linkStone Matrix Asphalt (SMA) and Asphalt Concrete (AC) are widely used in road construction due to their excellent mechanical properties and long-term durability. This study investigates the effect of sisal fiber and waste plastic as modifiers to enhance the performance of SMA and AC mixtures. The Marshall mix design method was employed to determine the optimum bitumen content (OBC) and optimum fiber content (OFC), evaluating parameters such as Marshall stability, flow value, air voids, voids in mineral aggregate (VMA), and voids filled with bitumen (VFB). VG 30 grade bitumen was used as a bitumen, and fly ash was utilized as a filler. Sisal fiber was incorporated to reduce bitumen drain down and improve crack resistance, with the optimal fiber content identified as 0.4% by total mix weight. Simultaneously, waste plastic was added to improve workability and mechanical performance, with 2.5% content enhancing handling characteristics and 3% improving drain-down resistance and tensile strength. Results from drain down and moisture susceptibility tests indicated that the combined use of sisal fiber and waste plastic significantly improved the durability and overall performance of the asphalt mixes
Influence of Aggregate Type and Size on Residual Mechanical Properties of Post-Heated Geopolymer Concrete: Experimental Study and Applications of Artificial Neural Networks
Full text linkTo mitigate environmental impacts from Portland cement (PC) production, the researcher’s efforts is introducing eco-friendly alternatives such as Geopolymer concrete (GPC). While GPC shows promise, further research is required to understand how fire or elevated temperatures affect GPC’s mechanical properties. This research investigates the effects of elevated temperatures (200℃, 400℃, 600℃, and 800℃) on the residual mechanical properties (compressive, flexural, splitting-tensile strengths, and modulus of elasticity) of ambient-cured fly-ash (FA)-based GPC compared to PC mixtures. The study examined various concrete types (GPC and PC), three coarse aggregate types (basalt, gravel, and crushed dolomite), and three crushed dolomite sizes (40 mm, 20 mm, and 14 mm). Additionally, Artificial Neural Network (ANN) models were developed to predict the residual compressive strength of both ambient-cured and heat-cured GPC after exposure to elevated temperatures. Results showed that basalt aggregate significantly enhanced the residual mechanical properties at 800 ℃, outperforming crushed dolomite and gravel in compressive, flexural, splitting-tensile strengths, and modulus of elasticity, with increases of (20%, 80%), (26%, 244%), (10%, 100%), and (14%, 140%), respectively. Moreover, the residual mechanical properties were found to be inversely proportion with max size of coarse aggregate. In addition, using ANN models proved its efficient in predicting the compressive strength for both ambient and heat-cured GPC with R² values of 0.94 and 0.887, respectively
Structural Health Monitoring of Steel Girder Bridge Using Photogrammetry and LiDAR Scan Technology: Proof of Concept
Full text linkBridges require regular inspection and maintenance; however, traditional inspections are performed manually at prescribed intervals, involving substantial manpower, high costs, and safety risks due to the challenging locations of many bridges. To address these limitations, the present study focused on developing a methodology to automate technical inspections of bridges using a hybrid approach combining LiDAR and photogrammetry. Unlike past drone inspections, which were largely limited to basic photography and videography, this approach integrates advanced technologies for more comprehensive data collection. For this purpose, a single-span steel girder bridge with a span of 45.7 meters, located between Beas and tto Tanda in the state of Punjab, India, was selected. A Proof-of-Concept (PoC) was developed using high-fidelity digital models, created through photogrammetry with UAV-mounted high-resolution cameras and LiDAR, to carry out 16 inspection missions. The development of these high-fidelity digital models enabled flexible viewing, analysis, and measurement of various structural parameters, including the schedule of dimensions diagram, camber, distortions, rail levels, creep, and eccentricity. The parameters measured from the digital models were compared with the limiting values specified by RDSO, as well as with manually collected data. It was observed that the dimensional measurements obtained through the automated technology were within ±5 mm of the drawings and previous inspection reports, indicating that photogrammetry combined with LiDAR is a reliable and effective alternative technology for bridge inspection
Comparative Study on Dynamic Behaviour of Thick Beams on Foundation: Winkler, Pasternak and Kerr Foundation
No full textA comparative study amongst different types of elastic foundation of a bi-directionally graded beam mounted on elastic foundation is carried out. A single parameter Winkler, two parameters Pasternak and three parameters Kerr foundation are considered as elastic foundation. Bi-directional variation of the beam material is considered along the both thickness and length directions following power law distribution function. The kinematics of the beam is defined following Timoshenko beam theory. To obtain the geometric nonlinear free vibration response the problem is solved in two stages. At initial stage the static part of the problem is solved under loaded condition. Small amplitude dynamic analysis is followed next on the pre-deflected beam to get large amplitude free vibrational response. Displacement based Rayleigh-Ritz principle is utilized to formulate the problem and employing a numerical method the problem is solved. New sets of results are prepared for various combinations of system parameters to investigate the effect of various types of elastic foundations on dynamic behaviour
Effect of different heat treatments on the fractural and microstructural behavior of pipeline steel
No full textAPIX70 pipeline steel is classified under the American Petroleum Institute (API) specification as one of the high-strength low-alloy (HSLA) steels. The APIX70 has a very fine-grained microstructure so they have high strength and ductility properties. In this research work, an attempt has been made to compare the microstructural and mechanical behaviour of base and heat treated APIX70 pipeline steel. Heat treatment was performed at two different temperatures 900 ̊C and 800 ̊C. Different phases such as ferrite, pearlite as well as blend of both were observed in base and heat treated APIX70 steel. Specimen heat-treated at 900°C shows an increase in hardness to 37.5 HRC as compared to the specimen heat treated at 800 ̊C which is 22.5 HRC. Base metal shows a 33.75 HRC hardness value. Microstructure of X70 base metal exhibit blend of ferritic and pearlitic phases. Heat treatment of X70 at 900 ̊C and 800 ̊C shows there is a significant grain growth takes place while lesser grain growth observed for specimen heat treated at 800 ̊C