Engineering and Technology Journal

Bridges when it crossing rivers often required multiple piers for support. One of has a limited investigation is the impact of piers on scouring and morphological aspects when a bridge crossing sharp-bend of river. Consequently, it is crucial to investigate the hydraulic behavior of water flow in these areas due to the presence of these piers. In present study, an experimental program was conducted on a laboratory flume featuring a two-pier bridge within a 180-degree (sharp) bend to accomplish this. The piers were strategically positioned at 90 and 150 degrees within the bend. The results indicated that the bridge within the 90o, under the threshold intensity condition, led to significant local scour depths around the piers. Specifically, the scour depths were found to be 1.80 and 1.15 times the width of the pier for the piers close to the outer and inner banks, respectively. The discharge increased from 240 l/min to 280 l/min while maintaining the same intensity of 0.85, resulting in a symmetric local scour depth at the pier near the outer bank. In contrast, the local scour depths in response to the piers in the 150o were considerably lower; at the threshold with a discharge of 280 l/min, the scour depths were measured to be 0.65 and 1.18 times the pier width for the inner and outer piers, respectively. Similar bed morphology was observed when the bridge was positioned at 150o for two discharge values (280 and 240 l/min) with the same intensity of 0.85. The findings showed that an increase or decrease in discharge value, with a constant intensity, did not influence the local scour depth and its extension around the pier close to the outer bank, indicating that the intensity component was more significant than the discharge.

This study aimed to develop an eco-friendly, lightweight, and synthetic aggregate (SLA) based on clay suitable for use in structural lightweight concrete. The researchers utilized the cold-bonded pelletization process to agglomerate pozzolanic materials, specifically attapulgite extracted from a quarry, and crushed into a fine filler. The appropriate calcination temperature for manufacturing this clay as a pozzolanic material is 750℃. A total of 22 mixes were created using a combination of high reactive attapulgite (HRA) and cement (PC), with the attapulgite replacement rate varying from 100-50% by a 10% decrement. Different types of curing methods, including oven-dry, oven-water, room-water, and room-room, were applied. The aggregate properties were evaluated to determine density, specific gravity, water absorption, aggregate impact value, crushing strength, and compressive strength. The results revealed that it could produce lightweight synthetic aggregate from clay-based materials with a bulk density of 793 kg/m3 with suitable physical and mechanical properties. As the percentage of cement in the mixture increased, the specific gravity and density were increased to 18.12% and 36.61%, whereas impact and crushing values of aggregate improved by 81.83%. This, in turn, leads to a significant boost in compressive strength up to 100.94%. Furthermore, there is a noticeable decrease in absorption. Moreover, the aggregate held under oven water positively impacts the strength development of cement-based composites.

In recent times, the production of concrete has become a significant concern due to the rapid population growth and the depletion of raw materials. In this research, we investigated the use of Uncracked Palm Kernel Shell (UPKS) as a replacement for crushed granite in concrete production, with replacement percentages of 0%, 10%, 20%, 30%, and 100%. The concrete mix combined Ordinary Portland Cement with river sand and coarse aggregates (granite and UPKS). The properties of fresh concrete were assessed using the slump test, while the compressive strength test was conducted after curing the samples for 7, 14, 21, and 28 days. A total of 60 concrete cubes were cast for this study. Our findings indicate that the workability of concrete decreased as the percentage of UPKS replacement for granite increased. Additionally, the compressive strength of the concrete decreased with higher percentages of UPKS replacement. On the 28th day of curing, the control concrete achieved a strength of 28.59 N/mm². However, concrete containing 10%, 20%, 30%, and 100% uncracked palm kernel shells achieved average strengths of 20.74 N/mm², 18.22 N/mm², 15.31 N/mm², and 12.23 N/mm², respectively. This represents a 27%, 36%, 46%, and 57% decrease in strength compared to the control concrete. Our study reveals that concrete with 10% to 30% replacement of granite with uncracked palm kernel shell can produce eco-friendly lightweight grade 15/20 concrete, making it suitable for sustainable construction. The developed model was tested and found adequate for predicting the concrete properties.

Free vibration analysis of thin beams under dynamic excitation is important in design to prevent resonance failures that occur when the excitation frequency coincides with the natural vibration frequency. In this paper, the Elzaki transform method (ETM) is used, for the first time, to solve the free vibration problem of thin beams. The beam is assumed to be homogeneous and prismatic, and the vibration is assumed to be harmonic. As a result, the field equation becomes a fourth-order homogeneous ordinary differential equation (ODE). The Elzaki transform method is chosen in this study due to its proven ability to solve ODEs, systems of ODEs, integro-differential equations, integral equations, and fractional differential equations. The Elzaki transformation simplifies the field equation into an algebraic equation in terms of the unknown deflection in the Elzaki space. By inverting the transformation, the general solution for the deflection is obtained in the physical domain, considering the initial conditions. The enforcement of boundary conditions for each case of end supports is utilized to determine the eigenequations, which are then solved for their roots using Symbolic Algebra methods. The eigenvalues are used to determine the exact natural frequencies of flexural vibration for each considered classical boundary condition. The eigenequations obtained are exact and identical to the ones previously derived by other scholars.

The determination of free vibration frequencies of thin beams on Winkler foundations is important in their design to avoid resonant failures when the excitation frequency equals the least natural frequency. This article presents the determination of natural transverse vibration frequencies of Euler-Bernoulli beams on Winkler foundations using the Generalized Integral Transform Method (GITM). The problem is governed by a fourth-order partial differential equation (PDE) and boundary conditions dependent on the end restraints. The governing PDE is transformed into an algebraic eigenvalue problem for harmonic vibrations and harmonic response. Analytical solutions of the governing equations are difficult and complex. Hence, other solution methods are needed. The main merit of the GITM is the apriori selection of kernel functions as orthogonal functions of vibrating thin beams with equivalent boundary conditions. This prior selection of the kernel functions and their orthogonality properties simplify the resulting integral equation formulation to an algebraic problem in the GITM space. Eigenfunctions of freely vibrating thin beams with identical restraints are used in the GITM to construct the displacement function as infinite series in terms of unknown parameters. The solution of the algebraic equation yielded exact solutions to the candidate problem. Exact solutions for frequency parameters are obtained for the four cases of boundary conditions for the various values of foundation parameters considered. The effectiveness of the GITM in obtaining a simplification of the governing PDE and reducing the problem to an algebraic problem is illustrated.

A 3D numerical model generated using PLAXIS-3D software was used in the present research to predict the behavior of under-reamed piles under pullout loading conditions with presumed soil Mohr-Coulomb failure. The under-reamed pile was embedded in homogeneous, layered clay soil, with stiff clay overlain by soft clay and soft clay overlain by stiff clay. The piles were chosen per the Indian Code (IS 2911) specification, and two variables were studied: bulb provision and soil layering. Inhomogeneous clay with varying cohesion values (20, 40, and 80 kPa) and under the same conditions, the pullout capacity was improved compared to a straight shaft (SP). The pullout capacity of the single bulb (SURP) increased once, while that of the double bulb (DURP) increased twice. The results revealed that anchoring the pile in a stronger stratum at a greater depth is advantageous when designing under-reamed pile foundations. In the case of stiff clay on top of soft clay, additional resistance against pullout is achieved, reducing the risk of pullout failure compared to soft clay in the upper layer.

The main objective of this study is to determine the appropriateness of unsaturated gypseous soil as a subgrade layer for carrying foundations. A comprehensive laboratory testing program was implemented to investigate the geotechnical characteristics and behavior of unsaturated gypseous soil. Tests that are physical included specific gravity, classification tests, relative density, Proctor compactions, single and double oedometer collapse potential, and static triaxial compression (CU-test). Chemical testing, Scanning Electron Microscopy (SEM), and Electronic Dissipation x-ray Scanning (EDS) analyses were also carried out. The tests were performed for samples prepared at 70% relative density of the natural gypseous soil. Tests are performed on the natural, unsaturated at degrees of saturation (30%, 60%, and 80%) and fully saturated gypseous soil to investigate the gypseous soil behaviors. In both single and double oedometer testing, it was discovered that the degree of specimen collapse is (Moderate) at 70% relative density, with a collapse index value ranging from (4%). The angle of internal friction for both total and effective stresses (φ' and φ) decreases as the moisture content of the gypseous soil increases at all saturation levels. In contrast, it was found that the strength of soil cohesion for both total and effective stresses (c' and c) increased with increasing gypseous soil moisture up to saturation (60%), which led to a rise in soil shear strength. The reduction value ranged from (38.50° to 7°) in respect of effective stresses and between (34.50° and 7°) with respect to total stresses. Effective stress increase varied from (10.0 – 26.0 kPa), and total stress increase ranged from (12.50 – 28.0 kPa). Then the strength started gradually decreasing at the saturation degrees 80 and 100%, respectively. As a result, the shear strength of the soil decreases with the value of reduction ranging from (20.0 – 11.50 kPa) for effective stresses and (21.50 – 11.50 kPa) for total stresses.

Geopolymer concrete is an inorganic composite material created by interacting alkaline substances with an aluminosilicate source and aggregate. Precast building units are considered the most prominent uses of geopolymer concrete, and the utilization of recycled steel fibres and rubber from damaged tires that are non-biodegradable to reduce environmental pollution. The results of this investigation show the possibility of using geopolymer concrete with and without the inclusion of crumbed rubber and recycled steel fibers from damaged tires in the production of paving flags with dimensions of 400 × 200 × 50 mm class c according to IQS 1107. Four types of geopolymer concrete flags were prepared, including flag specimens without wastes, flag specimens reinforced with recycled steel fibres waste from damaged car tires with a volume fraction of 0.125%, flag specimens containing 10% crumbed rubber waste aggregate as a partial volumetric replacement to natural coarse aggregate, as well as flag specimens containing two wastes of 10% crumbed rubber as a partial replacement to natural coarse aggregate and 0.125% recycled steel fibres. The experimental tests illustrate that it is possible to reduce the thickness from 50 mm to 35 mm of the paving flags to reduce their weight and cost. In addition, it was discovered that the total flexural energy of paving flags containing recycled steel fibers and rubber aggregate wastes increased by 390% and 271%, respectively, concerning paving flags without wastes. The failure modes changed from brittle to ductile when these wastes were used.

The cumulative quantities of non-biodegradable solid tire waste, which are byproducts of transport vehicles, contribute to environmental pollution.. This study seeks to address this issue by investigating the impact of using this waste as a replacement for natural coarse and fine aggregate in varying ratios (10%, 15%, and 20% as coarse aggregate, and 5%, 10%, and 15% as fine aggregate by volume) to create sustainable concrete. All mixtures incorporate 10% silica fume (SF) as a cement replacement by weight. Results reveal decreased workability, fresh density, compressive, and splitting tensile strength with increasing rubber replacement proportions. However, utilizing tire rubber aggregate leads to the production of structural lightweight concrete (LWC), with advantages such as reduced oven dry density. Notably, a 20% replacement of coarse rubber waste and 15% replacement of fine rubber waste yield compressive strengths of 48.80 MPa and an oven-dry density of 1952.5 kg/m3, respectively, classifying these concrete mixes as structural lightweight concrete.

Global warming on planet Earth results from the high emission of greenhouse gases, especially CO2. The Portland cement industry releases high amounts of CO2 and is responsible for about 5-8% of total emissions. Efforts have been made to look for alternative cementless binders to mitigate the impact on the environment. Geopolymers are one of the highlighted alternatives and can be obtained from the reaction of any aluminosilicate material with an alkaline solution. Aluminosilicate materials are found in byproduct materials such as fly ash. Geopolymer concrete is a promising environmentally friendly option. However, previous conventional mix proportioning methods for fly ash-based Geopolymer concrete have been limited. Most of these methods focused on a single weight ratio of SiO2/Na2O, which was 2. However, the sodium silicate solution is produced industrially with various concentrations depending on the weight ratio of SiO2/Na2O. Adding sodium hydroxide to the sodium silicate solution increases the alkalinity of the resulting activation liquid. This work proposes a new mix proportioning procedure named the "Ratio of the Resulting Sodium Silicate Method for Geopolymer Binder." The method has been successfully verified to achieve the desired compressive strength on the 7th and 28th days. We also tested different control specimens from previous studies using this new proposal to study the effect of different parameters on compressive strength predictions.

Formwork systems are required for almost all cast-in-place concrete construction. However, some forms cost too much, often exceeding 30% of the entire cost of the concrete construction. Thus, the stay-in-place (SIP) formwork, a premanufactured permanent constructional member that holds fresh concrete to the intended sizes and stays in the site to afford loads over the construction lifecycle, could be an auspicious alternative to the classic formwork procedure. Several types of stay-in-place (SIP) formworks for columns have been reviewed, like PVC tubes, CFRP, steel tubes, and the composite of two or more types of stay-in-place (SIP) formwork used together. Moreover, some types of concrete and mortar used as stay-in-place (SIP) formwork have been reviewed. The mechanical, restrain, and deformability characteristics of several types of stay-in-place (SIP) formwork system for concrete columns is discussed. Further, the effect of change in the thickness of several kinds of stay-in-place formworks is highlighted. The impact of the change in the strength level of the core of concrete-filled stay-in-place formworks on the confinement efficiency of stay-in-place formwork is also investigated. Finally, the recommendations for futurity researchers in this area are introduced.

Slurry-infiltrated fiber concrete (SIFCON) is a comparatively new and unique steel fiber-reinforced concrete (FRC) form. SIFCON possesses many desirable characteristics, including high strength and ductility. Sustainable concrete is one of the most critical types of concrete for the current environment. An enormous volume of waste rubber tires is produced globally due to the expansion of the automobile industry. This study's primary purpose is to assess the impact of employing pre-treated waste rubber tires in slurry-infiltrated fiber concrete on its flexural and compressive strengths. Based on flexural and compressive strengths, an experimental program was conducted to evaluate the flexural and compressive strengths of SIFCON containing 4% steel fiber and 6%, 8%, and 10% waste rubber. Different pre-treatment methods were used to improve the bonding between the cement paste and rubber particles, including Na(OH) solution, Ca(OH)2 solution, and pre-treatment using Cempatch AB solution. Compressive and flexural strength decreased with increasing waste rubber content, up to 43% and 37% for a 10% waste rubber content, respectively. Moreover, The test results showed that the pre-treatment of chopped rubber with NaOH solution produced the highest values for compressive and flexural strength, giving strong polarity groups to the surface of the rubber and generating a strong chemical interaction between the rubber and the cement matrix.

The foundation plays a significant role in safe and efficient turbo machinery operation. Turbomachinery generates harmonic load on the foundation due to its high-speed rotating motion, which causes vibration in the machinery foundation. Any increase in machine vibration reduces the machine's performance. In studying engineering problems, using numerical programs helps get a well-designed foundation. Before conducting a parametric study, the program used shall be validated and/or verified by conducting a series of analyses to ensure that the program output represents the reference studied cases well. In many cases, the real problem is simplified by assuming that the machine's loads are applied at the upper slab of the frame foundation. The present work included the effect of the machine's mass elevation on the response of a high-speed turbo machine's frame foundation. The mass elevations of (12.6, 13.0, 13.3, 13.6, 13.9, and 14.2) m are selected for the dynamic analyses. A verification process is carried out to calculate the three-dimensional frame foundation's natural frequencies and mode shapes using Ansys software. The results show that the machine's masses must be included and applied at its specific elevation to reflect the true dynamic vertical response of the system as far as the mass height to top slab elevation ratio exceeds 5%. The results show a good agreement in calculating static and modal analysis with the study case. When neglecting the machine mass, the difference between the calculated natural frequencies for any mode shape is less than 10%.

This paper derives buckling solutions for single variable thick plate buckling problems using the double finite sine transform method (DFSTM). The problem governing partial differential equation (GPDE), originally formulated by Shimpi and others, uses a refined plate theory (RPT) and accounts for transverse shear deformations, rendering it applicable to thick plates. The thick plate is simply supported and subjected to (i) uniform uniaxial compressive load in the x direction. (ii) uniform biaxial compressive load in the x and y axes. The DFSTM was applied to the GPDE, and the problem transformed into an algebraic equation, which was simpler in this case due to the Dirichlet boundary conditions satisfied by the sinusoidal kernel of the DFSTM. Analytical buckling solutions were determined for the two considered cases of uniaxial and biaxial compressive loads in terms of the buckling modes, Poisson’s ratio (μ), and thickness (h) to least dimension (a) ratio. Critical buckling loads (Pcr) determined at the first buckling modes agreed with previously obtained Navier solutions for Mindlin, Reddy, and Refined plates. Pcr calculated for ratios of h/a equal to 0.01 converged to the solutions obtained using Kirchhoff-Love plate theory (KLPT), illustrating the applicability of the GPDE to thin and thin plate buckling.

This study investigates the dynamic properties of Reactive Powder Underwater Concrete (RPUWC), a novel composite integrating attributes of Reactive Powder Concrete and underwater cast concrete. The study focuses on assessing the impact resistance, dynamic modulus of elasticity, rigidity, and Poisson's ratio. The influence of micro steel fibers (MS) at different volume fractions (1%, 1.25%, and 1.5%) and different anti-washout admixture (AWA) dosages (0.5%, 0.7%, and 0.9%) are examined. The findings indicate that increasing the MS content improves crack resistance and energy absorption, resulting in a substantial 155.6% enhancement in the first crack resistance when using 1.5% MS. Additionally, ultimate resistance improves by 158%. Furthermore, there are significant increases in the dynamic and modulus of rigidity as the MS percentage rises. The impact of AWA is rather limited, with a reduction in the dynamic modulus of 18.3% for 0.7% AWA and 30% for 0.9% AWA. Likewise, the modulus of rigidity decreases by 13% for 0.7% AWA and 23.9% for 0.9% AWA. Moreover, strong positive correlations between non-destructive testing (NDT) and ASTM C 215 equations are observed. This investigation addresses a significant knowledge gap, shedding light on optimizing underwater structures' performance by comprehending their dynamic response under varied MS and AWA ratios.