Journal of King Saud University, Engineering Sciences最新文献

Axial, flexure, and shear loads are the most common loads that could impact any structure. For instance, wall panels and columns majorly carry axial loads from the beam and slabs; they are also susceptible to flexure and shear loads from the wind or earthquake loads. Insulated concrete form (ICF) is a portable component of interconnected expanded polystyrene (EPS) panels filled with concrete. EPS remains in place and becomes part of the wall to enhance thermal resistance and structural performance. This paper focuses on an experiment that investigated the performance of ICF wall panels under axial compression and flexure. EPS with a higher density of 20 and 40 kg/m³ and a higher thickness of 50 and 100 mm was selected to prepare ICF wall panels for this experimental investigation. In addition, the plain concrete panel was cast for reference. Axial, flexure, and shear load-carrying capacity, load displacement, load–deflection profiles, crack propagation patterns, failure nature, and strain energy are analyzed and reported in this paper. It was observed that ICF panels were superior to plain concrete panels in terms of axial, flexure, and shear load-carrying capacity, failure nature, and absorbed strain energy.

Due to its inherent properties, concrete exhibits brittle failure once it attains its peak compressive and tensile strengths. As concrete is weak in tension, it is usually reinforced with steel bars to resist tensile stresses produced by the applied loading in its superstructure and infrastructure. However, over the last few decades, steel fibers have also been used in preparing concrete for the construction of structural components. Based on some published studies, it has been observed that the use of steel fibers significantly decreases the brittleness associated with concrete and causes an increase in peak compressive and tensile strengths. Furthermore, it was also observed that its behavior significantly differs under increasing compressive loading rates when compared under static loads. However, these studies have been unable to identify the causes of this change in behavior under increasing loading rates; therefore, in this study, a detailed numerical investigation has been carried out using non-linear finite-element analysis software, ABAQUS. It was found that the behavior exhibited by steel fiber reinforced concrete specimens under high rates of compressive loading represents a structural response rather than material behavior.

The utilization of innovative, lightweight, durable, and ecologically friendly polymer concrete is becoming more popular. Therefore, this research was conducted to investigate the mechanical performance of polymer concrete produced using Vinyl Ester (VE) resin and high-volume Fly Ash (FA) filler with a focus on compressive, tensile, and flexural strength of strong and weak axes using a three-point flexural test. It is important to note that the resin varied from 20 to 90%, FA from 10 to 20%, Mepoxe (MK) catalyst was 4.5%, and Cobalt (Co) was 1% of resin volume. Moreover, cube specimens were used to determine compressive strength and specific gravity at 3 days, cylindrical specimens were also used to determine compressive strength at the age of 1 and 2 days, and dog-bone-shaped specimens were used for tensile strength. This research also applied a three-point flexural test to both the strong and weak axes of the specimens. The result showed that the specimen with 30% VE and 70% FA (RUN-3) had the most effective compressive strength, specific gravity, price, and casting simplicity or workability as by the 66,2 MPa recorded for compressive strength and 1.88 gr/cm³ for specific gravity with two stages of elastic and plastic failures. The RUN-3 mixture was also used to produce cylindrical specimens and tensile strength was found to be 11.55 MPa while flexural strength in the transverse and lateral axis was 53.74 MPa, and 57.69 MPa respectively.

Due to its versatile properties polyvinyl chloride (PVC) based materials are employed in several applications. At high temperatures and in acidic media PVC is prone to release toxic materials into the environment. Several reports are available in the literature about the modification of PVC to minimize such problems. Herein, an attempt is made to prepare PVC/Halloysite nanotube (HNT) nanocomposites with a fixed amount of compatibilizer, OPTIM GE 344 (maleic anhydride modified very low-density polyethylene (VLDPE)) and characterize the composites with respect to thermal stability, mechanical properties, and structural aspects. Both tensile and flexural strength showed appreciable improvement for the 4 wt% loading of the nanofiller. Thermogravimetric analysis (TGA) showed that the maximum degradation temperature improved by approximately 24 °C for 4 wt% filled composites. PVC thermomat measurements of the samples were used to study the thermal stability of the composites. PVC without HNT showed 36 min as the stability time and it increased to 398 min for 4 wt% of HNT loading. To complement the thermal properties of the composites, the mass loss measurement and contact angle behavior of the composite surfaces were also done. The decrease in contact angle values denoted better surface wettability properties. The mass loss measurements showed a decrease with respect to the filler loading of HNT, indicating a better interaction between the polymer matrix and HNT.

This article investigates the volatilization characteristics of binary and ternary fuel blends of cottonseed partially hydrogenated biodiesel, ethanol, and conventional diesel. The vapor pressure, enthalpy of evaporation, and activation energy of the fuel blends were obtained by thermogravimetric analysis and kinetic calculation. The physicochemical properties of the fuel blends showed that the ternary fuel blend of suitable mixing ratio had satisfactory cetane number, improved oxidation stability, and oxygen content with a significant decrease in the kinematic viscosity. In addition, the vapor pressure of the PHCME ternary fuel blends was increased by 18.4%, 17.2%, and 20.4% compared with PHCME binary fuel blends, and the enthalpies of evaporation of the ternary fuel blends increased slightly with different mixing ratios. The activation energy of PHCME ternary fuel blends was decreased by 3.5%, 6.8%, and 16.3% respectively, compared to the PHCME binary fuel blends. In conclusion, ethanol addition in the PHCME fuel blend improved the volatilization characteristics and the kinematic viscosity of the fuel blend without a significant adverse effect on the fuel properties of hydrogenated biodiesel.

Due to the brittle nature of ceramic, the ceramic and construction industry produces a large volume of waste that imposes a severe environmental threat due to its non-biodegradability. In this study, the suitability of ceramic waste as a replacement of natural coarse and fine aggregate in concrete has been investigated by evaluating engineering properties such as bulk density, water absorption, workability, etc. with respect to different concrete samples made with different mix proportions. Furthermore, a prediction model is introduced to predict compressive and splitting tensile strength using the machine learning tool support vector machine (SVM). A data set containing 108 records either for compressive or tensile strength was used for the training and testing purposes of the SVM model. A total of 9 mix proportions was selected and cast cylinders were cured for 7, 28, and 56 days. Four different kernel functions were used to optimize the results and different accuracy parameters like the value of R², mean absolute error, mean square error, root mean square error, etc. were compared to find the best kernel function for this study. By primarily evaluating the coefficient of determination (R²), SVM showed an acceptable result with an accuracy of over 90%. Moreover, in terms of other accuracy measurement parameters result indicates that the SVM is an effective tool to predict the compressive and splitting tensile strength of concrete comprised of different proportions of ceramic content.

The effect of vertical vibrational loads on the bearing capacity of a foundation resting on salt-encrusted flat soil improved by cement addition was experimentally examined by conducting a physical model. The vibration foundation model resting on the finite dimensions of cemented sabkha was first subjected to incremental vertical monotonic loads to evaluate the bearing capacity for different subsoil conditions; the bearing capacity was calculated from the load–settlement curves. The cemented sabkha overlies the saturated sabkha soil. The influence of the vertical vibrational load for each increment in the vertical monotonic load on the settlement was studied, and a modified load–settlement curve was introduced. For a foundation with no large deformation or liquefaction due to vibrational loads, the vibrational loads insignificantly influence the bearing capacity of the foundation. With increasing frequency, the initial stiffness decreases, resulting in an increase in the settlement. The influence of the cement content and thickness of cemented sabkha on decreasing the foundation’s settlement decrease with increasing monotonic loads and operating frequency.

One of the most important and widely accepted pavement performance and ride quality indicators is the International Roughness Index (IRI). This study investigates the combined effect of pavement distress on flexible pavement performance in two climate regions (wet freeze and wet freeze) in the U.S. and Canada. The long-term pavement performance (LTPP) database was used to obtain pavement distress data. Data from forty-three of the LTPP pavement sections (333 observations) with no previous maintenance were collected. The proposed models predict the IRI as a function of pavement distress variables, namely the pavement age, rutting, fatigue cracking, block cracking, longitudinal cracking, transverse cracking, potholes, patching, bleeding, and ravelling. After the data were collected, modelling was conducted to predict IRI using two techniques: multiple linear regression (MLR) and artificial neural network (ANN). The coefficient of determination ($R^2$), root mean squared error (RMSE) and mean absolute error (MAE) were used to examine the performance of the two techniques adopted in this study. The models' results revealed that both ANN and MLR models could predict IRI with good accuracy. The MLR models yielded the $R^2$ values of 77.7% and 89.3%, whereas the ANN models resulted in the $R^2$ values of 99.1% and 97.5% for wet freeze and wet no freeze climate regions, respectively. As a result, ANN models are more accurate and efficient than MLR models.

The Global Navigation Satellite System (GNSS) provides geodetic coordinates referenced to the world ellipsoid WGS84, whereas positions are computed on the local ellipsoid adopted for geodetic computation in various countries. Thus, to take advantage of GNSS in geodetic applications, the need arises to transform coordinates from the global ellipsoid to the local ellipsoid. This is usually carried out by applying geometric transformation models to convert coordinates from The Global Geodetic System WGS84 into the local systems used in each country of the world and into the grid coordinates of local systems. Over the past years, with the increase in the utilization of GNSS in several geodetic projects, numerous methodologies are available for the solution of transformation issues. These methods can be classified into three categories, the first is based on direct mathematical formulas, the second on iteration approaches, and the last category depends on direct transformation from the global system to the local system based on the calculation of transformation parameters (three, seven, nine …etc.). In this study, a methodology has been proposed for direct transformation from global geodetic coordinates to local geodetic coordinates for a limited area in Syria. It is based on the properties of the ratio and proportion between the geometric elements of points on global and local ellipsoids without the calculation of transformation parameters. The results are compared with some studied methods (Bursa-Wolf, Molodensky Abridge, and Cassini). The resulting accuracy is about ± 3.5 cm. The main conclusion drawn is that the proposed method provides a promising alternative approach in coordinates transformation. Therefore, the capability of the suggested methodology as a powerful method for converting geodetic coordinates from one referenced frame to another has been demonstrated in this present study.