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This paper introduces the free vibrational response solution of a functionally graded (FG) “sandwich plate” resting on a viscoelastic foundation and subjected to a hygrothermal environment load using an accurate high-order shear deformation theory. In this study, three different types of FG “sandwich plate” geometries were investigated. Only four unknowns were considered in the displacement field, including an indeterminate integral, along with a sinusoidal shape function to represent transverse shear stresses. Hamilton’s principle was utilized to obtain the equation of motion by considering infinitesimal deformation theory combined with a generalized Hook’s law. The variables studied are the damping coefficient, aspect ratio, volume fraction density, moisture and temperature variation, and thickness. The results showed that the increase in damping coefficient (ct) as a property of the viscoelastic foundation would enhance the free-vibrational response of the plate. However, the degree of enhancement would be influenced by the hygrothermal environment.

In this study, the transverse shear strength (TSS) retention of two types of new-generation glass fiber-reinforced polymer (GFRP) bars, namely ribbed (RB) and sand-coated (SC) bars, was investigated under alkaline, acidic, and marine conditions in both high-temperature and laboratory environments for up to one year. The ribbed GFRP bars exhibited no notable reduction in strength under ambient conditions after 12 months, but under high-temperature conditions (60 °C), they showed TSS reductions of 10.6%, 9.7%, 11.1%, and 10.9% for exposure solutions E1, E2, E3, and E4, respectively. The sand-coated GFRP bars showed slight strength reductions under ambient conditions and moderate reductions under high-temperature conditions (60 °C), with TSS reductions of 22.5%, 29.0%, 13.0%, and 13.7% for the same solutions, highlighting the detrimental effect of high temperatures on the degradation of the resin matrix. Comparative analyses of older-generation ribbed (RB-O1 and RB-O2) and sand-coated (SC-O) GFRP bars exposed to similar conditioning solutions for the same duration were also performed. In addition, linear regression and artificial neural network (ANN) models were developed to predict strength retention. Models developed using linear regression and ANNs achieved coefficients of determination (R2) of 0.69 and 0.94, respectively, indicating that the ANN model is a more robust tool for predicting the TSS of GFRP bars than is the conventional linear regression model.

In this study, the short-beam shear strength (SBSS) retention of two types of glass fiber-reinforced polymer (GFRP) bars—sand-coated (SG) and ribbed (RG)—was subjected to alkaline, acidic, and water conditions for up to 12 months under both high-temperature and ambient laboratory conditions. Comparative assessments were also performed on older-generation sand-coated (SG-O) and ribbed (RG-O1 and RG-O2) GFRP bars exposed to identical conditions. The results demonstrate that the new-generation GFRP bars, SG and RG, exhibited significantly better durability in harsh environments and exhibited SBSS retentions varying from 61 to 100% in SG and 90–98% in RG under the harshest conditions compared to 56–69% in SG-O, 71–80% in RG-O1, and 74–88% in RG-O2. Additionally, predictive models using both artificial neural networks (ANNs) and linear regression were developed to estimate the strength retention. The ANN model, with an R2 of 0.95, outperformed the linear regression model (R2 = 0.76), highlighting its greater accuracy and suitability for predicting the SBSS of GFRP bars.

This paper presents a study on the shear behavior of reinforced concrete (RC) beams strengthened by jacketing the surfaces of the beams using ultra-high performance fiber reinforced concrete (UHPC). The surfaces of the RC beams were prepared by sandblasting and UHPC was cast in situ over the surfaces of RC beams. The beams were strengthened using two different strengthening configurations; (i) two longitudinal sides strengthening (ii) three sides strengthening. The bond between normal concrete and UHPC was examined by conducting splitting tensile strength and slant shear strength tests on composite cylindrical specimens cast using normal concrete and UHPC. The control and strengthened beam specimens were tested using four-point loading arrangement maintaining different shear span-to-depth ratios. The results of tested beams showed the beneficial effects of strengthening the RC beams using UHPC, as evident from enhancement of the shear capacity and shifting of the failure mode from brittle to ductile with more stiff behavior. In addition, a non-linear finite element model (FEM) was developed to examine the sufficiency of the experimental results used to study the shear behavior of control and strengthened beams. The failure loads and the crack patterns determined experimentally matched well with those predicted using the proposed model with a reasonably good degree of accuracy.

Reinforcing steel corrosion, caused by chloride ingress into concrete, is the leading cause of reinforced concrete deterioration. One of the main findings in the literature for reducing chloride ingress is the improvement of the durability characteristics of concrete by the addition of supplementary cementitious materials (SCMs) and/or chemical agents to concrete mixtures. In this study, standard ASTM tests—such as rapid chloride permeability (RCPT), bulk diffusion and sorptivity tests—were used to measure concrete properties such as porosity, sorptivity, salt diffusion, and permeability. Eight different mixtures, prepared with different SCMs and corrosion inhibitors, were tested. Apparent and effective chloride diffusion coefficients were calculated using bound chloride isotherms and time-dependent decrease in diffusion. Diffusion coefficients decreased with time, especially with the addition of SCMs and corrosion inhibitors. The apparent diffusion coefficient calculated using the error function was slightly lower than the effective diffusion coefficient; however, there was a linear trend between the two. The formation factor was found to correlate with the effective diffusion coefficient. The results of the laboratory tests were compared and benchmarked to their counterparts in the marine exposure site in the Arabian Gulf in order to identify laboratory key tests to predict concrete durability. The overall performance of concrete containing SCMs, especially fly ash, were the best among the other mixtures in the laboratory and the field.

This work explores the bending responses of functionally graded graphene platelet-reinforced ceramic–metal (FG-GPLRCM) plates on Kerr substrates within an integral higher-order shear deformation theory framework. The theory accurately observes zero stresses on the plate's top and bottom surfaces, satisfies boundary conditions, and obviates the requirement for unique shear correction factors using only four governing equations, fewer than other comparable shear deformation models. The plate's Young's modulus and Poisson's ratio are predicted via the Halpin–Tsai model and mixture rule, respectively. By applying Hamilton's principle, governing equations are derived, which are then solved utilizing Navier's technique to determine the deflection of a simply supported FG-GPLRCM plate. Numerical examples are introduced, solved, and compared with theoretical predictions from the literature to confirm the precision of the current theory. The effects of multiple parameters include thick-to-side ratio, length-to-width ratio, power-law gradient index, load type, and Kerr foundation parameters. In addition, the impact of GPL's weight fraction, geometry, size, and distribution pattern on bending behaviors is also investigated.

This work explores the bending responses of functionally graded graphene platelet-reinforced ceramic–metal (FG-GPLRCM) plates on Kerr substrates within an integral higher-order shear deformation theory framework. The theory accurately observes zero stresses on the plate's top and bottom surfaces, satisfies boundary conditions, and obviates the requirement for unique shear correction factors using only four governing equations, fewer than other comparable shear deformation models. The plate's Young's modulus and Poisson's ratio are predicted via the Halpin–Tsai model and mixture rule, respectively. By applying Hamilton's principle, governing equations are derived, which are then solved utilizing Navier's technique to determine the deflection of a simply supported FG-GPLRCM plate. Numerical examples are introduced, solved, and compared with theoretical predictions from the literature to confirm the precision of the current theory. The effects of multiple parameters include thick-to-side ratio, length-to-width ratio, power-law gradient index, load type, and Kerr foundation parameters. In addition, the impact of GPL's weight fraction, geometry, size, and distribution pattern on bending behaviors is also investigated.

The world's largest concrete structure reinforced with glass fiber-reinforced polymer (GFRP) bars was completed recently in Saudi Arabia. The 21.3 km long flood mitigation channel (FMC) was constructed in southwest Saudi Arabia on the outskirts of the new Jazan Economic City (JEC). JEC is located about 725 km south of the city of Jeddah and 80 km from Jazan city. It covers an area of about 103 km2 and has a 12 km long coastline on the southern end of the Red Sea. This huge endeavor also includes the development of the area to accommodate actual and future companies that, under the light of the new refinery, will bring new products, services, and jobs. The JEC-FMC is designed to prevent flooding of the low-lying JEC industries caused by floodwaters originating from the catcliments on the eastern plain of the city and the catchment of the Baish Dam further east.

This study examined experimentally different chemicals for inhibition of steel corrosion in a simulated aqueous solution for the industrial marine atmosphere of the Arabian Gulf region. The literature reported various inhibitors that can help in protection against metal corrosion in aqueous environments. Among them, 10 inhibitors (calcium silicate, cyclohexylamine, n-methylcyclohexylamine, dicyclohexylamine nitrite, sodium benzoate, sodium nitrate, sodium nitrite, sodium phosphate, sodium dihydrogen orthophosphate, and magnesium nitrate hexahydrate) were obtained and corrosion resistance of inhibitor applied steel specimens were examined in the simulated solution (2 wt.% NaCl and 1 wt.% Na^sub 2^SO^sub 4^). Test specimens were prepared from locally produced reinforcing steel products. Treatment of steel with either dicyclohexylamine nitrite or sodium dihydrogen orthophosphate both at 10 mM concentration for 1 day at room temperature resulted in significant inhibition of corrosion. No significant improvement in corrosion inhibition was observed either with an increase in inhibitor concentration at room temperature or with an increase in inhibitor application temperature at 10 mM concentration. A further study is planned to examine the inhibition performances of the two inhibitors under actual atmospheric conditions in the Arabian Gulf region (industrial marine environment).[PUBLICATION ABSTRACT]

The bond behavior between Fiber Reinforced Plastic (FRP) rods and concrete is one of the most important aspects to predict the short- and long-term performance of FRP-reinforced concrete structures. The objectives of this study are to understand the bond characteristics and to identify the important parameters that control the bond behavior and load transfer at the interface. Direct pull-out tests performed on cubic specimens were used to study the FRP/concrete bond behavior. This method allows the measurement of the loaded- and free-end slips of the FRP rod and placement of a strain probe inside the rod to measure internal strain distribution in both axial and radial directions along the bonded length without affecting the FRP/concrete interface. The internal probe technique was verified and found to be effective in measuring the strain values during pull-out tests. The direct pull-out tests were conducted on glass/vinylester, carbon/vinylester, and carbon/epoxy FRP rods with smooth, machined and wrapped FRP rods making axisymmetric configurations. In addition, commercially available glass/vinylester rods and carbon/epoxy cable and rods with different surface deformations were tested. The typical results are given as nominal bond or shear stress vs. free-and loaded-end slip. Experimental results obtained from strain probes used during the pull-out test are also presented as nominal bond or shear stress vs. strain. For the smooth, machined and wrapped FRP rods instrumented with an internal probe, the local bond and shear stress vs. global and local slip were calculated for the segments between the gage locations. For smooth rods the bond strength is low and tends to be controlled by the finish and composition of the resin-rich surface layer. In the case of the machined rods, the bond is developed through the interlock between the lugs and concrete and is controlled by the shear strength of the lugs, which is resin dependent. For the commercially available rods with spiral deformation and sand coating, the maximum bond was reached after a considerable amount of free-end slip. Bond behavior in these rods is controlled by friction due to sand particles and interlock with the rod deformations. The bond failure is FRP controlled and the strength of concrete appears to have no effect on the bond strength and failure mechanism of the machined FRP rods when appropriate concrete cover is provided.