Shear behaviour of RC beams retrofitted using UHPFRC panels epoxied to the sides

Mohammed A. Al-Osta 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.1

In this study, the shear behaviour of reinforced concrete (RC) beams that were retrofitted using precast panels of ultra-high performance fiber reinforced concrete (UHPFRC) is presented. The precast UHPFRC panels were glued to the side surfaces of RC beams using epoxy adhesive in two different configurations: (i) retrofitting two sides, and (ii) retrofitting three sides. Experimental tests on the adhesive bond were conducted to estimate the bond capacity between the UHPFRC and normal concrete. All the specimens were tested in shear under varying levels of shear span-to-depth ratio (a/d=1.0; 1.5). For both types of configuration, the retrofitted specimens exhibited a significant improvement in terms of stiffness, load carrying capacity and failure mode. In addition, the UHPFRC retrofitting panels glued in three-sides shifted the failure from brittle shear to a more ductile flexural failure with enhancing the shear capacity up to 70%. This was more noticeable in beams that were tested with a/d=1.5. An approach for the approximation of the failure capacity of the retrofitted RC beams was evolved using a multi-level regression of the data obtained from the experimental work. The predicted values of strength have been validated by comparing them with the available test data. In addition, a 3-D finite element model (FEM) was developed to estimate the failure load and overall behaviour of the retrofitted beams. The FEM of the retrofitted beams was conducted using the non-linear finite element software ABAQUS.

Influence of porosity on the hygro-thermo-mechanical bending response of an AFG ceramic-metal plates using an integral plate model

Mohammed A. Al-Osta,Hayat Saidi,Abdelouahed Tounsi,S.U. Al-Dulaijan,M.M. Al-Zahrani,Alfarabi Sharif,Abdeldjebbar Tounsi 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.4

In this project, the hygro-thermo-mechanical bending behavior of perfect and imperfect advanced functionally graded (AFG) ceramic-metal plates is analytically investigated using an integral plate model for the first time. The plate is assumed to be supported by a two-parameter elastic foundation. Because of the technical problems encountered in the manufacture of AFG, porosities and micro-voids can occur in AFG specimens, which can result in reduced density and strength of materials. Thus, due to the presence of porosity, a modified rule of mixture is adopted to predict the material properties of the AFG plates. The governing equations are deduced by adopting the "principle of virtual work" and an integral plate model. The analytical Navier's method is considered to solve the obtained differential equations for simply supported AFG porous plate. The results obtained are checked by comparing them for non-porous and porous AFG plates with those available in the open literature. Finally, this work will help us to design advanced functionally graded materials to ensure better durability and efficiency for hygro-thermal environments.

A four variable trigonometric integral plate theory for hygro-thermo-mechanical bending analysis of AFG ceramic-metal plates resting on a two-parameter elastic foundation

Abdelouahed Tounsi,S.U. Al-Dulaijan,Mohammed A. Al-Osta,Abdelbaki Chikh,M.M. Al-Zahrani,Alfarabi Sharif,Abdeldjebbar Tounsi 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.4

In this research, a simple four-variable trigonometric integral shear deformation model is proposed for the static behavior of advanced functionally graded (AFG) ceramic-metal plates supported by a two-parameter elastic foundation and subjected to a nonlinear hygro-thermo-mechanical load. The elastic properties, including both the thermal expansion and moisture coefficients of the plate, are also supposed to be varied within thickness direction by following a power law distribution in terms of volume fractions of the components of the material. The interest of the current theory is seen in its kinematics that use only four independent unknowns, while first-order plate theory and other higher-order plate theories require at least five unknowns. The "in-plane displacement field" of the proposed theory utilizes cosine functions in terms of thickness coordinates to calculate out-of-plane shear deformations. The vertical displacement includes flexural and shear components. The elastic foundation is introduced in mathematical modeling as a two-parameter Winkler-Pasternak foundation. The virtual displacement principle is applied to obtain the basic equations and a Navier solution technique is used to determine an analytical solution. The numerical results predicted by the proposed formulation are compared with results already published in the literature to demonstrate the accuracy and efficiency of the proposed theory. The influences of "moisture concentration", temperature, stiffness of foundation, shear deformation, geometric ratios and volume fraction variation on the mechanical behavior of AFG plates are examined and discussed in detail.

Study of heavy fuel oil fly ash for use in concrete blocks and asphalt concrete mixes

Al-Osta, Mohammed A.,Baig, Mirza G.,Al-Malack, Muhammad H.,Al-Amoudi, Omar S. Baghabra Techno-Press 2016 Advances in concrete construction Vol.4 No.2

Use of heavy fuel fly ash (HFFA) (diesel and cracked fuel) for power generation in Saudi Arabia has generated and accumulated large quantities of HFFA as a byproduct. In this research, HFFA is studied with the emphasis on the utilization of this waste material in concrete blocks and asphalt concrete mixes. Two types of mixes, one with low and other with high cement content, were studied for concrete blocks. Different mixes having varying percentages of HFFA (0% to 25%), as cement/sand replacement or as an additive, were studied. The performance of concrete blocks is evaluated in terms of compressive strength, water absorption, durability and environmental concerns. The results showed that blocks cannot be cast if more than 15% HFFA is used; also there is a marginal reduction in the strength of all the mixes before and after being exposed to the sulfate solution for a period of ten months. HFFA is studied in asphalt concrete mixes in two ways, as an asphalt modifier (3&5%) and as a filler (50%) replacement, the results showed an improvement in stiffness and fatigue life of mixes. However, the stability and indirect tensile strength loss were found to be high as compared to the control mix due to moisture damage, indicating a need of using antistripping agents. On environmental concerns, it was found that most of the concerned elements are within acceptable limits also it is observed that lower concentration of barium is leached out with the higher HFFA concentrations, which indicates that HFFA may work as an adsorbent for this leaching element.

Wave propagation investigation of a porous sandwich FG plate under hygrothermal environments via a new first-order shear deformation theory

Mohammed A. Al-Osta 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.1

This study investigates the wave propagation in porous functionally graded (FG) sandwich plates subjected to hygrothermal environments. A new simple three-unknown first-ordershear deformation theory (FSDT) incorporating an integral term is utilized in this paper. Only three unknowns are used to formulate the governing differential equation by applying the Hamilton principle. The FG layer of the sandwich plate is modeled using the power-law function with evenly distributed porosities to represent the defects of the manufacturing process. The plate is subjected to nonlinear hygrothermal changes across the thickness. The effects of the power-law exponent, core to thickness ratios, porosity volume, and the relations between volume fraction and wave properties of porous FG plate under the hygrothermal environment are investigated. The results showed that the waves’ phase velocities increase linearly with the waves number in the FGM plate. The porosity of the FG materials plate has a noticeable impact on the phase velocity when considering the high ratios of the core layer. It has a negligible effect on small core layers. Finally, it is observed that changing temperatures and moistures do not influence the relationship between the power law and the phase velocity.

Impact of viscoelastic foundation on bending behavior of FG plate subjected to hygro-thermo-mechanical loads

Ismail M. Mudhaffar,Abdelbaki Chikh,Abdelouahed Tounsi,Mohammed A. Al-Osta,Mesfer M. Al-Zahrani,Salah U. Al-Dulaijan 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.86 No.2

This work applies a four-known quasi-3D shear deformation theory to investigate the bending behavior of a functionally graded plate resting on a viscoelastic foundation and subjected to hygro-thermo-mechanical loading. The theory utilizes a hyperbolic shape function to predict the transverse shear stress, and the transverse stretching effect of the plate is considered. The principle of virtual displacement is applied to obtain the governing differential equations, and the Navier method, which comprises an exponential term, is used to obtain the solution. Novel to the current study, the impact of the viscoelastic foundation model, which includes a time-dependent viscosity parameter in addition to Winkler’s and Pasternak parameters, is carefully investigated. Numerical examples are presented to validate the theory. A parametric study is conducted to study the effect of the damping coefficient, the linear and nonlinear loadings, the power-law index, and the plate width-tothickness ratio on the plate bending response. The results show that the presence of the viscoelastic foundation causes an 18% decrease in the plate deflection and about a 10% increase in transverse shear stresses under both linear and nonlinear loading conditions. Additionally, nonlinear loading causes a one-and-a-half times increase in horizontal stresses and a nearly two-times increase in normal transverse stresses compared to linear loading. Based on the article’s findings, it can be concluded that the viscosity effect plays a significant role in the bending response of plates in hygrothermal environments. Hence it shall be considered in the design.

Use of UHPC slab for continuous composite steel-concrete girders

Alfarabi M. Sharif,Nizar A. Assi,Mohammed A. Al-Osta 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.3

The loss of composite action at the hogging moment zone for a continuous composite girder reduces the girder stiffness and strength. This paper presents an experimental investigation of the use of an ultra-high performance concrete (UHPC) slab at the hogging moment zone and a normal concrete (NC) slab at the sagging moment zone. The testing was conducted to verify the level of loading at which composite action is maintained at the hogging moment zone. Four two-span continuous composite girders were tested. The thickness of the UHPC varied between a half and a full depth of slab. The degree of shear connection at the hogging moment zone varied between full and partial. The experimental results confirmed the effectiveness of the UHPC slab to enhance the girder stiffness and maintain the composite action at the hogging moment zone at a load level much higher than the upper service load limit. To a lesser degree enhanced performance was also noted for the smaller thickness of the UHPC slab and partial shear connection at the hogging moment zone. Plastic analysis was conducted to evaluate the ultimate capacity of the girder which yielded a conservative estimation. Finite element (FE) modeling evaluated the girder performance numerically and yielded satisfactory results. The results indicated that composite action at the hogging moment zone is maintained for the degree of shear connection taken as 50% of the full composite action and use of UHPC as half depth of slab thickness.

Finite element modeling of corroded RC beams using cohesive surface bonding approach

Mohammed A. Al-Osta,Hamdi A. Al-Sakkaf,Alfarabi M. Sharif,Shamsad Ahmad,Mohammad H. Baluch 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.2

The modeling of loss of bond between reinforcing bars (rebars) and concrete due to corrosion is useful in studying the behavior and prediction of residual load bearing capacity of corroded reinforced concrete (RC) members. In the present work, first the possibility of using different methods to simulate the rebars-concrete bonding, which is used in three-dimensional (3D) finite element (FE) modeling of corroded RC beams, was explored. The cohesive surface interaction method was found to be most suitable for simulating the bond between rebars and concrete. Secondly, using the cohesive surface interaction approach, the 3D FE modeling of the behavior of non-corroded and corroded RC beams was carried out in an ABAQUS environment. Experimental data, reported in literature, were used to validate the models. Then using the developed models, a parametric study was conducted to examine the effects of some parameters, such as degree and location of the corrosion, on the behavior and residual capacity of the corroded beams. The results obtained from the parametric analysis using the developed model showed that corrosion in top compression rebars has very small effect on the flexural behaviors of beams with small flexural reinforcement ratio that is less than the maximum ratio specified in ACI-318-14 (singly RC beam). In addition, the reduction of steel yield strength in tension reinforcement due to corrosion is the main source of reducing the load bearing capacity of corroded RC beams. The most critical corrosion-induced damage is the complete loss of bond between rebars and the concrete as it causes sudden failure and the beam acts as un-reinforced beam.

A study on the structural behaviour of functionally graded porous plates on elastic foundation using a new quasi-3D model: Bending and free vibration analysis

Miloud Kaddari,Abdelhakim Kaci,Abdelmoumen Anis Bousahla,Abdelouahed Tounsi,Fouad Bourada,AbdeldjebbarTounsi,E.A. Adda Bedia,Mohammed A. Al-Osta 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.25 No.1

This work investigates a new type of quasi-3D hyperbolic shear deformation theory is proposed in this study to discuss the statics and free vibration of functionally graded porous plates resting on elastic foundations. Material properties of porous FG plate are defined by rule of the mixture with an additional term of porosity in the through-thickness direction. By including indeterminate integral variables, the number of unknowns and governing equations of the present theory is reduced, and therefore, it is easy to use. The present approach to plate theory takes into account both transverse shear and normal deformations and satisfies the boundary conditions of zero tensile stress on the plate surfaces. The equations of motion are derived from the Hamilton principle. Analytical solutions are obtained for a simply supported plate. Contrary to any other theory, the number of unknown functions involved in the displacement field is only five, as compared to six or more in the case of other shear and normal deformation theories. A comparison with the corresponding results is made to verify the accuracy and efficiency of the present theory. The influences of the porosity parameter, power-law index, aspect ratio, thickness ratio and the foundation parameters on bending and vibration of porous FG plate.

A simple quasi-3D HSDT for the dynamics analysis of FG thick plate on elastic foundation

Zoulikha Boukhlif,Mohammed Bouremana,Fouad Bourada,Abdelmoumen Anis Bousahla,Mohamed Bourada,Abdelouahed Tounsi,Mohammed A. Al-Osta 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.5

This work presents a dynamic investigation of functionally graded (FG) plates resting on elastic foundation using a simple quasi-3D higher shear deformation theory (quasi-3D HSDT) in which the stretching effect is considered. The culmination of this theory is that in addition to taking into account the effect of thickness extension (εz ≠ 0), the kinematic is defined with only 4 unknowns, which is even lower than the first order shear deformation theory (FSDT). The elastic foundation is included in the formulation using the Pasternak mathematical model. The governing equations are deduced through the Hamilton‟s principle. These equations are then solved via closed-type solutions of the Navier type. The fundamental frequencies are predicted by solving the eigenvalue problem. The degree of accuracy of present solutions can be shown by comparing it to the 3D solution and other closed-form solutions available in the literature.