A model to develop the porosity of concrete as important mechanical property

Rayed Alyousef,Hisham Alabduljabbar,Abdeliazim Mustafa Mohamed,Abdulaziz Alaskar,Kittisak Jermsittiparsert,Lanh Si Ho 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.2

This numerical study demonstrates the porosity conditions and the intensity of the interactions with the aggressive agents. It is established that the density as well as the elastic modulus are correlated to ultrasonic velocity The following investigation assessed the effects of cement grade and porosity on tensile strength, flexural and compressive of Ultra High Performance Concrete (UHPC) as a numerical model in PLAXIS 2d Software. Initially, the existing strength-porosity equations were investigated. Furthermore, comparisons of the proposed equations with the existing models suggested the high accuracy of the proposed equations in predicting, cement grade concrete strength. The outcome obtained showed a ductile failure when un-corroded reinforced concrete demonstrates several bending-induced cracks transfer to the steel reinforcement. Moreover, the outcome also showed a brittle failure when wider but fewer transverse cracks occurred under bending loads. Sustained loading as well as initial pre-cracked condition during the corrosion development have shown to have significant impact on the corrosion behavior of concrete properties. Moreover, greater porosity was generally associated with lower compressive, flexural, and tensile strength. Higher cement grade, on the other hand, resulted in lower reduction in concrete strength. This finding highlighted the critical role of cement strength grade in determining the mechanical properties of concrete.

Axial capacity of back-to-back built-up cold-formed stainless steel unlipped channels-Numerical investigation and parametric study

Krishanu Roy,Hieng Ho Lau,Zhiyuan Fang,Abdeliazim Mustafa Mohamed Ahmed,James B.P. Lim 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.5

In cold-formed steel structures, such as trusses, wall frames and portal frames, the use of back-to-back built-up cold-formed stainless steel unlipped channels as compression members are becoming popular. The advantages of using stainless steel as structural members are corrosion resistance and durability, compared with carbon steel. Current guidance by the American Iron and Steel Institute (AISI) and the Australian and New Zealand (AS/NZS) standards for built-up carbon steel sections describes a modified slenderness approach, to consider the spacing of the intermediate fasteners. The AISI and AS/NZS do not include the design of stainless-steel built-up channels and very few experimental tests or finite element (FE) analyses have been reported in the literature for such back-to-back cold-formed stainless steel unlipped channel section columns. This paper presents a numerical investigation on the behavior of back-to-back built-up cold-formed stainless steel unlipped channel section columns. Three different grades of stainless steel i.e., duplex EN1.4462, ferritic EN1.4003 and austenitic EN1.4404, were considered. The effects of screw spacing on the axial strength of such built-up unlipped channels were investigated. As expected, most of the short and intermediate columns failed by either local-global or local-distortional buckling interactions, whereas the long columns failed by global buckling. All three grades of stainless-steel stub columns failed by local buckling. A comprehensive parametric study was then carried out covering a wide range of slenderness and different cross-sectional geometries to assess the performance of the current design guidelines of carbon steel built-up sections in accordance with the AISI and AS/NZS. In total, 647 FE models were analyzed. From the results of the parametric study, it was found that the AISI and AS/NZS are conservative by around 14 to 20% for all three grades of stainless steel built-up unlipped channel section columns failed through global buckling. However, the AISI and AS/NZS carbon steel design rules can be un-conservative by around 8 to 13%, when they are used to calculate the axial capacity of those stainless steel built-up unlipped channels which are failed in local buckling.

Vibration characteristics of microplates with GNPs-reinforced epoxy core bonded to piezoelectric-reinforced CNTs patches

Forsat, Masoud,Musharavati, Farayi,Eltai, Elsadig,Zain, Azlan Mohd,Mobayen, Saleh,Mohamed, Abdeliazim Mustafa Techno-Press 2021 Advances in nano research Vol.11 No.2

In the current study, vibration characteristics of a three-layered rectangular microplate with Graphene nanoplatelets (GNPs)-reinforced Epoxy core which is fully bonded to piezoelectric-reinforced single-walled Carbon nanotubes (SWCNTs) patches are provided. The face sheets are subjected to the electric field and the microplate is assumed to be in a thermal environment and also, is located on the visco-Pasternak model of the elastic substrate. The GNPs and SWCNTs are dispersed through the core's and face's thickness according to the given functions. To account the shear deformation effect, tangential shear deformation theory (TGSDT) as a higher-order theory is employed and the modified strain gradient theory (MSGT) with tree independent length-scale parameters is selected to capture the size effect. Using the extended form of Hamilton's principle and variational formulation, the governing motion equations are derived and solved mathematically via Navier's scheme for simply supported edges microplate. By ensuring the validity of the results after comparing them in a simpler state with previously published ones, the effects of the most prominent parameters on the results are investigated. It is seen GNPs and CNTs dispersion patterns play an important role in the microplate vibrational behavior, as well as temperature variations. Since the under consideration microstructure can be accounted as smart structures, therefore, the outcomes of this study may help to design and create more efficient engineering structures, such as sensors and actuators and also micro/nano electromechanical systems.

Elevated temperature resistance of concrete columns with axial loading

Alaskar, Abdulaziz,Alyousef, Rayed,Alabduljabbar, Hisham,Alrshoudi, Fahed,Mohamed, Abdeliazim Mustafa,Jermsittiparsert, Kittisak,Ho, Lanh Si Techno-Press 2020 Advances in concrete construction Vol.9 No.4

The influence of temperature on the material of concrete filled columns (CFCs) under axial loading has been quantitatively studied in this research. CFCs have many various advantages and disadvantages. One of the important inefficiency of classic CFCs design is the practical lack of hooped compression under the operational loads because of the fewer variables of Poisson's rate of concrete compared to steel. This is the reason why the holder tends to break away from the concrete core in elastic stage. It is also suggested to produce concrete filled steel tube columns with an initial compressed concrete core to surpass their design. Elevated temperatures have essentially reduced the strengths of steel tubes and the final capacity of CFCs exposed to fire. Thus, the computation of bearing capacity of concrete filled steel tube columns is studied here. Sometimes, the structures of concrete could be exposed to the high temperatures during altered times, accordingly, outcomes have shown a decrement in compressive-strength, then an increase with the reduction of this content. In addition, the moisture content at the minimal strength is declined with temperature rising. According to Finite Element (FE), the column performance assessment is carried out according to the axial load carrying capacities and the improvement of ductility and strength because of limitations. Self-stress could significantly develop the ultimate stiffness and capacity of concrete columns. In addition, the design equations for the ultimate capacity of concrete columns have been offered and the predictions satisfactorily agree with the numerical results. The proposed based model (FE model of PEC column) 65% aligns with the concrete exposed to high temperature. Therefore, computed solutions have represented a better perception of structural and thermal responses of CFC in fire.

Elastic wave phenomenon of nanobeams including thickness stretching effect

Eyvazian, Arameh,Zhang, Chunwei,Musharavati, Farayi,Khan, Afrasyab,Mohamed, Abdeliazim Mustafa Techno-Press 2021 Advances in nano research Vol.10 No.3

The present work deals with an investigation on longitudinal wave propagation in nanobeams made of graphene sheets, for the first time. The nanobeam is modelled via a higher-order shear deformation theory accounts for both higher-order and thickness stretching terms. The general nonlocal strain gradient theory including nonlocality and strain gradient characteristics of size-dependency in order is used to examine the small-scale effects. This model has three-small scale coefficients in which two of them are for nonlocality and one of them applied for gradient effects. Hamilton supposition is applied to obtain the governing motion equation which is solved using a harmonic solution procedure. It is indicated that the longitudinal wave characteristics of the nanobeams are significantly influenced by the nonlocal parameters and strain gradient parameter. It is shown that higher nonlocal parameter is more efficient than lower nonlocal parameter to change longitudinal phase velocities, while the strain gradient parameter is the determining factor for their efficiency on the results.

Influence of crack on the permeability of plastic concrete

Yongqiang He,Rayed Alyousef,Abdulaziz Alaskar,Hisham Alabduljabbar,Abdeliazim Mustafa Mohamed,Nelson Maureira-Carsalade,Angel Roco-Videla,Alibek Issakhov,Hamid Assilzadeh 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.5

This study examined the relations between permeability of the concrete due to addition of new cracks. The different concrete types analyzed were standard concrete, reinforced steel fiber concrete, and reinforced concrete polypropylene fiber. In consideration of the improved polypropylene content of polypropylene fiber reinforced concrete, the crack diameter was decreased by 72-93% for up to 0.25% fiber and cracks were eliminated with 0.3% fiber inclusion. In terms of steel fiberreinforced concrete, the results showed that steel reinforcing macro fibers decrease the permeability of cracked concrete at wider crack widths. While the permeability of unreinforced concrete was the highest, 0.5% steel content resulted in lower permeability while a higher steel content concrete with 1% steel had the lowest permeability. Crack stitching phenomenon and the effect of multiple cracks may be attributed to the decrease in the permeability. With respect to normal concrete, the findings showed the crack opening displacement at the highest tension is less than 20 microns. At this loading stage, after unloading, around 80% of the displacement is restored and the residual crack opening is notably small, indicating the low impact of cracking on concrete permeability (CP) and showing that CP was increased with crack width. As a result, adding polypropylene aggregate to concrete could significantly reduce the width of crack, while adding steel fiber to concrete reduces the permeability of cracked concrete compared to normal concrete which may result in a minor crack on CP.

Investigation on the monotonic behavior of the steel rack upright-beam column connection

Yan Cao,Rayed Alyousef,Kittisak Jermsittiparsert,Lanh Si Ho,Abdulaziz Alaskar,Hisham Alabduljabbar,Fahed Alrshoudi,Abdeliazim Mustafa Mohamed 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.1

The cold-formed steel storage racks are extensively employed in various industries applications such as storing products in reliable places and storehouses before distribution to the market. Racking systems lose their stability under lateral loads, such as seismic actions due to the slenderness of elements and low ductility. This justifies a need for more investigation on methods to improve their behavior and increase their capacity to survive medium to severe loads. A standardized connection could be obtained through investigation on the moment resistance, value of original rotational stiffness, ductility, and failure mode of the connection. A total of six monotonic tests were carried out to determine the behavior of the connection of straight 2.0 mm, and 2.6 mm thickness connects to 5 lug end connectors. Then, the obtained results are benched mark as the original data. Furthermore, an extreme learning machine (ELM) technique has been employed to verify and predict both moment and rotation results. Out of 4 connections, increase the ultimate moment resistance of connection by 13% and 18% for 2.0 mm and 2.6 mm upright connection, respectively.

Computational analysis of three dimensional steel frame structures through different stiffening members

Abdulaziz Alaskar,Karzan Wakil,Rayed Alyousef,Kittisak Jermsittiparsert,Lanh Si Ho,Hisham Alabduljabbar,Fahed Alrshoudi,Abdeliazim Mustafa Mohamed 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.2

Ground motion records are commonly used for fragility curves (FCs) developing utilized in seismic loss estimating analysis for earthquake prone zones. These records could be ‘real’, say the recorded acceleration time series or ‘simulated’ records consistent with the regional seismicity and produced by use of alternative simulation methods. This study has focused on fragility curves developing for masonry buildings through computational ‘simulated’ ground motion records while evaluating the properness of these fragilities compared to the curves generated by the use of ‘real’ records. Assessing the dynamic responses of structures, nonlinear computational time history analyses through the equivalent single degree of freedom systems have been implemented on OpenSees platform. Accordingly, computational structural analyses of multi-story 3D frame structures with different stiffening members considering soil interaction have been carried out with finite element software according to (1992) Earthquake East-West component. The obtained results have been compared to each frame regarding soil interaction. Conclusion and recommendations with the discuss of obtaining findings are presented.

Computational estimation of the earthquake response for fibre reinforced concrete rectangular columns

Chanjuan Liu,Xinling Wu,Karzan Wakil,Kittisak Jermsittiparsert,Lanh Si Ho,Hisham Alabduljabbar,Abdulaziz Alaskar,Fahed Alrshoudi,Rayed Alyousef,Abdeliazim Mustafa Mohamed 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.5

Due to the impressive flexural performance, enhanced compressive strength and more constrained crack propagation, Fibre-reinforced concrete (FRC) have been widely employed in the construction application. Majority of experimental studies have focused on the seismic behavior of FRC columns. Based on the valid experimental data obtained from the previous studies, the current study has evaluated the seismic response and compressive strength of FRC rectangular columns while following hybrid metaheuristic techniques. Due to the non-linearity of seismic data, Adaptive neuro-fuzzy inference system (ANFIS) has been incorporated with metaheuristic algorithms. 317 different datasets from FRC column tests has been applied as one database in order to determine the most influential factor on the ultimate strengths of FRC rectangular columns subjected to the simulated seismic loading. ANFIS has been used with the incorporation of Particle Swarm Optimization (PSO) and Genetic algorithm (GA). For the analysis of the attained results, Extreme learning machine (ELM) as an authentic prediction method has been concurrently used. The variable selection procedure is to choose the most dominant parameters affecting the ultimate strengths of FRC rectangular columns subjected to simulated seismic loading. Accordingly, the results have shown that ANFIS-PSO has successfully predicted the seismic lateral load with R2 = 0.857 and 0.902 for the test and train phase, respectively, nominated as the lateral load prediction estimator. On the other hand, in case of compressive strength prediction, ELM is to predict the compressive strength with R2 = 0.657 and 0.862 for test and train phase, respectively. The results have shown that the seismic lateral force trend is more predictable than the compressive strength of FRC rectangular columns, in which the best results belong to the lateral force prediction. Compressive strength prediction has illustrated a significant deviation above 40 Mpa which could be related to the considerable non-linearity and possible empirical shortcomings. Finally, employing ANFIS-GA and ANFIS-PSO techniques to evaluate the seismic response of FRC are a promising reliable approach to be replaced for high cost and time-consuming experimental tests.

Optimizing reinforced concrete beams under different load cases and material mechanical properties using genetic algorithms

Enqiang Zhu,Rabi Muyad Najem,Du Dinh-Cong,Zehui Shao,Karzan Wakil,Lanh Si Ho,Rayed Alyousef,Hisham Alabduljabbar,Abdulaziz Alaskar,Fahed Alrshoudi,Abdeliazim Mustafa Mohamed 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.4

Genetic Algorithm (GA) is a meta-heuristic algorithm which is capable of providing robust solutions for optimal design of structural components, particularly those one needs considering many design requirements. Hence, it has been successfully used by engineers in the typology optimization of structural members. As a novel approach, this study employs GA in order for conducting a case study with high constraints on the optimum mechanical properties of reinforced concrete (RC) beams under different load combinations. Accordingly, unified optimum sections through a computer program are adopted to solve the continuous beams problem. Genetic Algorithms proved in finding the optimum resolution smoothly and flawlessly particularly in case of handling many complicated constraints like a continuous beam subjected to different loads as moments shear - torsion regarding the curbs of design codes.