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CONTENTS
Volume 29, Number 6, June 2022
 


Abstract
On the premise of ensuring that the automatic and quantitative discharging function of concrete conveyors is met, the accuracy of the weight forecast by the mathematical model of the screw conveying volume is improved, and the error of the weight of the concrete parts and the accumulation thickness is reduced. In this paper, the discrete element method (DEM) is used to simulate the macroscopic flow of concrete. Using the concrete discrete element model, the size of the screw conveyor is set, and establish the response model between the influencing factors (process and structure) and the concrete mass flow rate according to the design points of the screw discharging experiment. The nonlinear data fitting method is used to obtain the volumetric efficiency function under the influence of process and structural factors, and the traditional screw conveying volume model is improved. The mass flow rate of concrete predicted by the improved mathematical model of screw conveying volume is consistent with the test results. The model can accurately describe the conveying process of concrete and achieve the purpose of improving the accuracy of forecasting the weight of discharged concrete.

Key Words
concrete; DEM; numerical modelling; screw conveyor

Address
Wenda Yu, Ke Zhang, Dong Li, Defang Zou: School of Mechanical Engineering, Shenyang Jianzhu University, Shenyang 110168, China
Shiying Zhang: School of Mechanical Engineering, Shenyang Jianzhu University, Shenyang 110168, China; Northern Heavy Industries Group, Economic and Technological Development Zone Liaoning, Shenyang 110168, China

Abstract
This paper examined the impact of the cross-sectional structure on the structural results under different loading conditions of reinforced concrete (RC) members' management limited in Carbon Fiber Reinforced Polymers (CFRP). The mechanical properties of CFRC was investigated, then, totally 32 samples were examined. Test parameters included the crosssectional shape as square, rectangular and circular with two various aspect rates and loading statues. The loading involved concentrated loading, eccentric loading with a ratio of 0.46 to 0.6 and pure bending. The results of the test revealed that the CFRP increased ductility and load during concentrated processing. A cross sectional shape from 23 to 44 percent was increased in load capacity and from 250 to 350 percent increase in axial deformation in rectangular and circular sections respectively, affecting greatly the accomplishment of load capacity and ductility of the concentrated members. Two Artificial Intelligence Models as Extreme Learning Machine (ELM) and Particle Swarm Optimization (PSO) were used to estimating the tensile and flexural strength of specimen. On the basis of the performance from RMSE and RSQR, C-Shape CFRC was greater tensile and flexural strength than any other FRP composite design. Because of the mechanical anchorage into the matrix, C-shaped CFRCC was noted to have greater fiber-matrix interfacial adhesive strength. However, with the increase of the aspect ratio and fiber volume fraction, the compressive strength of CFRCC was reduced. This possibly was due to the fact that during the blending of each fiber, the volume of air input was increased. In addition, by adding silica fumed to composites, the tensile and flexural strength of CFRCC is greatly improved.

Key Words
concrete canvas and CFRP; cross section shape; efficiency; management; metaheuristic optimization algorithms; reinforced columns

Address
Genwang Ge: Department of Civil Engineering, Ma'anshan University, Ma'anshan 243100, China
Yingzi Liu: Department of Civil Engineering, Anhui University of Technology, Ma'anshan 243032, China
Haneen M. Al-Tamimi: Air Conditioning and Refrigeration Techniques Engineering Department, Al-Mustaqbal University College, Babylon 51001, Iraq
Towhid Pourrostam: Department of Civil Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran
Xian Zhang: Economic and Technical Research Institute of Anhui Power Corporation, Hefei 230022, China
H. Elhosiny Ali: Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha, Saudi Arabia; Research Center for Advanced Materials Science (RCAMS), King Khalid University, Abha 61413, P.O. Box 9004, Saudi Arabia; Physics Department, Faculty of Science, Zagazig University, 44519 Zagazig, Egypt
Amin Jan: Faculty of Hospitality, Tourism and Wellness, Universiti Malaysia Kelantan, City Campus, 16100, Kota Bharu, Kelantan, Malaysia
Anas A. Salameh: Department of Management Information Systems, College of Business Administration, Prince Sattam Bin Abdulaziz University, 65 Al-Kharj 11942, Saudi Arabia

Abstract
Lightweight concrete is a superior material due to its light weight and high strength. There however remain significant lacunae in engineering knowledge with regards to shear failure of lightweight fiber reinforced concrete beams. The main aim of the present study is to investigate the optimum usage of steel fibers in lightweight fiber reinforced concrete (LWFRC). Multi-scale finite element model calibrated with experimental results is developed to study the effect of steel fibers on the mechanical properties of LWFRC beams. To decrease the amount of steel fibers, it is preferred to reinforce only the middle section of the LWFRC beams, where the flexural stresses are higher. For numerical simulation, a multi-scale finite element model was developed. The cement matrix was modeled as homogeneous and uniform material and both steel fibers and lightweight coarse aggregates were randomly distributed within the matrix. Considering more realistic assumptions, the bonding between fibers and cement matrix was considered with the Cohesive Zone Model (CZM) and its parameters were determined using the model update method. Furthermore, conformity of Load-Crack Mouth Opening Displacement (CMOD) curves obtained from numerical modeling and experimental test results of notched beams under center-point loading tests were investigated. Validating the finite element model results with experimental tests, the effects of fibers' volume fraction, and the length of the reinforced middle section, on flexural and residual strengths of LWFRC, were studied. Results indicate that using steel fibers in a specified length of the concrete beam with high flexural stresses, and considerable savings can be achieved in using steel fibers. Reducing the length of the reinforced middle section from 50 to 30 cm in specimens containing 10 kg/m3 of steel fibers, resulting in a considerable decrease of the used steel fibers by four times, whereas only a 7% reduction in bearing capacity was observed. Therefore, determining an appropriate length of the reinforced middle section is an essential parameter in reducing fibers, usage leading to more affordable construction costs.

Key Words
center-point loading bending test; concrete notched beam; fiber reinforced concrete; lightweight concrete; multi-scale finite element model; residual flexural strength

Address
Jamshid Esmaeili and Mahdi Ghaffarinia: Department of Civil Engineering, University of Tabriz, Tabriz, Iran

Abstract
This paper numerically investigates the effect of changes in the mechanical properties (displacement, strain, and stress) of the ultra-high-performance concrete (UHPC) without rebar and the reinforced concrete (RC) using steel re-bars. This reinforced concrete is mostly used in the concrete bridge decks. A mixture of sand, gravel, cement, water, steel fiber, superplasticizer, and micro silica was used to fabricate UHPC specimens. The extended finite element method as used in the ABAQUS software is applied for considering the mechanical properties of UHPC, RC, and ordinary concrete specimens. To calibrate the ABAQUS, some experimental tests have been carried out in the laboratory to measure the direct tensile strength of UHPC by the compressive-to-tensile load converting (CTLC) device. This device contains a concrete specimen and is mounted on a universal tensile testing apparatus. In the experiments, three types of mixed concrete were used for UHPC specimens. The tensile strength of these specimens ranges from 9.24 to 11.4 MPa, which is relatively high compared with ordinary concrete specimens, which have a tensile strength ranging from 2 to 5 MPa. In the experimental tests, the UHPC specimen of size 150x60x190 mm with a central hole of 75 mm (in diameter)x60 mm (in thickness) was specially made in the laboratory, and its direct tensile strength was measured by the CTLC device. However, the numerical simulation results for the tensile strength and failure mechanism of the UHPC were very close to those measured experimentally. From comparing the numerical and experimental results obtained in this study, it has been concluded that UHPC can be effectively used for bridge decks.

Key Words
ABAQUS; bridge decks; direct tensile strength; extended finite element method; ultra high-performance concrete

Address
Alireza Bagher Shemirani: Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran

Abstract
This article deals with the vibrational response of a nanobeam made of bi-directional FG materials which is modeled via nonlocal strain gradient theory along with HSDT. Also, the nanobeam is placed on a Winkler-Pasternak foundation and is under axial mechanical loading. By using the variational energy method, the formulation and end conditions are obtained. Then, DSC-IM, as the numerical solution procedure is employed to extract the results. The material properties of the nanobeam are FG which varies in two directions with in exponential manner. The results from DDN are verified by using other papers. Lastly, a thorough parametric investigation is presented to investigated the effect of different parameters.

Key Words
bi-directional FG concrete nanobeam; DSC-IM; NS/SGT; physics-informed neural networks; vibrational problem

Address
Zhonghong Li: School of Architectural Engineering and Art Design, Chongqing Chemical Industry Vocational College, Chongqing 401228, China
Gongxing Yan: School of Intelligent Construction, Luzhou Vocational and Technical College, Luzhou, 646000 Sichuan, China

Abstract
Concrete's compressive strength is widely studied in order to understand many qualities and the grade of the concrete mixture. Conventional civil engineering tests involve time and resources consuming laboratory operations which results in the deterioration of concrete samples. Proposing efficient non-destructive models for the prediction of concrete compressive strength will certainly yield advancements in concrete studies. In this study, the efficiency of using radial basis function neural network (RBFNN) which is not common in this field, is studied for the concrete compressive strength prediction. Complementary studies with back propagation neural network (BPNN), which is commonly used in this field, have also been carried out in order to verify the efficiency of RBFNN for compressive strength prediction. A total of 13 input parameters, including novel ones such as cement's and fly ash's compositional information, have been employed in the prediction models with RBFNN and BPNN since all these parameters are known to influence concrete strength. Three different train: test ratios were tested with both models, while different hidden neurons, epochs, and spread values were introduced to determine the optimum parameters for yielding the best prediction results. Prediction results obtained by RBFNN are observed to yield satisfactory high correlation coefficients and satisfactory low mean square error values when compared to the results in the previous studies, indicating the efficiency of the proposed model.

Key Words
back propagation; cement composition; compressive strength of concrete; factors affecting concrete strength; non-destructive strength prediction; radial basis function neural network

Address
Saddam N.A. Al-Gburi: International Organization for Migration, Izmir, Turkey
Pinar Akpinar: Department of Civil Engineering, Bahçeşehir Cyprus University, Nicosia, N. Cyprus, via Mersin 10, Turkey
Abdulkader Helwan: Department of Electrical and Computer Engineering, Lebanese American University, Lebanon


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