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CONTENTS
Volume 83, Number 4, August25 2022
 


Abstract
Eighteen (18) (120x300x2200 mm) beams were prepared and tested to evaluate the shear strength of Glass Fiber Reinforced Concrete (GFRC) beams with no shear reinforcement, and evaluate the effectiveness of various innovative strengthening systems to increase the shear capacity of the GFRC beams. The test variables are the amount of discrete glass fiber (0.0, 0.6, and 1.2% by volume of concrete) and the type of longitudinal reinforcement bars (steel or GFRP), the strengthening systems (externally bonded (EB) sheet, side near-surface mounted (SNSM) bars, or the two together), strengthening material (GFRP or steel) links, different configurations of NSM GFRP bars (side bonded links, full wrapped stirrups, side C-shaped stirrups, and side bent bars), link spacing, link inclination angle, and the number of bent bars. The experimental results showed that adding the discrete glass fiber to the concrete by 0.6%, and 1.2% enhanced the shear strength by 18.5% and 28%, respectively in addition to enhancing the ductility. The results testified the efficiency of different strengthening systems, where it is enhanced the shear capacity by a ratio of 28.4% to 120%, and that is a significant improvement. Providing SNSM bent bars with strips as a new strengthening technique exhibited better shear performance in terms of crack propagation, and improved shear capacity and ductility compared to other strengthening techniques. Based on the experimental shear behavior, an analytical study, which allows the estimation of the shear capacity of the strengthened beams, was proposed, the results of the experimental and analytical study were comparable by a ratio of 0.91 to 1.15.

Key Words
GFRC beam; strengthening technique; (EB) sheet; (SNSM) bars; Steel link; GFRP link

Address
Marwa Hany, Mohamed H. Makhlouf, Gamal Ismail and Ahmed S. Debaiky: Department of Civil Engineering, Benha Faculty of Engineering, Benha University, Egypt

Abstract
Constitutive modeling that could reasonably predict and effectively evaluate the post-peak structural behavior while eliminating the mesh-dependency in numerical simulation remains to be developed for general engineering applications. Based on the previous work, a simple one-dimensional modeling procedure is proposed to predict and evaluate the post-peak response, as characterized by the evolution of localized strain field, of a steel member to monotonically uniaxial tension. The proposed model extends the classic one-dimensional softening with localization model as introduced by (Schreyer and Chen 1986) to account for the localization length, and bifurcation and rupture points. The new findings of this research are as follows. Two types of strain-softening functions (bilinear and nonlinear) are proposed for comparison. The new failure criterion corresponding to the constitutive modeling is formulated based on the engineering strain inside the localization zone at rupture. Furthermore, a new mathematical expression is developed, based on the strain rate inside and outside the localization zone, to describe the displacement field at which bifurcation occurs. The model solutions are compared with the experimental data on four lowcarbon cylindrical steel bars of different lengths. For engineering applications, the model solutions are also compared to the experimental data of a cylindrical steel bar system (three steel bars arranged in series). It is shown that the bilinear and nonlinear softening models can predict the energy dissipation in the post-peak regime with an average difference of only 4%.

Key Words
bifurcation; constitutive modeling; low carbon steel; size effect; softening; strain localization

Address
Saif L. Altai, Sarah L. Orton and Zhen Chen: Department of Civil and Environmental Engineering, University of Missouri, Columbia, MO 65211, USA

Abstract
The present study deals with forced vibrations of an elastic circular plate supported along its circular edge by unilateral elastic springs. The plate is assumed to be subjected to a uniformly distributed and a concentrated load. Under the combination of these loads, equations of motion are explicitly derived for static and dynamic response analyses by assuming a series of the displacement functions of time and other unknown parameters which are to be determined by employing Lagrangian functional. The approximate solution is sought by applying the Lagrange equations of motions by using the potential energy of the external forces that includes the contributions of the edge forces and the external moments, i.e., those of the effects of the boundary condition to the analysis. For the numerical treatment of the problem in the time domain, the linear acceleration procedure is adopted. The tensionless character of the support is taken into account by using an iterative process and, the coordinate functions for the displacement field are selected to partially fulfill the boundary conditions so that an acceptable approximation can be achieved faster. Numerical results are presented in the figures focusing on the nonlinearity of the problem due to the plate lift-off from the unilateral springs at the edge support.

Key Words
elastic circular plate; forced vibrations; static and dynamic response; tensionless support

Address
Zekai Celep: Department of Civil Engineering, Faculty of Engineering, Fatih Sultan Mehmet Vakif University, TR-34445 Sütlüce, Istanbul, Turkey
Mustafa Gençoğlu: Department of Civil Engineering, Faculty of Civil Engineering, Istanbul Technical University, TR-34469 Maslak, Istanbul, Turkey

Abstract
In this research, a numerical study has been provided for examining the nonlinear stability behaviors of sandwich beams having a cellular core and two face sheets made of nanocomposites. The nonlinear stability behaviors of the sandwich beam having geometrically perfect/imperfect shapes have been studied when it is subjected to a compressive buckling load. The nanocomposite face sheets are made of epoxy reinforced by graphene oxide powders (GOPs). Also, the core has the shape of a honeycomb with regular configuration. Using finite element method based on a higher-order deformation beam element, the system of equations of motions have been solved to derive the stability curves. Several parameters such as face sheet thickness, core wall thickness, graphene oxide amount and boundary conditions have remarkable influences on stability curves of geometrically perfect/imperfect sandwich beams.

Key Words
finite element method; nonlinear stability; numerical simulation; sandwich beam

Address
Ke Ding, Hu Jia, Jun Xu, Yi Liu: Department of Civil Engineering and Architecture, Nanyang Normal University, Nanyang 473061, Henan, China; Nanyang Lingyu Machinery Co., Ltd., Nanyang 473000, Henan, China
Haneen M. Al-Tamimi: Air Conditioning and Refrigeration Techniques Engineering Department, Al-Mustaqbal University College, Babylon, Iraq
Mohamed Amine Khadimallah: Civil Engineering Department, College of Engineering, Prince Sattam Bin Abdulaziz University, Al-Kharj, 16273, Saudi Arabia; Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia

Abstract
The results of research focusing on the experimental and numerical performance of ferrocement RC beams with openings reinforced with welded steel mesh, expanded steel mesh, fiber glass mesh, and polyethylene mesh independently are presented in this article. Casting and testing of fourteen reinforced concrete beams with dimensions of 200x100x2000 mm under concentric compression loadings were part of the research program. The type of reinforcing materials, the volume fraction of reinforcement, the number of mesh layers, and the number of stirrups are the major parameters that change. The main goal is to understand the impact of using new appealing materials in reinforcing RC beams with openings. Using ANSYS-16.0 Software, nonlinear finite element analysis (NLFEA) was used to demonstrate the behavior of composite RC beams with openings. A parametric study is also conducted to discuss the variables that can have the greatest impact on the mechanical behavior of the proposed model, such as the number of openings. The obtained experimental and numerical results demonstrated the FE simulations

Key Words
Ansys-16; composite material; experimental; ferrocement; NLFE modeling; openings; RC beams

Address
Yousry B.I. Shaheen: Civil Engineering Department, Faculty of Engineering, Menoufia University, Menoufia, Egypt
Ashraf M. Mahmoud: Civil Engineering Department, Faculty of Engineering, Modern University for Technology and Information (MTI), Al-Mokattam, Cairo, Egypt

Abstract
This paper aims to study the fracture mechanism of rocks under the 'u' shape cutters considering the effects of crack (pre-existing crack) distances, crack spacing and crack inclination angles. The effects of loading rates on the rock fragmentation underneath these cutters have been also studied. For this purpose, nine experimental samples with dimensions of 5 cmx10 cmx10 cm consisting of the non-persistent cracks were prepared. The first three specimens' sets had one non-persistent crack (pre-existing crack) with a length of 2 cm and angularity of 0o, 45o, and 90o. The spacing between the crack and the 'u' shape cutter was 2 cm. The second three specimens' set had one non-persistent crack with a length of 2 cm and angularity of 0o, 45o, and 90o but the spacing between pre-existing crack and the 'u' shape cutter was 4 cm. The third three specimens' set has two non-persistent cracks with lengths of 2 cm and angularity of 0o, 45o and 90o. The spacing between the upper crack and the 'u' shape cutter was 2 cm and the spacing between the lower crack and the upper crack was 2 cm. The samples were tested under a loading rate of 0.005 mm/s. concurrent with the experimental investigation. The numerical simulations were performed on the modeled samples with non-persistent cracks using PFC2D. These models were tested under three different loading rates of 0.005 mm/s, 0.01 mm/sec and 0.02 mm/sec. These results show that the crack number, crack spacing, crack angularity, and loading rate has important effects on the crack growth mechanism in the rocks underneath the 'u' shape cutters. In addition, the failure modes and the fracture patterns in the experimental tests and numerical simulations are similar to one another showing the validity and accuracy of the current study.

Key Words
crack growth mechanism; loading rate; non-persistent cracks' angles; pre-existing cracks' number and spacing; U shape cutter

Address
Jinwei Fu, Hadi Haeri: School of Civil Engineering and Transportation, North China University of Water Resources and Electric Power, Zhengzhou, 450046, China
Vahab Sarfarazi, Sh. Mohamadi Bolban Abad: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
Mohammad Fatehi Marji: Department of Mine Exploitation Engineering, Faculty of Mining and Metallurgy, Institute of Engineering, Yazd University, Yazd, Iran
Gholamreza Saeedi: Department of Mining Engineering, Shahid Bahonar University of Kerman, Kerman, Iran
Yibing Yu: School of Civil Engineering and Transportation, North China University of Water Resources and Electric Power, Zhengzhou, 450046, China

Abstract
The strength models for fiber-reinforced polymer (FRP)-confined normal strength concrete (NC) cylinders available in the literature have been suggested based on small databases using limited variables of such structural members portraying less accuracy. The artificial neural network (ANN) is an advanced technique for precisely predicting the response of composite structures by considering a large number of parameters. The main objective of the present investigation is to develop an ANN model for the axial strength of FRP-confined NC cylinders using various parameters to give the highest accuracy of the predictions. To secure this aim, a large experimental database of 313 FRP-confined NC cylinders has been constructed from previous research investigations. An evaluation of 33 different empirical strength models has been performed using various statistical parameters (root mean squared error RMSE, mean absolute error MAE, and coefficient of determination R2) over the developed database. Then, a new ANN model using the Group Method of Data Handling (GMDH) has been proposed based on the experimental database that portrayed the highest performance as compared with the previous models with R2=0.92, RMSE=0.27, and MAE=0.33. Therefore, the suggested ANN model can accurately capture the axial strength of FRP-confined NC cylinders that can be used for the further analysis and design of such members in the construction industry.

Key Words
artificial neural networks; axial strain; axial strength; CFRP confinement; confined concrete; statistical analysis

Address
Mohammed Berradia: Department of Civil Engineering, Laboratory of Structures, Geotechnics and Risks (LSGR), Hassiba Benbouali University of Chlef, B.P 78C, Ouled Fares Chlef 02180, Algeria
Marc Azab: College of Engineering and Technology, American University of the Middle East, Egaila, 54200, Kuwait
Zeeshan Ahmad: Department of Civil Engineering, University of Engineering and Technology, Taxila, 47050, Pakistan
Oussama Accouche: College of Engineering and Technology, American University of the Middle East, Egaila, 54200, Kuwait
Ali Raza: Department of Civil Engineering, Laboratory of Structures, Geotechnics and Risks (LSGR), Hassiba Benbouali University of Chlef, B.P 78C, Ouled Fares Chlef 02180, Algeria
Yasser Alashker: Civil Engineering Department, College of Engineering, King Khalid University, Saudi Arabia; Structural Engineering Department, Faculty of Engineering, Zagazig University, Egypt

Abstract
In this paper, a novel multi-feature model predictive control (MPC) framework with real-time and adaptive performances is proposed for intelligent structural control in which some drawbacks of the algorithm including, complex control rule and non-optimality, are alleviated. Hence, Linear Programming (LP) is utilized to simplify the resulted control rule. Afterward, the Whale Optimization Algorithm (WOA) is applied to the optimal and adaptive tuning of the LP weights independently at each time step. The stochastic control rule is also achieved using Kalman Filter (KF) to handle noisy measurements. The Extreme Learning Machine (ELM) is then adopted to develop a data-driven and real-time control algorithm. The efficiency of the developed algorithm is then demonstrated by numerical simulation of a twenty-story high-rise benchmark building subjected to earthquake excitations. The competency of the proposed method is proven from the aspects of optimality, stochasticity, and adaptivity compared to the KF-based MPC (KMPC) and constrained MPC (CMPC) algorithms in vibration suppression of building structures. The average value for performance indices in the near-field and far-field (El earthquakes demonstrates a reduction up to 38.3% and 32.5% compared with KMPC and CMPC, respectively.

Key Words
adaptive control; data-driven control; Extreme Learning Machine (ELM); Model Predictive Control (MPC); stochastic control; Whale Optimization Algorithm (WOA)

Address
Javad Katebi, Afshin Bahrami Rad and Javad Palizvan Zand: Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran

Abstract
In this paper, the effect of fire conditions according to ISO 834 standard on the behavior of carbon fibre-reinforced plastic (CFRP) reinforced steel beams coated with gypsum-based mortar has been investigated numerically. To study the efficiency of these beams, 3D coupled temperature-displacement finite element analyzes have been conducted. Mechanical and thermal characteristics of three different parts of composite beams, i.e., steel, CFRP plate, and fireproof coating, were considered as a function of temperature. The interaction between steel and CFRP plate has been simulated employing the adhesion model. The effect of temperature, CFRP plate reinforcement, and the fireproof coating thickness on the deformation of the beams have been analyzed. The results showed that within the first 120 min of fire exposure, increasing the thickness of the fireproof coating from 1 mm to 10 mm reduced the maximum temperature of the outer surface of the steel beam from 380oC to 270oC. This increase in the thickness of the fireproof layer decreased the rate of growth in the temperature of the steel beam by approximately 30%. Besides excellent thermal resistance and gypsum-based mortar, the studied fireproof coating method could provide better fire resistance for steel structures and thus can be applied to building materials.

Key Words
CFRP plate; finite element analysis; fireproof coating; steel beam; thermal loading

Address
Alim Al Ayub Ahmed: Jiujiang University, 551 Qianjindonglu, Jiujiang, Jiangxi, China
Majid M. Kharnoob: Civil Engineering Department, University of Baghdad, Baghdad, Iraq
Ravil Akhmadeev: Plekhanov Russian University of Economics, Russian Federation, Stremyanny lane, 36, Moscow, 117997, Russia
Andrei Sevbitov: Department of Propaedeutics of Dental Diseases, Sechenov First Moscow State Medical University, Moscow, Russia
Abduladheem Turki Jalil: Medical Laboratories Techniques Department, Al-Mustaqbal University College, Babylon, Hilla, 51001, Iraq
Mustafa M. Kadhim: Medical Laboratory Techniques Department, Al-Farahidi University, Baghdad, Iraq
Zahra J. Hansh: College of Petroleum Engineering, Al-Ayen University, Thi-Qar, Iraq
Yasser Fakri Mustafa: Department of Pharmaceutical Chemistry, College of Pharmacy, University of Mosul, Mosul, Iraq
Irina Akhmadullina: Kazan Federal University, Russia, Legal Department, Russia

Abstract
This study aimed to evaluate the progressive collapse potential of buildings designed using conventional design codes for the merchant occupancy classification and subjected to a sudden column failure. For this purpose, three reinforced concrete buildings having different story numbers were designed according to the seismic design recommendations of TSCB-2019. Later on, the buildings were analyzed using the GSA-2016 and UFC 4-023-03 to observe their progressive collapse responses. Three columns were removed independently in the structures from different locations. Nonlinear dynamic analysis method for the alternate path direct design approach was implemented for the design evaluation. The plasticity of the structural members was simulated by using nonlinear fiber hinges. The moment, axial, and shear force interaction on the hinges was considered by the Modified Compression Field Theory. Moreover, an existing experimental study investigating the progressive collapse behavior of reinforced concrete structures was used to observe the validation of nonlinear fiber hinges and the applied analysis methodology. The study results deduce that a limited local collapse disproportionately more extensive than the initial failure was experienced on the buildings designed according to TSCB-2019. The mercantile structures designed according to current seismic codes require additional direct design considerations to improve their progressive collapse resistance against the risk of a sudden column loss.

Key Words
fiber hinge; mercantile buildings; progressive collapse; reinforced concrete; Turkish seismic code

Address
Aydin Demir: Department of Civil Engineering, Faculty of Engineering, Sakarya University, Esentepe Kampusu Kemalpasa Mahallesi Universite Caddesi Serdivan, Sakarya 54050, Turkey; Department of Civil, Environmental and Geodetic Engineering, College of Engineering, The Ohio State University, 2070 Neil Avenue Columbus, OH 43210, USA


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