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CONTENTS
Volume 82, Number 2, April25 2022
 


Abstract
This study investigates the resistance of sustainable ultra-high performance concrete (UHPC) on steel reinforcement corrosion. For enhancing the sustainability of UHPC, concrete mixes were prepared with ordinary Portland cement main binder, and mixes with moderate to high percentages of blast furnace cement (CEM III), fly ash (FA), and slag cement as partial replacements of the full quantity of the used cement. Linear polarization resistance technique was employed to estimate the electrochemical behavior of the concrete specimens. Results showed that the compressive strength and the resistance of steel to corrosion in marine environments can be enhanced by improving the sustainability of UHPC through incorporation of CEM III, FA, and slag cement. FA replacement of up to 50% with the addition of 15% SF content produced better compressive strength and steel corrosion resistance than slag cement whether with the use of ordinary Portland cement or blast furnace cement as the main binder.

Key Words
corrosion; electrochemical; linear polarization; sustainability; ultra-high performance concrete

Address
Ahmed M. Tahwia, Gamal M. Elgendy: Structural Engineering Department, Faculty of Engineering, Mansoura University, Egypt
Mohamed Amin: Civil and Architectural Constructions Department, Faculty of Technology and Education, Suez University, Egypt

Abstract
In this study, the effect of porosity distribution pattern on the free vibration analysis of porous FG plates with various boundary conditions is studied. The material properties of the plate and the porosities within the plate are considered to vary continuously through the thickness direction according to the volume fraction of constituents defined by the modified rule of the mixture, this includes porosity volume fraction with four different types of porosity distribution over the cross-section. The governing partial differential equation of motion for the free vibration analysis is obtained using hyperbolic shear deformation theory. An analytical solution is presented for the governing PDEs for various boundary conditions. Results of the presented solution are compared and validated by the available results in the literature. Moreover, the effects of material and porosity distribution and geometrical parameters on vibrational properties are investigated.

Key Words
free vibration; functionally graded materials; Hamilton's principle; porosity

Address
Lazreg Hadji: Department of Civil Engineering, University of Tiaret, BP 78 Zaaroura, Tiaret, 14000, Algeria; Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City 70000, Vietnam
Ali Fallah: Sabanci University Integrated Manufacturing Technologies Research and Application Center, Istanbul, 34906, Turkey
Mohammad Mohammadi Aghdam: Mechanical Engineering Department, Amirkabir University of Technology, Tehran 15875-4413, Iran

Abstract
Zinc-rich epoxy (ZRE) is used to overcome corrosion problems in reinforced concrete (RC) beams and coat steel rebars to protect them from humidity and chlorides. An extra coating layer of Sikadur-31 epoxy (SDE) is utilised to increase bond strength because the use of ZRE reduces the bond strength between concrete and steel rebars. However, the low melting point of SDE indicates that concrete specimens are vulnerable to fire. An experimental investigation on flexural performance of RC beams incorporating ZRE-SDE coating of steel rebars that were destroyed by fire is performed in this study. Twenty beams of five concrete mixes with different cementitious contents were tested to compare fire exposure for coated and uncoated rebars of the same beams at room temperature and determine the optimal cementitious content. Scanning electron microscopy (SEM) was also applied to investigate characteristics of fired mixture samples. Results showed that the use of SDE-ZRE at room temperature improves flexural strengths of the five mixes compared with uncoated rebars with percentages ranging from 8.5% to 12.3%. All beams with SDE-ZRE lost approximately 50% of their flexural strength due to firing. Moreover, the mix incorporating SF (silica fume) of 15% and cement content of 400 kg/m3 introduces optimum behaviour compared with other mixes. All results were supported and verified by the SEM analysis and compressive strength of cubic specimens of the same mixes.

Key Words
epoxy resin bonding agent; fire resistance; flexural strength; RC beams; Zinc-rich

Address
Dina E. Tobbala: Department of Civil and Architecture Constructions, Suez University, Egypt
Ahmed S. Rashed: Department of Physics and Engineering Mathematics, Faculty of Engineering, Zagazig University, Egypt; Faculty of Engineering, Delta University for Science and Technology, Gamasa, Egypt
Bassam A. Tayeh: Department of Civil Engineering, Faculty of Engineering, Islamic University of Gaza, P.O. Box 108, Gaza Strip, Palestine

Abstract
This study presents an experimental and numerically study about the effects of fiber reinforcement ratio on the behavior of concrete-filled steel tubes (CFST) under dynamic impact loading. In literature have examined the behavior of GFRP and FRP wrapped strengthened CFST elements impact loads. However, since the direction of potential impact force isn't too exact, there is always the probability of not being matched the impact force of the area where the reinforced. Therefore, instead of the fiber textile wrapping method which strengthens only a particular area of CFST element, we used fiber-added concrete-filled elements which allow strengthening the whole element. Thus, the effect of fiber-addition in concrete on the behavior of CFST elements under impact loads was examined. To do so, six simply supported CFST beams were constructed with none fiber, 2% fiber and 10% fiber reinforcement ratio on the concrete part of the CFST beam. CFST beams were examined under two different impact loads (75 kg and 225 kg). The impactors hit the beam from a 2000 mm free fall during the experimental study. Numerical models of the specimens were created using ABAQUS finite element software and validated with experimental data. The obtained results such as; mid-span displacement, acceleration, failure modes and energies from experimental and numerical studies were compared and discussed. Furthermore, the Von Misses stress distribution of the CFST beams with different ratio of fiber reinforcements were investigated numerically. To sum up, there is an optimum amount limit of the fiber reinforcement on CFST beams. Up to this limit, the fiber reinforcement increases the structural performances of the beam, beyond that limit the fiber reinforcement decreases the performances of the CFST beam under transverse impact loadings.

Key Words
CFST beam; fiber reinforcement; finite element analysis; polyamide fiber; transverse impact load

Address
Zeynep Yaman: Department of Civil Engineering, Engineering Faculty, Sakarya University, 54187 Sakarya, Turkey

Abstract
A three-mass vehicle model including one rigid mass and two unsprung masses is adopted to predict the vehicle-bridge interaction (VBI) and to establish the nonlinear coupled governing equations. To overcome the numerical instability and large computation problems concerning the vehicle-bridge system, the perturbation method is used to convert the nonlinear coupled governing equations into a set of linear uncoupled equations. Formulas for bridge's natural frequencies considering both the VBI and the dynamic responses of bridge and vehicle are proposed. Compared with the numerical results obtained by the Newmark-B method, the theoretical solutions for natural frequencies and dynamic responses are validated. The effects of the important factors of unsprung mass, vehicle damping, surface irregularity on the natural frequencies and dynamic responses of bridge and vehicle are discussed, based on the theoretical solutions.

Key Words
Newmark-B method; perturbation method; three-mass vehicle model; unsprung mass; vehicle-bridge interaction

Address
Yongchao Tan: School of Civil Engineering, Central South University, Changsha 410075, China
Liang Cao: College of Civil Engineering, Hunan University, Changsha 410082, China; Key Laboratory for Damage Diagnosis of Engineering Structures of Hunan Province, Hunan University, Changsha 410082, China
Jiang Li: School of Civil Engineering, Chongqing University, Chongqing 400045, China

Abstract
This paper presents a refined finite element formulation for nonlinear static and dynamic analysis of sliding cable structures, overcoming the limitation of the existing approaches that neglect or approximate the friction, pulley dimension, temperature and geometric nonlinearity. A new family of elements with the same framework is proposed, consisting of the cable-pulley (CP) elements considering sliding friction, and the non-sliding cable-pulley (NSCP) elements considering static friction. Thereafter, the complete procedure of static and dynamic analysis using the proposed elements is developed, with the capability of accurately dealing with the friction at each pulley. Several examples are utilized to verify the validity and accuracy of the proposed elements and analysis strategy, and investigate the frictional, thermal and pulley-dimension effects as well. The numerical examples show that the results obtained in this work are in good accordance with the existing works when using the same approximations of friction, pulley dimension and temperature. By avoiding the approximations, the proposed formulation can be effectively adopted in predicting the more precise nonlinear responses of sliding cable structures.

Key Words
cable-pulley elements; cable structures; friction; nonlinear analysis; sliding; temperature

Address
Menggang Yang, Shizai Chen and Shangtao Hu: School of Civil Engineering, Central South University, Changsha 410075, PR China

Abstract
In this paper, the physical neutral surface concept is applied to study the wave propagation of functionally graded (FG) circular plate, the wave equation is derived by Hamiltonian variational principle and the first-order shear deformation plate model. Then, we convert the equations to dimensionless equations. The exact solution of wave propagation problem is obtained by Laplace integral transformation, the first order Hankel integral transformation and the zero order Hankel integral transformation. The results obtained by the current model are very close to those obtained in the existing literature, which indicates the correctness and reliability of this study. Moreover, the effects of the functionally graded index parameters and pore volume fraction on the wave propagation are also discussed in detail.

Key Words
circularplate; functionally graded materials; physical neutral surface concept; pores; wave propagation

Address
Gui-Lin She, Hao-Xuan Ding and Yi-Wen Zhang: College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China

Abstract
Following a loss of control, the impact against a road barrier in a turn predominates among the most severe motorcyclist accidents. These road restraint devices can be equipped with a motorcycle screen, the function of which is to restrain the rider and minimize the consequences of the impact in terms of the severity of injuries. The performance of these screens is evaluated by the European normative procedure EN1317-8, which specifies the test conditions, based on one or two configurations. In practice, however, these impact conditions are very diverse, difficult to extrapolate from accident analysis and therefore poorly investigated. This study is interested in improving knowledge of these impact conditions in terms of impact speed, impact angle and particularly position of the rider. A finite element model has been developed to simulate the dynamic behavior of the rider from loss of control to impact on the screen. Statistical analysis of the results shows a high variability of the impact conditions, in particular with regard to the direction of turn (to the right or to the left). Some improvements are suggested in order to overcome the limitations inherent in standard procedures.

Key Words
EN1317-8; impact condition; motorcyclist; numerical simulation; restraint system

Address
Li Peng, Denis Brizard and Michel Massenzio: Univ Lyon, Univ Gustave Eiffel, Univ Claude Bernard Lyon 1, LBMC UMR_T 9406, F-69622 Lyon, France

Abstract
Many Structural Health Monitoring (SHM) methods have been proposed for structural damage diagnosis and prognosis. However, SHM for pinched hysteretic structures can be problematic due to the high level of nonlinearity. The model-free hysteresis loop analysis (HLA) has displayed notable robustness and accuracy in identifying damage for full-scaled and scaled test buildings. In this paper, the performance of HLA is compared with seven other SHM methods in identifying lateral elastic stiffness for a six-story numerical building with highly nonlinear pinching behavior. Two successive earthquakes are employed to compare the accuracy and consistency of methods within and between events. Robustness is assessed across sampling rates 50-1000 Hz in noise-free condition and then assessed with 10% root mean square (RMS) noise added to responses at 250 Hz sampling rate. Results confirm HLA is the most robust method to sampling rate and noise. HLA preserves high accuracy even when the sampling rate drops to 50 Hz, where the performance of other methods deteriorates considerably. In noisy conditions, the maximum absolute estimation error is less than 4% for HLA. The overall results show HLA has high robustness and accuracy for an extremely nonlinear, but realistic case compared to a range of leading and recent model-based and model-free methods.

Key Words
hysteresis loop analysis (HLA); model-free SHM; piecewise linear regression (PLR); pinched hysteretic structure; structural health monitoring (SHM)

Address
Mohammad Rabiepour: Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
Cong Zhou: Department of Civil Aviation, Northwestern Polytechnical University, Xi'an, China
James G. Chase, Geoffrey W. Rodgers: Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
Chao Xu: School of Astronautics, Northwestern Polytechnical University, Xi'an, China


Abstract
The paper investigates the residual stresses arising in a thermoviscoelastic cylinder as a result of layer-by-layer deposition of material on its lateral surface. Internal stresses are caused by incompatible deformations that accumulate in the assembly as a result of joining parts with different temperatures. For the analysis of internal stresses, an analytical solution to the axisymmetric quasi-static problem of thermoelasticity for a growing cylinder is constructed. It is shown that the distribution of residual stresses depends on the scenario of the surfacing process. In this case, the supply of additional heat to the growing body can significantly reduce the unevenness of temperature fields and reduce the intensity of residual stresses. The most effective is uneven heating, which can be realized, by the action of an alternating current with a tunable excitation frequency. The temperature and residual stresses fields on the growing surface is analyzed numerically for Titanium and Copper materials.

Key Words
additive manufacturing; coupling effects; growing solids; internal dissipation; residual stresses; thermal dissipation

Address
Montaser Fekry: Department of Mechanics and Control Processes, Moscow Institute of Physics and Technology (National Research University), Moscow, Russia; Department of Mathematics, Faculty of Science, South Valley University, Qena, Egypt


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