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CONTENTS
Volume 81, Number 5, March10 2022
 


Abstract
The present research is to study the effect of inclined load in a two-dimensional homogeneous orthotropic magnetothermoelastic solid without energy dissipation with fractional order heat transfer in generalized thermoelasticity with twotemperature. We obtain the solution to the problem with the help of Laplace and Fourier transformations. The field equations of displacement components, stress components and conductive temperature are computed in transformed domain. Further the results are computed in physical domain by using numerical inversion method. The effect of fractional order parameter and inclined load has been depicted on the resulting quantities with the help of graphs.

Key Words
Fourier transform; fractional order; hall current; inclined load; Laplace transform; orthotropic; rotation; twotemperature; uniformly and linearly distributed loads

Address
Parveen Lata and Himanshi: Department of Basic and Applied Sciences, Punjabi University Patiala, Punjab, India

Abstract
A detailed experimental program was conducted to investigate the flexural behavior of ultra high performance concrete (UHPC) beams reinforced with high strength steel (HSS) rebars with a specified yield strength of 600 MPa via direct tensile test and monotonic four-point bending test. First, two sets of direct tensile test specimens, with the same reinforcement ratio but different yield strength of reinforcement, were fabricated and tested. Subsequently, six simply supported beams, including two plain UHPC beams and four reinforced UHPC beams, were prepared and tested under four-point bending load. The results showed that the balanced-reinforced UHPC beams reinforced with HSS rebars could improve the ultimate loadbearing capacity, deformation capacity, ductility properties, etc. more effectively owing to interaction between high strength of HSS rebar and strain-hardening characteristic of UHPC. In addition, the UHPC with steel rebars kept strain compatibility prior to the yielding of the steel rebar, further satisfied the plane-section assumption. Most importantly, the crack pattern of the UHPC beam reinforced with HSS rebars was prone to transform from single main crack failure corresponding to the normal-strength steel, to multiple main cracks failure under the condition of balanced-reinforced failure, which validated by the conclusion of direct tensile tests cooperated with acoustic emission (AE) source locating technique as well.

Key Words
acoustic emission; crack pattern; ductility; high strength steel; ultra high performance concrete

Address
Jun-Yan Wang: Key Laboratory of Advanced Civil Engineering Materials, Tongji University, Ministry of Education, Tongji University, No.4800, Caoan Road, Jiading District, Shanghai, China
Jin-Ben Gu: Key Laboratory of Advanced Civil Engineering Materials, Tongji University, Ministry of Education, Tongji University, No.4800, Caoan Road, Jiading District, Shanghai, China; College of Civil Engineering, Tongji University, No.1239, Siping Road, Yangpu District, Shanghai, China
Chao Liu, Yu-Hao Huang, Ru-Cheng Xiao: College of Civil Engineering, Tongji University, No.1239, Siping Road, Yangpu District, Shanghai, China
Biao Ma: Shanghai Municipal Engineering Design Institute (Group) Co., Ltd., No.901, Zhongshanbeier Road, Yangpu District, Shanghai, China

Abstract
Bolted connector could be an alternative to replace the conventional welded headed stud in steel-ultra high performance concrete (UHPC) lightweight composite structures. In this paper, a novel demountable bolted shear connector, consisting of a high-strength bolt (HSB) and a specially-designed nut which is pre-embedded in a thin UHPC slab, is proposed, which may result in the quick installation and disassembly, due to the mountable, demountable and reusable features. In order to study the shear behavior of the new type of bolted shear connector, static push-out tests were conducted on five groups of the novel demountable bolted shear connector specimens and one group of conventional welded headed stud specimen for comparison. The effect of the bolt shank diameter and aspect ratio of bolt on failure mode, shear stiffness, peak slip at the steel-UHPC interface, shear strength and ductility of novel bolted connectors is investigated. Additionally, design formula for the shear strength is proposed to check the suitability for assessment of the novel demountable bolted shear connectors.

Key Words
demountable; lightweight; reusable; shear behavior; ultra high performance concrete

Address
Jin-Ben Gu: Key Laboratory of Advanced Civil Engineering Materials, Tongji University, Ministry of Education, Tongji University, No.4800, Caoan Road, Jiading District, Shanghai, China; College of Civil Engineering, Tongji University, No. 1239, Siping Road, Yangpu District, Shanghai, China
Jun-Yan Wang: Key Laboratory of Advanced Civil Engineering Materials, Tongji University, Ministry of Education, Tongji University, No.4800, Caoan Road, Jiading District, Shanghai, China

Abstract
The infrastructures such as offshore, bridges, power plant, oil and gas piping and aircraft operate in a harsh environment during their service life. Structural integrity of engineering components used in these industries is paramount for the reliability and economics of operation. Two regression models based on the concept of Gaussian process regression (GPR) and Minimax probability machine regression (MPMR) were developed to predict stress intensity factor range (K). Both GPR and MPMR are in the frame work of probability distribution. Models were developed by using the fatigue crack growth data in MATLAB by appropriately modifying the tools. Fatigue crack growth experiments were carried out on Eccentrically-loaded Single Edge notch Tension (ESE(T)) specimens made of API 5L X65 Grade steel in inert and corrosive environments (2.0% and 3.5% NaCl). The experiments were carried out under constant amplitude cyclic loading with a stress ratio of 0.1 and 5.0 Hz frequency (inert environment), 0.5 Hz frequency (corrosive environment). Crack growth rate (da/dN) and stress intensity factor range (K) values were evaluated at incremental values of loading cycle and crack length. About 70 to 75% of the data has been used for training and the remaining for validation of the models. It is observed that the predicted SIF range is in good agreement with the corresponding experimental observations. Further, the performance of the models was assessed with several statistical parameters, namely, Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Coefficient of Efficiency (E), Root Mean Square Error to Observation's Standard Deviation Ratio (RSR), Normalized Mean Bias Error (NMBE), Performance Index (p) and Variance Account Factor (VAF).

Key Words
API 5L grade X65 steel; corrosion fatigue; Gaussian process regression; minimax probability machine regression; statistical analysis; stress intensity factor range

Address
A. Ramachandra Murthy, S. Vishnuvardhan, M. Saravanana and P. Gandhi: Fatigue & Fracture Laboratory, CSIR-Structural Engineering Research Centre, Chennai, 600 113, India

Abstract
In order to enhance the greenness in the strain-hardening composites and to reduce the high cost of typical polyvinyl alcohol fiber reinforced engineered cementitious composite (PVA-ECC), an affordable strain-hardening composite with green binder content has been proposed. For optimizing the strain-hardening behavior of cementitious composites, this paper investigates the effects of polypropylene fibers on the first cracking strength, fracture properties, and micromechanical parameters of cementitious composites. For this purpose, digital image correlation (DIC) technique was utilized to monitor crack propagation. In addition, to have an in-depth understanding of fiber/matrix interaction, scanning electron microscope (SEM) analysis was used. To understand the effect of fibers on the strain hardening behavior of cementitious composites, ten mixes were designed with the variables of fiber length and volume. To investigate the micromechanical parameters from fracture tests on notched beam specimens, a novel technique has been suggested. In this regard, mechanical and fracture tests were carried out, and the results have been discussed utilizing both fracture and micromechanical concepts. This study shows that the fiber length and volume have optimal values; therefore, using fibers without considering the optimal values has negative effects on the strainhardening behavior of cementitious composites.

Key Words
cementitious composite; digital image correlation (DIC); fracture behavior; greenness; ground granulated blast furnace slag (GGBFS); micromechanics; strain-hardening

Address
Hossein Karimpour and Moosa Mazloom: Department of Civil Engineering, Shahid Rajaee Teacher Training University, Lavizan, Tehran, Iran

Abstract
When the friction pendulum system and shear keys work together to resist the ground motion ,which inclined inputs (non 45o) to the bridge structure, the shear keys in XY direction will be sheared asynchronously, endowed the friction pendulum system with a violent curvilinear motion on the sliding surface during earthquakes. In view of this situation, firstly, this paper abandons the equivalent linearization model of friction and constructs a Spring-Coulomb friction plane isolation system with XY shear keys, and then makes a detailed mechanical analysis of the movement process of friction pendulum system, next, this paper establishes the mathematical model of structural time history response calculation by using the step-by-step integration method, finally, it compiles the corresponding computer program to realize the numerical calculation. The results show that the calculation method in this paper takes advantage of the characteristic that the friction force is always umg, and creatively uses the "circle making method" to express the change process of the friction force and resultant force of the friction pendulum system in any calculation time step, which can effectively solve the temporal nonlinear action of the plane friction; Compared with the response obtained by the calculation method in this paper, the peak values of acceleration response and displacement response calculated by the unidirectional calculation model, which used in the traditional research of the friction pendulum system, are smaller, so the unidirectional calculation model is not safe.

Key Words
equivalent linearization; friction pendulum system; numerical analysis; plane friction nonlinearity; shear keys sheared asynchronously

Address
Biao Wei, Yunji Fu, Lizhong Jiang and Shanshan Li: School of Civil Engineering, Central South University, 22 Shaoshan Nan Road, Changsha, China; National Engineering Laboratory for High Speed Railway Construction, 22 Shaoshan Nan Road, Changsha, China

Abstract
In this work, the free vibration problem of a rotating Rayleigh beam is solved using the meshless Petrov-Galerkin method which is a truly meshless method. The Rayleigh beam includes rotatory inertia in addition to Euler-Bernoulli beam theory. The radial basis functions, which satisfy the Kronecker delta property, are used for the interpolation. The essential boundary conditions can be easily applied with radial basis functions. The results are obtained using six nodes within a subdomain. The results accurately match with the published literature. Also, the results with Euler-Bernoulli are obtained to compare the change in higher natural frequencies with change in the slenderness ratio. The mass and stiffness matrices are derived where we get two stiffness matrices for the node and boundary respectively. The non-dimensional form is discussed as well.

Key Words
mechanical vibration; meshless Petrov-Galerkin method; radial basis function; Rotating Rayleigh beam

Address
Vijay Panchore: Department of Mechanical Engineering, Maulana Azad National Institute of Technology, Bhopal, 462003, India

Abstract
In this paper the viscoelastic responses of four experimental steel-concrete composite beams subjected to highly variable environmental conditions are investigated by means of a finite element (FE) model. Concrete specimens submitted to stepped stress changes are also evaluated to validate the current formulations. Here, two well-known approaches commonly used to solve the viscoelastic constitutive relationship for concrete are employed. The first approach directly solves the integraltype form of the constitutive equation at the macroscopic level, in which aging is included by updating material properties. The second approach is postulated from a rate-type law based on an age-independent Generalized Kelvin rheological model together with Solidification Theory, using a micromechanical based approach. Thus, conceptually both approaches include concrete hardening in two different manners. The aim of this work is to compare and analyze the numerical prediction in terms of longterm deflections of the studied specimens according to both approaches. To accomplish this goal, the performance of several well-known model codes for concrete creep and shrinkage such as ACI 209, CEB-MC90, CEB-MC99, B3, GL 2000 and FIB-2010 are evaluated by means of statistical bias indicators. It is shown that both approaches with minor differences acceptably match the long-term experimental deflection and are able to capture complex oscillatory responses due to variable temperature and relative humidity. Nevertheless, the use of an age-independent scheme as proposed by Solidification Theory may be computationally more advantageous.

Key Words
creep and shrinkage; finite elements; steel-concrete composite beams; viscoelastic

Address
Marcela P. Miranda, Jorge L.P. Tamayo and Inacio B. Morsch: Department of Civil Engineering, Engineering School, Federal University of Rio Grande do Sul, AV. Osvaldo Aranha 99-3o Floor, 90035-190, Porto Alegre, RS, Brazil

Abstract
The active tuned mass damper (ATMD) is an efficient and reliable structural control system for mitigating the dynamic response of structures. The inertial force that an ATMD exerts on a structure to attenuate its otherwise large kinetic energy and undesirable vibrations and displacements is proportional to its excursion. Achieving a balance between the inertial force and excursion requires a control law or feedback mechanism. This study presents a technique for the optimum design of a sliding mode controller (SMC) as the control law for ATMD-equipped structures subjected to earthquakes. The technique includes optimizing an SMC under an artificial earthquake followed by testing its performance under real earthquakes. The SMC of a real 11-story shear building is optimized to demonstrate the technique, and its performance in mitigating the displacements of the building under benchmark near- and far-fault earthquakes is compared against that of a few other techniques (proportional-integral-derivative [PID], linear-quadratic regulator [LQR], and fuzzy logic control [FLC]). Results indicate that the optimum SMC outperforms PID and LQR and exhibits performance comparable to that of FLC in reducing displacements.

Key Words
active tuned mass dampers; nonlinear control; optimum design; sliding mode control; structural control

Address
Hussein Eliasi: Department of Electrical and Computer Engineering, University of Birjand, Birjand, Iran
Hessam Yazdani: Department of Civil and Environmental Engineering, Howard University, Washington, DC, USA
Mohsen Khatibinia: Department of Civil Engineering, University of Birjand, Birjand, Iran
Mehdi Mahmoudi: Department of Civil Engineering, Khayyam University, Mashhad, Iran

Abstract
The powerful data mapping capability of computational deep learning methods has been recently explored in academic works to develop strategies for structural health monitoring through appropriate characterization of dynamic responses. In many cases, these studies concern laboratory prototypes and finite element models to validate the proposed methodologies. Therefore, the present work aims to investigate the capability of a deep learning algorithm called Sparse Autoencoder (SAE) specifically focused on detecting structural alterations in real-case studies. The idea is to characterize the dynamic responses via SAE models and, subsequently, to detect the onset of abnormal behavior through the Shewhart T control chart, calculated with SAE extracted features. The anomaly detection approach is exemplified using data from the Z24 bridge, a classical benchmark, and data from the continuous monitoring of the San Vittore bell-tower, Italy. In both cases, the influence of temperature is also evaluated. The proposed approach achieved good performance, detecting structural changes even under temperature variations.

Key Words
damage detection; deep learning; machine learning; sparse autoencoder; structural health monitoring

Address
Rafaelle P. Finotti: Graduate Program in Computational Modeling, Federal University of Juiz de Fora, Brazil
Carmelo Gentile: Department of Architecture, Built Environment and Construction Engineering, Politecnico di Milano, Italy
Flavio Barbosa: Graduate Program in Computational Modeling, Federal University of Juiz de Fora, Brazil; Graduate Program in Civil Engineering, Federal University of Juiz de Fora, Brazil
Alexandre Cury: Graduate Program in Civil Engineering, Federal University of Juiz de Fora, Brazil


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