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CONTENTS
Volume 22, Number 4, October 2018
 

Abstract
Novel design of interdigitated electrodes capable of increasing the performance of piezoelectric transducers are proposed. The new electrodes\' geometry improve the electromechanical coupling by offering an enhanced adaptation of the electric field to the interdigitated electrode configuration. The proposed analysis is based on finite element modeling and takes into account local polarization effect. It is shown that the proposed electrodes considerably increase the strain generation compared to flat electrode arrangement used for Macro Fiber Composite (MFC) and Active Fiber Composite (AFC) actuators. Also, electric field singularities are reduced allowing better reliability of the transducer against electric failure.

Key Words
interdigitated electrodes; piezoelectricity; sensor and actuator; polarization; piezocomposite

Address
Ahmed Jemai:Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, BP 743, La Marsa 2078, University of Carthage, Tunisia
Fehmi Najar: Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, BP 743, La Marsa 2078, University of Carthage, Tunisia;
IPEIEM, B.P 244, Tunis 2092, University of Tunis El Manar, Tunisia


Abstract
Traditional base isolation systems focus on isolating the seismic response of a structure in the horizontal direction. However, in regions where the vertical earthquake excitation is significant (such as near-fault region), a traditional base-isolated building exhibits a significant vertical vibration. To eliminate this shortcoming, a rocking-isolated system named Telescopic Column (TC) is proposed in this paper. Detailed rocking and isolation mechanism of the TC system is presented. The seismic performance of the TC is compared with the traditional elastomeric bearing (EB) and friction pendulum (FP) base-isolated systems. A 4-storey reinforced concrete moment-resisting frame (RC-MRF) is selected as the reference superstructure. The seismic response of the reference superstructure in terms of column axial forces, base shears, floor accelerations, inter-storey drift ratios (IDR) and collapse margin ratios (CMRs) are evaluated using OpenSees. The results of the nonlinear dynamic analysis subjected to multi-directional earthquake excitations show that the superstructure equipped with the newly proposed TC is more resilient and exhibits a superior response with higher margin of safety against collapse when compared with the same superstructure with the traditional base-isolation (BI) system.

Key Words
base Isolation; structural fuse; repairable structure; resilience; fragility curve; collapse margin; multi-components excitation; near-field; OpenSees

Address
Ehsan Noroozinejad Farsangi: Department of Earthquake Engineering, Graduate University of Advanced Technology (KGUT), Kerman, Iran
Abbas Ali Tasnimi: Department of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran
T.Y. Yang: International Joint Research Laboratory of Earthquake Engineering, Tongji University, Shanghai, China;
Department of Civil Engineering, University of British Columbia, Vancouver, Canada
Izuru Takewaki: Department of Architecture and Architectural Engineering, Kyoto University, Kyoto, Japan
Mohammad Mohammadhasani: Seismology Engineering & Risk Department, Road, Housing & Urban Development Research Center (BHRC), Tehran, Iran


Abstract
The difficulty in modeling complex nonlinear structures lies in the presence of significant sources of uncertainties mainly attributed to sudden changes in the structure\'s behavior caused by regular aging factors or extreme events. Quantifying these uncertainties and accurately representing them within the complex mathematical framework of Structural Health Monitoring (SHM) are significantly essential for system identification and damage detection purposes. This study highlights the importance of uncertainty quantification in SHM frameworks, and presents a comparative analysis between intrusive and non-intrusive techniques in quantifying uncertainties for SHM purposes through two different variations of the Kalman Filter (KF) method, the Ensemble Kalman filter (EnKF) and the Polynomial Chaos Kalman Filter (PCKF). The comparative analysis is based on a numerical example that consists of a four degrees-of-freedom (DOF) system, comprising Bouc-Wen hysteretic behavior and subjected to El-Centro earthquake excitation. The comparison is based on the ability of each technique to quantify the different sources of uncertainty for SHM purposes and to accurately approximate the system state and parameters when compared to the true state with the least computational burden. While the results show that both filters are able to locate the damage in space and time and to accurately estimate the system responses and unknown parameters, the computational cost of PCKF is shown to be less than that of EnKF for a similar level of numerical accuracy.

Key Words
system identification; uncertainty quantification; sequential data assimilation; ensemble Kalman filter; polynomial chaos Kalman filter

Address
Dana E. Nasr, Wael G. Slika and George A. Saad: Department of Civil and Environmental Engineering, American University of Beirut, Beirut, Lebanon

Abstract
The factors affecting the shear strength of the angle shear connectors in the steel-concrete composite beams can play an important role to estimate the efficacy of a composite beam. Therefore, the current study has aimed to verify the output of shear capacity of angle shear connector according to the input provided by Support Vector Machine (SVM) coupled with Firefly Algorithm (FFA). SVM parameters have been optimized through the use of FFA, while genetic programming (GP) and artificial neural networks (ANN) have been applied to estimate and predict the SVM-FFA models\' results. Following these results, GP and ANN have been applied to develop the prediction accuracy and generalization capability of SVM-FFA. Therefore, SVM-FFA could be performed as a novel model with predictive strategy in the shear capacity estimation of angle shear connectors. According to the results, the Firefly algorithm has produced a generalized performance and be learnt faster than the conventional learning algorithms.

Key Words
C-shaped shear connector; channel; estimation; prediction; support vector machine; firefly algorithm

Address
E. Sadeghipour Chahnasir: Department of Civil Engineering, Qeshm International Branch, Islamic Azad University, Qeshm, Iran
Y. Zandi: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
M. Shariati: Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran;
Department of Civil Engineering, Faculty of engineering, University of Malaya, Kuala Lumpur, Malaysia
E. Dehghani: Department of Civil Engineering, University of Qom, Qom, Iran
A. Toghroli and M. Safa: Department of Civil Engineering, Faculty of engineering, University of Malaya, Kuala Lumpur, Malaysia
E. Tonnizam Mohamad: Centre of Tropical Geoengineering (GEOTROPIK), Faculty Civil Engineering, Universiti Teknologi Malaysia, Johor Bahru, Malaysia
A. Shariati: Department of Civil Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran
K. Wakil: Information Technology Department, Technical College of Informatics, Sulaimani Polytechnic University, Iraq;
University of Human Development, Iraq
M. Khorami: Facultad de Arquitectura y Urbanismo, Universidad Tecnológica Equinoccial, Calle Rumipamba s/n y Bourgeois, Quito, Ecuador


Abstract
Predicting the compressive strength of concrete has been considered as the initial phase across the cement production processing. The current study has focused on the integration of the concrete compressive strength in 28 days with the mix of the major oxides and fine aggregates as an experimental formula through the use of two types of Portland cement resulting the compressive strength of the concrete highly dependent on time.

Key Words
Portland cement; major oxides; fine aggregates; compressive strength of concrete

Address
A. Nosrati: Department of Civil Engineering, Islamic Azad University, Qeshm International Branch, Qeshm, Iran
Y. Zandi and M.B. Mahdizadeh: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
M. Shariati: Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran;
Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia
K. Khademi: Department of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran
M. Darvishnezhad Aliabad: Department of Civil Engineering, Bandar Abbas Branch, Islamic Azad University, Bandar Abbas, Iran
A. Marto: Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia
M.A. Mu\'azu: Department of Civil Engineering, Jubail University College, Royal Commission of Jubail and Yanbu, Jubail, Saudi Arabia
E. Ghanbari: Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
A. Shariati: Department of Civil Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran
M. Khorami: Facultad de Arquitectura y Urbanismo, Universidad Tecnológica Equinoccial, Calle Rumipamba s/n y Bourgeois, Quito, Ecuador


Abstract
Pavements porous concrete is a noble structure design in the urban management development generally enabling water to be permeated within its structure. It has also capable in the same time to cater dynamic loading. During the technology development, the quality and quantity of waste materials have led to a waste disposal crisis. Using recycled materials (secondary) instead of virgin ones (primary) have reduced landfill pressure and extraction demanding. This study has reviewed the waste materials (Recycled crushed glass (RCG), Steel slag, Steel fiber, Tires, Plastics, Recycled asphalt) used in the pavement porous concretes and report their respective mechanical, durability and permeability functions. Waste material usage in the partial cement replacement will cause the concrete production cost to be reduced; also, the concretes\'s mechanical features have slightly affected to eliminate the disposal waste materials defects and to use cement in Portland cement (PC) production. While the cement has been replaced by different industrial wastes, the compressive strength, flexural strength, split tensile strength and different PC permeability mixes have depended on the waste materials

Key Words
Pavements Porous Concrete (P.P.C); waste materials; pavements porous concrete; glass waste; recycled crushed glass; steel slag; steel fiber; tires waste; plastic waste; recycled asphalt; Pervious concrete

Address
Ali Toghroli, Zainah Ibrahim and Suhana Koting: Department of Civil Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia
Mahdi Shariati: Department of Civil Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia;
Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran;
Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia
Fathollah Sajedi: Department of Civil Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
Edy Tonnizam Mohamad: Centre of Tropical Geoengineering (GEOTROPIK), Faculty Civil Engineering, Universiti Teknologi Malaysia, Johor Bahru, Malaysia
Majid Khorami: Facultad de Arquitectura y Urbanismo, Universidad Tecnológica Equinoccial, Calle Rumipamba s/n y Bourgeois, Quito, Ecuador



Abstract
Characteristic parameter values of seismic isolators deviate from their nominal design values due to uncertainties and/or errors in their material properties and element dimensions, etc. Deviations may increase over service life due to environmental effects and service conditions. For accurate evaluation of the seismic safety level, all such effects, which would result in deviations in the structural response, need to be taken into account. In this study, the sensitivity of the probability of failure of the structures equipped with nonlinear base isolation systems to the uncertainties in various isolation system characteristic parameters is investigated in terms of various isolation system and superstructure response parameters in the context of a realistic three-dimensional base-isolated building model via Monte Carlo Simulations. The inherent record-to-record variability nature of the earthquake ground motions is also taken into account by carrying out analyses for a large number of ground motion records which are classified as those with and without forward-directivity effects. Two levels of nominal isolation periods each with three different levels of uncertainty are considered. Comparative plots of cumulative distribution functions and related statistical evaluation presented here portray the potential extent of the deviation of the structural response parameters resulting from the uncertainties and the uncertainty levels considered, which is expected to be useful for practicing engineers in evaluating isolator test results for their projects.

Key Words
probabilistic analysis; sensitivity analysis; Monte Carlo simulation method; uncertainty; seismic performance; base isolation

Address
Hatice Gazi and Cenk Alhan: Department of Civil Engineering, İstanbul University - Cerrahpaşa, Avcilar Campus, Avcilar, İstanbul, Turkey

Abstract
In this paper, the effect of non-persistent joints was determined on the behavior of concrete specimens subjected to biaxial loading through numerical modeling using particle flow code in two dimensions (PFC2D). Firstly, a numerical model was calibrated by uniaxial, Brazilian and triaxial experimental results to ensure the conformity of the simulated numerical model\'s response. Secondly, sixteen rectangular models with dimension of 100 mm by 100 mm were developed. Each model contains two non-persistent joints with lengths of 40 mm and 20 mm, respectively. The angularity of the larger joint changes from 30 to 90. In each configuration, the small joint angularity changes from 0 to 90 in 30 increments. All of the models were under confining stress of 1 MPa. By using of the biaxial test configuration, the failure process was visually observed. Discrete element simulations demonstrated that macro shear fractures in models are because of microscopic tensile breakage of a large number of bonded discs. The failure pattern in Rock Bridge is mostly affected by joint overlapping whereas the biaxial strength is closely related to the failure pattern.

Key Words
rock bridge; non-persistent joint; PFC2D

Address
Vahab Sarfarazi: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
Hadi Haeri: Young Researchers and Elite Club, Bafgh Branch, Islamic Azad University, Bafgh, Iran
Kourosh Bagheri: Department of civil engineering, Malard Branch, Islamic Azad University, Malard, Iran

Abstract
The present research study utilizes a multi-objective optimization method for Pareto optimization of an eight-degree of freedom full vehicle vibration model, adopting a non-dominated sorting genetic algorithm II (NSGA-II). In this research, a full set of ride comfort as well as ride safety parameters are considered as objective functions. These objective functions are divided in to two groups (ride comfort group and ride safety group) where the ones in one group are in conflict with those in the other. Also, in this research, a special optimizing technique and combinational method consisting of weighted sum method and Pareto optimization are applied to transform Pareto double-objective optimization to Pareto full-objective optimization which can simultaneously minimize all objectives. Using this technique, the full set of ride parameters of three dimensional vehicle model are minimizing simultaneously. In derived Pareto front, unique trade-off design points can selected which are non-dominated solutions of optimizing the weighted sum comfort parameters versus weighted sum safety parameters. The comparison of the obtained results with those reported in the literature, demonstrates the distinction and comprehensiveness of the results arrived in the present study.

Key Words
full vehicle vibration model; multi-objective optimization; non-dominated sorting genetic algorithm II; passenger vehicle suspension model; weighted sum Pareto optimization

Address
Mohammad Reza Bagheri, Masoud Mosayebi and Asghar Mahdian:School of Mechanical Engineering, Malek-Ashtar University of Technology, ShahinShahr, Isfahan, Iran
Ahmad Keshavarzi: Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University, Isfahan, Iran

Abstract
Ultrasonic guided waves have attracted increasing attention for non-destructive testing (NDT) and structural health monitoring (SHM) of bridge cables. They offer advantages like single measurement, wide coverage of acoustical field, and long-range propagation capability. To design defect detection systems, it is essential to understand how guided waves propagate in cables and how to select the optimal excitation frequency and mode. However, certain cable characteristics such as multiple wires, anchorage, and polyethylene (PE) sheath increase the complexity in analyzing the guided wave propagation. In this study, guided wave modes for multi-wire bridge cables are identified by using a semi-analytical finite element (SAFE) technique to obtain relevant dispersion curves. Numerical results indicated that the number of guided wave modes increases, the length of the flat region with a low frequency of L(0,1) mode becomes shorter, and the cutoff frequency for high order longitudinal wave modes becomes lower, as the number of steel wires in a cable increases. These findings were used in design of transducers for defect detection and selection of the optimal wave mode and frequency for subsequent experiments. A magnetostrictive transducer system was used to excite and detect the guided waves. The applicability of the proposed approach for detecting and locating wire breakages was demonstrated for a cable with 37 wires. The present ultrasonic guided wave method has been found to be very responsive to the number of broken wires and is thus capable of detecting defects with varying sizes.

Key Words
ultrasonic guided waves; bridge cables with multi-wires; SAFE; dispersion curves; magnetostrictive transducer; wire breakage detection

Address
Pengfei Zhang and Fuzai Lv: Institute of Advanced Manufacturing Engineering, Zhejiang University, Hangzhou 310027, PR China
Zhifeng Tang: Institute of Advanced Digital Technologies and Instrumentation, Zhejiang University, Hangzhou 310027, PR China
Yuanfeng Duan and Chung Bang Yun: College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310027, PR China


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