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CONTENTS
Volume 24, Number 4, October 2019
 

Abstract
This study investigates the structural integrity of the amphibious tour bus under the rollover condition. The multi-purpose bus called Dual Mode Tour Bus (DMTB) which explores on land and water has been designed on top of a truck platform. Prior to the fabrication of new upper body and sailing equipment of DMTB, computational analysis investigates the rollover protection of the proposed structure including superstructure, wheels, and axles. The Computer-Aided Design (CAD) of the whole vehicle model is meshed and preprocessed under high performance using the Altair HyperMesh to attain the best mesh model suited for finite element analysis (FEA) on the proposed system. Meanwhile, the numerical model is analyzed by employing LS-DYNA to evaluate the superstructure strength. The numerical model includes detail information about the microstructure and considers wheels and axles as rigid bodies but excludes window glasses, seats, and interior parts. Based on the simulation analysis and proper modifications especially on the rear portion of the bus, the local stiffness significantly increased. The vehicle is rotated to the contact point on the ground based on the mathematical method presented in this study to save computational cost. The results show that the proposed method of rollover analysis is highly significant not only in bus rollover tests but in crashworthiness studies for other application. The critical impartments in our suggested dual-purpose bus accepted and passed \"Economic Commission for Europe (ECE) R66\".

Key Words
rollover analysis; ECE R66; superstructure; crashworthiness; LS-DYNA; finite element modeling

Address
Javad Mehrmashhadi: Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, United States
Philippe Mallet and Paul Michel: S.A.S Les Canards De Paris, 92316 Sevres, France
Amin TermehYousefi:Department of Mechanical Engineering, Tufts University, Medford, MA, 02155, United States

Abstract
The existing piezoelectric spherical transducers with fixed prescribed dynamic characteristics limit their application in scenarios with multi-frequency or frequency variation requirement. To address this issue, this work proposes an improved design of piezoelectric spherical transducers using the resistance tuning method. Two piezoceramic shells are the functional elements with one for actuation and the other for tuning through the variation of load resistance. The theoretical model of the proposed design is given based on our previous work. The effects of the resistance, the middle surface radius and the thickness of the epoxy adhesive layer on the dynamic characteristics of the transducer are explored by numerical analysis. The numerical results show that the multi-frequency characteristics of the transducer can be obtained by tuning the resistance, and its electromechanical coupling coefficient can be optimized by a matching resistance. The proposed design and derived theoretical solution are validated by comparing with the literature given special examples as well as an experimental study. The present study demonstrates the feasibility of using the proposed design to realize the multi-frequency characteristics, which is helpful to improve the performance of piezoelectric spherical transducers used in underwater acoustic detection, hydrophones, and the spherical smart aggregate (SSA) used in civil structural health monitoring, enhancing their operation at the multiple working frequencies to meet different application requirements.

Key Words
piezoelectric spherical transducer; spherical smart aggregate (SSA); piezoelasticity; multi-frequency characteristics; structural health monitoring

Address
Lei Qin: Research Center of Sensor Technology, Beijing Information Science & Technology University, Beijing 100192, P. R. China
Jianjun Wang and Donghuan Liu: Department of Applied Mechanics, University of Science and Technology Beijing, Beijing 100083, P. R. China
Lihua Tang: Department of Mechanical Engineering, University of Auckland, 20 Symonds Street, Auckland 1010, New Zealand
Gangbing Song: Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA

Abstract
The use of Tuned mass dampers (TMD) has proved to be effective in reducing the effects of vibrations caused by wind loads and far-field seismic action. However, its effectiveness in controlling the dynamic response of structures under near-fault earthquakes is still under discussion. In this case, the uncertainty about the TMD performance arises from the short significant duration of near-fault ground motions. In this work, the TMD effectiveness for increasing the safety margin against collapse of structures subjected to near-fault earthquakes is investigated. In order to evaluate the TMD performance in the proposed scenario, the nonlinear dynamic response of two reinforced concrete (RC) frames was analyzed. TMDs with different mass values were added to these structures, and a set of near-fault records with frequency content close to the fundamental frequency of the structure was employed. Through a series of nonlinear dynamic analysis, the minimum amplitude of each seismic record that causes the structural collapse was found. By comparing this value, called collapse acceleration, for the case of the structures with and without TMD, the benefit produced by the addition of the control device was established.

Key Words
tuned mass damper; seismic action; near-fault earthquakes; reinforced concrete structures

Address
Martin N. Domizio, Daniel Ambrosini and Oscar Curadelli: 1Faculty of Engineering, National University of Cuyo, Mendoza, Argentina
2CONICET, National Research Council, Argentina


Abstract
This study develops a novel recursive algorithm to significantly enhance the computation efficiency of a recently proposed stochastic subspace identification (SSI) methodology based on an alternative stabilization diagram. Exemplified by the measurements taken from the two investigated office buildings, it is first demonstrated that merely one sixth of computation time and one fifth of computer memory are required with the new recursive algorithm. Such a progress would enable the realization of on-line and almost real-time monitoring for these two steel framed structures. This recursive SSI algorithm is further applied to analyze 20 months of monitoring data and comprehensively assess the environmental effects. It is certified that the root-mean-square (RMS) response can be utilized as an excellent index to represent most of the environmental effects and its variation strongly correlates with that of the modal frequency. More detailed examination by comparing the monthly correlation coefficient discloses that larger variations in modal frequency induced by greater RMS responses would typically lead to a higher correlation.

Key Words
stochastic subspace identification; recursive algorithm; alternative stabilization diagram; structural health monitoring; office building; environmental effect

Address
Wen-Hwa Wu, Jhe-Wei Jhou, Chien-Chou Chen and Gwolong Lai: Department of Construction Engineering, National Yunlin University of Science and Technology,
123 University Road, Douliu, Yunlin 640, Taiwan


Abstract
The detection of structural damage without a priori information on the healthy state is challenging. In order to address the issue, the study presents a baseline-free approach to detect damage in beam structures based on an actual influence line. In particular, a multi-segment function-fitting calculation is developed to extract the actual deflection influence line (DIL) of a damaged beam from bridge responses due to a passing vehicle. An intact basis function based on the measurement position is introduced. The damage index is defined as the difference between the actual DIL and a constructed function related to the intact basis, and the damage location is indicated based on the local peak value of the damage index curve. The damage basis function is formulated by using the detected damage location. Based on the intact and damage basis functions, damage severity is quantified by fitting the actual DIL using the least-square calculation. Both numerical and experimental examples are provided to investigate the feasibility of the proposed method. The results indicate that the present baseline-free approach is effective in detecting the damage of beam structures.

Key Words
baseline-free; damage detection; beam structure; multi-segment function; actual influence line

Address
Ning-Bo Wang and Tian-Li Huang: School of Civil Engineering, Central South University, Changsha 410075, China
Wei-Xin Ren: Department of Civil Engineering, Hefei University of Technology, Hefei 230009, China

Abstract
Literature regarding concrete walls reinforced by super elastic shape memory alloy (SMA) bars is rather limited. The seismic behavior of a system concurrently including a distinct steel reinforced concrete (RC) wall, as well as another wall reinforced by super elastic SMA at the first story, and steel rebar at upper stories, would be an interesting matter. In this paper, the seismic response of such a COMBINED system is compared to a conventional system with steel RC concrete walls ( STEEL-Rein.) and also to a wall system with SMA rebar at the first story and steel rebar at other stories ( SMA-Rein.). Nonlinear time history analysis at maximum considered earthquake (MCE) and design bases earthquake (DBE) levels is conducted and the main responses like maximum inter-story drift ratio and residual inter-story drift ratio are investigated. Furthermore, incremental dynamic analysis is used to accomplish probabilistic seismic studies by creating fragility curves. Results demonstrated that the SMA-Rein. system, subjected to DBE and MCE ground motions, has almost zero and 0.27% residual maximum inter-story drifts, while the values for the COMBINED system are 0.25% and 0.51%. Furthermore, fragility curves show that using SMA rebar at the base of all walls causes a larger probability of exceedance 3% inter-story drift limit state compared to the COMBINED system. Static push over analysis demonstrated that the strength of the COMBINED model is almost 0.35% larger than that of the two other models, and its general post-yielding stiffness is also approximately twice the corresponding stiffness of the two other models.

Key Words
shape memory alloy; reinforced concrete wall; earthquake; drift

Address
Hamid Beiraghi: Department of Civil Engineering, Mahdishahr Branch, Islamic Azad University, Mahdishahr, Iran

Abstract
A Bayesian dynamic linear model (BDLM) is presented for a data-driven analysis for response prediction and load effect separation of a revolving auditorium structure, where the main loads are self-weight and dead loads, temperature load, and audience load. Analyses are carried out based on the long-term monitoring data for static strains on several key members of the structure. Three improvements are introduced to the ordinary regression BDLM, which are a classificatory regression term to address the temporary audience load effect, improved inference for the variance of observation noise to be updated continuously, and component discount factors for effective load effect separation. The effects of those improvements are evaluated regarding the root mean square errors, standard deviations, and 95% confidence intervals of the predictions. Bayes factors are used for evaluating the probability distributions of the predictions, which are essential to structural condition assessments, such as outlier identification and reliability analysis. The performance of the present BDLM has been successfully verified based on the simulated data and the real data obtained from the structural health monitoring system installed on the revolving structure.

Key Words
Bayesian dynamic linear model; data-driven method; response prediction; load effect separation; revolving structure; structural health monitoring

Address
Zhi Ma, Chung-Bang Yun, Yan-Bin Shen, Feng Yu,
Hua-Ping Wan and Yao-Zhi Luo: College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, Zhejiang, China
:

Abstract
In this study, vibration characteristics of a gravity-based caisson-foundation breakwater system are investigated for ambient and geometric parameters such as various waves, sea levels, and foundation conditions. To achieve the objective, following approaches are implemented. Firstly, operational modal analysis methods are selected to identify vibration modes from output-only dynamic responses. Secondly, a finite element model of an existing caisson-foundation breakwater system is established by using a structural analysis program, ANSYS. Thirdly, forced vibration analyses are performed on the caisson-foundation system for two types of external forces such as controlled impacts and wave-induced dynamic pressures. For the ideal impact, the wave force is converted to a triangular impulse function. For the wave flow, the wave pressure acting on the system is obtained from wave field analysis. Fourthly, vibration modes of the caisson-foundation system are identified from the forced vibration responses by combined use of the operational modal analysis methods. Finally, vibration characteristics of the caisson-foundation system are investigated under various waves, sea levels, and foundations. Relative effects of foundation conditions on vibration characteristics are distinguished from that induced by waves and sea levels.

Key Words
caisson breakwater; wave-induced vibration response; various sea level; various foundation condition

Address
So-Young Lee, Ngoc-Loi Dang and Jeong-Tae Kim: Department of Ocean Engineering, Pukyong National Univ., 45 Yongso-ro, Nam-gu, Busan 48513, Republic of Korea
Thanh-Canh Huynh: Center for Construction, Mechanics and Materials, Institute of Research and Development, Duy Tan University, 03 Quang Trung, Hai Chau, Danang 550000, Vietnam

Abstract
Construction development and greenhouse gas emissions have globally required a strategic management to take some steps to stain and maintain the environment. Nowadays, recycled aggregates, in particular ceramic waste, have been widely used in concrete structures due to the economic and environmentally friendly solution, requiring the knowledge of recycled concrete. Also, one of the materials used as a substitute for concrete cement is wollastonite mineral to decrease carbon dioxide (CO2) from the cement production process by reducing the concrete consumption in concrete. The purpose of this study is to investigate the effect of wollastonite on the mechanical properties and durability of conventional composite concrete, containing recycled aggregates such as compressive strength, tensile strength (Brazilian test), and durability to acidic environment. On the other hand, in order to determine the strength and durability of the concrete, 5 mixing designs including different wollastonite values and recovered aggregates including constant values have been compared to the water - cement ratio (w/c) constant in all designs. The experimental results have shown that design 5 (containing 40% wollastonite) shows only 6.1% decrease in compressive strength and 4.9% decrease in tensile strength compared to the control plane. Consequently, the use of wollastonite powder to the manufacturing of conventional structural concrete containing recycled ceramic aggregates, in addition to improving some of the properties of concrete are environmentally friendly solutions, providing natural recycling of materials.

Key Words
wollastonite powder; recycled concrete; ceramic waste; durability in the acidic environment

Address
Du Dinh-Cong: Division of Construction Computation, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam;
Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Viet Nam
Mohammad. H Keykhosravi: Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia
Rayed Alyousef and Hisham Alabduljabbar: Department of Civil Engineering, College of Engineering, Prince Sattam bin Abdulaziz University, Al-kharj 11942, Saudi Arabia
Musab N A Salih: School of Civil engineering, Faculty of Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Malaysia
Abdulaziz Alaskar and Fahed Alrshoudi:Department of Civil Engineering, College of Engineering, King Saud University, Riyadh 11362, Saudi Arabia
Shek Poi-Ngian: Construction Research Center (CRC), Institute for Smart Infrastructure & Innovative Construction (ISIIC), School of Civil Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia
Hoang Nguyen: Institute of Research and Development, Duy Tan University, Da Nang 550000, Viet Nam

Abstract
This study aimed to categorize pervious rubberized concrete into fresh and hardened concrete analyzing its durability, permeability and strength. During the globalization of modern life, growing population and industry rate have signified a sustainable approach to all aspects of modern life. In recent years, pervious concrete (porous concrete) has significantly substituted for pavements due to its mechanical and environmental properties. On the other hand, scrap rubber tire has been also contributed with several disposal challenges. Considering the huge amount of annually tire wastes tossing out, the conditions become worse. Pervious concrete (PC) gap has graded surface assisted with storm water management, recharging groundwater sources and alleviate water run-offs. The results have shown that the use of waste tires as aggregate built into pervious concrete has tremendously reduced the scrap tire wastes enhancing environmental compliance.

Key Words
pervious concrete; rubber tire; waste; sustainability; environment

Address
Mahdi Shariati: Division of Computational Mathematics and Engineering, Institute for Computational Science,
Ton Duc Thang University, Ho Chi Minh City, Viet Nam;
Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Viet Nam
Arian Heirati: Department of Civil Engineering, Islamic Azad University, Central Tehran Branch, Tehran, Iran
Yousef Zandi: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
Hossein Laka: Department of Civil Engineering, Qeshm International Branch, Islamic Azad University, Qeshm, Iran
Ali Toghroli: Department of Civil Engineering, Islamic Azad University, SouthTehran Branch, Tehran, Iran
Peiman Kianmehr: Department of Civil Engineering, American University in Dubai, Media City, Dubai, UAE
Maryam Safa: Institute of Research and Development, Duy Tan University, Da Nang 550000, Viet Nam
Musab N A Salih: School of civil engineering, faculty of engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Malaysia
Shek Poi-Ngian: Construction Research Center (CRC), Institute for Smart Infrastructure & Innovative Construction (ISIIC),
School of Civil Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia



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