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Volume 30, Number 5, November 2022

Despite efforts to reduce unexpected accidents at confined construction sites, choking accidents continue to occur. Because of the poorly ventilated atmosphere, particularly in long, confined underground spaces, workers are subject to dangerous working conditions despite the use of artificial ventilation. Moreover, the traditional monitoring methods of using portable gas detectors place safety inspectors in direct contact with hazardous conditions. In this study, a long-range (LoRa)-based wireless safety monitoring system that features the network organization, fault-tolerant, power management, and a graphical user interface (GUI) was developed for underground construction sites. The LoRa wireless data communication system was adopted to detect hazardous gases and oxygen deficiency within a confined underground space with adjustable communication range and low power consumption. Fault tolerance based on the mapping information of the entire wireless sensor network was particularly implemented to ensure the reliable operation of the monitoring system. Moreover, a sleep mode was implemented for the efficient power management. The GUI was also developed to control the entire safety-monitoring system and to manage the measured data. The developed safety-monitoring system was validated in an indoor testing and at two full-scale water pipeline construction sites.

Key Words
confined underground space; fault tolerance; LoRa communication; mapping information; underground construction site; wireless safety monitoring

(1) Sahyeon Lee, Sung-Han Sim:
School of Civil, Architectural Engineering and Landscape Architecture, Sungkyunkwan University, Suwon 16419, Republic of Korea;
(2) Sang-Kyun Gil:
Korea Water Resources Corporation (K-water), Daejeon 34350, Republic of Korea;
(3) Soojin Cho:
Department of Civil Engineering/Graduate School of Urban Big-data Convergence, University of Seoul, Seoul 02504, Republic of Korea;
(4) Sung Woo Shin:
Department of Safety Engineering, Pukyong National University, Busan 48513, Republic of Korea.

The viscosity of a shear-thickening fluid damper (STFD) can increase dramatically when the STFD undergoes highrate of excitation. Therefore, accurate numerical modelling of the STFD has been considered difficult due to this distinct feature. This study aims to develop a numerical model to accurately simulate the response of the STFD. First, a STFD is designed, fabricated, and installed in the laboratory. Then, performance tests are conducted in which sine waves with nine frequencies at three amplitude levels are adopted as the displacement excitations to the STFD. A novel numerical model which contains two parameter sets of the discrete Bouc-Wen model as well as two parameters for transiting the two parameter sets. Therefore, a total number of eighteen parameters need to be identified in the damper model. The symbiotic organisms search is applied to optimize the parameters. Numerical simulation results demonstrate that the proposed STFD model with transit parameter sets outperforms the conventional discrete Bouc-Wen model. The proposed STFD model can be applied to analyses of structures in which STFDs are installed in the future.

Key Words
numerical modelling; shear-thickening fluid damper; symbiotic organisms search; transit parameters

(1) Chung-Han Yu, Shen-Kai Peng:
National Center for Research on Earthquake Engineering, National Applied Research Laboratories, No. 200, Sec. 3, Xinhai Rd., Da'an Dist., Taipei City 106219, Taiwan;
(2) Yohanes K. Surjanto, Pei-Ching Chen:
Department of Civil and Construction Engineering, National Taiwan University of Science and Technology, No.43, Keelung Rd., Sec.4, Da'an Dist., Taipei City 106335, Taiwan;
(3) Kuo-Chun Chang:
Department of Civil Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Da'an Dist., Taipei City 10617, Taiwan.

In this paper, a hybrid vibration-impedance-based damage monitoring approach is experimentally evaluated for prestressed concrete (PSC) structures with local strand breakage. Firstly, the hybrid monitoring scheme is designed to alert damage occurrence from changes in vibration characteristics and to localize strand breakage from changes in impedance signatures. Secondly, a full-scale PSC anchorage is experimented to measure global vibration responses and local impedance responses under a sequence of simulated strand-breakage events. Finally, the measured data are analyzed using the hybrid monitoring framework. The change of structural condition (i.e., damage extent) induced by the local strand breakage is estimated by changes in a few natural frequencies obtained from a few accelerometers in the structure. The damaged strand is locally identified by tomography analysis of impedance features measured via an array of PZT (lead-zirconate-titanate) sensors mounted on the anchorage. Experimental results demonstrate that the strand breakage in the PSC structure can be accurately assessed by using the combined vibration and impedance features.

Key Words
hybrid monitoring; impedance response; prestressed concrete structure; PZT interface; strand breakage; vibration response

(1) Ngoc-Loi Dang:
Urban Infrastructure Faculty, Mien Tay Construction University, Vinh Long 890000, Vietnam;
(2) Quang-Quang Pham, Jeong-Tae Kim:
Department of Ocean Engineering, Pukyong National University, Nam-gu, Busan 48513, Korea.

In this study, a new type of isolation bearing is proposed by combining S-shaped steel plate dampers (SSDs) with a spherical steel bearing, and the seismic control effect of a five-span standard high-speed railway bridge is investigated. The advantages of the proposed S-shaped steel damping friction bearing (SSDFB) are that it cannot only lengthen the structural periods, dissipate the seismic energy, but also prevent bridge unseating due to the restraint effectiveness of SSDs in the large relative displacements between the girders and piers. This study first presents a detailed description and working principle of the SSDFB. Then, mechanical modeling of the SSDFB was derived to fundamentally define its cyclic behavior and obtain key mechanical parameters. The numerical model of the SSDFB's critical component SSD was verified by comparing it with the experimental results. After that, parameter studies of the dimensions and number of SSDs, the friction coefficient, and the gap length of the SSDFBs were conducted. Finally, the longitudinal seismic responses of the bridge with SSDFBs were compared with the bridge with spherical bearing and spherical bearing with strengthened shear keys. The results showed that the SSDFB can not only significantly mitigate the shear force responses and residual displacement in bridge substructures but also can effectively reduce girder displacement and prevent bridge unseating, at a cost of inelastic deformation of the SSDs, which is easy to replace. In conclusion, the SSDFB is expected to be a cost-effective option with both multi-stage energy dissipation and restraint capacity, making it particularly suitable for seismic isolation application to high-speed railway bridges.

Key Words
combination energy dissipation; flexural-tensile behavior; high-speed railway bridge; isolation bearing; numerical modelling; seismic control; S-shaped steel damper

(1) Wei Guo, Yang Wang, Qiaodan Du:
School of Civil Engineering, Central South University, Changsha, China;
(2) Wei Guo, Yang Wang:
National Engineering Research Center of High-Speed Railway Construction Technology, Changsha, China;
(3) Zhipeng Zhai:
Earthquake Engineering Research and Test Center, Guangzhou University, Guangzhou, China.

Three-dimensional (3D) models have become crucial for improving civil infrastructure analysis, and they can be used for various purposes such as damage detection, risk estimation, resolving potential safety issues, alarm detection, and structural health monitoring. 3D point cloud data is used not only to make visual models but also to analyze the states of structures and to monitor them using semantic data. This study proposes automating the generation of high-quality 3D point cloud data and removing noise using deep learning algorithms. In this study, large-format aerial images of civilian infrastructure, such as cut slopes and dams, which were captured by drones, were used to develop a workflow for automatically generating a 3D point cloud model. Through image cropping, downscaling/upscaling, semantic segmentation, generation of segmentation masks, and implementation of region extraction algorithms, the generation of the point cloud was automated. Compared with the method wherein the point cloud model is generated from raw images, our method could effectively improve the quality of the model, remove noise, and reduce the processing time. The results showed that the size of the 3D point cloud model created using the proposed method was significantly reduced; the number of points was reduced by 20-50%, and distant points were recognized as noise. This method can be applied to the automatic generation of high-quality 3D point cloud models of civil infrastructures using aerial imagery.

Key Words
automatic model generation; deep learning algorithm; noise reduction; point cloud; semantic segmentation

(1) Ji-Hye Kwon, Jun-Haeng Heo:
School of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul, 03722, Republic of Korea;
(2) Shekhroz Khudoyarov:
SISTech Co., LTD, 209, Neungdong-ro, Gwangjin-gu, Seoul, 05006, Republic of Korea;
(3) Namgyu Kim:
Research Strategic Planning Department, Korea Institute of Civil Engineering and Building Technology, 283, Goyangdae-Ro, Ilsanseo-Gu, Goyang-Si, Gyeonggi-Do, 10223, Republic of Korea.

During the long-time service of a bolt, its preload may suffer slight perturbations or significant reductions. It is a dilemma to monitor preload changes at high resolution and full scale. Approaches for bolt preload monitoring with multiresolution should be developed. In this paper, a simple and effective multi-resolution bolt preload monitoring approach using ultrasonic guided waves (UGW) is proposed. A linear relationship between the time-of-flight (TOF) variation of multi-reflected waves and preload is derived to theoretically reveal the multi-resolution properties of UGW. The variations of TOF before and after the slight preload perturbations are extracted by using a global evaluation method. Experimental results show that the signal-to-noise ratio (SNR) of the 1st, 2nd, and 3rd-reflected UGWs is larger than 20 dB. The resolution of the 2nd-reflected UGW is higher than that of the 1st-reflected UGW and lower than that of the 3rd-reflected UGW. The ultimate detectable resolutions of bolt preload (DRBP) of the 1st and 3th-reflected UGWs are 0.9% and 0.5%, respectively. By using the 1st and 3th-reflected guided waves, the bolt looseness with different degrees can be monitored simultaneously.

Key Words
acoustoelastic effect; bolt preload; multi-resolution; structural health monitoring; ultrasonic guided waves

(1) Ruili Fu:
College of Harbour, Coastal and Offshore Engineering, Hohai University, Nanjing, Jiangsu, 210098, P.R. China;
(2) Ruiwei Mao, Dongdong Chen:
College of Civil Engineering, Nanjing Forestry University, Nanjing, Jiangsu, 210037, P.R. China;
(3) Bo Yuan:
School of Mechanical Engineering, Dalian University of Technology, Dalian, Liaoning, 116024, P.R. China;
(4) Linsheng Huo:
State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, Liaoning, 116024, P.R. China.

Efficient management of deteriorating civil infrastructure is one of the most important research topics in many developed countries. In particular, the remote displacement measurement of bridges using linear variable differential transformers, global positioning systems, laser Doppler vibrometers, and computer vision technologies has been attempted extensively. This paper proposes a remote displacement measurement system using closed-circuit televisions (CCTVs) and a computer-vision-based method for in-situ bridge bearings having relatively large displacement due to temperature change in long term. The hardware of the system is composed of a reference target for displacement measurement, a CCTV to capture target images, a gateway to transmit images via a mobile network, and a central server to store and process transmitted images. The usage of CCTV capable of night vision capture and wireless data communication enable long-term 24-hour monitoring on wide range of bridge area. The computer vision algorithm to estimate displacement from the images involves image preprocessing for enhancing the circular features of the target, circular Hough transformation for detecting circles on the target in the whole field-of-view (FOV), and homography transformation for converting the movement of the target in the images into an actual expansion displacement. The simple target design and robust circle detection algorithm help to measure displacement using target images where the targets are far apart from each other. The proposed system is installed at the Tancheon Overpass located in Seoul, and field experiments are performed to evaluate the accuracy of circle detection and displacement measurements. The circle detection accuracy is evaluated using 28,542 images captured from 71 CCTVs installed at the testbed, and only 48 images (0.168%) fail to detect the circles on the target because of subpar imaging conditions. The accuracy of displacement measurement is evaluated using images captured for 17 days from three CCTVs; the average and root-meansquare errors are 0.10 and 0.131 mm, respectively, compared with a similar displacement measurement. The long-term operation of the system, as evaluated using 8-month data, shows high accuracy and stability of the proposed system.

Key Words
bridge expansion displacement; circular hough transformation; closed-circuit televisions; computer visionbased displacement measurement; homography transformation

(1) Byunghyun Kim, Soojin Cho:
Department of Civil Engineering, University of Seoul, 163 Seoulsiripdae-ro, Dongdaemun-gu, Seoul 02504, Republic of Korea;
(2) Junhwa Lee:
Department of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan 44919, Republic of Korea;
(3) Sung-Han Sim:
School of Civil, Architectural Engineering and Landscape Architecture, Sungkyunkwan University, 2066 Seoburo, Jangan-gu, Suwon 16419, Republic of Korea;
(4) Byung Ho Park:
Technology Innovation Center, Seoul Facilities Corporation, 527-6 Majang-dong, Seongdong-gu, Seoul 04704, Republic of Korea.

The optimal design of structural composite materials is a research topic that attracts the attention of lots researchers. For many more thirty years, there has been increasing interest in the applications in all kinds of topics, which means taking advantage of fuzzy set theory, fuzzy analysis, and fuzzy control for designing high-performance and efficient structural systems is a fundamental concern for engineers, and many applications require the use of a systems approach to combine structural and active control systems. Therefore, an intelligent method can be designed based on the mitigation method, and by establishing the stable of the closed-loop fuzzy mitigation system, the behavior of the closed-loop fuzzy mitigation system can be accurately predicted. In this article, the intelligent algorithm and optimum design of fuzzy theory for structural control has been provided and demonstrated effective and efficient in practical engineering issues.

Key Words
composite structures; energy equations; intelligent control function; structural control; tuned mass damper

(1) Z.Y. Chen, Ruei-Yuan Wang, Yahui Meng:
School of Science, Guangdong University of Petrochemical Technology, Maoming, Guangdong 525000, China;
(2) Timothy Chen:
California Institute of Technology, Pasadena, CA 91125, USA.

Through the examination of literatures, electronic commerce is a subject which is accepted in enterprises to define e-commerce adoption, trends, and issues that are assisting and obstructing its efficacy. E-commerce offers numerous advantages to consumer satisfaction in any place and helps the company to get a competitive benefit over its competitors. The Internet has expanded the scope of business. Many business information is available by the global network that supports information gathering between organizations, businesses and their clients, while various divisions of a business is increasing at anexponential rate. Meanwhile, there are a few barriers to proper e-commerce usage and adoption, such as reliable internet connections, poor e-commerce supporting infrastructures, logistics systems presenting socio-regulatory and poor transportation barriers and demonstrating the significant improvement of e-commerce reliable and affordable Internet provisions, i.e., Internet cost, intensity, and reasonable level of e-readiness. The operational and strategic significance of information-based virtual value chains for all organizations cannot be emphasized. As a consequence, this study confirms worldwide market elements of e-commerce, such as its issues, benefits, relevance, scope, facilitators and projects prospective obstacles in a developing economy.

Key Words
benefits; disadvantageous; e-commerce; economic; globe market; theoretical analysis

(1) Xiaoqiang He:
School of Economics and Management, Chongqing Creation Vocational, Chongqing, Yongchuan, China;
(2) Jialing Li:
College of Engineering Management, Nueva Ecija University of Science and Technology, Cabanatuan, Philippines;
(3) Ibrahim Rasool Hani:
Department of Business Administration, Mustaqbal University College, Babylon 51001, Iraq;
(4) B.N. Nhu:
Institute of Research and Development, Duy Tan University, Da Nang, Vietnam;
(5) B.N. Nhu:
School of Engineering & Technology, Duy Tan University, Da Nang, Vietnam;
(6) H. Assilzadeh:
Department of Biomaterials, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Sciences, Chennai 600 077, India;
(7) H. Elhosiny Ali:
Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413, Saudi Arabia;
(8) H. Elhosiny Ali:
Research Center for Advanced Materials Science (RCAMS), King Khalid University, P.O. Box 9004, Abha 61413, Saudi Arabia;
(9) H. Elhosiny Ali:
Physics Department, Faculty of Science, Zagazig University, Zagazig 44519, Egypt;
(10) Samia Elattar:
Department of Industrial and Systems Engineering, College of Engineering, Princess Nourah Bint Abdulrahman University, Riyadh 84428, Saudi Arabia;
(11) Samia Elattar:
Department of Industrial Engineering, Alexandria Higher Institute of Engineering and Technology (AIET), Alexandria 21311, Egypt.

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