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CONTENTS
Volume 11, Number 5, May 2013
 

Abstract
High-rise buildings are a common feature of urban cities around the world. These flexible structures frequently exhibit large vibration due to strong winds and earthquakes. Structural control has been employed as an effective means to mitigate excessive responses; however, structural control mechanisms that can be used in tall buildings are limited primarily to mass and liquid dampers. An attractive alternative can be found in outrigger damping systems, where the bending deformation of the building is transformed into shear deformation across dampers placed between the outrigger and the perimeter columns. The outrigger system provides additional damping that can reduce structural responses, such as the floor displacements and accelerations. This paper investigates the potential of using smart dampers, specifically magnetorheological (MR) fluid dampers, in the outrigger system. First, a high-rise building is modeled to portray the St. Francis Shangri-La Place in Philippines. The optimal performance of the outrigger damping system for mitigation of seismic responses in terms of damper size and location also is subsequently evaluated. The efficacy of the semi-active damped outrigger system is finally verified through numerical simulation.

Key Words
semi-active damped outriggers; MR dampers; seismic control; high-rise buildings; LQG/clipped-optimal control

Address
Chia-Ming Chang : Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
Zhihao Wang : School of Civil Engineering and Communication, North China Institute of Water Conservancy and Hydroelectric Power, Zhengzhou, China, 450011
Billie F. Spencer : Department of Civil Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
Zhengqing Chen: College of Civil Engineering, Hunan University, Changsha, China, 410082


Abstract
DuraMote is a remote sensing system developed for the \"NIST TIP project: next generation SCADA for prevention and mitigation of water system infrastructure disaster\". It is designed for supervisory control and data acquisition (SCADA) of ruptures in water pipes. Micro-electro mechanical (MEMS) accelerometers, which record the vibration of the pipe wall, are used detect the ruptures. However, the performance of Duramote cannot be verified directly on a water distribution system because it lacks an acceptable recordable level of ambient vibration. Instead, a long-span cable-stayed bridge is an ideal test-bed to validate the accuracy, the reliability, and the robustness of DuraMote because the bridge has an acceptable level of ambient vibration. The acceleration data recorded on the bridge were used to identify the modal properties of the structure and to verify the performance of DuraMote. During the test period, the bridge was subjected to heavy rain, wind, and a typhoon but the system demonstrates its robustness and durability.

Key Words
remote sensing network; structural health monitoring; system identification; remote monitoring

Address
Marco Torbol, Sehwan Kim and Masanobu Shinozuka : University of California, Irvine, USA

Abstract
Due to their cost-effectiveness and ease of installation, wireless smart sensors (WSS) have received considerable recent attention for structural health monitoring of civil infrastructure. Though various wireless smart sensor networks (WSSN) have been successfully implemented for full-scale structural health monitoring (SHM) applications, monitoring of low-level ambient strain still remains a challenging problem for WSS due to A/D converter (ADC) resolution, inherent circuit noise, and the need for automatic operation. In this paper, the design and validation of high-precision strain sensor board for the Imote2 WSS platform and its application to SHM of a cable-stayed bridge are presented. By accurate and automated balancing of the Wheatstone bridge, signal amplification of up to 2507-times can be obtained, while keeping signal mean close to the center of the ADC span, which allows utilization of the full span of the ADC. For better applicability to SHM for real-world structures, temperature compensation and shunt calibration are also implemented. Moreover, the sensor board has been designed to accommodate a friction-type magnet strain sensor, in addition to traditional foil-type strain gages, facilitating fast and easy deployment. The wireless strain sensor board performance is verified through both laboratory-scale tests and deployment on a full-scale cable-stayed bridge.

Key Words
structural health monitoring; wireless smart sensor; high-sensitivity strain sensor; full-scale deployment

Address
Hongki Jo and B.F. Spencer : Department of Civil and Environmental Engineering, UIUC, Urbana 61800, USA
Jong-Woong Park and Hyung-Jo Jung : 2Department of Civil and Environmental Engineering, KAIST, Daejeon 305-701, Korea

Abstract
Quick, accurate damage monitoring is strongly required for damage assessment in the aftermath of a large natural disaster. Wireless sensor networks are promising technologies to acquire damage information in a citywide area. The wireless sensor networks, however, would be faced with difficulty to collect data in real-time and to expand the scalability of the networks. This paper discusses a scheme of network architecture to cove a whole city in multi-tier heterogeneous networks, which consist of wireless sensor networks, access networks and a backbone network. We first review previous studies for citywide damage monitoring, and then discuss the feature of multi-tier heterogeneous networks to cover a citywide area.

Key Words
multi-tier networks; heterogeneous network; sensor networks; disaster damage monitoring

Address
Takahiro Fujiwara : 1Depertment of Computer Engineering, Hakodate National College of Technology, Hakodate, Japan
Takashi Watanabe : Graduate School of Science and Technology, Shizuoka University, Hamamatsu, Japan
Masanobu Shinozuka: Department of Civil and Environmental Engineering, University of California Irvine, Irvine, U.S.A

Abstract
Recent advances in low-cost remote monitoring systems have made it possible and practical to perform structural health monitoring (SHM) on a large scale. However, it is difficult for a single remote monitoring system to cover a wide range of SHM applications due to the amount of specialization required. For the remote monitoring system to be flexible, sustainable, and robust, this article introduces a new cost-effective, advanced remote monitoring and inspection system named DuraMote that can serve as a next generation supervisory control and data acquisition (SCADA) system for civil infrastructure systems. To evaluate the performance of DuraMote, we conduct experiments at two representative counterpart sites: a bridge and water pipelines. The objectives of this article are to improve upon the existing SCADA by integrating the remote monitoring system (i.e., DuraMote), to describe a prototype SCADA for civil engineering structures, and to validate its effectiveness with long-term field deployment results.

Key Words
structural health monitoring; SCADA system; remote monitoring system

Address
Sehwan Kim and Pai H. Chou :Department of Electrical and Computer Engineering, Univ. of California, Irvine, 92697, USA
Marco Torbol :Department of Civil and Environmental Engineering, Univ. of California, Irvine, 92697, USA

Abstract
In this paper, system identification of a cable-stayed bridge in Korea, the Hwamyung Bridge, is performed using vibration responses measured by a wireless sensor system. First, an acceleration based-wireless sensor system is employed for the structural health monitoring of the bridge, and wireless sensor nodes are deployed on a deck, a pylon and several selected cables. Second, modal parameters of the bridge are obtained both from measured vibration responses and finite element (FE) analysis. Frequency domain decomposition and stochastic subspace identification methods are used to obtain the modal parameters from the measured vibration responses. The FE model of the bridge is established using commercial FE software package. Third, structural properties of the bridge are updated using a modal sensitivity-based method. The updating work improves the accuracy of the FE model so that structural behaviors of the bridge can be represented better using the updated FE model. Finally, cable forces of the selected cables are also identified and compared with both design and lift-off test values.

Key Words
system identification; model updating; cable-stayed bridge; SHM; wireless sensor

Address
Jeong-Tae Kim, Khac-Duy Nguyen and Dong-Soo Hong : Department of Ocean Engineering, Pukyong National University, Busan, Korea
Duc-Duy Ho : Faculty of Civil Engineering, Ho Chi Minh City University of Technology, Ho Chi Minh City, Vietnam
Sung Woo Shin: Department of Safety Engineering, Pukyong National University, Busan, Korea
Chung-Bang Yun : School of Urban and Environmental Engineering, UNIST, Ulsan, Korea
Masanobu Shinozuka: Department of Civil and Environmental Engineering, Univ. of California, Irvine, USA

Abstract
An Remote Corrosion Monitoring (RCM) system consists of an anode with low potential, the metallic structures against corrosion, an electrode to provide reference potential, and a data-acquisition system to ensure the potential difference for anticorrosion. In more detail, the data-acquisition (DAQ) system monitors the potential difference between the metallic structures and a reference electrode to identify the correct potential level against the corrosion of the infrastructures. Then, the measured data are transmitted to a central office to remotely keep track of the status of the corrosion monitoring (CM) system. To date, the RCM system is designed to achieve low power consumption, so that it can be simply powered by batteries. However, due to memory effect and the limited number of recharge cycles, it can entail the maintenance fee or sometimes cause failure to protect the metallic structures. To address this issue, the low-overhead energy harvesting circuitry for the RCM systems has designed to replenish energy storage elements (ESEs) along with redeeming the leakage of supercapacitors. Our developed energy harvester can scavenge the ambient energy from the corrosion monitoring environments and store it as useful electrical energy for powering local data-acquisition systems. In particular, this paper considers the energy harvesting from potential difference due to galvanic corrosion between a metallic infrastructure and a permanent copper/copper sulfate reference electrode. In addition, supercapacitors are adopted as an ESE to compensate for or overcome the limitations of batteries. Experimental results show that our proposed harvesting schemes significantly reduce the overhead of the charging circuitry, which enable fully charging up to a 350-F supercapacitor under the low corrosion power of 3 mW (i.e., 1 V/3 mA).

Key Words
energy harvesting; cathodic protection; remote corrosion monitoring system

Address
Sehwan Kim : Department of Electrical & Computer Engineering, Univ. of California, Irvine, 92697, USA
Ungjin Na: Ministry of Land, Transport and Maritime Affairs, Gwachun, Korea


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