• 제목/요약/키워드: Civil & Environmental Engineering

검색결과 14,601건 처리시간 0.039초

Triaxial shear behavior of calcium sulfoaluminate (CSA)-treated sand under high confining pressures

  • James Innocent Ocheme;Sakiru Olarewaju Olagunju;Ruslan Khamitov;Alfrendo Satyanaga;Jong Kim;Sung-Woo Moon
    • Geomechanics and Engineering
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    • 제33권1호
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    • pp.41-51
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    • 2023
  • Cementitious materials such as Ordinary Portland Cement (OPC), fly ash, lime, and bitumen have been employed for soil improvement over the years. However, due to the environmental concerns associated with the use of OPC, substituting OPC with calcium sulfoaluminate (CSA) cement offers good potential for ground improvement because it is more eco-friendly. Although earlier research has investigated the stabilizing effects of CSA cement-treated sand, no attempt has been made to examine soil behavior under high confining pressure. As a result, this study aimed to investigate the shear strength and mechanical behavior of CSA cement-treated sand using a consolidated drained (CD) triaxial test with high confining pressure. The microstructure of the examined sand samples was investigated using scanning electron microscopy. This study used sand with CSA cement contents of 3%, 5%, and 7% and confining pressures of 0.5, 1.0, and 1.5 MPa. It revealed that the confining pressures and CSA cement content significantly affected the stress-strain and volumetric change behavior of CSA cement-treated sand at high confining pressures.

Structural health monitoring of a cable-stayed bridge using smart sensor technology: deployment and evaluation

  • Jang, Shinae;Jo, Hongki;Cho, Soojin;Mechitov, Kirill;Rice, Jennifer A.;Sim, Sung-Han;Jung, Hyung-Jo;Yun, Chung-Bangm;Spencer, Billie F. Jr.;Agha, Gul
    • Smart Structures and Systems
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    • 제6권5_6호
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    • pp.439-459
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    • 2010
  • Structural health monitoring (SHM) of civil infrastructure using wireless smart sensor networks (WSSNs) has received significant public attention in recent years. The benefits of WSSNs are that they are low-cost, easy to install, and provide effective data management via on-board computation. This paper reports on the deployment and evaluation of a state-of-the-art WSSN on the new Jindo Bridge, a cable-stayed bridge in South Korea with a 344-m main span and two 70-m side spans. The central components of the WSSN deployment are the Imote2 smart sensor platforms, a custom-designed multimetric sensor boards, base stations, and software provided by the Illinois Structural Health Monitoring Project (ISHMP) Services Toolsuite. In total, 70 sensor nodes and two base stations have been deployed to monitor the bridge using an autonomous SHM application with excessive wind and vibration triggering the system to initiate monitoring. Additionally, the performance of the system is evaluated in terms of hardware durability, software stability, power consumption and energy harvesting capabilities. The Jindo Bridge SHM system constitutes the largest deployment of wireless smart sensors for civil infrastructure monitoring to date. This deployment demonstrates the strong potential of WSSNs for monitoring of large scale civil infrastructure.

Downtime cost analysis of offloading operations under irregular waves in Malaysian waters

  • Patel, M.S.;Liew, M.S.;Mustaffa, Zahiraniza;Abdurasheed, Abdurrasheed Said;Whyte, Andrew
    • Ocean Systems Engineering
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    • 제10권2호
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    • pp.131-161
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    • 2020
  • The objective of this study was to evaluate the downtime cost of side-by-side offloading operations in Malaysian waters. With the help of a numerical time domain tool, the structure and cable response of moored FPSO vessel was simulated for heading and beam sea-states under irregular waves. The weather downtime was assessed by comparing the response under operational wave condition with the pre defined industrial safe offloading criteria. Additionally, two cases of cable failure were simulated for each sea-state. The novel study on downtime cost was presented for three different location of Malaysia subcontinent for which the location specific wave scatter diagram facilitated to estimate the probability of occurrence of operational wave condition. It was concluded that an unpredictable increment in wave height by 0.5 m can significantly impact the production cost.

Ultrasonically enhancing flowability of cement grout for reinforcing rock joint in deep underground

  • Junho Moon;Inkook Yoon;Minjin Kim;Junsu Lee;Younguk Kim
    • Geomechanics and Engineering
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    • 제33권2호
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    • pp.211-219
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    • 2023
  • This study analyzes the changes in the physical properties of grout by irradiating it with ultrasonic energy and assesses the injectability of the grout into deep rock fractures. The materials used in the research are OPC (Ordinary Portland Cement) and MC (Micro Cement), and are irradiated depending on the water/cement ratio. After irradiating the grout with ultrasonic energy, viscosity, compressive strength, and particle size are analyzed, and the results of the particle size analysis were applied to Nick Barton's theory to evaluate the injectability of the grout into deep rock fractures under those conditions. It was found that the viscosity of the grout decreased after ultrasonic wave irradiation, and the rate of viscosity reduction tended to decrease as the water/cement ratio increased. Additionally, an increase in compressive strength and a decrease in particle size were observed, indicating that the grout irradiated with ultrasonic energy was more effective for injection into rock fractures.