Damage constitutive model based on energy dissipation for intact rock subjected to cyclic loading

Community resilience has been addressed across multiple disciplines including environmental sciences, engineering, sociology, psychology, and economics. Interest in community resilience gained momentum following several key natural and human-caused hazards in the United States and worldwide. To date, a comprehensive community resilience model that encompasses the performance of all the physical and socio-economic components from immediate impact through the recovery phase of a natural disaster has not been available. This paper summarizes a literature review of previous community resilience studies with a focus on natural hazards, which includes primarily models of individual infrastructure systems, their interdependencies, and community economic and social systems. A series of national and international initiatives aimed at community resilience are also summarized in this study. This paper suggests extensions of existing modeling methodologies aimed at developing an improved, integrated understanding of resilience that can be used by policy-makers in preparation for future events.

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State of the research in community resilience: progress and challenges.

The first large scale geotechnical centrifuge in Korea has recently been developed at KAIST under the Korea Construction Engineering Development (KOCED) Collaboratory program. A 5 m platform radius, 240 g-tons state-of-the-art geotechnical centrifuge has been installed in a new facility. The centrifuge has the unique feature of an automatic balancing system and includes parts for general testing purposes such as fluid rotary joints, slip rings, a fiber optic rotary joint and an Ethernet network system. In addition, a four degree-of-freedom in-flight robot can be equipped to simulate complex construction or in-situ testing process during centrifuge flight. In order to simulate earthquake motion during operation, a self-balancing type biaxial shaking table has also been developed. Since the KOCED program promotes collaboration and remote use, tele-presence and tele-participation environments have been implemented in this facility.

A Newly Developed State-of-the-Art Geotechnical Centrifuge in Korea

Analysis of buried pipelines subjected to reverse fault motion

The concept of disaster resilience has received considerable attention in recent years and is increasingly used as an approach for understanding the dynamic response to natural disasters. In this paper, a new performance index measuring the functionality of a gas distribution network has been proposed, which includes the restoration phase to evaluate the resilience index of the entire network. The index can also be used for any type of natural or artificial hazard, which might lead to the disruption of the system. The gas distribution network of the municipalities of Introdacqua and Sulmona, two small towns in the center of Italy that were affected by the 2009 earthquake, has been used as a case study. The pipeline network covers an area of 136 km2, with three metering pressure reduction (M/R) stations and 16 regulation groups. Different analyses simulating different breakage scenario events due to an earthquake have been considered. The numerical results showed that the functionality of the medium-pressure gas distribution network is crucial for ensuring an acceptable delivery service during the post earthquake response. Furthermore,the best retrofit strategy to improve the resilience index of the entire network should include emergency shutoff valves along the steel pipes.

/pdf/resilience-based-design-of-natural-gas-distribution-networks-44djcxln2l.pdf

Resilience-Based Design of Natural Gas Distribution Networks

Centrifuge Tests of Monopod and Tripod Bucket Foundations for Offshore Wind Turbine Tower

The safety barrier is installed on road embankment to prevent vehicles from falling into road side slope. Among the safety barrier, flexible guardrails are usually installed. The flexible guardrail generally consists of a protection cross-beam and supporting in-line piles. These guardrail piles are installed nearby slope edge of road embankment because the side area of the road is much narrow. The protection cross-beam absorbs impact energy caused by vehicle collision. The pile-soil interaction also absorbs the rest of the impact energy and then, finally, the flexible guardrail system resists the impact load. This paper aims to investigate the pile-soil interaction subjected to impact load using centrifuge model tests. In this study, a single pile was installed in compacted residual soil and loaded under lateral impact load. An impact loading system was designed and developed available on centrifuge tests. Using this loading system, a parametric study was performed and the parameters include types of loading and ground. Finally, the ultimate bearing capacity of supporting pile under impact load was analyzed using load-displacement curve and soil reaction pressure distributions at ultimate were evaluated and compared with previous studies.

http://koreascience.or.kr:80/article/JAKO201907750243656.pdf

Ultimate Capacity of Guardrail Supporting Pile Subjected to Lateral Impact Load Using Centrifuge Model Test

Centrifuge tests were performed to investigate the effect of the relative density of the sandy layer on the lateral response of 6-m-diameter offshore monopiles. The end tips of the monopiles are socketed into rock-bearing layers. For the simulation of the rock-socketed monopiles in sands with different relative densities (dense and medium dense sand layers), centrifuge tests at an acceleration of 60 g were conducted using well-instrumented model monopiles under significant lateral loads and bending moments. Based on the centrifuge test results, the p–y relationship and the initial stiffness (initial gradient of a p–y curve) changed with an increasing depth for both dense and medium dense sand layers. As a result, the newly developed p–y curves for rock-socketed large-diameter monopiles in this study were quite different from the existing API (American Petroleum Institute) p–y curves, which were developed based on relatively small-diameter driven piles. It was found that the initial stiffness for the medium dense sand layer was significantly lower than that for the dense sand layer at a shallow depth; however, the ratio of initial stiffness of the medium dense sand layer to that of the dense sand layer decreases significantly as the depth increases and approaches the stiff rock-bearing layer.

Comparison of Lateral Behavior of Rock-Socketed Large-Diameter Offshore Monopiles in Sands with Different Relative Densities

Development of Electrical Resistivity Survey System for Geotechnical Centrifuge Modeling

To investigate the behavior of dredged-sea-sand fill compacted inside tide embankments with a damaged geosynthetic mat, centrifugal model tests and numerical simulation were conducted, both considering variations in sea level. The results from the three centrifugal model tests demonstrate that the subsidence of the dredged-sea-sand fill inside tide embankments with a damaged geosynthetic mat was strongly affected by the loss of dredged-sea-sand into the filter layers with large particles and a decrease in the bearing capacity of the filter layers with small particles. In addition, a comparison of the test and simulation results confirms that the loss of sand into the filter layer and the subsidence of the dredged-sea-sand fill were well reproduced by the numerical simulation.

Yun Wook Choo

Papers

Centrifuge Tests of Monopod and Tripod Bucket Foundations for Offshore Wind Turbine Tower

Ultimate Capacity of Guardrail Supporting Pile Subjected to Lateral Impact Load Using Centrifuge Model Test

Comparison of Lateral Behavior of Rock-Socketed Large-Diameter Offshore Monopiles in Sands with Different Relative Densities

Development of Electrical Resistivity Survey System for Geotechnical Centrifuge Modeling

Stability Study of a Tide Embankment Subjected to Sea Level Variations Using Centrifugal Model Tests