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.

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Resilience-Based Design of Natural Gas Distribution Networks

Coarse granular material is used as important fill material in most of large embankments such as railway, road, dam and so on. Therefore, the accurate design parameters of the coarse granular material are necessarily required in design and construction. The behavior of the coarse granular material was not well understood because of the lack of large testing equipment capable of coarse granular material. A large triaxial testing system was developed in this research, capable of large specimens of 500 mm, 300 mm and 150 mm in diameter. In the new large triaxial testing system, the load cell is installed inside the triaxial cell and axial displacement is measured locally on a specimen in order to improve control and measurement in small strain level. Urethane specimens of 300 mm and 50 mm in diameter were prepared. The large triaxial tests were performed on the 300 mm diameter urethane specimens while RC/TS and impact echo tests on the 50 mm diameter urethane specimens to verify this testing system. In this verification test results, we could ascertain the reasonable test results of the KRRI large triaxial testing system.

Development and Verification of Large Triaxial Testing System for Dynamic Properties of Granular Materials

The authors present a method for calculating a mooring line’s tension and angle of inclination at the anchor pad eye to analyze the behavior of a mooring line embedded in sand. They adopted the governing equation from a previous study for clay and reanalyzed the frictional and bearing resistances. The authors performed a number of centrifuge tests at two anchor depths while maintaining relative densities of 76 or 51% in the cylindrical test box to validate the proposed analytical method. The analytical solutions agreed well with the test results and the results of the simplified method. The authors conducted a parametric study to evaluate the effects of various factors on the behavior of an embedded mooring line in sand, including the depth of the attachment point, the internal friction angle of sand, the submerged unit weight of sand, the angle of the mooring line on the seabed, and the self-weight and nominal diameter of the mooring line. The results demonstrated that the proposed analytical met...

Profile and Frictional Capacity of a Mooring Line Embedded in Sand via Centrifuge Model Testing

In centrifuge modeling, it is important to evaluate the in-flight strength and stiffness parameters of the soil model to understand soil behavior. Both the shear-wave velocity (Vs) and cone...

Correlation between the Shear-Wave Velocity and Tip Resistance of Quartz Sand in a Centrifuge

Sandy gravel materials have recently been utilized in place of crushed rock materials as the main rockfill materials in Concrete Faced Rockfill Dams (CRFD) to address geological and environmental problems. In this paper, an experimental scheme for centrifuge modeling was developed to simulate a Concrete Faced Gravel-fill Dam (CFGD). The dam considered in this study was designed to implement a drainage zone of high permeability in the main gravel-fill zone to enhance safety against accidental water infiltration into the dam. Two centrifuge tests were performed and compared to investigate the performance of the drainage zone. The first test was done with the drainage zone and the second without the drainage zone. In the centrifuge tests, water infiltration was simulated by raising the water table over pre-implemented cracks on the model face slab. The infiltration behaviors were monitored by pore water pressure transducers. The centrifuge tests showed that the drainage zone of the CFGD effectively drains infiltrating water out of the dam body in a short time. Numerical modeling was also performed to help understand the process of seepage through cracks.

Seepage behavior of drainage zoning in a concrete faced gravel-fill dam via centrifuge and numerical modeling

In this study, a new large-scale triaxial testing apparatus was constructed and calibrated. To verify the new testing system, synthetic specimens were prepared and tested by three different testing methods: tests using the newly constructed large-scale triaxial testing apparatus, resonant column/torsional shear tests, and free–free resonant column tests. Young’s moduli of the synthetic specimens measured by the three methods were compared, providing comparable results. In addition, cyclic triaxial tests were performed under various experimental conditions on coarse grain materials. Two series of parallel graded samples were prepared by mixing crushed rock. The samples were tested using the new triaxial testing apparatus under various testing conditions. The influence of grain size, loading pattern, loading frequency, and fine contents were analyzed and discussed.

Yun Wook Choo

Papers

Development and Verification of Large Triaxial Testing System for Dynamic Properties of Granular Materials

Profile and Frictional Capacity of a Mooring Line Embedded in Sand via Centrifuge Model Testing

Correlation between the Shear-Wave Velocity and Tip Resistance of Quartz Sand in a Centrifuge

Seepage behavior of drainage zoning in a concrete faced gravel-fill dam via centrifuge and numerical modeling

Young’s Modulus of Coarse Granular Materials via Cyclic Large Triaxial Tests: Effect of Parallel Grading and Loading Pattern