• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.4
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• pp.13-23
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• 2007

This paper focuses on providing a practical approach for decision making in Performance-Based Design (PBD). Satisfactory performance is defined by several performance objectives that place limits on direct (monetary) loss and on a tolerable probability of collapse. No specific limits are placed on conventional engineering parameters such as forces or deformations, although it is assumed that sound capacity design principles are followed in the design process. The proposed design procedure incorporates different performance objectives up front, before the structural system is created, and assists engineers in making informed decisions on the choice of an effective structural system and its stiffness (period), base shear strength, and other important global structural parameters. The tools needed to implement this design process are (1) hazard curves for a specific ground motion intensity measure, (2) mean loss curves for structural and nonstructural subsystems, (3) structural response curves that relate, for different structural systems, a ground motion intensity measure to the engineering demand parameter (e.g., interstory drift or floor acceleration) on which the subsystem loss depends, and (4) collapse fragility curves. Since the proposed procedure facilitates decision making in the conceptual design process, it is referred to as a Design Decision Support System, DDSS. Implementation of the DDSS is illustrated in an example to demonstrate its practicality.

• Journal of Korean Society of societal Security
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• v.2 no.4
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• pp.75-81
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• 2009

This paper presents the geotechnical characteristics of tunnel co \l apse based on the case studies. For domestic cases, most collapses are likely to happen along the weakest zone of shear strength due to the change of stresses induced by excavation specially when soft or weathered rock exist in front of a tunnel. In other words, the collapse of a tunnel occurs along the highly weathered fractured zone due to blasting and excavation. In Europe, collapses have been occurred by one joint group even though the ground is relatively fresh and for the rocks of which RQD is over 50%. In addition, the amount of ground water flow does not seem to be seriously affected by the RQD range.

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.83-93
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• 2010

The purpose of this study is to present emergency rehabilitation, cause and the countermeasure of reinforcement about reinforced retaining wall and the slope collapse of the phyllite ground. The study area is broken easily because this area has rock mass discontinuity such as stratification, foliation, joint and fold. And this area consists of the ground where it happens easily to the failure of structure like reinforced retaining wall because of the phyllite ground sensitive to weathering. Counterweight fill in front of reinforced retaining wall was performed as emergency rehabilitation about displacement of reinforced retaining wall and the failure at the rear of slope on phyllite ground. After that, additional displacement didn't occur. Boring and geophysical exploration were launched to present emergency rehabilitation and develop the long-term method of reinforcement. This could grasp anticipated range of the failure section and identify internal and external factors of the cause of the slope collapse. Several methods of reinforcement were suggested by conducting the numerical analysis. When conducting design and construction of major structures at the ground which has complex discontinuities, the precise site investigation should be conducted. During construction, immediate action for over-displacement should be taken by performing the periodic measurement.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.593-600
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• 2000

Most of ground investigations can be grasped geological distribution which like rock name, geological structure, soil condition, underwater condition, land slide, ground cave-in, ground collapse by geological survey. But geological survey is limited to part region geological structure, not wide region. Therefore, Image Processing Method must need to grasp wide region geological structure. The object of this research is presented analysis data of geotechnical engineering in first step investigation.

• Earthquakes and Structures
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• v.9 no.1
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• pp.49-71
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• 2015

The present paper aims at evaluating damage and collapse behavior of low-rise buildings with unidirectional mass irregularities in plan (torsional buildings). In previous earthquake events, such buildings have been exposed to extensive damages and even total collapse in some cases. To investigate the performance and collapse behavior of such buildings from probabilistic points of view, three-dimensional three and six-story reinforced concrete models with unidirectional mass eccentricities ranging from 0% to 30% and designed with modern seismic design code provisions specific to intermediate ductility class were subjected to nonlinear static as well as extensive nonlinear incremental dynamic analysis (IDA) under a set of far-field real ground motions containing 21 two-component records. Performance of each model was then examined by means of calculating conventional seismic design parameters including the response reduction (R), structural overstrength (${\Omega}$) and structural ductility (${\mu}$) factors, calculation of probability distribution of maximum inter-story drift responses in two orthogonal directions and calculation collapse margin ratio (CMR) as an indicator of performance. Results demonstrate that substantial differences exist between the behavior of regular and irregular buildings in terms of lateral load capacity and collapse margin ratio. Also, results indicate that current seismic design parameters could be non-conservative for buildings with high levels of plan eccentricity and such structures do not meet the target "life safety" performance level based on safety margin against collapse. The adverse effects of plan irregularity on collapse safety of structures are more pronounced as the number of stories increases.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.2
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• pp.81-88
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• 2007

In case of an urban tunnel, the displacement of ground base controls the tunnel design because it is built on shallow and unconsolidated ground many times. There are more insufficiency to describe the ground movement which coincides in the measured result of the situ because the design of an urban tunnel is dependent on the method of numerical analysis used to the existing elastic and elasto-plastic models. We studied about the prediction for the ground movement of a shallow tunnel in unconsolidated ground, mechanism of collapse, and settlement. Also this paper shows comparison with the existing elastic and elasto-plastic model using the unlinear analysis of the strain-softening model. We can model the real ground movement as the increasement of ground surface inclination or occurrence of shear band by using strain-softening model for the result of ground movement of an urban NATM tunnel.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.411-416
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• 2003

As rapid industrialization continues in these days, construction in the down town areas increases. Since constructions are performed around old and existing structures, the need to provide reinforcements to protect the existing structures from collapse and damage arises. Furthermore, if the construction is to take place in the down town area, difficult work space and damage caused by noise, vibration and collapse of structure can't be ignored. Among the remedial measures available today, micropile reinforcement is considered the best method to remedy these problems. But up to the present the characteristics of micropiles and ground behaviour has not been proven and no standard design is not yet available. Therefore, most design are performed based on previous experiences. In this study, the difference in the bearing capacity with changing reinforcement angle, space and sphere around foundation was monitored. These results were induced to broaden heighten the limits of micropile application.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.129-136
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• 2005

Concentrically braced steel frames are considered as being quite prone to soft-story response due to the degradation in brace compressive resistance after buckling under severe ground motions. When combined with the system P-Delta effects, collapse of the concentrically braced frames by dynamic instability becomes a highly probable. In this study, a new, relatively simple dynamic instability coefficient was proposed for diagonally braced steel frames by considering the strength degradation of the brace after buckling. Nonlinear dynamic analysis was conducted to check the robustness of the proposed index based on simulated ground motions. The analysis results showed that the dynamic instability index proposed predicts the collapse potential more consistently than the conventional one. Dynamic instability was triggered when the index value was close to 0.7.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.835-844
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• 2009

In this study, a database composed by 46 cases of tunnel collapses has been built up. Based on the database, comprehensive data analysis is carried out, providing us a number of the technical lessons, which can be considered in future design and construction to minimize possibility of tunnel collapse disaster. For making a better understanding, the technical lessons are given in two divisions: mountain tunnel and urban tunnel. Tunnel collapses taking place in the former tunnel are generally due to bad discontinuity condition of jointed rock mass. Otherwise, urban tunnel has weak condition generally on ground water and weathering of ground. Most of technical comments given in this paper are made based on the cases of tunnel collapses only used in this study, so that the comments seems to be hard to be available to all the tunnelling cases. However, the comment should be valuable technical lessons for tunnel engineers to consider in tunnel design or construction.

• Structural Engineering and Mechanics
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• v.23 no.2
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• pp.177-193
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• 2006

Determining the hysteretic energy demand and dissipation capacity and level of damage of the structure to a predefined earthquake ground motion is a highly non-linear problem and is one of the questions involved in predicting the structure's response for low-performance levels (life safe, near collapse, collapse) in performance-based earthquake resistant design. Neural Network (NN) analysis offers an alternative approach for investigation of non-linear relationships in engineering problems. The results of NN yield a more realistic and accurate prediction. A NN model can help the engineer to predict the seismic performance of the structure and to design the structural elements, even when there is not adequate information at the early stages of the design process. The principal aim of this study is to develop and test multi-layered feedforward NNs trained with the back-propagation algorithm to model the non-linear relationship between the structural and ground motion parameters and the hysteretic energy demand in steel moment resisting frames. The approach adapted in this study was shown to be capable of providing accurate estimates of hysteretic energy demand by using the six design parameters.