• 대한조선학회 특별논문집
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• 대한조선학회 2015년도 특별논문집
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• pp.34-40
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• 2015

The design, procurement and fabrication of FPSO project ordered by Inpex Browse, Ltd. have been currently carried out by DSME(Daewoo Shipbuilding Marine and Engineering Co.). The unit will be installed and operated in the Ichthys field offshore of North-Western Australia and there are the particular design requirements to do with performance on the environment loads corresponding to max. 10,000 years return period wave. Also, the operational life of FPSO has to be over 40 years. With this background, this paper introduces the structural design procedure of crane pedestal foundation operated in north-western Australia offshore. The design of crane pedestal foundation structure is basically based on international design code (i.e. API Spec. 2C), Classification society's rule and project specifications. The design load cases are mainly divided into the crane normal operating conditions and crane stowed conditions according to environment conditions of the offshore with 1-year, 5-year, 10-year, 200-year and 10,000-year return period wave. This design experience for crane pedestal foundation operated in north-western Australia offshore will be useful to do engineering of other offshore crane structures.

• 한국지진공학회논문집
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• 제25권6호
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• pp.283-292
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• 2021

In this study, a structural health monitoring system for cable-stayed bridges is developed. In the system, condition assessment of the structure is performed based on measured records from seismic accelerometers. Response indices are defined to monitor structural safety and serviceability and derived from the measured acceleration data. The derivation process of the indices is structured to follow the transformation from the raw data to the outcome. The process includes noise filtering, baseline correction, numerical integration, and calculation of relative differences. The system is packed as a condition assessment program, which consists of four major processes of the structural health evaluation: (i) format conversion of the raw data, (ii) noise filtering, (iii) generation of response indices, and (iv) condition evaluation. An example set of limit states is presented to evaluate the structural condition of the test-bed and cable-stayed bridge.

• Earthquakes and Structures
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• 제12권1호
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• pp.13-21
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• 2017

Recent seismic events occurred in Italy (Emilia-Romagna 2012, Abruzzo 2009) and worldwide (New Zealand 2010 and 2011) highlighted some of the weaknesses of precast concrete industrial buildings, especially those related to the connecting systems traditionally employed to fasten the cladding panels to the internal framing. In fact, one of the most commons fails it is possible to observe in such structural typologies is related to the out-of-plane collapse of the external walls due to the unsatisfactory behaviour of the connectors used to join the panels to the perimeter beams. In this work, the strengthening of a traditional industrial building, assumed as a case study, made by precast reinforced concrete is proposed by the adoption of a dual system allowing the reinforcement of the structure by acting both internally; by pendular columns and, externally, on the walls. In particular, traditional connections at the top of the walls are substituted by devices able to work as a slider with vertical axis while, the bottom of the walls is equipped with two or more hysteretic dampers working on the uplift of the cladding panels occurring under seismic actions. By means of this approach, the structure is stiffened; obtaining a reduction of the lateral drifts under serviceability limit states. In addition, its seismic behaviour is improved due to the additional source of energy dissipation represented by the dampers located at the base of the walls. The effectiveness of the suggested retrofitting approach has been checked by comparing the performance of the retrofitted structure with those of the structure unreinforced by means of both pushover and Incremental Dynamic Analyses (IDA) in terms of behaviour factor, assumed as a measure of the ductility capacity of the structure.

• Computers and Concrete
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• 제2권1호
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• pp.31-53
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• 2005

In the present structural codes the safety verification is based on a linear analysis of the structure and the satisfaction of ultimate and serviceability limit states, using a semi-probabilistic security format through the consideration of partial safety factors, which affect the action values and the characteristic values of the material properties. In this context, if a non-linear structural analysis is wanted a difficulty arises, because the global safety coefficient, which could be obtained in a straightforward way from the non-linear analysis, is not directly relatable to the different safety coefficient values usually used for the different materials, as is the case for reinforced concrete structures. The work here presented aims to overcome this difficulty by proposing a methodology that generalises the format of safety verification based on partial safety factors, well established in structural codes within the scope of linear analysis, for cases where non-linear analysis is needed. The methodology preserves the principal assumptions made in the codes as well as a reasonable simplicity in its use, including a realistic definition of the material properties and the structural behaviour, and it is based on the evaluation of a global safety coefficient. Some examples are presented aiming to clarify and synthesise all the options that were taken in the application of the proposed methodology, namely how to transpose the force distributions obtained with a non-linear analysis into design force distributions. One of the most important features of the proposed methodology, the ability for comparing the simplified procedures for second order effects evaluation prescribed in the structural codes, is also presented in a simple and systematic way. The potential of the methodology for the development and assessment of alternative and more accurate procedures to those already established in codes of practice, where non-linear effects must be considered, is also indicated.

• Earthquakes and Structures
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• 제13권2호
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• pp.151-164
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• 2017

This article aims to investigate the possible retrofitting of a deficient building with soft story failure mode by connecting it to an adjacent building which is designed based on current code with friction dampers at all floors. Low cost and high performance reliability along with significant energy dissipation pertaining to stable hysteretic loops may be considered in order to choose the proper damper for connecting adjacent buildings. After connecting two neighbouring floors by friction dampers, the sliding forces of dampers at various stories are set in two arrangements: uniform sliding force and then variable sliding force. In order to account for the stochastic nature of the seismic events, incremental dynamic analyses are employed prior and after the installation of the friction dampers at the various floors. Based on these results, fragility curves and mean annual rate of exceedance of serviceability and ultimate limit states are obtained. The results of this study show that the collapse mode of the deficient building can affect the optimum arrangement of sliding forces of friction dampers at Collapse Prevention (CP) performance level. In particular, the Immediate Occupancy (IO) performance level is not tangible to the sliding force arrangement and it depends solely on sliding force value. Generally it can be claimed that this rehabilitation scheme can turn the challenge of pounding two adjacent buildings into the opportunity of dissipating a large amount of the seismic input energy by the friction dampers, thus improving significantly the poor seismic performance of the deficient structure.

• Earthquakes and Structures
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• 제24권2호
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• pp.81-90
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• 2023

The maximum drifts are important to the seismic evaluation of steel buildings and connections, but the information can hardly be obtained from the post-earthquake field investigation. This research studies the feasibility of using the loss rate of bolt pretension as an earthquake damage predictor. Full-scale tests were made on four steel connections using bolted-web-welded-flange details. One connection was unreinforced (UN), another was reinforced with double shear plates (DS), and the other two used reduced beam sections (RBS). The preinstalled strain gauges were used to control the pretensions and monitor the losses of the high-strength bolts. The results showed that the loss rate of bolt pretension was highly related to the damage of the connections. The pretensions lost up to 10% in all the connections at the yield drifts of 0.5% to 1%. After yielding of the connections, the pretensions lost significantly until fracture occurred. The UN and DS connections failed with a maximum drift of 4 %, and the two RBS connections showed better ductility and failed with a maximum drift of 6%. Under the far-field-type loading protocol, the loss rate grew to 60%. On the contrary, the rate for the specimen under near-fault-type loading protocol was about 40%. The loss rate of bolt pretension is therefore recommended to use as an earthquake damage predictor. Additionally, the 10% and 40% loss rates are recommended to predict the limit states of connection yielding and maximum strength, respectively, and to define the performance levels of serviceability and life-safety for the buildings.

• 토지주택연구
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• 제2권3호
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• pp.287-297
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• 2011

본 논문은 적층고무형베어링을 갖는 15층 면진 무량판 아파트건물의 내진거동을 진동대실험을 통하여 검증한 결과를 제시하고 있다. 진동대실험은 중국의 CABR에서 1/10규모의 모형실험체를 대상으로 수행되었다. 실험의 진행은 4개의 지진파를 이용하여 X, Y, X+Y방향으로 다양한 크기의 지진동이 입력되었다. 실험결과, 비 면진건물은 중진레벨에서 진동주기가 현저히 감소하고, 비선형적인 거동을 보였으며, 가속도가 건물의 높이에 따라 현저하게 증가하고, 층간변위도 허용한계를 넘는 거동을 보였다. 반면, 면진건물은 중진레벨에서 거의 일정한 진동주기의 탄성적인 거동을 나타내었으며, 지진하중과 층 가속도가 현저하게 감소하는 응답을 나타내었다. 또한 면진층의 변위는 허용범위 내에서 거동하고, 층간변위는 무시할 수 있을 만큼 작은 강체거동을 나타내었다. 결론적으로 면진은 건물에 대한 지진의 영향을 감소시키는데 매우 효과적이며, 층 가속도의 감소를 통하여 사용성을 증가시키고, 건물 내 설비 등을 안전하게 보호할 수 있음이 입증되었다.