• Structural Engineering and Mechanics
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• 제64권2호
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• pp.213-223
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• 2017

Bridges are lifeline and integral components of transportation system that are susceptible to seismic actions, their vulnerability assessment is essential for seismic risk assessment and mitigation. The vulnerability assessment of bridges common in Pakistan is very important as it is seismically very active region and the available code for the seismic design of bridges is obsolete. This research presents seismic vulnerability assessment of three real case simply supported multi-span reinforced concrete bridges commonly found in northern Pakistan, having one, two and three bents with circular piers. The vulnerability assessment is carried through the non-linear dynamic time history analyses for the derivation of fragility curves. Finite element based numerical models of the bridges were developed in MIDAS CIVIL (2015) and analyzed through with non-linear dynamic and incremental dynamic analyses, using a suite of bridge-specific natural spectrum compatible ground motion records. Seismic responses of shear key, bearing pad, expansion joint and pier components of each bridges were recorded during analysis and retrieved for performance based analysis. Fragility curves were developed for the bearing pads, shear key, expansion joint and pier of the bridges that first reach ultimate limit state. Dynamic analysis and the derived fragility curves show that ultimate limit state of bearing pads, shear keys and expansion joints of the bridges exceed first, followed by the piers ultimate limit state for all the three bridges. Mean collapse capacities computed for all the components indicated that bearing pads, expansion joints, and shear keys exceed the ultimate limit state at lowest seismic intensities.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.594-595
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• 2006

Porous bearings are lubricated the oil that is contained in porous metal. Then they are always used with no oil supply, because of that, widely used electric motors. But, if oil flow out less than the limit, troubles often happen. This report shows that attempt of estimating oil quantity in porous bearing by using calculation that based Reynols' equation and Darcy's law, aimed of developing long life bearing. And comparing with experimental and calculation result, we show possibility of estimating rest oil quantity in porous bearing at steadry state by calculation.

• Earthquakes and Structures
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• 제16권5호
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• pp.575-588
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• 2019

Seismic design method based on bearing capacity has been widely adopted in building codes around the world, however, damage and collapse state of structure under strong earthquake can not be reflected accurately. This paper aims to present a deformation-based seismic design method based on the research of RC component deformation index limit, which combines with the feature of Chinese building codes. In the proposed method, building performance is divided into five levels and components are classified into three types according to their importance. Five specific design approaches, namely, "Elastic Design", "Unyielding Design", "Limit Design", "Minimum Section Design" and "Deformation Assessment", are defined and used in different scenarios to prove whether the seismic performance objectives are attained. For the components which exhibit ductile failure, deformation of components under strong earthquake are obtained quantitatively in order to identify the damage state of the components. For the components which present brittle shear failure, their performance is guaranteed by bearing capacity. As a case study, seismic design of an extremely irregular twin-tower high rise building was carried out according to the proposed method. The results evidenced that the damage and anti-collapse ability of structure were estimated and controlled by both deformation and bearing capacity.

• KIEAE Journal
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• 제11권1호
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• pp.9-14
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• 2011

Currently, the multi-residential apartments used in Korea are mostly bearing wall apartments which don't satisfy consumers for the lack of architectural plan flexibility. And due to remodelling-incompatible, bearing wall apartments have to be reconstructed. It is, thus, necessary to develop multi-residential apartments utilizing composite beam that can replace the conventional bearing wall-type apartment buildings. Composite beams proposed in this paper ensure modification of space and quality control, while the floor heights are maintained at the same floor height as in bearing wall structures. This study analyzes the experimental behavior of composite beams with proper combination of structural steel, reinforced concrete, and precast concrete. By comparing with the theoretical analysis and experimental results, the accuracy of flexural moment capacity and neutral axis was evaluated. The experiments were performed by two simply-supported specimens using loading and unloading. When the analysis results were compared with the experimental results, the flexural moment capacity of the composite beam was shown with an error of approximately -0.5 to 0.1% at the maximum load limit state.

• 한국해안·해양공학회논문집
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• 제25권2호
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• pp.112-121
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• 2013

쇄석다짐말뚝의 한계상태설계법에서 신뢰성이론에 기반한 저항계수를 보정하기 위해서는 신뢰도 높은 극한지지력의 평가가 요구되고 있으며, 실무에서는 극한지지력을 예측하기 위하여 주로 정재하시험을 이용하고 있다. 정재하시험의 하중-침하량 곡선을 여러 도해법 등을 이용하여 극한지지력을 예측하는 평가법들이 설계기준에 제시되어 있으나, 기술자의 판단에 따라 극한하중이 일정하게 산정되지 못함으로써 신뢰성을 확보하기 어려운 단점이 있었다. 본 연구에서는 쇄석다짐말뚝의 정재하시험 결과를 비선형 회귀분석을 이용하여 극한지지력을 예측하고, 기존의 극한지지력 판정법과 비교함으로써 실제 극한지지력을 예측하는데 적합한 비선형 회귀모형을 제안하였다. 또한 극한지지력 판정법이 저항편향계수에 미치는 영향을 분석하고, 한계상태설계법을 위한 데이터베이스 축적을 목적으로 정재하시험을 계획하는데 필요한 시험조건을 검토하였다.

• Steel and Composite Structures
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• 제6권2호
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• pp.103-122
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• 2006

The capacity of tubular truss chords subjected to concentrated reaction forces in the vicinity of the open end (i.e., the bearing region) is not directly treated by existing design specifications; although capacity equations are promulgated for related tubular joint configurations. The lack of direct treatment of bearing capacity in existing design specifications seems to represent an unsatisfactory situation given the fact that connections very often control the design of long-span tubular structures comprised of members with slender cross-sections. The case of the simple-span overhead highway sign truss is studied, in which the bearing reaction is applied near the chord end. The present research is aimed at assessing the validity of adapting existing specifications' capacity equations from related cases so as to be applicable in determining design capacity in tubular truss bearing regions. These modified capacity equations are subsequently used in comparisons with full-scale experimental results obtained from testing carried out at the University of Pittsburgh.

• 한국해안·해양공학회논문집
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• 제22권3호
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• pp.156-162
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• 2010

중력식 안벽 및 방파제 등은 편심 경사하중에 지배받는 항만구조물으로서 구조물 설계시 신뢰성이론에 근거하여 지반지지력 산정에 필요한 부분안전계수를 평가하였다. 현재 항만 및 어항 설계기준(2005)에서는 구조물에 편심 경사하중이 작용하는 경우에 지반지지력을 간편 Bishop법 등에 의해 검토하도록 규정되어 있다. 이러한 설계규정은 설계자에게 지반의 허용지지력과 지반반력을 비교하는 방법으로 그동안 가장 많이 사용되어 왔다. 그러나, 지반반력에 의한 설계검토는 지지력 계산이 단순하고 편리하지만 지반의 허용지지력이 현장의 지반물성에 따라 변화하지만 단일수치로 결정하여 설계하므로 이러한 지반특성을 설계에 반영하지 못한다는 큰 문제점이 있었다. 그래서 본 논문에서는 간편 Bishop법에 의하여 Level 1 신뢰성해석이 가능하도록 각각의 설계변수에 대한 부분안전계수를 결정하였다. 이를 위해서 신뢰성 이론인 일계신뢰도법(FOSM)을 통하여 신뢰도지수와 민감도지수를 추정하고 각각의 확률변수의 변동성도 고려하였다. 마지막으로는 연구결과에서 결정된 부분안전계수를 선진국의 설계기준에서 제시한 것과 비교하여 합리적임을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1165-1169
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• 2003

This paper presents an approach to optimally design the air-bearing surface (ABS) of the optical flying head for near-field recording technology (NFR). NFR is an optical recording technology using very small beam spot size by overcoming the limit of beam diffraction. One of the most Important problems in NFR is a head disk interface (HDI) issue over the recording band during the operation. A multi-criteria optimization problem is formulated to enhance the flying performances over the entire recording band during the steady state. The optimal solution of the slider, whose target flying height is 50 nm, is automatically obtained. The flying height during the steady state operation becomes closer to the target values than those fur the initial one. The pitch and roll angles are also kept within suitable ranges over the recording band. Especially, all of the air-bearing stiffness are drastically increased by the optimized geometry of the air bearing surface.

• Advances in Computational Design
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• 제2권1호
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• pp.43-56
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• 2017

The aim of this paper is to develop software for designing of steel reinforced elastomeric isolator (SREI) according to American Association for State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) Specifications. SREI is used for almost all bridge types and special structures. SREI-structures interface defines support boundary conditions and may affect the seismic performance of bridges. Seismic performance of the bridge is also affected by geometrical and materials properties of SREI. The selection of SREI is complicated process includes satisfying all the design constraints arising from code provisions and maximizing performance at the lowest possible cost. In this paper, design stage of SREI is described up to AASHTO LRFD 2012. Up to AASHTO LRFD 2012 analysis and design program of SREI performed different geometrical and material properties are created with C# object-oriented language. SREI-CAD, name of the created software, allows an accurate design for economical estimation of a SREI in a short time. To determine types of SREI effects, two different types of bearings, rectangular and circular with similar materials and dimension properties are selected as an application. Designs of these SREIs are completed with SREI-CAD. It is seen that ensuring the stability of circular elastomer bearing at the service limit state is generally complicated than rectangular bearing.

• 한국지반공학회논문집
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• 제22권6호
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• pp.63-69
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• 2006

본 연구에서는 얕은 기초의 지지력을 평가할 수 있는 개별요소법에 근거한 해석기법이 제안되었다. 제안된 해석기법은 토체 간의 거동에 관한 적합조건을 탄소성 Winkler 스프링으로 모사함으로써 파괴면에서의 응력상태와 극한지지력을 함께 구할 수 있다. 기법의 적용성을 검토하기 위하여 단일층 및 이층지반에 설치된 얕은 기초의 지지력 해석을 수행하였다.