• 한국가스학회지
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• 제25권1호
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• pp.7-13
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• 2021

재액화 드럼은 과냉각된 LNG를 증발가스에 직접 분사하기 위해 상부에 스프레이 노즐을 설치하고, 기액 분리가 용이하도록 데미스터를 설치한 제품으로, 소형 재액화 설비의 재액화 효율을 높이기 위해 개발한 제품이다. 드럼의 상온 내압기밀시험에서는 설계압력의 1.5배 이상의 압력에서도 누설(Leak)이 없었으나, 단열성능시험 중 온도변화에 따른 수축/팽창으로 인해 볼트풀림 현상이 발생하였다. 제품의 지속적인 사용을 위해 플랜지 결합부의 단열 시공은 탈부착이 가능하도록 개발하였으며, 기존 단열과의 열침입량 비교 결과 드럼 내 유입 유량 대비 매우 미미함을 확인하였다.

• Computers and Concrete
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• 제28권5호
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• pp.497-506
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• 2021

Steel-concrete composite structures and precast concrete elements have a common prefabrication process and allow fast construction. The use of hollow-core slabs associated with composite floors can be advantageous. However, there are few studies on the subject, impeding the application of such systems. In this paper, a numerical model representing the considered system using the FE (finite element)-based software DIANA is developed. The results of an experimental test were also presented in Souza (2016) and were used to validate the model. Comparisons between the numerical and test results were performed in terms of the load versus displacement, load versus slip, and load versus strain curves, showing satisfactory agreement. In addition, a wide parametric study was performed, evaluating the influence of several parameters on the behaviour of the composite system: The strength of the steel beam, thickness of the web, thickness and width of the bottom flange of the steel beam and concrete cover thickness on top of the beam. The results indicated a great influence of the steel strength and the thickness of the bottom flange of the steel beam on the capacity of the composite floor. The remaining parameters had limited influences on the results.

• Steel and Composite Structures
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• 제21권3호
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• pp.629-659
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• 2016

In cold-formed stainless steel lipped channel-sections, web openings are becoming increasingly popular. Such openings, however, result in the sections becoming more susceptible to web crippling, especially under concentrated loads applied near the web opening. This paper presents the results of a finite element parametric study into the effect of circular web openings on the web crippling strength of cold-formed stainless steel lipped channel-sections for the interior-one-flange (IOF) loading condition. This involves a bearing load applied to the top flange of a length of member, away from the end supports. The cases of web openings located centred beneath the bearing load (i.e. beneath the bearing plate delivering the load) and offset to the bearing plate, are considered. Three grades of stainless steel are considered: duplex EN1.4462, austenitic EN1.4404 and ferretic EN1.4003. In total, 2218 finite element models were analyzed. From the results of the parametric study, strength reduction factors for load bearing capacity are determined, where these reduction factors are applied to the bearing capacity calculated for a web without openings, to take account the influence of the web openings. The strength reduction factors are first compared to equations recently proposed for cold-formed carbon steel lipped channel-sections. It is shown that for the case of the duplex grade, the strength reduction factor equations for cold-formed carbon steel are conservative but only by 2%. However, for the cases of the austentic and ferritic grades, the cold-formed carbon steel equations are around 9% conservative. New strength reduction factor equations are proposed for all three stainless steel grades.

• Steel and Composite Structures
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• 제27권3호
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• pp.337-353
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• 2018

In previous weak-axis moment connection tests, brittle fracture always initiated near the edge of the beam flange groove weld due to force flow towards the stiffer column flanges, which is the opposite pattern as strong-axis moment connections. As part of the China NSFC (51278061) study, this paper tested two full-scale novel weak-axis reduced beam section moment connections, including one exterior frame connection specimen SJ-1 under beam end monotonic loading and one interior frame joint specimen SJ-2 under column top cyclic loading. Test results showed that these two specimens were able to satisfy the demands of FEMA-267 (1995) or ANSI/AISC 341-10 (2010) without experiencing brittle fracture. A parametric analysis using the finite element software ABAQUS was carried out to better understand the cyclic performance of the novel weak-axis reduced beam section moment connections, and the influence of the distance between skin plate and reduced beam section, a, the length of the reduced beam section, b, and the cutting depth of the reduced beam section, c, on the cyclic performance was analyzed. It was found that increasing three parametric values reasonably is beneficial to forming beam plastic hinges, and increasing the parameter a is conducive to reducing stress concentration of beam flange groove welds while increasing the parameters b and c can only reduce the peak stress of beam flange groove welds. The rules recommended by FEMA350 (2000) are suitable for designing the proposed weak-axis RBS moment connection, and a proven calculation formulation is given to determine the thickness of skin plate, the key components in the proposed weak-axis connections. Based on the experimental and numerical results, a design procedure for the proposed weak-axis RBS moment connections was developed.

• Steel and Composite Structures
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• 제43권2호
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• pp.165-183
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• 2022

Most transportation departments have recognized and developed procedures to address the ever-increasing weights of trucks traveling on bridges in a service today. Transportation agencies also recognize the issues with overheight vehicles' collisions with bridges, but few stakeholders have definitive countermeasures. Bridges are becoming more vulnerable to collisions from overheight vehicles. The exact response under lateral impact force is difficult to predict. In this paper, nonlinear impact analysis shows that the degree of deformation recorded through the modeling of the unprotected vehicle-girder model provides realistic results compared to the observation from the US-61 bridge overheight vehicle impact. The predicted displacements are 0.229 m, 0.161 m, and 0.271 m in the girder bottom flange (lateral), bottom flange (vertical), and web (lateral) deformations, respectively, due to a truck traveling at 112.65 km/h. With such large deformations, the integrity of an impacted bridge becomes jeopardized, which in most cases requires closing the bridge for safety reasons and a need for rehabilitation. We proposed different sacrificial cushion systems to dissipate the energy of an overheight vehicle impact. The goal was to design and tune a suitable energy absorbing system that can protect the bridge and possibly reduce stresses in the overheight vehicle, minimizing the consequences of an impact. A material representing a Sorbothane high impact rubber was chosen and modeled in ANSYS. Out of three sacrificial schemes, a sandwich system is the best in protecting both the bridge and the overheight vehicle. The mitigation system reduced the lateral deflection in the bottom flange by 89%. The system decreased the stresses in the bridge girder and the top portion of the vehicle by 82% and 25%, respectively. The results reveal the capability of the proposed sacrificial system as an effective mitigation system.

• 한국강구조학회 논문집
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• 제29권1호
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• pp.25-36
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• 2017

1994년 노스리지 지진 당시 발생한 용접모멘트 접합부의 취성파괴는 주로 보 하부 플랜지에서 발생하였다. 특히 국내 기존 용접철골모멘트 접합부의 경우 과다한 전단스터드 배치에 따른 의도치 않은 합성작용로 인해 지진 내습 시 보 하부 플랜지의 취성파단이 더욱 우려되는 실정이다. 본 논문에서는 합성효과로 인한 접합부 성능저하를 개선하기 위한 목적으로 중량전단탭/수평헌치/삼각헌치로 보강된 접합부 및 RBS가 도입된 접합부에 대한 실험을 실시하였다. 통상 기존 접합부 상부 플랜지의 수정이 불가하다는 점을 고려하여, 본 연구에서는 보 하부 플랜지에만 수평/삼각헌치를 보강하거나 RBS를 도입하여 이 때의 내진성능을 평가하였다. 실물대 실험 결과 수평/삼각헌치 혹은 중량전단탭으로 보강한 실험체는 모두 합성작용으로 인한 부작용을 극복하고 특수모멘트접합부가 요구하는 수준 이상의 소성회전각 5%이상을 발현함을 확인하였다. 또한 SRC 기둥에 RBS를 도입할 경우 접합부에 소요되는 변형의 대부분을 RBS측에서 일어나도록 유도함으로써 SRC기둥에 발생하는 손상을 방지하는 효과가 있음을 규명하였다. 이 중 중량전단탭 보강에 따른 접합부의 거동을 분석하기 위하여 추가의 수치해석 연구를 실시하였으며, 제시한 각각의 보강안에 대한 권장상세를 제시하였다.

• 한국강구조학회 논문집
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• 제9권1호통권30호
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• pp.37-49
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• 1997

The buckling behavior of the web of steel girders are largely dependent on the size and the location of stiffeners and the restraining effect of top and bottom flanges. Elastic and inelastic buckling analyses based or the Spline Finite Strip Method were executed to study the stiffening effect of the longitudinal stiffener on the web of box girders and to find how the top and bottom flanges had effects on the web, where geometric boundary conditions were limited by both hinged, both fixed and the flange sections. The basic assumption for the longitudinal end boundary conditions was that the vertical stiffeners had the rigidity enough to force nil deflection line on the web panel so that the junction line between web and vertical stiffener was assumed to be hinged boundary conditions. The provisions on the longitudinal stiffener of the plate and box girders of the Korean Standard Highway Bridge Specifications(1995) and AASHTO Specifications(1994 LRFD) were compared with the results obtained numerically for the various longitudinal stiffener size of box girders. Simple equations and design curves for the longitudinal stiffener of the web were proposed for the practical use.

• Corrosion Science and Technology
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• 제13권4호
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• pp.139-144
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• 2014

In corrosion-sensitive area of exsisting unpainted weathering steel bridge with closed box girder structure. there are some serious local corrosion problems because of rain water or dew water which can not be solved by conventional maintenance method. These problems must be technically controled because of the influence on the safety of bridge. This study is the first stage of developing the economic corrosion control manual for these local corrosion problems. Through the injecting experiment of tar sealant into the crevice of mock-up equipment, it was proofed that the corrosive sealant can be useful to corrosion control at crevice of corrosion sensitive area.

• 한국안전학회지
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• 제17권2호
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• pp.76-84
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• 2002

The seismic behaviors of steel moment connections with different structural characteristics are investigated. The rupture index, which represents the fracture potential, is adopted to study the effect of concrete slab and the relative strength between the coin the beam, and Panel zone on the ductility of connections. The results show that the presence of slab increases the beam strength, imposes constraint near the beam top flange, and consequently, induces concentrated deformation near the beam access hall, which reduces the ductility of the connection. The total deformation capacity of the connection depends not only on the beam but also on the column and panel zone. Therefore, the detrimental slab effects and the relative strength should be considered in the seismic design of the connection.

• Steel and Composite Structures
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• 제14권3호
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• pp.243-265
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• 2013

Distortional and local buckling are important factors that influences the bearing capacity of steel-concrete composite box-beam. Through theoretical analysis of distortional buckling forms, a stability analysis calculation model of composite box beam considering rotation of steel beam top flange is presented. The critical bending moment calculation formula of distortional buckling is established. In addition, mechanical behaviors of a steel beam web in the negative moment zone subjected separately to bending stress, shear stress and combined stress are investigated. Elastic buckling factors of steel web under different stress conditions are calculated. On the basis of local buckling analysis results, a limiting value for height-to thickness ratio of a steel web in the elastic stage is proposed. Numerical examples are presented to verify the proposed models.