• 콘크리트학회논문집
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• 제18권5호
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• pp.595-602
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• 2006

본 연구의 목적은 중력 하중에 저항하도록 설계된 플랫 플레이트 외부 접합부의 이력 거동을 평가하는 데 있다. 이러한 목적을 위하여 2/3의 크기가 조정된 PT 슬래브-기둥 외부 접합부 2개와 RC 슬래브-기둥 외부 접합부 1개를 대상으로 실험적 연구를 수행하였다. 여기서 각각의 PT 실험체는 서로 다른 강선 배치 형태를 띄고 있다. 중력 하중은 동일하게 설정하였고, 지속적인 정적 하중 하에서 유사 정적 횡하중을 적용하였다. 한편 모든 실험체는 ACI 318-05과 ACI 352.1R-89에 근거하여 기둥 폭 내에 하부 철근을 배근 하였다. 또한 PT 외부 접합부의 이력 거동에 대한 일반적인 결론을 얻기 위하여 기존 연구자들의 실험 결과와 함께 비교하였다. 이번 연구를 통하여 강선의 배치는 PT 접합부의 이력 거동을 결정하는 중요한 변수임을 확인하였다. 즉 횡변형 성능, 에너지 소산 능력, 파괴 메커니즘, 그리고 연성 능력이 강선의 배치에 따라 다르게 나타났다. 또한 ACI 352.1R-89에서 구조적 일체성을 위해 제공된 하부 철근의 양은 모멘트 역전에 의해 발생된 정모멘트를 저항하는데 있어서도 적절하다는 것이 밝혀졌다. 또한 실험체의 전단 강도는 강선의 포스트 텐션에 의한 평균 콘크리트 압축 응력($f_{pc}$)의 효과가 고려된 식이 그렇지 않은 식보다 전단 강도를 정확히 예측하는 것으로 나타났다.

• Steel and Composite Structures
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• 제13권3호
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• pp.239-258
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• 2012

In this paper, experimental investigations on high strength steel (HSS) stud connected steel-concrete composite (SCC) girders to understand the effect of shear connector density on their flexural behaviour is presented. SCC girder specimens were designed for three different shear capacities (100%, 85%, and 70%), by varying the number of stud connectors in the shear span. Three SCC girder specimens were tested under monotonic/quasi-static loading, while three similar girder specimens were subjected to non-reversal cyclic loading under simply supported end conditions. Details of casting the specimens, experimental set-up, and method of testing, instrumentation for the measurement of deflection, interface-slip and strain are discussed. It is found that SCC girder specimen designed for full shear capacity exhibits interface slip for loads beyond 25% of the ultimate load capacity. Specimens with lesser degree of shear connection show lower values of load at initiation of slip. Very good ductility is exhibited by all the HSS stud connected SCC girder specimens. It is observed that the ultimate moment of resistance as well as ductility gets reduced for HSS stud connected SCC girder with reduction in stud shear connector density. Efficiency factor indicating the effectiveness of high strength stud connectors in resisting interface forces is estimated to be 0.8 from the analysis. Failure mode is primarily flexure with fracturing of stud connectors and characterised by flexural cracking and crushing of concrete at top in the pure bending region. Local buckling in the top flange of steel beam was also observed at the loads near to failure, which is influenced by spacing of studs and top flange thickness of rolled steel section. One of the recommendations is that the ultimate load capacity can be limited to 1.5 times the plastic moment capacity of the section such that the post peak load reduction is kept within limits. Load-deflection behaviour for monotonic tests compared well with the envelope of load-deflection curves for cyclic tests. It is concluded from the experimental investigations that use of HSS studs will reduce their numbers for given loading, which is advantageous in case of long spans. Buckling of top flange of rolled section is observed at failure stage. Provision of lips in the top flange is suggested to avoid this buckling. This is possible in case of longer spans, where normally built-up sections are used.

• Steel and Composite Structures
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• 제9권1호
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• pp.1-17
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• 2009

This paper is focused on the buckling and post buckling behaviour of rectangular corrugated board panels simply supported and subjected to compression load. The aim of the work is to understand the failure mechanism of investigated structure in order to quantify the effect of design parameters on the strength of a panel of given geometry. Two numerical models were developed adopting the finite element method. In the first one the corrugated board is represented by means of shell elements adopting an equivalent material, in the second the local structure is described in full detail modelling both straight and corrugated layers by means of shell elements and representing the connection between layers by special interface elements. The model correctness was checked by the comparison between out of plane central displacement predicted by the models and the experimental values found in literature. For the same case the effect of panel planarity error was evaluated. Finally a parametric analysis to investigate the effect of design parameters was carried out.

• 대한기계학회논문집A
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• 제26권5호
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• pp.896-903
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• 2002

The susceptibility of SCC for the weldment and PWHT specimens of HT-60 steel was evaluated using a slow strain rate method under applied potential by means of the potentiostat in synthetic seawater. In case of the parent, anodic polarization voltage was inappropriate in elongating the time to failure(TTF). -0.8V corresponding to cathodic protection range is most effective in improving the SCC resistance against corrosive environment. In case of the weldment, the values of reduction of area(ROA) and TTF at -0.68V corresponding to cathodic polarization value were 45.2% and 715,809sec which were the largest and longest life among other applied potentials. Those were vise versa at -1.1V. In case of the PWHT specimens, TTF and ROA at -0.68V was longest and largest like the weldment. Besides, PWHT is effective in prolonging the time to failure of the welded off-shore structure due to softening of effect. Regardless of the weldment and PWHT specimen, as corrosion rate gets higher, TTF becomes shorter and deformation behaviour for the weldment and PWHT specimen at -1.1V was shown to be irregular. Finally, it was found that specimens showed brittle fracture at -1.1V, but more ductile fracture accompanying the micro-cracks at applied potential of -0.68V.

• Steel and Composite Structures
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• 제36권3호
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• pp.321-337
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• 2020

Contemporary design and construction of steel-concrete composite structures employs the use of prefabricated concrete elements and demountable shear connectors in order to reduce the construction time and costs and enable dismantling of elements for their potential reuse at the end of life of buildings. Bolted shear connector with mechanical coupler is presented in this paper. The connector is assembled from mechanical coupler and rebar anchor, embedded in concrete, and steel bolt, used for connecting steel to concrete members. The behaviour and ultimate resistance of bolted connector with mechanical coupler in wide and narrow members were analysed based on push-out tests and FE analyses conducted in Abaqus software, with focus on concrete edge breakout and bolt shear failure modes. The effect of concrete strength, concrete edge distance and diameter and strength of bolts on failure modes and shear resistance was analysed. It was demonstrated that premature failure by breakout of concrete edge occurs when connectors are located 100 mm or closer from the edge in low-strength and normal-strength reinforced concrete. Furthermore, the paper presents a relatively simple model for hand calculation of concrete edge breakout resistance when bolted connectors with mechanical coupler are used. The model is based on the modification of prediction model used for cast-in and post-installed anchors loaded parallel to the edge, by implementing equivalent influence length of connector with variable diameter. Good agreement with test and FE results was obtained, thus confirming the validity of the proposed method.

• 전산구조공학
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• 제5권1호
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• pp.97-108
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• 1992

이 논문에서는 구조시스템신뢰성해석에 있어서 부재의 파괴후 잔류강도의 불확실성을 고려하였다. 이를 위하여 확율유한요소법(Stochastic Finite Element Method: SFEM)을 시스템신뢰성해석과정에 접합하였다. 확율유한요소법은 신뢰성해석시 재료와 기하학적 변수의 불확실성을 좀더 함축적으로 고려할 수 있는 것으로 알려져 있으며, 본 논문에서 이 방법을 구조부재와 구조시스템의 신뢰성해석에 적용해 보았다. 이 논문의 방법과 파괴된 부재의 잔류응력을 확정적으로 취급하는 방법과 그 결과를 비교하였으며, 부재가 파괴된 후 그 잔류강도의 불확실성이 구조시스템 신뢰성에 주는 영향을 보기위해 여러 경우를 고찰해 보았다. 그 결과로부터 부재의 파괴 후 잔류강도가 구조시스템신뢰성에 대단히 큰 영향을 준다는 것을 다시 확인할 수 있었다. 이 논문의 여러경우에 대한 연구로 부터 좀 더 나은 구조시스템신뢰성의 평가를 위해서 부재의 파괴후 거동이 갖는 불확실성을 구조시스템신뢰성해석시, 특히 부재의 파괴후 거동이 semi-brittle인 경우에, 고려해야 한다는 결론을 내릴 수 있겠다. 이점을 받아들인다면 확율유한요소법이 구조시스템신뢰성해석에 있어서 적합한 방법일 것이다.

• Geomechanics and Engineering
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• 제18권5호
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• pp.535-543
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• 2019

Building on/with expansive soils with no treatment brings complications. Compacted expansive soils specifically fall short in satisfying the minimum requirements for transport embankment infrastructures, requiring the adoption of hauled virgin mineral aggregates or a sustainable alternative. Use of hauled aggregates comes at a high carbon and economical cost. On average, every 9m high embankment built with quarried/hauled soils cost $12600MJ.m^{-2}$ Embodied Energy (EE). A prospect of using mixed cutting-arising expansive soils with industrial/domestic wastes can reduce the carbon cost and ease the pressure on landfills. The widespread use of recycled materials has been extensively limited due to concerns over their long-term performance, generally low shear strength and stiffness. In this contribution, hydromechanical properties of a waste tyre sand-sized rubber (a mixture of polybutadiene, polyisoprene, elastomers, and styrene-butadiene) and expansive silt is studied, allowing the short- and long-term behaviour of optimum compacted composites to be better established. The inclusion of tyre shred substantially decreased the swelling potential/pressure and modestly lowered the compression index. Silt-Tyre powder replacement lowered the bulk density, allowing construction of lighter reinforced earth structures. The shear strength and stiffness decreased on addition of tyre powder, yet the contribution of matric suction to the shear strength remained constant for tyre shred contents up to 20%. Reinforced soils adopted a ductile post-peak plastic behaviour with enhanced failure strain, offering the opportunity to build more flexible subgrades as recommended for expansive soils. Residual water content and tyre shred content are directly correlated; tyre-reinforced silt showed a greater capacity of water storage (than natural silts) and hence a sustainable solution to waterlogging and surficial flooding particularly in urban settings. Crushed fine tyre shred mixed with expansive silts/sands at 15 to 20 wt% appear to offer the maximum reduction in swelling-shrinking properties at minimum cracking, strength loss and enhanced compressibility expenses.

• 한국공간구조학회논문집
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• 제6권4호
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• pp.35-44
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• 2006

대공간 구조형식에는 기존의 기둥-보 구조형식에서 벗어나 쉘구조형식과 같은 형태저항 구조형식이 가장 유효한 구조형식으로 인식되고 있다. 특히 지간 $200m{\sim}300m$ 이상의 대공간구주 형식으로는 중량구조인 연속체의 쉘보다는 래티스 돔과 같은 공간 트러스형식 등의 유리하다. 시공, 제작상의 편리성, 구조미 등을 이유로 복층래티스 돔과 더불어 단층의 래티스 돔 형식도 실제 구조물에서 많이 적용되고 있다. 그러나 대공간 단층 래티스 돔의 경우 아직까지 외력의 작용으로 인한 변형과 파괴경로가 명확하게 해명되지 못한 부분이 있다. 본 연구에서는 대공간 구조형식에 적합한 래티스 돔을 대상으로 좌굴의 특성을 규명하여 안정적인 구조 설계의 기초 자료를 제시하기 위하여 실험을 수행하였다. 주된 실험변소는 격자의 간격과 돔의 지붕 강성 유무를 대상을 하였으며, 격자의 간격은 돔을 4분할, 5분할, 6분할, 7분할로 하여 정하였다. 가력은 돔의 전면에 걸쳐 구심의 등분포하중이 작용하도록 하였다.

• Structural Engineering and Mechanics
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• 제19권2호
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• pp.185-198
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• 2005

In the design of reinforced concrete beams, it is a standard practice to use the yield stress of the steel reinforcement for the evaluation of the flexural strength. However, because of strain hardening, the tensile strength of the steel reinforcement is often substantially higher than the yield stress. Thus, it is a common belief that the actual flexural strength should be higher than the theoretical flexural strength evaluated with strain hardening ignored. The possible increase in flexural strength due to strain hardening is a two-edge sword. In some cases, it may be treated as strength reserve contributing to extra safety. In other cases, it could lead to greater shear demand causing brittle shear failure of the beam or unexpected greater capacity of the beam causing violation of the strong column-weak beam design philosophy. Strain hardening may also have certain effect on the flexural ductility. In this paper, the effects of strain hardening on the post-peak flexural behaviour, particularly the flexural strength and ductility, of reinforced normal- and high-strength concrete beams are studied. The results reveal that the effects of strain hardening could be quite significant when the tension steel ratio is relatively small.

• Computers and Concrete
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• 제22권6호
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• pp.527-538
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• 2018

Buckling of longitudinal bars is a brittle failure mechanism, often recorded in reinforced concrete (RC) structures after an earthquake. Studies in the literature highlights that it often occurs when steel is in the post elastic range, by inducing a modification of the engineered stress-strain law of steel in compression. A proper evaluation of this effect is of fundamental importance for correctly evaluating capacity and ductility of structures. Significant errors can be obtained in terms of ultimate bending moment and curvature ductility of an RC section if these effects are not accounted, as well as incorrect evaluations are achieved by non-linear static analyses. This paper presents a numerical investigation aiming to evaluate the engineered stress-strain law of reinforcing steel in compression, including second order effects. Non-linear FE analyses are performed under the assumption of local buckling. A role of key parameters is evaluated, making difference between steel with strain hardening or with perfectly plastic behaviour. Comparisons with experimental data available in the literature confirm the accuracy of the achieved results and make it possible to formulate recommendations for design purposes. Finally, comparisons are made with analytical formulations available in the literature and based on obtained results, a modification of the stress-strain law model of Dhakal and Maekawa (2002) is proposed for fitting the numerical predictions.