• Steel and Composite Structures
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• 제29권2호
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• pp.273-286
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• 2018

In recent years, significant progress has been made in developing design rules for stainless steel members, while the investigation on bolted connections is relatively limited, in particular at elevated temperatures. In this paper, experimental and numerical investigations on stainless steel bolted connections at ambient and elevated temperatures from the literature were reviewed. Firstly, the research program that focused on structural behavior of cold-formed stainless steel (CFSS) bolted connections at elevated temperatures carried out by the authors were summarized. Over 400 CFSS single shear and double shear bolted connection specimens were tested. The tests were conducted in the temperature ranged from 22 to $950^{\circ}C$ using both steady state and transient state test methods. It is shown that the connection strengths decrease as the temperature increases in the similar manner for the steady state test results and the transient state test results. Generally, the deterioration of the connection strengths showed a similar tendency of reduction to those of the material properties for the same type of stainless steel regardless of different connection types and different configurations. It is also found that the austenitic stainless steel EN 1.4571 generally has better resistance than the stainless steel EN 1.4301 and EN 1.4162 for bolted connections at elevated temperatures. Secondly, extensive parametric studies that included 450 specimens were performed using the verified finite element models. Based on both the experimental and numerical results, bearing factors are proposed for bearing resistances of CFSS single shear and double shear bolted connections that subjected to bearing failure in the temperature ranged from 22 to $950^{\circ}C$. The bearing resistances of bolted connections obtained from the tests and numerical analyses were compared with the nominal strengths calculated from the current international stainless steel specifications, and also compared with the predicted strengths calculated using the proposed design equations. It is shown that the proposed design equations are generally more accurate and reliable than the current design rules in predicting the bearing resistances of CFSS (EN 1.4301, EN 1.4571 and EN 1.4162) bolted connections at elevated temperatures. Lastly, the proposed design rules were further assessed by the available 58 results of stainless steel bolted connections subjected to bearing failure in the literature. It is found that the proposed design rules are also applicable to the bearing resistance design of other stainless steel grades, including austenitic stainless steel (EN 1.4306), ferritic stainless steel (EN 1.4016) and duplex stainless steel (EN 1.4462).

• Steel and Composite Structures
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• 제30권6호
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• pp.551-565
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• 2019

A total of 36 carbon steel and stainless steel bolted connections subjected to shear loading at different strain rates was experimentally investigated. The connection specimens were fabricated from carbon steel grades 1.20 mm G500 and 1.90 mm G450, as well as cold-formed stainless steel types EN 1.4301 and EN 1.4162 with nominal thickness 1.50 mm. The connection tests were conducted by displacement control test method. The strain rates of 10 mm/min and 20 mm/min were used. Structural behaviour of the connection specimens tested at different strain rates was investigated in terms of ultimate load, elongation corresponding to ultimate load and failure mode. Generally, it is shown that the higher strain rate on the bolted connection specimens, the higher ultimate load was obtained. The ultimate loads were averagely 2-6% higher, while the corresponding elongations were averagely 8-9% higher for the test results obtained from the strain rate of 20 mm/min compared with those obtained from the lower strain rates (1.0 mm/min for carbon steel and 1.5 mm/min for stainless steel). The connection specimens were generally failed in plate bearing of the carbon steel and stainless steel. It is shown that increasing the strain rate up to 20 mm/min generally has no effect on the bearing failure mode of the carbon steel and stainless steel bolted connections. The test strengths and failure modes were compared with the results predicted by the bolted connection design rules in international design specifications, including the Australian/New Zealand Standard (AS/NZS4600 2018), Eurocode 3 - Part 1.3 (EC3-1.3 2006) and North American Specification (AISI S100 2016) for cold-formed carbon steel structures as well as the American Specification (ASCE 2002), AS/NZS4673 (2001) and Eurocode 3 - Part 1.4 (EC3-1.4 2015) for stainless steel structures. It is shown that the AS/NZS4600 (2018), EC3-1.3 (2006) and AISI S100 (2016) generally provide conservative predictions for the carbon steel bolted connections. Both the ASCE (2002) and the EC3-1.4 (2015) provide conservative predictions for the stainless steel bolted connections. The EC3-1.3 (2006) generally provided more accurate predictions of failure mode for carbon steel bolted connections than the AS/NZS4600 (2018) and the AISI S100 (2016). The failure modes of stainless steel bolted connections predicted by the EC3-1.4 (2015) are more consistent with the test results compared with those predicted by the ASCE (2002).

• Steel and Composite Structures
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• 제53권2호
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• pp.227-241
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• 2024

Advancements in additive manufacturing technology, notably for its efficiency, accuracy, automation, and streamlined procedures, are increasingly relevant in civil engineering. This study evaluates the mechanical properties of 316L stainless steel bolted connections fabricated using Powder Bed Fusion (PBF) additive manufacturing. Eleven single-lap bolted connection specimens were tested under monotonic loading to assess the influence of various factors, including plate thickness, manufacturing direction, bolt end and edge distances, and bolt quantity, on the connections' anti-sliding and shear capacities. Material tests conducted prior to the connection tests revealed that PBF-manufactured stainless steel plates possess higher yield and ultimate strength, as well as greater elongation capacity, compared to traditional stainless steel plates. The connection tests indicated that the anti-sliding coefficient values range from 0.348 to 0.698, aligning with current standards for stainless steel bolted connections. Three distinct failure modes were identified: net section failure in the stainless-steel plate, bolt shear failure, and plate shear failure. It was determined that existing standards for anti-sliding capacity may not be entirely applicable to PBF-manufactured connections. Therefore, a modified model for the anti-sliding capacity of these connections is proposed. Additionally, a more accurate formula for calculating their shear capacity, which addresses the oversight of friction forces in current standards, is introduced.

• 한국강구조학회 논문집
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• 제25권5호
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• pp.463-474
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• 2013

일면전단 오스테나이트계 스테인리스강 및 탄소강에 관한 많은 실험 및 해석적 연구가 수행되어졌고, 수정된 내력평가식이 제안되었다. 본 연구에서는 볼트배열(2행 1열, 2행 2열)과 하중방향 연단거리를 주요변수로 하여 이면전단 볼트접합부 실험체가 제작되었고, 단순인장실험이 실시되었다. 고정변수로는 하중직각방향 연단거리, 볼트직경, 피치, 게이지를 설정하였다. 최대내력과 파단형태와 같은 실험결과와 현행기준식에 의한 예측결과와 비교 검토되었다. 볼트배열에 따른 블록전단내력평가식이 제안되었다.

• 한국강구조학회 논문집
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• 제23권1호
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• pp.29-39
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• 2011

강구조물에서 접합부의 구조적 거동을 파악하기 위해서 국내외에서 많은 이론과 실험을 통한 연구가 진행되고 있다. 특히, 국내에서는 탄소강 ㄱ형강의 블록전단파단과 전단지체현상 등에 대한 연구가 수행되어 왔다. 본 연구에서는 오스테나이트계 스테인레스강 앵글의 하중방향의 연단거리와 볼트배열(1행 1열,1행 2열)을 주요변수로 실험체를 계획하여, 앵글 볼트 접합부의 파단형태와 면외변형의 영향을 조사한다. 또한, 현행 기준식에 의한 예측결과와 실험결과의 파단양상과 최대내력을 비교하고 면외변형으로 인한 내력저하정도를 평가한다.

• 한국구조물진단유지관리공학회 논문집
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• 제21권5호
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• pp.1-11
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• 2017

This study focused on the ultimate behaviors(ultimate strength and fracture mode ) of single shear bolted connection with austenitic sainless steel(STS201) and curling effect on the ultimate strength using finite element analysis based on test results. Main variables are end distance in the parallel direction to loading and edge distance in the perpendicular direction to loading. The validation of finite element analysis procedures was verified through the comparisons of ultimate strength, fracture mode and curling(out-of-plane deformation) occurrence between test results and numerical predictions. Curling was observed in both test and analysis results and it reduced the ultimate strength of single- shear bolted connections with relatively long end distances. Strength reduction ratios caused by curling were estimated quantitatively by maximum 19%, 32%, respectively for specimens with edge distance, 48 mm and 60 mm compared with strengths of uncurled connections with restrained out-of-plane deformation. Finally, analysis strengths were compared with current design strengths and it is found that design block shear equations did not provide the accurate predictions for bolted connections with strength reduction by curling.

• 한국강구조학회 논문집
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• 제25권6호
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• pp.659-669
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• 2013

본 연구는 페라이트계 스테인리스강 일면전단 볼트접합부의 구조거동에 관한 기존실험연구를 바탕으로 유한요소해석법을 이용하여 접합부의 최대내력과 면외변형에 대해 조사하는 것을 목적으로 한다. 유한요소해석결과와 실험결과의 비교를 통해 접합부의 구조거동을 예측하는데 있어 해석의 타당성을 검증하였다. 면외변형에 의해 유발되는 접합부의 연단거리 조건을 조사하고 최대내력저하정도를 정량적으로 평가하였다. 또한, 변수해석을 통해 얻어진 해석결과의 최대내력과 현행기준식인 AISC, KBC2009, AIJ 및 AISI에 의해 예측된 내력과 비교하여 그 적용성을 검토하였다.

• 국제강구조저널
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• 제18권4호
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• pp.1139-1152
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• 2018

Many studies on the application of stainless steels as structural materials in buildings and infra-structures have been performed thanks to superior characteristics of corrosion resistance, fire resistance and aesthetic appeal. Experimental investigation to estimate the ultimate strength and fracture mode of the fillet-welded connections of cold-formed austenitic stainless steel (STS304L) with better intergranular corrosion resistance than that of austenitic stainless steel, STS304 commonly used has carried out by authors. Specimens were fabricated to fail by base metal fracture not weld metal fracture with main variables of weld lengths according to loading direction. All specimens showed a block shear fracture mode. In this paper, finite element analysis model was developed to predict the ultimate behaviors of welded connection and its validity was verified through the comparison with test results. Since the block shear behavior of welded connection due to stress triaxiality and shear-lag effects is different from that of bolted connection, stress and strain distributions in the critical path of tensile and shear fracture section were investigated. Test and analysis strengths were compared with those by current design specifications such as AISC, EC3 and existing researcher's proposed equations. In addition, through parametric analysis with extended variables, the conditions of end distance and longitudinal weld length for block shear fracture and tensile fracture were suggested.

• 한국구조물진단유지관리공학회 논문집
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• 제22권5호
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• pp.55-63
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• 2018

최근에 오스테나이트와 페라이트의 조직을 갖는 듀플렉스계 스테인리스강이 개발되었고 오스테나이트계 스테인리스강에 비해 고강도, 응력부식균열에 대한 고내식성과 재료비절감으로 다양한 산업분야에서 사용량이 증가되고 있다. 그러나, 현재 스테인리스강은 한국 건축구조기준에 구조용재료로 지정되어 있지 않고 구조설계기준도 마련되어 있지 않는 실정이다. 이 연구에서는 2행 1열 듀플렉스계 스테인리스강(STS329FLD) 볼트접합부에 대한 구조적 성능을 조사하기 위한 실험적 연구를 수행하였다. 주요변수는 전단접합형태(일면전단과 이면전단)과 하중방향 연단거리이다. 종국파단형태는 전형적인 블록전단파단, 인장파단과 면외변형이 관찰되었다. 일면전단 접합부에서 면외변형발생으로 최대 20%까지 내력저하가 발생되었다. 실험최대내력은 현행설계기준 AISC/AISI/KBC, EC3와 AIJ 및 기존연구자에 의한 제안된 식에 의한 예측내력과 비교하였다. 면외변형이 발생하지 않은 접합부에 대해서 실제 전단파단단면을 고려한 Clement & The의 식에 의한 예측내력이 실험내력에 가장 근접했고 면외변형을 동반한 접합부에 대해서는 면외변형을 고려해 제안한 Kim & Lim식에 의해서 과대평가하는 것으로 나타났다.

• Steel and Composite Structures
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• 제50권3호
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• pp.281-298
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• 2024

Stainless steel bolts (SSB) are increasingly utilized in bolted steel connections due to their good mechanical performance and excellent corrosion resistance. Fire accidents, which commonly occur in engineering scenarios, pose a significant threat to the safety of steel frames. The post-fire behavior of SSB has a significant influence on the structural integrity of steel frames, and neglecting the effect of temperature can lead to serious accidents in engineering. Therefore, it is important to evaluate the performance of SSB at elevated temperatures and their residual strength after a fire incident. To investigate the mechanical behavior of SSB after fire, 114 bolts with grades A4-70 and A4-80, manufactured from 316L austenitic stainless steel, were subjected to elevated temperatures ranging from 20℃ to 1200℃. Two different cooling methods commonly employed in engineering, namely cooling at ambient temperatures (air cooling) and cooling in water (water cooling), were used to cool the bolts. Tensile tests were performed to examine the influence of elevated temperatures and cooling methods on the mechanical behavior of SSB. The results indicate that the temperature does not significantly affect the Young's modulus and the ultimate strength of SSB. Up to 500℃, the yield strength increases with temperature, but this trend reverses when the temperature exceeds 500℃. In contrast, the ultimate strain shows the opposite trend. The strain hardening exponent is not significantly influenced by the temperature until it reaches 500℃. The cooling methods employed have an insignificant impact on the performance of SSB. When compared to high-strength bolts, 316L austenitic SSB demonstrate superior fire resistance. Design models for the post-fire mechanical behavior of 316L austenitic SSB, encompassing parameters such as the elasticity modulus, yield strength, ultimate strength, ultimate strain, and strain hardening exponent, are proposed, and a more precise stress-strain model is recommended to predict the mechanical behavior of 316L austenitic SSB after a fire incident.