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RISS 인기검색어
- 검색키워드
- 저자 : De Backer, H. (검색결과 5 건)
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Experimental and Numerical Investigation of Stress Concentration at Rib-to-Crossbeam Joint
Heng Fang,Nouman Iqbal,Gilles Van Staen,Hans De Backer 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.1
In orthotropic steel decks (OSDs), the rib-to-crossbeam joint is the most vulnerable detail that has not been drawn enough attention. The failure mode of cracks initiate from the lower weld end on rib wall is governing its fatigue performance. However, relevant detail categories are still missing in prevailing codes. This paper mainly focuses on the stress concentrations at the rib-to-crossbeam joint induced by rib distortions. A series of static load tests were fi rst performed on a full-scale OSD specimen with diff erent weld length between the ribs and the crossbeam. Then, corresponding numerical simulations were fi nished. Several possibilities that may cause the diff erences between the measurements and the calculations are investigated. At last, fatigue assessments based on infl uence lines of structural hot spot stress (SHSS) are completed. Research results reveal that the measurement results of reference points for SHSS method would be very sensitive to the exact location of strain gauges. Due to the manual welding, the deviation of strain gauge positions induced by the irregular weld shape is thought to be the main reason that causes the diff erences between measurements and calculations. Raising the location of cope hole terminations would decrease distortional stresses. However, the infl uence of this parameter on fatigue lives is rather small. The fatigue lives of points along the lower weld toe are very close. Hence, the point at the middle plane of crossbeam could be used as the reference point for fatigue assessments. Meanwhile, the center between ribs could be used as the reference transverse load position for fatigue assessments of this joint.
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Wim Nagy,Benjin Wang,Bohumil Culek,Philippe Van Bogaert,Hans De Backer 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.4
Orthotropic Steel Decks (OSDs) are widely used in long span steel bridges since they are extremely light weighted and very efficient for resisting localized traffic loads. As this type of bridge deck consists of a complex network of longitudinal and transverse stiffeners, it is very sensitive to fatigue. Moreover, there is a lack of understanding concerning the actual fatigue behaviour. Therefore, a small-scale fatigue test has been designed for which the stresses would correspond with actual OSDs. Taking into account the possibilities available in laboratory conditions, the stress distribution at the considered weld does not perfectly match when using only one longitudinal stiffener. Nevertheless, relevant test data was obtained showing the dominance of weld toe cracks. In addition, beach marks are added during the tests. As a result, more information became available about the crack propagation. This information is very helpful when using fatigue assessment tools such as fracture mechanics.
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Chen Chen,Caiqian Yang,Yong Pan,Honglei Zhang,Hans De Backer 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.4
In this paper, the structural performance of the prestressed concrete T-girder bridge with a newly proposed diaphragm transverse connections (DTCs) have been investigated. The DTCs are composed of diagonal braces and horizontal brace, and the braces are structural steel with square cross section. A series of simulations have been carried out to study the eff ectiveness of the proposed DTCs on enhancing the transverse connection of the prestressed concrete T-girder bridge. Load Model 1 in accordance with Eurocode 1 is considered in the simulations, which consists of tandem system and uniformly distributed loads (UDL system). The Von Mises stress of the DTCs has been checked and corresponding steel grade has been given. The force on the surface between the T-girder bridge and the proposed DTCs has been studied and detailed connection design has been given for both new bridge construction and existing bridge retrofi tting. The simulation results show that the maximum defl ection arises when the deck is fully loaded with the UDL system and with lane 1 centrally located on exterior girder, and the tandem systems are applied at midspan simultaneously. It is revealed that with the proposed DTCs installed at midspan, the maximum defl ection of the prestressed concrete T-girder bridge reduces 12.8% in the most unfavorable load case. In all the discussed load cases, the Von Mises stress of the proposed DTCs is within the reasonable range and can be borne by normal steel material. Additionally, connection methods have been given for the DTCs’ application to new bridge and existing bridge. For the use of chemical anchor in existing bridge, the concrete and prestress tendons should be checked in case of any additional damage during the installing of the DTCs.
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Properties Augmentation of Cast Hypereutectic Al–Si Alloy Through Friction Stir Processing
William P. Bates,Vivek Patel,Harikrishna Rana,Joel Andersson,Jeroen De Backer,Mattias Igestrand,Livan Fratini 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.1
The present endeavour is to augment mechanical attributes via friction stir processing (FSP) in hypereutectic aluminium–siliconcastings by the means of microstructural modifications and defects reduction. Wherein, the study proceeds with mainlytwo approaches namely, alteration in tool revolution (TR) and the number of FSP passes. The prepared specimens wereevaluated investigating volume fraction of porosities, microstructural characterizations and microhardness. Therefrom, thespecimen with highest number of passes delivered most uniform properties resulting from the reduction in casting porositiesand refined silicon particle uniform distribution throughout friction stir processed zone. This endeavour may be consideredas a footstep towards more industrial readied material transformation.
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Cheymol, A.,Gonzalez Sotelino, L.,Lam, K. S.,Kim, J.,Fioletov, V.,Siani, A. M.,De Backer, H. Copernicus GmbH 2009 Atmospheric chemistry and physics Vol.9 No.2
<P>Abstract. The Langley plot method applied on the Brewer Ozone measurements can provide accurate Aerosol Optical Depth (AOD) in the UV-B. We present seven intercomparisons between AOD retrieved from Brewer Ozone measurements at 320 nm and AOD measured by CIMEL sunphotometer at 340 nm or 440 nm (shifted to 320 nm in using the Angström's law), which are stored in the international AERONET database. Only the intercomparisons between co-located instruments can be used to validate the Langley Plot Method applied to the Brewer measurements: in this case, all the correlation coefficients are above 0.82. If the instruments are not at the same site, the correlation between the AOD retrieved by both instruments is much lower. In applying the Angström's law the intercomparison is improved compared to previous study. </P>
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