Application limits for continuously welded rails on temporary bridge decks

2016 ◽  
Vol 231 (4) ◽  
pp. 482-497 ◽  
Author(s):  
Hans De Backer ◽  
Amelie Outtier ◽  
Ben Ferdinande ◽  
Ken Schotte ◽  
Jan Mys
Keyword(s):  
Thermal Loading ◽  
Bridge Decks ◽  
Complex Structure ◽  
Safety Margin ◽  
Identification Code ◽  
Temperature Variations ◽  
Rail Track ◽  
Main Factors ◽  
Continuously Welded Rail ◽  
Ballast Resistance

The possibility of omitting rail expansion devices from the track configuration, when continuously welded rail is continued over temporary bridge decks, is investigated in detail. More specifically, the related rail track to temporary bridge interaction phenomena are analysed using finite element modelling. A first parametric analysis assesses the additional rail stresses due to moving trainloads and temperature variations, based on stipulations provided in the unit identification code 774-3R. In addition the model is expanded to a more complex structure that is able to simulate the buckling behaviour of the rail track using non-linear methods. Using this model, a second parametric study is performed in which only thermal loading is considered. This allows for determining the parameters, which are predominant in determining the critical buckling temperature of the rails, and for assessing the magnitude of the safety margin necessary, when it comes to thermal buckling of the rails and the temporary bridges. It can be concluded that, depending on the magnitude of two main factors, the lateral ballast resistance and the amplitude of the initial track misalignment, a considerable reduction of the track stability might arise. Therefore, a minimal characteristic lateral ballast resistance of 4 kN is recommended along with a maximal allowable misalignment amplitude of 7 mm has to be prescribed when thermal track buckling has to be considered in the design.

scholarly journals Project risk management in complex petrochemical system

2012 ◽  
Vol 66 (1) ◽  
pp. 135-148 ◽  
Author(s):  
Snezana Kirin ◽  
Aleksandar Sedmak ◽  
Lela Nesic ◽  
Ilija Cosic
Keyword(s):  
Risk Management ◽  
Complex Structure ◽  
Implementation Process ◽  
Project Risk Management ◽  
Project Risk ◽  
Industrial Systems ◽  
Factors Influencing ◽  
Modern Methods ◽  
Main Factors ◽  
Petrochemical Company

Investigation of risk in complex industrial systems, as well as evaluation of main factors influencing decision making and implementation process using large petrochemical company as an example, has proved the importance of successful project risk management. This is even more emphasized when analyzing systems with complex structure, i.e. with several organizational units. It has been shown that successful risk management requires modern methods, based on adequate application of statistical analysis methods.

scholarly journals Track – Bridge Interaction on High Speed Railways – the ONCF Experience

2019 ◽  
Vol 8 (4) ◽  
pp. 4607-4612
Keyword(s):  
High Speed ◽  
Study Phase ◽  
Limit Values ◽  
Temperature Variations ◽  
Track Geometry ◽  
Geometry Measurement ◽  
Track Bridge ◽  
Continuously Welded Rail ◽  
To Receive ◽  
Current Standards

This paper aims to describe the Moroccan experience on Track – Bridge interaction in railway domain. In fact, that phenomenon may induce a general track instability compromising train security if it’s not taken into account in the study phase. To that end, a numerical method, used to compute the additional longitudinal stresses on a continuously welded rail (CWR) mainly associated to relative displacements between track and deck on account of temperature variations, is presented. Therefore, the conditions of laying an expansion device will be concluded, particularly when the additional rail stresses exceed the maximum limit values defined on the current standards. An application of that method will be performed on MHARHAR viaduct where a non-compliance of track dilatation device laying was noticed. This study will emphasize the beginning of a track grid general instability due to ballast layer deconsolidation, the all based on a track geometry measurement. This study may be widely used in order to conceive properly a bridge supposed to receive a CWR track.

Statistical Analysis on Continuously Welded Rail Track Failure under High Axle Load Conditions

ICRT 2017 ◽  
2018 ◽  
Author(s):  
Yingying Wang ◽  
Li Li ◽  
Wei Ding ◽  
Zhenkun Gao ◽  
Jinhua Li ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Rail Track ◽  
Continuously Welded Rail ◽  
Load Conditions

Fracture Assessment for Pressurized Water Reactor Vessel Nozzles Subjected to Pressure and Thermal Loading

2021 ◽  
Author(s):  
Qibao Chu ◽  
Qing Wang ◽  
Yonggang Fang ◽  
Wei Tan
Keyword(s):  
Crack Front ◽  
Thermal Loading ◽  
Structural Integrity ◽  
Safety Margin ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Integrity Assessment ◽  
Main Challenge ◽  
Fracture Assessment ◽  
3D Finite Element Method

Abstract To ensure the structure integrity of the RPV, the main challenge is the embrittlement of beltline material. However, the stress of inlet or outlet nozzles of the RPV which are in general reinforced in comparison with the beltline, is more complex especially under the thermal loads. In recently studies, a lot of works have been done to show that the nozzle region may be more challenging under some conditions. In this paper, a fracture assessment for the RPV nozzles subjected to pressure and thermal loading is discussed using the software ABAQUS 6.12 and Zen Crack 7.9-3. It includes: SIF calculation based on 3D finite element method; structural integrity assessment under a typical LOCA transient; and the fatigue crack growth evaluation under cyclic loading situations. The results show that the SIF along the crack front is obviously asymmetric, and only to assess the safety of the deepest point along the crack front in the ASME and RCC-MR codes may be reconsider. If the KIa criteria is applied, under a typical LOCA transient, it is difficult to obtain an effective fracture safety margin for a 1/4 thickness crack, while based on the KIC criteria, the nozzle is shown to be safe in the case study. The shape of the surface elongated crack (which is often easily produced in the nozzle area) tends to be circle under the cyclic pressure loading situation which shows the crack shape assumed in the ASME and RCC-MR codes is reasonable.

On the Reliability and Risk Analysis of Subsea Blowouts Preventers With Focused Attention on DP Rigs

2005 ◽  
Author(s):  
Nilo de Moura Jorge
Keyword(s):  
Risk Analysis ◽  
Water Depth ◽  
Rio De Janeiro ◽  
Safety Margin ◽  
Focused Attention ◽  
Dynamic Positioning ◽  
Years Of Experience ◽  
Main Factors ◽  
Operational Practices ◽  
Selection Of

This paper provides a selection of findings on the reliability and risk analysis of submarine blowout preventers (BOPs) achieved in recent studies, which the author has participated among technicians in Petrobras and Rio de Janeiro Federal University - UFRJ. Petrobras is a deepwater E&P leading company and special attention has been given on the deepwater and ultra deepwater scenarios. Particular factors on the BOP for dynamic positioning (DP) rigs need to be accounted as far as risks on safety and downtime are concerned. The analyses have considered a comprehensive BOP reliability database that covers more than 12 years of experience, as well as, a collection of DP experience has been accessed during work. The riser safety margin tends to be unavailable as the water depth becomes deeper, and, so, in an emergency disconnection, the safety isolation of the well tends to be relied on the BOP mechanical barriers only. In this context, risks on different configurations of the BOP are compared and their results discussed with focused attention on main factors of risk. Finally, there has been visible progress on BOP reliability within recent years and a number of good operational practices in place are also mentioned in the paper.

Stratification and Heat Transfer of Molten Corium Pool for In-Vessel Retention

2020 ◽  
Author(s):  
Qingan Xiang ◽  
Jian Deng ◽  
Dahuan Zhu ◽  
Xiaoli Wu ◽  
Jinsheng Bi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Loading ◽  
Metal Layer ◽  
Safety Margin ◽  
Light Metal ◽  
Reactor Vessel ◽  
Physicochemical Interaction ◽  
Thermal Failure ◽  
Mechanical Loads ◽  
Lower Head

Abstract In-vessel retention (IVR) consists in cooling the molten corium contained in the lower head of reactor vessel by natural convection and reactor cavity flooding. The general approach which is used to study IVR problems is a “bounding” approach which consists in assuming a specified corium pool stratification in the vessel and then demonstrating that the vessel can cope with the resulting thermal and mechanical loads. Thermal loading on the vessel is controlled by the convective heat transfer inside the molten corium pool. Traditionally molten corium pool in the lower head was expected to stratify into two-layer with the dense oxide pool at the bottom and the light metal layer on the top. Based on the MASCA experiments, the increased density of the metal layer attributed to a transfer of uranium metal leads to inverse stratification with a heavy metal layer relocating below the oxide pool. This behavior can be explained by physicochemical interaction between the oxidic and metallic phases of the corium pool. Therefore, a methodology which couples physicochemical effects and thermal hydraulics has been developed to address the IVR issue. The main purpose of this paper is to present this methodology and its application for calculate stratification probability of two-layer and three-layer configuration, analyze the safety margin of IVR in two-layer and three-layer configuration, and evaluate the lower head heat thermal failure probability.

Evaluation of Fatigue Crack Propagation by ΔJ Approach

2019 ◽  
Author(s):  
Jia Li ◽  
Olivier Ancelet ◽  
Alexandre Double ◽  
Stephane Chapuliot
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Numerical Scheme ◽  
Thermal Loading ◽  
Elastic Analysis ◽  
Temperature Variations ◽  
Asme Code ◽  
Thermal Transient

Abstract An analysis of fatigue crack growth is required for large cast components to evaluate the possible defect evolution during the service life. These components are subjected to both mechanical loading and thermal loading. Due to their high thickness, temperature variations through the thickness can be significant. Thus, a conventional elastic analysis of fatigue crack propagation could be over conservative. In order to take into account the effect of plasticity, the ΔJ approach of fatigue crack propagation evaluation is implemented in FE software SYSTUS [9]. The quarter of cycle method [11] (or twice-yield method in ASME code) will be used in this work to calculate ΔJ values under both thermal transient and mechanical loadings. Two strategies will be proposed to create the virtual monotonically increasing loading in 3D elastic–plastic FE calculations. The result in terms of numerical scheme will be validated by comparing with FE software CAST3M [10] and the RSE-M [3] simplified ΔKcp method.

scholarly journals ANALYSIS OF ORDER OF STRESS SINGULARITY AT A VERTEX IN 3D TRANSVERSELY ISOTROPIC PIEZOELECTRIC DISSIMILAR BONDED JOINTS

2014 ◽  
Vol 44 (1) ◽  
pp. 1-5
Author(s):  
Md. Shahidul Islam ◽  
Md. Golam Kader ◽  
M. M. Kamal Uddin ◽  
Mohiuddin Ahmed
Keyword(s):  
Thermal Loading ◽  
Electric Displacement ◽  
Stress Singularity ◽  
Transversely Isotropic ◽  
Field Analysis ◽  
Bonded Joints ◽  
Angular Function ◽  
Main Factors ◽  
Distribution Of Stress ◽  
Interface Edge

The order of singularity near the vertex of bonded joints is one of the main factors responsible fordebonding under mechanical or thermal loading. The distribution of stress singularity field near the vertex ofbonded joints is very important to maintain the reliability of intelligent materials. In this paper, order of stresssingularity at vertex in 3D transversely isotropic piezoelectric dissimilar bonded joints is analyzed. Eigenanalysis based on FEM is used for stress singularity field analysis of piezoelectric bonded joints. The eigenequation is used for calculating the order of stress singularity, and the angular function. The numerical resultshows that the angular functions have large value near the interface edge than the inner portion of the joint.Therefore, there is a possibility to debond and delamination may occur at the interface edge of the piezoelectricbonded joints due to the higher stress and electric displacement concentration at the free edge.DOI: http://dx.doi.org/10.3329/jme.v44i1.19490

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