The number of roof fires due to the passage of chimneys is high. Since the experimental procedure necessary to identify all the variables affecting the temperature reached by roof in the vicinity of a chimney would be expensive, a 2D numerical model for the estimation of the temperatures in the roof has been designed. The model has been validated by means of experimental tests in which a certified chimney has been installed in three roofs and spaced from flammable materials as prescribed by the manufacturer. In order to reproduce the diverse conditions that may occur in real installations, the clearance between chimney and roof has been sealed in three ways (sealed with insulating panels, sealed with metal sheets, and filled with insulating materials). Good agreement between measured and estimated data is shown, and the estimated temperatures are in favour of safety. The effects of the clearance sealing mode and the chimney installation quality on flammable materials temperature are also shown.
European standards regulate the certification procedure for determining chimney class temperature\ud
and the distance at which to install chimneys from combustible materials. These standards\ud
prescribe the heat stress test and the thermal shock test. The high number of roof fires due to\ud
the presence of a chimney that have recently occurred in European countries seems to be due to\ud
a weak certification procedure. In this article, experimental tests and numerical simulations have\ud
been performed to highlight the major differences between real and test conditions to identify\ud
critical aspects of the current certification procedure. The influence of the position of the chimney\ud
in the test structure, the thermocouples’ positioning and the thermal shock test initial condition\ud
have been investigated. It has been shown that flammable materials’ temperatures measured\ud
in the certification procedure can be lower than those in real installations, and this is mainly\ud
due to the fact that exhaust gas temperature in the certification procedure of chimneys can be\ud
even 350°C lower than in real installations. Then, real installations represent a more severe\ud
condition
This research deals with the fatigue life investigation using experiment and FEM simulation on longitudinal fillet weld of structural offshore steel S460G2+M with a thickness of 10mm. The experimental fatigue test is conducted based on nominal stress (NS) approach while the simulation uses the effective notch stress (ENS) approach for fatigue life assessment. The investigation begins with the preparation of the longitudinal fillet weld fatigue specimen using Milling Machine based on the IIW fatigue specimen design recommendation and joined using the semi-automatic GMAW process following the AWS D1.1 procedure. Fatigue testing on non-load carrying fillet weld is conducted using the Instron Fatigue Machine with a stress ratio of 0.1 with constant amplitude loading and stress loading from 50%-75% of the yield strength of the base material. For the simulation approach, the 3D longitudinal fillet weld geometry is created using CAD based on the ENS design procedures of IIW where the sizes and dimensions are similar to the experimental fatigue specimen. The static elastic stress analysis of the model is conducted using MSC Marc/Mentat FEM software. Based on the IIW fatigue data evaluation, it is found that the natural mean curve of the longitudinal fillet weld obtained 146 MPa of FAT class which exceeds approximately 106% from the IIW FAT class recommendation for a longitudinal fillet joint. However, the characteristic curve of 97.7% failure probability of the parts only attained 95 MPa of FAT class, but still exceeds approximately 33% form the IIW FAT class. In the ENS fatigue assessment of the 3D longitudinal fillet weld, it is found that the model obtained 195MPa of FAT class which is inferior approximately 15 % from the FAT class recommendation of IIW. Also, it is found that both S-N curves of NS after conversion to ENS system have a good agreement with the S-N curve of ENS of 3D longitudinal fillet weld model and the IIW recommendation due to only 16 % and 34% lower as compared with the IIW FAT class recommendation for ENS.
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