This paper investigates the influence of long-duration blast loads on the structural response of aluminium cylindrical shell structures. Full scale coupled non-linear dynamics are examined experimentally at one of the worlds' most powerful air blast testing facilities. Evaluating structural response to blast loads of this magnitude is exceptionally difficult using only computational fluid dynamics; typically not achievable without incurring unmanageable solution domains. Clearing, diffraction and exhaust of a long-duration blast wave across any comparatively small structure imposes constraints leading to the use of approximated drag coefficients, designed primarily to expedite the calculation of net translational forces. In this research, detailed pressure histories measured experimentally on the surface of the cylindrical shell are used to accurately configure a computational analysis dispensing with the requirement to utilise approximated drag forces. When further combined with accurate material test data, fibre optic controlled strain gauge instrumentation and high-speed video photography, a full comparative model was possible. This paper shows that without exact knowledge of long-duration flow-field effects a priori, it is very difficult to reliably determine the mode of structural response and degree of blast resistance.Preliminary modelling predicted a global sway and localised plate buckling; however, subsequent experimental testing showed a crushing failure of the shell before any translational movement occurred. Results in this paper will be of direct interest to both practitioners and researchers considering the dynamic response of cylindrical shell structures subject to high power explosive blasts from sources such as hydrocarbon vapour cloud ignition.
6Blast loading of structures is a complex system dependent on a vast number of parameters from both the 7 structure and blast wave. Even for the simplest of structures, small changes to its size and shape can have 8 a large effect on the result when subjected to blast; additionally, small changes to the pressure or duration 9 of the blast wave can drastically alter its interaction with a specific structure. This paper, as part of a 10 larger in-depth research study, investigates the breakage patterns and debris distribution of masonry panels 11 subjected to blast loads with a positive phase duration typically exceeding 100ms. Three experimental 12 trials were conducted, in which ten masonry panels of varying geometries were subjected to blast loads with
As rainfall intensities increase so does the risk of scour damage to river crossings. Scour inspections are traditionally carried out by divers, but the water around bridge piers is often turbulent and murky such that little can be seen. This paper reports on a trial inspection of the underwater foundations of the 1889River Hamble railway viaduct in Hampshire, UK using state-of-the-art high-resolution sonar and marine laser technologies. The trial was so successful it could transform the way such inspections are carried out in future. Three different sonar systems and a laser scanner produced a holistic assessment of the viaduct structure above and below the waterline. A three-dimensional record of all scour erosion features was digitally mapped along with the condition of the substructure. Significant scour was identified, contradictory to previous diver-based assessments. As discussed in the paper, sonar technologies can be rapidly deployed for emergency inspections as well as be immersed longer term for routine or periodic assessments. BackgroundThe UK climate impacts programme (UKCIP) supplies a range of future scenarios driven by likely climate change in the UK up to 2080, predicting that extreme rainfall events will become more frequent and intense. This climate scenario poses increased risk for UK railway bridges since extreme rainfall is associated with violent flood events that ultimately threaten bridge foundations as they substantially worsen scour.It is widely accepted that scour is one among the most common causes of bridge failures and therefore it is imperative to establish strategies to assess resilience against future and more violent hydraulic load cases.There are approximately 60 000 highway and railway bridges that cross watercourses in the UK. Many of these structures are in excess 150 years old with foundation depths that are either uncertain or simply unknown. Archive records for these structures can sometimes be out-of-date or missing altogether. A significant number of bridges are extremely susceptible to scour as a function of hydraulic and geotechnical conditions.No well-established inspection methodologies currently exist that can adequately reveal the physical processes, conditions and likely extent of scour to bridge foundations (Manes, 2014). As a direct consequence, engineers charged with the responsibility of design or assessment cannot readily underwrite structural performance and longevity leaving a residual concern connected to risk management and limiting the possibility of catastrophic failure.The most common methodology to assess scour and the net risk of future scour in rail bridges is based on surveys carried out by commercial divers. It is readily appreciated that inspection by diving suffers from considerable limitations related to poor visibility in water. In fact, it is quite plausible for divers to overlook critical defects if the area for concern does not fall within the inspection track followed by the diver and support craft.Bridge scour is primarily caused by the...
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