Accidental loads

Impact problems are becoming increasingly important to industry, with respect to safety issues. The designer has to take into account accidental loads of the material caused by dropped objects, collisions or explosions. In particular with respect to aramid materials, ballistic protection applications are an important issue. Advantageously, the materials should have a large capacity to absorb kinetic energy. 

The aforementioned provision on accidental loads is accompanied by an official guideline recommending the use of inter alia several specified NORSOK standards for the purpose of designing the stmcture in such a way that the function requirement is met. 

An interesting application of composite materials in the field of masonry structures concerns the reinforcement of vaults, which can be carried out over vaulted members with different geometries, such as the single or double curvature. From a static point of view, the stability of a vaulted structure is guaranteed when the curve of pressures, that is, the funicular polygon of permanent load and accidental load resting upon it, is transferred to the internal composite material of the central inertia core of each section. Until the eccentricity remains limited compared with the inertia central core. 

Interval analysis and DSTE, for the modeling of epistemic variables, have been compared with classical probabilistic approach on a realistic example concerning the failure risk of an industrial component during an accidental loading. 

Damage on the bridge exposed to normal and accidental loads is then estimated on the basis of system modelling considering the effects of applied protective measures. 

In this study, only environmental loads such as wave, wind, and current were taken into consideration for estimation of the external loads applied to the PGS. Considering other types of environmental loads and accidental loads such as mooring loads and ship collisions would be required. 

In this situation, a concept of Design Accidental Loads (DAL) is introduced to ensure safety of offshore installations. The purpose of identifying and assessing accidental loads is to verify that accidents do not cause risks exceeding defined criteria for design of structures (ABS 2013, DNV 2010). 

DNV, 2010. Design Against Accidental Loads. Recommended Practice DNV-RP-C204. Hovik Det Norske Veritas. 

ABS, 2013. Accidental Load Analysis and Design for Offshore Structures. Guidance Notes. Huston American Bureau of Shipping. 

All penetrations through the containment shall meet the same design requirements as the contaimnent stmcture itself. They shall be protected against reaction forces stemming from pipe movement or accidental loads such as those due to missiles, jet forces and pipe whip. 

The contractor updates the REPA to include the results of concept optimisation. Norskoil s project SHE manager supervises this work. It is shown that the concept meets all appUcable acceptance criteria, provided that a number of assumptions are met. These define the accidental loads from fire, explosion, dropped objects and ship collisions that the semi mnst be able to withstand. Another set of assumptions defines the safety and communication systems that have to be operable during an accident. There are also assumptions regarding the collision warning system and the withdrawal of the platform from the snbsea wells in case of blow-out. The REPA also results in a number of recommendations based on the ALARP principle. The assumptions and recommendations serve as input to design development and to specifications and need to be followed up in later project phases. 

As a result of this update of the analysis, the specifications concerning accidental loads and safety requirements to systems during accidents are revised. Engineering has to assess the cost-consequences of the revised requirements and the modifications of design that follow, before they are implemented. 

Owing to the nature of a riser being submerged in deep water in an approximately vertical position, its loading conditions are more complicated than onshore pipehnes. In the design of a riser, the different loads can be categori2ed into functional loads, environmental loads, installation loads and accidental loads. 

Accidental loads are those that occur inadvertently due to abnormal operating conditions, technical failure and human error. Accidental loads are those that are unpredictable and situational dependent, such as sod-sliding, earthquakes, and impacts from foreign objects. It is normally not necessary to combine these loads with other funetional and environmental loads unless site-specific conditions indicate such requirement. 

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