Collapse chimneys

VIII - Destructive Felt in moving vehicles, chimneys collapse, poorly constructed buildings are seriously damaged 6... 

The Izmit earthquake induced serious damages in the Tupras refinery. An entire unit was destroyed by the collapse of a chimney of a furnace 105 m high (Figure 3a). The top of the chimney collapsed on the furnace, whereas the bottom part collapsed on a pipe system. Even if the furnace was designed according to ACI-307, it has been subjected to an important damage. 

Top spray systems During top-spray cooling of an overheated core, the wall temperature is usually higher than the Leidenfrost temperature, which causes water to be sputtered away from the wall by violent vapor formation and then pushed upward by the chimney effect of the steam flow generated at lower elevations (as shown in Fig. 4.25). A spray-cooling heat transfer test with BWR bundles was reported by Riedle et al. (1976). They found the dryout heat flux to be a function of spray rate and system pressure. The collapsed level required to keep the bundle at saturation for various pressures compared reasonably well with that in the literature (Duncan and Leonard, 1971 Ogasawara et al., 1973). 

Local dissolution features are recognized in the Delaware Basin. These may be of either shallow or deep origin, and it is the latter which may pose the greater potential hazard to the repository. These features, often called collapse chimneys or breccia pipes, form when localized dissolution occurs deep in the evaporite section, possibly at the base of the salt beds, resulting in a cavern into which overlying beds... 

The collapse of the cavity causes stress modification (known as readjustments) in the medium around the chimney, and can generate secondary fracturing. This fracturing can take the form of either vertical fractures, roughly parallel to the walls of the chimney, or radial fractures caused by the subsidence of the geological layers near the chimney. 

Fig. 10.7. Radiochemical sampling drill zone. The trajectory of the radioactive low sampling drillhole avoids the collapsed zones of the chimney as far as possible, as they are difficult to drill.

A representative example is certainly the Izmit Earthquake in Turkey (Erdik and Durukal, 2000), which induced severe damages to Tupras refineiy (area of the plant, farm tanks, and landing place). An example of domino effect caused by a structural collapse was the breakdown of a concrete chimney that caused a big release of dangerous substances and damages to surroxmding equipment (see Figure lb). 

Fig. 3. (a) Collapse of a chimney at Tupa-as Refinery, (Itzmit, 1999), (b) Damages to tanks with floating roof (Tokachi-oki, 2003), (c) Elephant foot buckling (Anchorage, Alaska, 1964), (d) Elastic diamond buckling (San Fernando, Cafifomia, 1971), (e) Collapse of an electric transformer, (f) Overtopping phenomenon in a big tank (Itzmit, 1999). 

Finally, collapse of the entire supporting structure due to the failure of the surrounding structures cannot be excluded. For example during the Itzmit earthquake in 1999 the chimney of Fig. 3a fallen down on a piping system causing important damages (Figure 7b)... 

Fig. 8 Vapor voliome fraction at time 0.31 s in RUNl showing collapse of steam chimney.

VII Damaging Most people are frightened and run outdoors. Furniture is shifted and objects fall from shelves in large numbers. Many ordinary buildings suffer moderate damage small cracks in walls partial collapse of chimneys. 

VIII Heavily damaging Furniture may be overturned. Many ordinary buildings suffer damage chimneys fall large cracks appear in walls and a few buildings may partially collapse... 

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