collapse

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Collapse after earthquake
Collapse of an abandoned building
Ceiling collapse with a view of the bathroom above

The term collapse describes the failure of the supporting structure of a building . The reason for the failure are forces that exceed the load-bearing capacity of the building material. If a structure is not in danger of collapsing, it is considered stable . Structural engineering (theory of the balance of forces) deals with the stability of buildings .

history

Even when man began to erect simple structures in prehistoric times, he was confronted with making them as stable and stable as possible. However, it happened again and again that structures could not withstand the loads and collapsed.

Failure stages

The load-bearing structures of a building include walls , ceilings , foundations , beams , columns , beams , vaults , arches and roofs . A building often consists of many different supporting structures.

If one of these supporting structures fails, it does not necessarily collapse, but the building structure is weakened. This is often visible or audible through clear cracks in walls and ceilings, excessive bending of components or through corresponding noises.

If the excessive load persists, additional loads or impacts are added or additional supporting structures fail, parts of the building or even the entire supporting system of the building collapse. Often this process does not happen suddenly, but takes several seconds to hours, so that sometimes there is time to escape.

Collapse objects

At first, one only thinks of buildings that can collapse, but the supporting structures of bridges , tunnels , retaining walls and excavations can also fail in the course of their lifetime.

Actions

Effects on a building

Buildings must be able to withstand a wide variety of loads and influences. Primarily they carry their own weight . Earth pressure and water pressure act on components and structures below the earth's surface . These effects are also called permanent effects.

The weather loads the structure with snow and wind loads as well as constraints from temperature changes. Also payloads (people, furniture, vehicles) act on the support system. These loads are called variable effects.

Structures must be able to withstand both constant and changing effects for the entire duration of their existence without problems. Loads and impacts that are difficult to calculate are impacts from earthquakes, fires, impacts with vehicles and subsoil settlements.

Security against failure

In order for a building not to collapse, there must be a static equilibrium in it. The structure is only stable if the total of the resisting forces is equal to or greater than the sum of the acting forces. It is the job of the structural engineer to create this security . By means of a so-called static calculation, the proof of stability , it proves that a structural failure is almost impossible. He is liable for this evidence and can be prosecuted if people or objects are damaged in the event of a collapse. To z. For example, to record scattering of the material parameters, the influence of simplifying assumptions or the like (on the resistance side) or actions not taken into account (on the action side), so-called partial safety factors are included in the static calculation . The size of these safety factors is determined by the building regulations of the federal states; these result in a failure probability (which is still considered acceptable to the general public).

In order to ensure the stability of structures in the long term, they must be maintained, i. H. checked and serviced. If the important supporting structures are regularly checked and tired materials or materials that have been impaired by environmental influences are replaced at an early stage, the level of safety aimed at during construction is maintained.

In order to reduce the risk of collapse due to earthquakes, one tries, for example, to design earthquake-proof buildings. A current example of this is the Taipei 101 in Taipei (Taiwan). There, too, by installing a vibration damper with a steel ball as a movable counter- mass, increased earthquake resistance is achieved by dampening building vibrations induced by earthquakes, especially in the area of ​​the natural frequency of the high-rise building.

This construction principle reduces the effects of earthquakes on the building to such a low level that (almost) no damage occurs to the building.

The Erich-Edegger-Steg, built around 1992 for pedestrians and cyclists in Graz over the Mur, was closed in 2006 after a structural engineering student analyzed with her thesis that the 60 m long steel structure of the footbridge could be dangerously vibrated by stimulation. The bridge remained closed for two months until an expert opinion was delivered and in 2007 it was retrofitted with a vibration damper with two weights for 40,000 euros under the center of the bridge.

Use

Humans have been making use of the collapse of buildings by gravity for many years. Often this is the only way to quickly and easily remove structures that are no longer needed. In addition to the classic wrecking ball , blasting should be mentioned here, which deliberately damages or completely destroys load-bearing structures in buildings in order to bring them to a controlled collapse.

See also

Individual evidence

  1. ↑ http://stmv1.orf.at/stories/212097 Mursteg should no longer swing in future, August 3, 2007. Accessed March 8, 2015.