Earthquake-proof construction

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Earthquake-proof construction refers to the entire effort to design , equip or retrofit structures so that they can withstand earthquakes up to a certain strength . There are two different approaches.

  • Earthquake-proof construction with the protection goal of keeping escape routes open in large earthquakes
  • Earthquake-proof construction with the protection goal of failure safety
    • Elastic structural behavior through earthquake isolation
    • Non-destructive reaction behavior of the internals

standardization

The Eurocodes have been valid throughout Europe as the design rules since their appearance . The design of structures against earthquakes is regulated in the series of standards in Eurocode 8 (EN 1998-1 to 6). The boundary conditions that differ from country to country, e.g. B. the expected earthquake intensities and ground accelerations are recorded in the respective national user documents.

This article or paragraph presents the situation in Germany . Help us to describe the situation in other countries.

Logo of the German Institute for Standardization DIN EN 1998
Area Construction
title Eurocode 8: Design of structures against earthquakes (6 parts)
Latest edition 2006 ... 2011
ISO -
Logo of the German Institute for Standardization DIN 4149
Area Construction
title Buildings in German earthquake areas - load assumptions, dimensioning and execution of common high-rise buildings
Latest edition 2005-04 (withdrawn, but applicable under building law)
ISO -
Earthquake zones according to Eurocode 8, part 1, national user document for Germany.

For Germany, the adopted version of the Eurocode, DIN EN 1998 with its 6 parts, applies. The forerunner was the DIN standard DIN 4149 "Buildings in German earthquake areas - load assumptions, dimensioning and execution of common building structures". Until further notice, the already withdrawn standard DIN 4149: 2005 is to be used in terms of building law, as Eurocode 8 is not in the lists of the technical building regulations introduced by the federal states.

A national user document is an important part of the German edition of the Eurocode. The dimensioning is based on an earthquake zone map contained therein, which was also included in DIN 4149. The zones specified in the map are based on the 475-year earthquake, an earthquake of a certain magnitude that will be exceeded in 50 years with a probability of 10%.

Most of the federal territory is not considered to be earthquake endangered, that is, the earthquake that occurs once every 475 years has an intensity ≤ 6 on the European Macroseismic Scale (EMS). The most endangered areas in Zone 3 (EMS intensity I ≥ 7.5) are around Basel and Aachen as well as in the Hohenzollern Lands . Large areas on both sides of the Rhine , southern Wuerttemberg, the Danube valley up to the mouth of the Altmühl, and the Vogtland and its surroundings up to Leipzig and finally the Alps and the foothills of the Alps are considered to be endangered per se (including zone 0 ) .

The subsurface there is also decisive for the specific risk at the location.

Construction

Construction methods that allow large deformations under horizontal loading and only fail with advance notice ( ductile , not brittle) are considered beneficial. If it is designed and executed to withstand earthquakes, this can include:

  • Steel structures,
  • Reinforced concrete structures in in-situ concrete construction,
  • Steel-reinforced concrete composite construction,
  • Wooden construction ,
  • Truss .

In addition, the following construction principles have a beneficial effect on resistance to earthquake loads:

  • statically overdetermined systems,
  • redundant components,
  • symmetrical floor plans of the buildings (especially round),
  • Arrangement of vertically continuous solid cores,
  • horizontal reinforcements by z. B. shear walls,
  • ductile materials and connections,
  • Center of gravity as close to the ground as possible
  • low-mass, lightweight construction

Seismic isolation

overview

The decoupling of structures from their subsurface in order to reduce the effect of the earthquake waves on them can be achieved through various types of storage . The essential principle is based on an increase in the self- oscillating period of the building together with storage. Occurring in three dimensions acting earthquake forces are controlled by a shift in the response spectrum reduced the building.

Elastomer bearings

Large solid rubber bearings

Highly elastic cylindrical elastomer bearings have an insulating and damping effect in all directions (3D). If designed accordingly, they are suitable for protection against the largest earthquakes (RSL: Spatially floating storage).

Modified bridge bearings

Elastomer bearings (modified bridge bearings) have an isolating and damping effect in the horizontal direction (2D; vertically stiff). They are suitable for protection against smaller earthquakes if they are capable of shear deformation (HSL: horizontally floating storage).

Lead core bearings

Lead core bearings consist of a rubber bearing with an additional lead core, which has a damping effect through plastic deformation and absorbs energy.

bearings

Plain bearings enable the structure to move horizontally (2D) on the subsurface and are mostly used in combination with other methods of absorption and damping.

Sliding pendulum bearing

These structural bearings combine different methods and use a concave sliding plate. Among other things, they were used at the Acropolis Museum.

Soft components such as a floating bearing or the suspension of a suspension bridge are further options for bearing structures to reduce the load from earthquakes.

Scientists at the University of Marseille have developed a simulation that suggests that Rayleigh waves can be derived through concentric rings made of selected materials and thus protect buildings in the center of the facility. However, no practical application is foreseeable.

Vibration absorber

Vibration absorbers (vibration pendulums) are used especially in high-rise buildings . In the event of an earthquake, your task is to absorb the vibration energy and thereby prevent the actual building from vibrating. Such systems can be designed as active, passive or hybrid systems and can be found, for example, in the John Hancock Building in Boston or the Centerpoint Tower in Sydney.

Structurally, such systems involve a large mass, sometimes several hundred tons, which are slidably mounted or installed as a pendulum in the upper part of a high-rise building and absorb and dissipate the vertical energy introduced without the actual supporting structure being stressed. As a rule, damper systems are also integrated into these constructions to prevent resonance effects and excessive movements.

Special buildings

The Fukushima nuclear disaster since March 2011 drew attention worldwide to the fact that nuclear power plants cannot withstand every quake and that, despite their sometimes massive construction , they can be significantly damaged by tidal waves .

After the devastating Kobe earthquake in 1995 , in which more than 6,400 people died, the regulations in Japan were tightened. Reactors built since then must be able to withstand tremors of at least Richter magnitude M 7.75; in particularly endangered regions even earthquakes up to M 8.25. The Tōhoku earthquake of 2011 , however, had a moment magnitude of M 9.0.

  • This shows that Richter magnitudes (as a measure of the released wave energy) and destruction intensities according to the Mercalli-Sieberg scale (as a measure of the global extent of destruction) do not have to be representative of the specific destructive effect on individual structures.
  • Three sizes are representative of the destructive effect on individual structures.
    • Seismic parameters (3D) on the rock horizon of the site: parameters for the 3-dimensional earthquake waves (greatest acceleration, speed, displacement - earthquake type - duration of the intensive movement)
    • Any reinforcement in loose soil between the rock horizon and the foundation ("subsoil")
    • Earthquake exposure (from full to no exposure due to local wave patterns)
  • In the Töhoku earthquake (the seaquake responsible for the worst-case scenario at three nuclear power plants in Fukushima, Japan), a sea ditch about 130 km outside actually "swallowed" a considerable portion of the wave energy before it reached the mainland.

In California (November 2011) there are two old nuclear power plants at exposed locations that are often mentioned in connection with the topic of earthquake safety: the San Onofre nuclear power plant (since 1968 and now closed) and the Diablo Canyon nuclear power plant (since 1984/1985). The latter is 3 km from an earthquake crevice (discovered during construction); both are near the San Andreas Fault .

Web links

Individual evidence

  1. ↑ List of technical building regulations, Bavaria  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.stmi.bayern.de  
  2. ↑ Hamid Isfahany and Georg Pegels: Earthquake- proof houses for developing countries . Alexander von Humboldt Foundation. Retrieved August 8, 2009.
  3. ↑ Georg Küffner: feet in shells. In: FAZ.net . October 11, 2005, accessed December 14, 2014 .
  4. ↑ Suzanne Krause: Invisibility cap against earthquakes. Concentric rings secure buildings . Retrieved August 8, 2009.
  5. ↑ Konstantin Meskouris: Earthquake-proof building . Federal Ministry of Education and Research. Archived from the original on May 5, 2015. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved May 22, 2015. @1@ 2Template: Webachiv / IABot / www.weltderphysik.de
  6. ↑ Lena Jakat: Reactors in Risk Areas - The Most Dangerous Nuclear Power Plant Sites in the World. In: sueddeutsche.de. March 7, 2012, accessed May 26, 2015 .