- Building science
Building science is the collection of scientific knowledge that focuses on the analysis and control of the physical phenomena affecting buildings. This includes the detailed analysis of
building materialsand building envelopesystems.
The practical purpose of building science is to provide predictive capability to optimize
building performanceand understand or prevent building failures.
All kinds of
structuresare projected according to two strain conditions: staticand dynamic.The static ones are tied to the structure’s dead loads added to the so-called accidental loads (of people, furniture, etc.), the dynamic ones are tied to the natural and artificial movements ( earthquakeand wind) the structure can sustain during its life cycle.The parameterswhich characterize structure dynamics are tied to the geometryof the building and to the physical and mechanicproperties of its composition. The parameters are:
- The fundamental frequency of vibration (f) and the respective oscillation period (T=1/f) (see
equivalent dumping coefficient(neq);
mode shape(the way in which the structure buckles);
The first parameter varies according to the structure stiffness; very tall and then very flexible buildings as
skyscrapers(low oscillation frequencies) oscillate slowly with respect to lower and squat buildings, and according to the building mass.The second parameter takes into account all the dissipationphenomena tied to the viscosityof materials and to friction phenomena.The mode shapedescribes the way of deformationwhich the structure is subjected to during the seismicevent, and highlights whether or not the structures presents a good seismic behavior.
Reducing the effect of earthquakes on buildings
By monitoring the response of structures subject to earthquakes and by applying new knowledge and technologies, scientists and engineers continuously develop design and repair techniques on buildings, so that their ability to control the earthquake effects will grow. In order to reduce the destructive effects of earthquakes both on new-built buildings and especially on older ones, there exist some seismic adjustment techniques, with the aim of reducing the strain effects that earthquake causes. These techniques can be divided into two different categories:
isolation": it is aimed to untie the ground-foundation system, so that the structure can be seen as it is “floating” on the ground during the seismic event, thus reducing the strains.
Dissipationsystems": there exist various types of dissipation systems, but they all have in common the effect of increasing the previously seen viscous dissipation coefficient of the structure. The better known base isolation technique consists of inserting some special equipment ( isolator (building design)) in the proximity of foundations. This equipment offers a high stiffnessfor vertical loads so that the structure is not subject to sinking, while offering a low stiffness for horizontal ones, which are peculiar of seismic events. This way all seismic effects are absorbed by the equipment, whereas the structure is subject to low oscillations and consequently to low strains.
The dissipation systems (
dissipator (building design)) are made by a series of devices inserted on the inside of the building frame using different techniques, with the aim of slowing down the structure oscillationand dispelling seismic energy.
* [http://www.eng.monash.edu.au/uicee/worldtransactions/WorldTransAbstractsVol1No1/Microsoft%20Word%20-%2014_Tan.pdf To go into the oscillation phenomena and their characterizing parameters issue ]
* [http://www.kettering.edu/~drussell/Demos.html Do you like to watch at some animations of mechanical vibrations subjected to particular loads?]
* [http://web.ics.purdue.edu/~braile/edumod/building/building.htm Build your own model buildings and verify their behavior in the case of earthquake]
* [http://www.scieds.com/spinet/historical/mexico_bldngs.html Click here to see how you can adopt new design strategies in order to protect structures from earthquakes]
* [http://www.succeed.ufl.edu/asce/Program/Extras%5CPres_855_1010.ppt Close examinations about all types and effects of isolation systems]
* [http://www.wheel.eng.fsu.edu/research/wbarnawi/REUJATPresentation.ppt Close examinations about dissipation systems]
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