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Building science

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Building science

Small furnace capable of 600°C and of applying a static load for testing building materials

Building science is the collection of scientific knowledge and experience that focuses on the analysis and control of the physical phenomena affecting buildings and architecture.[1] It traditionally includes the detailed analysis of building materials and building envelope systems. In Europe, building physics is a term used for the knowledge domain that overlaps heavily with building science,[2] and includes fire protection, sound control, and daylighting as well as the heat and moisture concerns that tend to dominate North American building science. The practical purpose of building science is to provide predictive capability to optimize building performance and understand or prevent building failures.

Overview

Building science is the architectural-engineering-construction technology discipline that concerns itself with the 'mainly detail-design' of buildings in response to naturally occurring physical phenomenon such as:

  • the weather (sun, wind, rain, temperature, humidity), and related issues:e.g. freeze/thaw cycles, dew point/frost point, snow load & drift prediction, lightning patterns etc.
  • subterranean conditions including (potential for seismic or other soil + ground-water activity, frost penetration etc.).
  • characteristics of materials,(e.g. Galvanic corrosion between dissimilar metals, permeability of materials to water and water vapor, construct-ability, compatibility, material-adjacency and longevity issues).
  • characteristics of physics, chemistry and biology such as capillary-action, absorption, condensation ("will the dew point occur at a good or bad place within the wall?"), gravity, thermal migration/transfer (conductivity, radiation and convection), vapor pressure dynamics, chemical reactions (incl. combustion process), adhesion/cohesion, friction, ductility, elasticity, and also the physiology of fungus/mold.
  • human physiology (comfort, sensory reaction e.g.radiance perception, sweat function, chemical sensitivity etc.).
  • energy consumption, environmental control-ability, building maintenance considerations, longevity/sustainability, and occupant (physical) comfort/health.

The building science of a project refers to strategies implemented in the general and specific arrangement of building materials and component-assemblies.

The practical outcome of building science knowledge is reflected in the design of the architectural details of the building enclosure (see building envelope), and ultimately in the long-term performance of the building's 'skin'. The scope can be, and is, much wider than this on most projects; after all,engineering is applied science mixed with experience and judgement. When architects talk of "building science", they usually mean the 'science' issues that traditional engineering disciplines traditionally avoided, albeit there are emerging disciplines of 'building scientists', 'envelope consultants', and 'building engineers'.

Many aspects of building science are the responsibility of the architect (in Canada, many architectural firms employ an architectural technologist for this purpose), often in collaboration with the engineering disciplines that have evolved to handle 'non-building envelope' building science concerns: Civil engineering, Structural engineering, Earthquake engineering, Geotechnical engineering, Mechanical engineering, Electrical engineering, Acoustic engineering, & fire code engineering. Even the interior designer will inevitably generate a few building science issues.

Earthquake/seismic design

All kinds of structures are projected according to two strain conditions: static and dynamic. The static ones are tied to the structure’s dead loads added to the so-called live loads (of people, furniture, etc.), the dynamic ones are tied to the natural, abnormal, and artificial movements (earthquake and loads wind) the structure can sustain during its life cycle. The parameters which characterize structure dynamics are tied to the geometry of the building and to the physical and mechanic properties of its composition. The parameters are:

- The fundamental frequency of vibration (f) and the respective oscillation period (T=1/f) (see oscillation frequency);

- The equivalent dumping coefficient (neq);

- The 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 dissipation phenomena tied to the viscosity of materials and to friction phenomena. The mode shape describes the way of deformation which the structure is subjected to during the seismic event, 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:

Base 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.

Dissipation systems: 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 stiffness for 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 oscillation and dispelling seismic energy.

Indoor environment

Building indoor environment covers the environmental aspects in the design, analysis, and operation of energy-efficient, healthy, and comfortable buildings. Fields of specialization include architecture, HVAC design, thermal comfort, indoor air quality (IAQ), lighting, acoustics, and control systems.

Certification

In the US contractors certified by the Building Performance Institute, an independent organization, advertise that they operate businesses as Building Scientists. This is questionable due to their lack of scientific background and credentials. This is true in Canada for most of the Certified Energy Advisors.

See also

External links

  • Construction Specifications Institute
  • www.buildingscience.com
  • JRS Engineering Group
  • Building Science Textbook for Building Enclosures
  • The National Institute of Building Sciences
  • Building Science Blog, Green Building Advisor
  • To go into the oscillation phenomena and their characterizing parameters issue
  • Do you like to watch at some animations of mechanical vibrations subjected to particular loads?
  • Build your own model buildings and verify their behavior in the case of earthquake
  • Click here to see how you can adopt new design strategies in order to protect structures from earthquakes
  • Close examinations about all types and effects of isolation systems
  • Close examinations about dissipation systems

References

  1. ^ Manson, J. Leask. Experimental building science,. Cambridge, Eng.: University Press, 1917. v. Print.
  2. ^ Rose, William B.. Water in buildings: an architect's guide to moisture and mold. Hoboken, N.J.: John Wiley & Sons, 2005. 15. Print.
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