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. 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, 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.
SUBSCRIBERS - ( LINKS) :FOLLOW / REF / 2 /
findleverage.blogspot.com
Krkz77@yahoo.com
+234-81-83195664
No comments:
Post a Comment