Summary Building Technology (check hatches!!!)
0.Building Technology
Structural demands: strength, stiffness, stability, cohesion
Physical and material demands: thermal insulation, vapor control, waterproofing,
frostproofing, airtightness, pressure, equalization, ventilation, sound insulation,
acoustics, fire safety, shrink/expand tolerance.
Science demands: frostproofing, shrink/expand tolerance, corrosion proofing, fire
proofing
Construction demands: sequence, transport, aides, labor, equipment, conditions
1.Substructures
(foundations, basements, floors on soil)
Clay → foundation piles needed to reach firmer layer of soil
We need foundation piles when the top layers of soil cannot carry the building.
Sand → small and medium structures can be built directly on this layer
Rock → everything can be built directly on this layer
One does find out at which depth layers of soil are firm enough to build on by
pushing down a cone while measuring the force needed to do so at each depth
(probing (diagram)).
Frost is a point of concern for substructures. Water expands (9%) when it freezes
and then exerts a lot of force (frost wedging). To prevent frost-damage in
substructures start the foundation at frost free-depth. Foundation runs minimally to
frost line to avoid being lifted, or lifted unequally. Or you can use concrete and other
frost-proof materials (that don’t absorb water). The frost-free depth in the
Netherlands is >80cm below surface level.
Pad footings are designed especially for loads
(columns/truss legs) that concentrate in one
point.
Strip foundation for small and equal loads.
(width depends on load). A strip foundation plan
responds to concentrated point loads and linear
loads by becoming wider where more load is
concentrated.
Rib foundation for somewhat bigger a/o unequal
loads.
,The three functions of a bedding (thick foil or non-reinforced concrete) for casting on
are:
- It serves to assemble and position reinforcement steel
- It prevents portions leaking away from curing concrete
- It prevents mixing between concrete and sand/mud
Three options for (making) piles:
- Hammered precast reinforced piles
(Cutting pile heads to expose connecting steel)
- Piles cast in a hammered shaft
- Piles cast in a drilled shaft
,The minimum dimension of a square section of a precast concrete foundation pile is
140 x 140 mm2.
The purpose of cutting the head off of precast piles is to expose the steel for making
a structural connection later on with beams (or basements).
On a construction site in the center of Amsterdam an office is being built. Noise and
vibrations are not acceptable in relation to possible damage for the neighbors. The
type of foundation that should be applied is a foundation on piles that are cast in
drilled shafts.
How does a pile plan respond to concentrated point loads and linear loads? There
are more piles where more load is concentrated.
When a foundation has a low but wide section the foundation is directly supported by
soil. When a foundation has a high and more narrow section the foundation is
supported by piles.
Two types of foundation beams are cast-in-place in ‘’lost’’ formwork or precast and
assembled on site.
The other function of the ‘’lost formwork’’ of a foundation beam is thermal insulation.
Construction process for a cast-in-place beam, given precast piles: Piles heads are
cut, exposing the connection steel. Lost formwork is placed. Piles heads and steel go
through the bottom of the formwork. Concrete is cast.
The construction process for a precast beam,
given precast piles: Piles are hammered to the
right height. A hole is drilled in the head. A steel
connection bar is glued into this shaft. The
beam with gaines is lifted in place. The steel bar
is in the gaine. Mortar is poured into the gaine,
connecting pile and beam. There is a mortar
bed for leveling the beams (40 mm).
Crawl space is the empty space below the
ground level floor. It results from excavating a
pit for making a pile foundation. With a crawl
space, pipes and conduits remain accessible for
maintenance, via a man hole.
The air in a crawl space can be humid and polluted (radon gas). This means that the
ground level should be carefully made airtight.
Ventilation prevents humid air and fungus. A crawl space is ventilated with a Z-tube
connecting the crawl space, via the cavity (=empty space within a solid object) , with
the outside air.
Cellular glass / foamglass can be used for thermal bridge interruption and capillary
interruption in low load-bearing walls between foundation and ground level floor.
, A temporarily soil supported floor
has an integrated edge beam.
A permanently soil supported floor
is separated/detached from the
foundation.
Casting concrete directly on (dry) bare soil is never a good idea. The water and fine
parts will leak away from the concrete mix (and both can mix). This reduces the
quality of the concrete.
A basement is thermally insulated under the floor and to the walls, all-around (to
avoid thermal bridges). Not all types of insulation material can be used for insulating
the floor of a basement. The material should not only be insulating, it should also be
compression proof and water proof (keep insulating regardless of water).
Bitumen paste acts as glue and prevents water cooling. Closed (rough) seams
prevent (cold) water entry.
Concrete is ideally waterproof (25 cm), but there can be weak spots. Two measures
you can take to make sure that a (cast-in-place) concrete basement will indeed be
waterproof are: galvanized steel strip in the seam/joint floor-wall or chrystalline fillers
in the seam/joint floor-wall.
Self-healing concrete→ chrystalline fillers react with water so they seal the micro-
cracks in concrete if/when/where they get in touch with water.