MONOLITHIC DOME S.PADMASHREE

IIIrd YEAR C SECTION

INTRODUCTIONMonolithic Dome is thin wall reinforced concrete shell structure.

The structure provides safe shelter for the people area with hurricanes,fires,bomb blasts and earthquakes.

Building consist of : an outer airtight form,polyuretane foam, reinforced concrete.

2

This technique is an effective alternative to conventional methods.

A curve rotated about a central axis to form a surface, creates a DOME.

A Monolithic dome is a structure cast in a one piece form.

3

4

MONOLITHIC DOME5

HISTORYThe igloo may be the earliest form of monolithic dome. While it is constructed of blocks of compressed snow, these blocks melts and re-freeze to form a strong, homogeneous structure.The strength is due to the natural strength of the arch and insulation is due to the minimal surface area of the spherical section.

6

Turtle Reams was built by first creating mould of dirt in the desired shape of the shell, an ellipsoidal section 73m long,49m wide and 12m high.

The mould was then covered in a grid of rebar, to provide strength and a layer of concrete 100mm thick.

7

After the concrete was cured, the dirt was excavated through the doorways, leaving the roof standing in its place.

The floor was then poured to finish the structure.

8

MATERIALS USEDFOOTING :

A monolithic dome starts as a concrete ring foundation, reinforced with steel rebars. For smaller domes, an integrated floor and ring foundation may be used. Vertical steel bars embedded in the ring beam foundation are later attached to the steel reinforcing of the dome itself.

9

AIRFORM KITS : The kit consisted of a 1220cm(40ft) diameter form along with reinforced steel anchors.It is ordered in the shape of half sphere with no custom windows or door augmentations.

10

POLYURETHANE FOAM :Sprayed on polyurethane foam insulation was of type using a part process in which Diaphenylmethane-4,4-diisocynate was mixed with blended polyolresin.

11

REINFORCING STEEL : Steel in the foundation and slab was 16mm and grade 40 rebar. Dome shell 13mm and 9.5mm grade 60 rebar was used.

12

CONCRETE : Foundation and slab a standard sack concrete foundation mix was used. Concrete used in the dome shell was 9 sack per cubic yard mix. This was made up of 385kg Portland Cemnt,992kg sand,178kg(1cm) gravel,0.7kg plastic fibres and 118ml of air entraining agent in additional to that of water.

13

EXTERIOR : Exterior coatings are an essential aspect in the longevity to the Dome Exterior.Coatings serve as a UV shield to protect the Airform and foam insulation as well as achieve a desired appearance.

14

CONSTRUCTION OF DOME

Monolithic dome is a rounded building structure typically made of concrete and rigid steel rods.

It consist of an outer airtight form, polyurethane foam insulation and reinforced concrete.

15

The building process of monolithic domes entailed : Lay down the foundation of the dome , usually made of reinforced concrete. An air form or fabric is inflated over the foundation . Polyurethane foam is then added to the inside of the form in two layers of (7.6cm)thick.

16

Special clips are affixed to the foam interior, and rebar is installed. Finally concrete is poured over the air form, rebar, and foam supporters and dome like shape emerges.

17

18

STEPS OF CONSTRUCTION

STEP ONE : Ring Beam Foundation Monolithic Dome starts as a concrete ring foundation. Continuous reinforcing bars are embedded in the ring beam foundation. The ring creates a solid base to construct the dome.

19

Concrete ring foundation20

STEP TWO : Inflate Air form Made of tough, weather -impermeable material. The air form is inflated with dual inflator fans. It determines the final shape of the dome.

21

STEP THREE : Polyurethane foam Foam is applied in the interior to stiffen the air form, and provide a secure surface to which reinforcement bar is affixed. It get hardens and creates a superior insulation layer.

22

STEP FOUR : Steel Reinforcing Steel reinforcing rebar is attached to the foam using a specially engineered layout of hoop and vertical steel bar. Small domes need small diameter bars with wide spacing. Large domes require

larger bars with closer spacing

23

STEP FIVE : Shotcrete It is a special spray mix of concrete, applied to the interior surface of the dome.The steel rebar is embedded in the concrete and when about 7cm

of shotcrete is applied.

24

Concrete was applied by shotcrete process over a period of four days. Each day from(1.25cm to 3.8cm)of concrete is applied.Blowers were left on for 8 hours and then shut off.The airlock was then closed for 30days to allow curing on the concrete.

25

To provide a smooth finished surface, a layer of cement based plaster was alter hand applied and finished.This was primed with water based acrylic latex and finished with acrylic latex enamel.

26

PROFILE AND SHAPESThe profile of a dome determines the size of its surface area or dome shell, and the amount of surface area affects the construction cost.The surface area of hemisphere dome is twice that of its floor area i.e., 2*pi*radius*radius. Most of the monolithic dome have an oblate ellipse profile.

27

SHAPESDOME

VARIATIONS/CONFIGURATIONS a) Low profile spherical segment :

Most efficient shape. Used for large domes.

28

b) Hemisphere : Surface area is double the floor area.Useful for high-volume storage buildings and smaller structures ,such as homes.

29

c) High profile spherical segment : Most volume for the least floor area. Used for e water tanks, storage buildings, homes etc.

30

d) Oblate ellipsoid : Very efficient for single structures. Wall have maximum vertical slope vs. structure size

31

e) Prolate ellipsoid (Long axis horizontal): Elliptical base creates a very unique space

f) Prolate ellipsoid (Long axis vertical) : It is very tall. Useful for bulk storage and buried building.

32

Horizontal Vertical Prolate ellipsoid

33

g) Torus : Not as space -efficient as dome. These are homes with a centre courtyard or garden.

34

DOME PROFILESLower the profile the less expense.Windows and doors on the second floor can be augmented. If the land is a premium, go up with integrated stem wall.

35

Caterpillar combination Dome profiles

36

MULTI-DOME COMBINATION

The caterpillar is great design . 60 feet wide , 300-500 feet long. Easy to build and allow for linear functions.

37

DOME OPENINGS If dome is not huge, then all kinds of openings are possible. Stresses are higher in domes having diameter larger than 100 feet. Build the openings for the uses.

38

STRESSES ACTING ON DOMES

Generally, a spherical dome may be imagining consisting of a number of horizontal rings placed one over the other. The diameters of the successive rings increase in the downward direction and the equilibrium is maintained independently of the rings above it.

39

The circle of each ring is called latitude while the circle drawn through two diametrically opposite points on a horizontal diameter and the crown is known as a meridian circle. The entire meridian circles coverage at the crown of the spherical dome.

40

Two types of stresses acting on the domes are :Meridian thrust (T) along the direction of meridianHoop stress along latitudes

41

ADVANTAGESAdvantages of a monolithic dome fall

into three general categories : a)Economy in construction :

Cost of a dome is less . Streamlined construction process and use of only four ingredients contribute to the domes economy. Require less maintenance.

42

b)Security : Ability to survive tornadoes, hurricanes and earthquakes. Provides fire protection.They are very good for circulation of air and heat so they are also for very cold climates.

43

c)Aesthetics and comfort : Any structure appears bare and unattractive when its first built and unenhanced. But just as enhancement can soften and beautify straight lines and corners.

44

d)Rapid construction : Most are prefabricated.The prefab elements are relatively small and light weight.This makes easy to transport them to the site.

45

DISADVANTAGESDisadvantages of monolithic dome :a)Engineering :

Only specially trained construction crews. Using the modern techniques. Wasted space in narrow corners. Lack of seams.

46

b)Social : Different appearance of the domes decreases the appeal for their use as private residences and the strange appearance and design may run afoul of neighbourhood building covenants.Depending on the situation a large variety of variations available from the standard circular shape can avoid some of these problems.

47

Building permits may be difficult to obtain if local officials are not familiar with the monolithic dome. Resale of a monolithic dome home may be difficult because of its unconventional appearance.

48

CONCLUSIONMonolithic Dome building technique is an effective alternative to conventional methods. Monolithic domes are disaster -resistant, energy efficient and cost effective. Safest buildings that can be built and can be designed for many uses. Monolithic domes are designated as tornado shelters.

49

REFERENCEShttps://en.wikipedia.org/wiki/Monolithic_domewww.monolithic.org/round2it/technical-journal-think-roundSouth D.B et.al 1990, “Economics and the thin shell dome” , Concrete International Reprint. Nanette South M.S, engr. Str. & Mech , et.al “Finite Element Modelling of Monolithic Dome structures”.

50

51

52