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ARCHES AND DOMES

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ARCHES AND DOMES

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ARCHES AND DOMES

  1. 1. Building Construction present by:- AHmed layth ismaeel
  2. 2. 1. Arches and its form 2. Arches and its construction technique 3. Domes and its form 4. Domes and its construction technique
  3. 3. Arches: Is a structure that spans a space and supports a load. Provides a structure which eliminates tensile stresses in spanning a great amount of open space. All the forces are resolved into compressive stresses. Building materials such as stone, cast iron and concrete can strongly resist compression but are very weak when tension, shear or torsional stress is applied to them. Arches consists of different components.
  4. 4. Arches: Element Of Arches: 1. Keystone 2. Voussoir 3. Extrados 4. Impost 5. Intrados 6. Rise 7. Clear span 8. Abutment
  5. 5. Wind analysis: To analyse the standard house we need to consider wind direction as the house will present a very different surface shape depending on the direction of the wind, calculations for stress and aerodynamic performance should be carried out on a minimum of 4 wind directions but preferably 8 even a very plain box type house will have 3 different aerodynamic profiles. A pure dome however has the same aerodynamic performance in any wind direction as it presents the same surface area and shape from all elevations. Load analysis: The house example above will have a wide variety of different timber length, thickness and depth measurements, from large roof trusses of mayor structural importance to smaller, short framing timbers that interact with the major structural elements differently depending on the angles, joints used and fixing methods of these elements. A geodesic dome on the other hand has timber struts of a similar length and size throughout the whole structure and all are jointed in the same way with only a small variation in connection angles.
  6. 6. Conclusions: Geodesic domes are generally thought to be a more complex and challenging exercise when it comes to structural analysis, however when we look closely at the design and construction of geodesic domes they are incredibly simple and efficient structures. Structural analysis is in fact greatly simplified rather than made more complex by the geodesic layout and spherical shape of the structure. We’ve dealt with basic some of the basic concepts of structural analysis so now we’ll take a look at a 3 frequency geodesic dome in a little more detail. In the diagram below we’ve placed a force on top of our 3v dome and colour coded the struts to show approximately how much compressive or tensile force is applied to each strut. Compressive forces are shown in red and tensile forces are shown in blue (deeper colours show higher forces).
  7. 7. Arches And Its Construction Technique : Construction Of An Arch: An arch requires all of its elements to hold it together. Firstly build a frame which exactly follows the form of the underside of the arch. This is known as a centre or centring. The voussoirs are laid on it until the arch is complete and self-supporting.  For an arch higher than head height, scaffolding should be used by the builders. So that the scaffolding can be combined with the arch support.  Arches would fall down when the frame was removed if construction or planning had been incorrect.  The interior and lower line or curve of an arch is known as the intrados. Old arches sometimes need reinforcement due to decay of the keystones, forming what is known as bald arch.
  8. 8. Different Types Of Arches: Flat Arch ( Jack/Straight Arch) •Appears to be the most easiest. •Construction is tricky •Require skill to make them look good •Provides support at openings •efficiently uses the compressive strength of the masonry Corbelled Arch (False Arch) •Easiest to construct & Not a true arch •Not entirely self supporting structure •Constructed by offsetting successive courses of stone •Require significantly thickened walls and an abutment of other stone or fill to counteract the effects of gravity. Triangular Arch (Miter Arch) •Simple single piece stone laid together. •The span is limited by the size of the available material. •Formed by two large diagonal stones that mutually support each other to span an opening. Semicircular Arch • First created before the Roman times. • Known as the Roman Arch after the people that brought it to perfection • A round arch drawn from a single center. Bullseye Arch (Circular arch) • Used for windows • A double arch with two or four keystones. • Made of two semicircular identical arches. • The top portion of the circular arches is called The Upper Arch and the lower portion is called The Invert . Bell Arch • A Roman arch sat on corbels that are imposts. • Often carved from one piece of stone. • Rests on two rounded corbels resulting in a shape somewhat similar to a bell.
  9. 9. Different Types Of Arches: Islamic Arch • Also known the Moorish Arch, • Defines the feature of Moorish architecture. Segmental Arch • Based on a segment of a circle. • Curve is a less than semicircular segment of a circle. Foil Arch • Embellishments of Gothic architecture. • Also known as Trefoil Arch. Pointed Islamic Arch • A pointed variation of the Moorish arch. Gothic Arch • The defining feature of the late middle ages in Europe • Is a sharp-pointed arch. • Formed of two arc segments (parts of a circle). Arch based on circular arcs • There are many varieties of these. • This one is known as the three centre arch.
  10. 10. Different Types Of Arches: Geometrical Arch • Based on geometrical or mathematical curves. • Also known an elliptical arch. Venetian Arch • A variation of the bell arch. Ogee Arch • Based on opposing circular arcs. • Pointed arch. • Each side consists of two contrasting curves. Skewed Arch • An arch that is not at right angle to the wall it traverses. • Most famously first used in early railway viaducts.
  11. 11. Domes: Is a type of shell structure Are hemispherical in shape. Used as roof structure. Transmits load more than 2 directions to support Transmits load without bending or twisting. Constructed of stone , concrete & brick. Supported on circular / regular polygon shaped walls. Have certain height & diameter ratio. Have very small thickness. Can b constructed with or without lanterns.
  12. 12. Different Types Of Domes: Onion dome Also known as bulbous dome Is a bulbous shape tapering smoothly to a point, strongly resembling an onion, larger in diameter than the drum Its height usually exceeds its width. Geodesic Dome • Geodesic domes are the upper portion of geodesic spheres. • They are composed of a framework of triangles in a polyhedron pattern. Corbel dome • Different from a 'true dome' • Consists of purely horizontal layers • As the layers get higher, each is slightly corbeled toward the center until meeting at the top. Oval dome • Oval in shape • Sometimes oval in plan • Sometimes oval in profile • Sometimes oval in both
  13. 13. Different Types Of Domes: Parabolic dome • a unique structure. • Bending stress due to the is zero. • However if a point load is applied on the apex of a parabolic dome, the bending stress becomes infinite. • the apex of the dome is stiffened or the shape modified to avoid the infinite stress. Saucer dome • It’s a low pitched shallow dome • a circular base and a segmental section. • A section across the longer axis results in a low dome, capping the volume. • A very low dome is a saucer dome. Polygonal dome • Also known as domical vaults, cloister vaults, or coved vaults. • Are domes which maintain a polygonal shape in their horizontal cross section. Umbrella dome • Also known as pumpkin, melon, scalloped, or parachute domes • Are a type of dome segmented by ribs radiating from the center of the dome to the base.
  14. 14. Thanx for your attention Thank You

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