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Arches and domes


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THIS IS A STUDY OF ARCHES AND DOMES. CONSTRUCTION TECHNIQUES ARE ALSO MENTIONED. comment in the section below, if you want the soft copy! :)

Published in: Engineering
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Arches and domes

  1. 1. Arches and Domes
  2. 2. What is an Arch?  Arch, in architecture ,is a curved member that is used to span an opening and to support loads from above.  It is constructed of wedge shape block of stones or bricks, joined together using mortar and provided across the opening to carry the weight of the structure above the opening.
  3. 3. Parts of arch  The basic parts of an arch are as follows:
  4. 4. Loading in an arch
  5. 5. Types of arches  Arches have many forms, but all fall into three basic categories:  Circular  pointed  parabolic
  6. 6.  1.Semi-circular arch -A roman arch is semi circural arch .It is made of brick masonary.  2.Segmental arch - It forms a partial curve since it has a small rise in the center and semi - elliptical across the top.  3.Flattened gothic arch - Also known as Tudor arches.Tudor arches have low rise because of which they are named flattened gothic arches .Gothic arches are generally narrower than flattened gothic arches.
  7. 7.  4.Flat arch - It is also known as straight arch.The arch spans straight across the opening without any curvation .Introdos with voissoirs radiating from center below.  5. Gothic /lancet/pointed arches- These are narrow arches with a pointed opening.It was considered to be a more sinuous and elegant successor to the roman arch style.It have been used in cathedrals of middle ages across Europe.  6. Horseshoe arches- It is also called Moorish arch .It resembles the look of a horseshoe mangnet .The curved line extends beyond the semi-circular line of the arch.
  8. 8. Application  Arched bridges  Aqueducts  Large span openings
  9. 9. Arched bridges  Arch bridges are one of the oldest types of bridges  They have great natural strength.  They were originally built of Stone and Brick, but now can be built of Reinforced Cement Concrete or Steel.  This has allowed the Arch Bridges to be longer with lower span.  In supporting the load, every part of the Arch is under Compression. Materials good in compression should be used.  Example: Salginatobel Bridge, Switzerland.
  10. 10. Salginatobel Bridge  Salginatobel Bridge is a reinforced concrete arch bridge designed by renowned Swiss civil engineer Robert Maillart. It was constructed across an alpine valley in Schiers, Switzerland between 1929 and 1930. Design three-hinged reinforced concrete hollow box girder arch bridge Material Reinforced concrete Total length 133 metre (436 ft) Width 3.5 metre (11 ft) Height 90 metre (300 ft) Longest span 90 metre (300 ft) Number of spans 1
  11. 11. Load transfer in Arched Bridges  Instead of pushing down, the load of an arch bridge is carried outward along the curve of the arch to supports at each ends.  These weight is transferred to the supports at either ends, called as Abutments. They keep the ends of bridge from spreading out.  All abutments except the intermediate one are same in width. The intermediate one is wider because , If one of the arch splits or fail under compression, it disturbs the entire loading. In this case the wider abutment prevents the successive failure of Arches by controlling the load transfer.
  12. 12. Intermediate abutment wider than others to prevent the successive failure of arches in case of failure in compression.
  13. 13. To span large span openings Roman Aquaducts Church openings
  14. 14. Example GateWay Arch, Missouri, U.S.A.  Location: Memorial Drive, St Louis, Missouri, USA  Year of completion:  Architect: Eero Saarinen  Civil Engineer: Severud Associates  Material: Stainless steel  Height: 630 Ft.
  15. 15. Inside the Arch View of the city Location of the Arch
  16. 16. What is a dome?  A dome is an element of architecture that resembles the hollow upper half of a sphere.  A dome is a rounded vault made of either curved segments or a shell of revolution, meaning an arch rotated around its central vertical axis.
  17. 17. loading  A dome is composed of a series of rings, resting on each other  A dome is characterized by a thrust, with pushes on the walls.  Two forces acting in a dome are  Thrust (T),which pushes down with an angle on the walls.  The thrust (T)is composed of 2 forces: A horizontal forces (HT),WHICH TENDS TO PUSH THE WALLS APART. The weight (w),which is the weight of the masonry. A concentric thrust (CT),which acts in every ring and compresses it.
  18. 18. Construction techniques  PENDENTIVES 1) A pendentive is a constructive device permitting the placing of a circular dome over a square room or an elliptical dome over a rectangular room. 2) The pendentives, which are triangular segments of a sphere, taper to points at the bottom and spread at the top to establish the continuous circular or elliptical base needed for the dome. 3) The curvature of the pendentives is that of a sphere with a diameter equal to the diagonal of the square bay.
  19. 19. 1) SQUINCH, in architecture, a piece of construction used for filling in the upper angles of a square room so as to form a proper base to receive an octagonal or spherical dome. 2) A squinch can be a single arch or a set of multiple projecting nested arches placed diagonally over an internal corner. 3) Squinches can take a variety of other forms, as well, including trumpet arches and niche heads, or half-domes.
  20. 20. Types  The General types of domes are: Beehive dome • Also called a corbelled dome, or false dome, these are different from a 'true dome' in that they consist of purely horizontal layers. • As the layers get higher, each is slightly cantilevered, or corbeled, toward the centre until meeting at the top. • A famous Example is the Mycenaean Treasury of Atreus
  21. 21. • Rather than meeting in the centre of the dome, the ribs characteristically intersect one another off- centre, forming an empty polygonal space in the centre. • Geometry is a key element of the designs, with the octagon being perhaps the most popular shape used. • Whether the arches are structural or purely decorative remains a matter of debate. • Examples are found in Spain, North Africa, Armenia, Iran, France, and Italy Crossed-arch dome
  22. 22. • Geodesic dome • Geodesic domes are the upper portion of geodesic spheres. • They are composed of a framework of triangles in a polyhedron pattern. • The structures are based upon octahedrons or tetrahedrons. • Such domes can be created using a limited number of simple elements and joints and efficiently resolve a domes internal forces. • Their efficiency is said to increase with size.
  23. 23. Hemispherical dome • The hemispherical dome is half of a sphere. • According to E. Baldwin Smith, it was a shape likely known to the Assyrians, defined by Greek theoretical mathematicians, and standardized by Roman builders.
  24. 24. • Onion dome • An onion dome is a greater than hemispherical dome with a pointed top in an ogee profile. • They are typically wooden, although masonry examples are found in late Mughal architecture. • are found mostly in eastern architecture, particularly in Russia, Turkey, India, and the Middle East. • An onion dome is a type of architectural dome usually associated with Russian Orthodox churches. • Such a dome is larger in diameter than the drum it is set upon and its height usually
  25. 25. • Oval dome • An oval dome is a dome of oval shape in plan, profile, or both. • The geometry was eventually defined using combinations of circular arcs, transitioning at points of tangency. • The Roman foundations of the oval plan Church of St. Gereon in Cologne point to a possible example. • Domes in the Middle Ages also tended to be circular, although the church of Santo Tomás de lasOllas in Spain has an oval dome over its oval plan. • The dome built for the basilica of Vicoforte by Francesco Gallo was one of the largest and most complex ever made.
  26. 26. • Parabolic dome • A parabolic dome is a unique structure in which bending stress due to the uniformly distributed load of its dead load is zero. • Hence it was widely used in buildings in ancient times, before the advent of composite structures. • However if a point load is applied on the apex of a parabolic dome, the bending stress becomes infinite. • Hence it is found in most ancient structures, the apex of the dome is stiffened or the shape modified to avoid the infinite stress.
  27. 27. • Saucer dome • Also called a calotte, this is a low pitched, shallow dome that is described geometrically as having a circular base and a segmental section. • Many of the largest existing domes are of this shape