Arches - Notes
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The document defines an arch and describes its key functions and structural behavior. It then provides details on different arch typologies including: - Shape (flat, triangular, round, pointed) - Geometry (single, double, three, four, five centered) - Materials used (stone, brick, concrete, timber, metal) - Construction methods (using centering, not using centering, domes without centering) It also defines important arch terminology and provides examples of different arch types classified by shape, geometry, materials and construction methods. Diagrams are included to illustrate various arch configurations.
Arches - Notes
- 1. SANJEEV TRIVEDI – SVIT, VASAD ARCHES
- 2. SANJEEV TRIVEDI – SVIT, VASAD DEFINITION AN ARCH MAY BE DEFINED AS MECHANICAL ARRANGEMENT OF WEDGE-SHAPED BLOCKS OF STONES OR BRICKS MUTUALLY SUPPORTING EACH OTHER AND SUPPORTED AT THE END BY PIERS OR ABUTMENTS AN ARCH IS AN STRUCTURE THAT SPANS A SPACE AND SUPPORTS STRUCTURE AND TRANSFERS WEIGHT BELOW IT ARCHES APPEARED AS EARLY AS THE 2ND MILLENNIUM BC IN MESOPOTAMIAN BRICK ARCHITECTURE AND THEIR SYSTEMATIC USE STARTED WITH THE ANCIENT ROMANS WHO WERE THE FIRST TO APPLY THE TECHNIQUE TO A WIDE RANGE OF STRUCTURES FUNCTION OF ARCH THE FUNCTION OF ARCH IS TO CARRY WEIGHT OF THE STRUCTURE ABOVE THE OPENING 01.0. STRUCTURAL BEHAVIOUR OF ARCHES TYPOLOGY OF ARCHES • ACCORDING TO THE SHAPE - Flat / Triangular / Round / Pointed • ACCORDING TO THE GEOMETRY - Single / Double / Three / Four / Five / Seven Centered • ACCORDING TO THE MATERIAL USED - Stone / Brick / Concrete / Timber / Metal • ACCORDING TO THE CONSTRUCTION METHOD - Arches needing centering / Arches not needing centering / Domes without centering
- 3. SANJEEV TRIVEDI – SVIT, VASAD TERMINOLOGIES USED IN ARCHES ABUTMENT - The masonry or combination of masonry and other structural members which support one end of the arch at the skewback. ARCH - A form of construction in which masonry units span an opening by transferring vertical loads laterally to adjacent voussoirs and, thus, to the abutments. CAMBER - The relatively small rise of a jack arch. CENTERING - Temporary shoring used to support an arch until the arch becomes self-supporting. CROWN - The apex of the arch's extrados. In symmetrical arches, the crown is at the mid-span. DEPTH - The dimension of the arch at the skewback which is perpendicular to the arch axis, except that the depth of a jack arch is taken to be the vertical dimension of the arch at the springing. EXTRADOS - The curve which bounds the upper edge of the arch. INTRADPS - The curve which bounds the lower edge of the arch. The distinction between soffit and intrados is that the intrados is a line, while the soffit is a surface. KEYSTONE - The voussoir located at the crown of the arch, also called the key. LABEL COURSE - A ring of projecting brickwork that forms the extrados of the arch. RISE - The maximum height of the arch soffit above the level of its spring line. SKEWBACK - The surface on which the arch joins the supporting abutment. SKEWBACK ANGLE - The angle made by the skewback from horizontal. SOFFIT - The surface of an arch or vault at the intrados. SPAN - The horizontal clear dimension between abutments. SPANDREL - The masonry contained between a horizontal line drawn through the crown and a vertical line drawn through the upper most point of the skewback. SPRINGING - The point where the skewback intersects the intrados. SPRINGER - The first voussoir from a skewback. SPRING LINE - A horizontal line which intersects the springing VOUSSOIR - One masonry unit of an arch.
- 4. SANJEEV TRIVEDI – SVIT, VASAD 01 - ACCORDING TO THE SHAPE FLAT ARCH / FRENCH ARCH TRIANGULAR / CORBEL ARCH ROUND ARCH POINTED ARCH / GOTHIC ARCH 01. FLAT ARCH / FRENCH ARCH • A spanning member constructed of mutually supporting Voussoirs and having a straight or almost straight horizontal intrados and extrados • Flat intrados - Acts as a base of equilateral triangle (Formed by the horizontal angle of 60° by skew-backs) • Intrados is given a slight rise of camber of about 10 to 15 mm per meter width of opening • Are generally used for light loads, and for spans up to 1.5m. 02. TRIANGULAR ARCH / CORBEL ARCH • A false arch formed by corbelling courses from each side of an opening until they meet at a midpoint, where a capstone is laid to complete the work. • The stepped reveals may be removed but no arch action is affected.
- 5. SANJEEV TRIVEDI – SVIT, VASAD FLAT ARCH / FRENCH ARCH TRIANGULAR / CORBEL ARCH ROUND ARCH POINTED ARCH / GOTHIC ARCH 03. ROUND ARCH a. Semi-circular / Roman Arch: • A Strong rounded arch with a semicircular intrados. • In this type of arch, the Centre lies exactly on the springing line. b. Segmental Arch • Centre of arch lies below the springing line. • Thrust is transferred in inclined direction. c. Stilted Arch • Consists of a semi-circular arch with two vertical portions at the springing. • Centre lies on the horizontal line
- 6. SANJEEV TRIVEDI – SVIT, VASAD d. Bell Arch • A semi-circular arch, carved from one piece of stone, resting on two rounded corbels resulting in a shape similar to bell e. Horse Shoe Arch • Horse shoe shaped, incorporating more than a semi-circle. • Are provided mainly from architectural compositions f. Basket Handle / anse de panier A three centered arch having a crown with a radius much greater than that of the outer pair of curves
- 7. SANJEEV TRIVEDI – SVIT, VASAD FLAT ARCH / FRENCH ARCH TRIANGULAR / CORBEL ARCH ROUND ARCH POINTED ARCH / GOTHIC ARCH 04. POINTED ARCH a. Gothic Arch • Consists of two arches of circles meeting at the apex. • The triangle formed may be equilateral or isosceles; in the latter case it is known as Lancet arch. b. Lancent Arch • A pointed arch having two centers and radii greater than the span
- 8. SANJEEV TRIVEDI – SVIT, VASAD c. Drop / Depressed Arch • A pointed arch having two centers and radii less than the span • Also called Sur-based arch, having a rise of less than half its span. d. Ogee Arch A pointed arch, each haunch of which is double curve with the concave side uppermost e. Venetian Arch • This is another form of pointed arch which has deeper depth at crown than at springing. • It has four centers, all located on the springing line. • A round–headed opening containing two semi–circular–headed lights separated by a colonnette, with a roundel located in the space above.
- 9. SANJEEV TRIVEDI – SVIT, VASAD 02 – ACCORDING TO THE GEOMETRY SINGLE CENTERED ARCH DOUBLE CENTERED ARCH THREE CENTERED ARCH FOUR CENTERED ARCH FIVE CENTERED ARCH SINGLE CENTERED ARCH • Segmental arches, semicircular arches, flat arches, horse-shoe arch and stilted arches come under this category. • Sometimes, a perfectly circular arch, known as bull’s eye arch is provided for circular windows.
- 10. SANJEEV TRIVEDI – SVIT, VASAD DOUBLE CENTERED ARCH • Pointed arches come under this category. Semi-elliptical arch and Florentine arch come under this category.
- 11. SANJEEV TRIVEDI – SVIT, VASAD THREE CENTERED ARCH • Elliptical arches come under this category.
- 12. SANJEEV TRIVEDI – SVIT, VASAD
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- 14. SANJEEV TRIVEDI – SVIT, VASAD FOUR CENTERED ARCH It has four centers. Venetian arch is a typical example of this type. Another example is the Tudor arch. DRAWING A CLASSIC 4-CENTERED ARCH
- 15. SANJEEV TRIVEDI – SVIT, VASAD DRAWING A 4-CENTERED ARCH WITH A KNOWN HEIGHT AND WIDTH
- 16. SANJEEV TRIVEDI – SVIT, VASAD DRAWING A 4-CENTERED ARCH WITH A KNOWN HEIGHT AND WIDTH
- 17. SANJEEV TRIVEDI – SVIT, VASAD DRAWING A PSEUDO 4-CENTERED ARCH
- 18. SANJEEV TRIVEDI – SVIT, VASAD FIVE CENTERED ARCH This type of arch, having five centers, gives a good semi-elliptical shape. Step 1 Step 2 Step 3 • Draw the major and minor axes of the • Construct line C1-C4 and extend it to T. The true ellipse is shown in red, the ellipse and draw a rectangle around them Using C1 as center, draw arc YU. approximation in purple. The approximation Construct XY and draw P-C1perpendicular • Construct line C4-C2 and extend it to L. is quite good for slightly or moderately to XY eccentric ellipses but becomes obviously • Let X-C2 = r and locate Q such that • Using C4 as a center, construct arc UV. Incorrect for very elongated ellipses YQ = 2r. Draw a circle of radius r centered The successive arcs YUVX are an on C2. By symmetry, everything on the approximation to the ellipse right side of the diagram is repeated exactly on the left. • Using C1 as center and C1-Q as radius, draw an arc through Q. Call the intersection of this arc with the circle X-C2 C4.
- 19. SANJEEV TRIVEDI – SVIT, VASAD ACCORDING TO THE MATERIAL USED – STONE / BRICK / CONCRETE / TIMBER / METAL A. STONE ARCHES 01. Rubble Arch • Made of Rubble Stones, which are hammer dressed, roughly to the shape and size of ‘Voussoirs’ of the arch and fixed in cement mortar • These are used for small openings (Up to 1.0 Mt) • Are comparatively weak and is used for comparatively inferior work. - Also used as Relieving Arches, over wooden lintels. • Upto a depth of 37.5 cm – Are constructed in one ring. For greater depths (thickness) - Stones are laid in two rings in alternate course of headers and stretchers Dry Stone Bridge, Washington Pont del Diable, Spain – also known as Sant Bartomeu Bridge 02. Cut Stone or Ashlar Arch • Stones are cut to proper shape of Voussoirs and are fully dressed, properly joint with cement or lime • Up to depth of 60 cm - Voussoirs are made of full thickness of the arch. • Ashlar stone can also be used to make flat arches, in which the joints are either joggled or rebated.
- 20. SANJEEV TRIVEDI – SVIT, VASAD B. BRICK ARCHES 01. Rough Arch • Constructed with ordinary bricks without cutting to the shape Voussoirs. • Arch curve is provided by forming wedge shaped joints with greater thickness at extrados and smaller thickness at intrados. So, it looks unattractive. Thus not recommended for exposed brick work 02. Axed Brick Arch 03. Gauged Brick Arch • Bricks are cut to wedge shape • Bricks are cut to exact shape & size of required Voussoir with wire saw. • Are roughly dressed in shape and size. • Bricks are finely dressed and these bricks are joined by lime putty. • Only soft bricks are used.
- 21. SANJEEV TRIVEDI – SVIT, VASAD C. CONCRETE ARCHES 01. Cement Block Arch or Precast Concrete Block • In Precast concrete block arches the blocks are cast in molds to the exact shape and size of Voussoirs. • For key stone and skewbacks special molds are prepared. These will give good appearance because of exact shape and size. 02. Monolithic Concrete Arch 03. R.C.C Arch • Monolithic concrete arch is constructed from cast-in-situ concrete, either plain or reinforced, depending upon the span and magnitude of loading. • Arch is suitable for larger span – Thk. 15 cm (Up to 3 mt) • Form work is used
- 22. SANJEEV TRIVEDI – SVIT, VASAD D. TIMBER ARCHES E. METAL ARCHES
- 23. SANJEEV TRIVEDI – SVIT, VASAD ACCORDING TO THE CONSTRUCTION METHODS 01. Arches needing centering
- 24. SANJEEV TRIVEDI – SVIT, VASAD 02. Arches not needing centering 03. Domes without centering