Arch and it's technical aspects

It is a structure, normally curved. While undergoing vertical loads, it motivates its two end supports to produce reactions with interiorly headed horizontal components.

        Application:

—     Generally, the arches are utilized as a bridge, supporting a roadway, railroad track, or footpath, and as part of a building, where it arranges a large open space uninterrupted by columns. Arches are generally formed with steel, reinforced concrete, or timber.

Technical Aspects:

—     The arch produces a structure that reduces tensile stresses by stretching an open space. All the forces are settled into compressive stresses.

—     It is effective since some of the existing building materials like stone, cast iron and concrete can potently withstand compression but are very feeble when tension, shear or torsional stress is implemented to them. With the use of the arch configuration, substantial spans can be obtained.

       Hinge Introduction:

—     Two unknowns. The reaction are two components of Force, or the magnitude and direction Ф of the consequential force .

—     At the hinge joint moment is zero i.e. it can’t withstand the bending moment generated by external force.

Categorization

      Hinge less Arch:

—     The hinge-less arch applies no hinges and authorizes no rotation at the foundations.

      Two Hinged Arch:

—     The two hinged arch applied hinged bearings which permit rotation. The only forces produced at the bearings belong to horizontal and vertical forces.

Three Hinged Arch:

—     The three-hinged arch includes a supplementary hinge at the top or crown of the arch. The three-hinged arch is affected marginally if there exist movement in either foundation (because earthquakes, sinking, etc.)

Tied Arch:

—     The tied arch is a variation on the arch that facilitates construction although the ground is not solid enough to manage the horizontal forces.

Three hinged circular arch

• A three hinged system may or may not have a vertical axis of symmetry. In the first case the central hinge c will lie on the axis of symmetry and the hinges at the support A and B are at same level.

Various components of an arch

Arch comprises of the wedge-shaped blocks formed with stones or bricks which provides collaborative support to one other. These are supported at the end through piers or abutments. Similar to lintels, an arch is constructed to bear the weight of the structure over the opening.
Given below the details of the various sections of an arch:


1. ABUTMENT OR PIER:
It belongs to the portion of wall or pier upon which the arch is supported.

2. ARCH RING:
It is a series of stones or bricks which contain a curve same as that of the arch.

3. INTRADOS OR SOFFIT:
It stands for the under-surface of an arch.



4. EXTRADOS:
It belongs to the external surface of an arch or the exterior curve of the arch ring.

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5. VOUSSOIRS OR ARCH BLOCK:
It stands for the wedge-shaped units to develop the arch are called voussoirs or arch stones or arch block.

6. SPRINGING STONE:
Springing stone or springer is the initial voussoirs at springing level on both side of the arch.

7. SPRINGING LINE:
It belongs to an fictitious line that connects two springing points.

8. CROWN:
Crown stands for the uppermost point of the extrados or it is the top part of the arch.



9. KEY-STONE:
It stands for the uppermost central wedge-shaped block of an arch.

10. SKEW-BACK:
It belongs to the surface of the abutment on which the arch is supported on.

11. SPAN:
Span refers to the apparent horizontal gap among supports.

12. RISE:
Rise belongs to the vertical distance among the springing line and the uppermost point on the intrados.

13. SPRINGING POINT:
Springing points belongs to the points at extremities of the intrados.

14. DEPTH OF ARCH:
The depth of the arch signifies the perpendicular space among the intrados and the extrados.

15. HAUNCH:
Haunch of the arch belongs to the part of the arch that is located centrally among the key and skew backs.

16. SPANDRIL:
Spandril stands for the triangular walling surrounded by the extrados of the arch, a horizontal line from the crown of the arch and a perpendicular line from the rising of the outer curves.

Article Source : http://www.dailycivil.com