BUILDING MATERIALS & CONSTRUCTION TECHNOLOGY

UNIT-3ARCHES, LINTELS AND BALCONY

• Definition of Lintels - The definition of a lintel is a horizontal beam over an opening in a building that carries the weight of the wall above it.

OR• A piece of wood, brick, steel or stone that lies across the top of a door or window

and holds the weight of the structure above it, is called as Lintels.

Classification of Lintels• Lintels are classified into the following types, according to the materials of their

construction.

• Timber lintels• Stone lintels• Brick lintels• Steel lintels• Reinforced concrete lintels.

Timber lintels

• Timber lintels – Timber lintels are oldest lintels, so they are not commonly used now a days, except in hilly areas.

• Timber lintels are relatively costlier, structurally weak and vulnerable to fire

Timber lintel

• Stone lintels – These are the most common types. Specially where stone slab of greater thickness.

• Stone lintels can also be provided over opening in brick walls.

• Dressed stone lintels give good architectural appearance.

• Stone lintels may be used in the form of either one piece or more than one piece along the width of the wall.

• The depth of stone is kept 10cm per meter of span, with a minimum of 15cm.

• They are used up to span length of 2m. For wider spans, stone slabs are kept on edge.

• Stones are very weaker in tension. Also it cracks if subjected to vibratory loads.

• Brick lintels – Brick lintels are not structurally strong, and they are used when openings are small.(less than 1m) and loads are light.

• A brick lintel consists of bricks placed on end. Or edge, as shown in fig.

• The depth of brick lintel is varies from 10 to 20cm, depending upon the span.

It is constructed over temporary wooden centering.

• Steel lintels – Steel lintels are provided where the opening are large.And where the super imposed loads are also heavy.It consist of rolled steel joints or channel section either used singly or combination of two or three units.

• Reinforced concrete lintels- are replaced practically all other types of lintels because of their strength, rigidity, fire resistance, economy and ease in construction.

• These can be used on any span.

• Its width is kept equal to the width of the wall

• The depth of the RCC lintel and the reinforcement depends upon the span and magnitude of loading.

• Longitudinal reinforcement, consisting of mild steel bars, are provided near the bottom of lintel to take up tensile stresses.

Reinforced concrete lintels.

Arches• Definition of an arch-•  A structure, especially one of masonry, forming the curved, pointed, or flat 

upper edge of an open space and supporting the weight above it, as in a bridge or doorway.

• A curved structure at the top of a door, window, or gate.

• Terms used in arch

• Intrados - This is the inner curve of an arch•Soffit - It is the inner surface of an arch. Sometimes intrados and soffit are used

synonymously.

• Extrados - It is the outer curve of an arch.

• Voussoirs - These are wedge shaped units of masonry, forming an arch.

• Crown - It is the highest part of extrados and the horizontal line through the crown.

• Key - It is the wedge – shaped unit fixed at the crown of the arch

• Spandril - This is the curved triangular space formed between the extrados

and the horizontal line through the curve.

• Abutment - This the end support of an arch.

• Pier - This an intermediate support of an arch.

• Springing line- It is an imaginary line joining the spring points of either end.• Span – It is the clear vertical distance between the intrados and the springing line.• Haunch – It is an the lower half of the arch between the crown and skew back.