BUILDING TECHNOLOGY 1Materials and Methods of Construction

History of Materials

■ “ Architecture is inseparable from construction technique and material culture “ Kenneth Frampton

■ In ancient times, materials have had local use and have influenced the development of an indigenous architecture since there was a lack of conveyance methods.

■ Today, in contemporary times, with the perfection of industries and commercial consumption. Building materials are made to last and can be distributed in any location.

The availability of suitable materials fostered the crafts to exploit them and influenced the shapes of buildings. Large areas of the world were once forested, Though becoming scarce, timber remains an important building material.

Many kinds of stone lend themselves to building. Stone and marble were chosen for important monuments because they are incombustible and can be expected to endure. Stone is also a sculptural material; stone architecture was often integral with stone sculpture. The use of stone has declined, however, because a number of other materials are more amenable to industrial use and assembly.

Some regions lack both timber and stone; their peoples used the earth itself, tamping certain mixtures into walls or forming them into bricks to be dried in the sun. Later they baked these substances in kilns, producing a range of bricks and tiles with greater durability.

Building with stones or bricks is called masonry. The elements cohere through sheer gravity or the use of mortar, first composed of lime and sand. The Romans found a natural cement that, combined with inert substances, produced concrete. They usually faced this with materials that would give a better finish. In the early 19th century a truly waterproof cement was developed, the key ingredient of modern concrete.

In the 19th century also, steel suddenly became abundant; rolling mills turned out shapes that could make structural frames stronger than the traditional wooden frames. Moreover, steel rods could be positioned in wet concrete so as to greatly improve the versatility of that material, giving impetus early in the 20th century to new forms facilitated by reinforced concrete construction. The subsequent profusion of aluminum and its anodized coatings provided cladding (surfacing) material that was lightweight and virtually maintenance free. Glass was known in prehistory and is celebrated for its contributions to Gothic architecture. Its quality and availability have been enormously enhanced by industrial processing, which has revolutionized the exploitation of natural light and transparency.

Stress – Strain Ratio

■ Stress : the internal resistance or reaction of an elastic body to external forces applied to it .

( force per unit area )

■ Strain : the deformation of a body under the action of an applied force equal to the ratio of a change in size or shape from the original size or shape of an stressed element.

Internal Properties of Materials

■ Properties are : elasticity, strength and stiffness.

■ Elasticity : the ability of an object or substance to return quickly to its original shape and size after being bent, stretched, or squashed

■ Strength : the ability to withstand force, pressure, or stress

■ Stiffness : measure of a force required to push or pull a material into its elastic limit.

■ Best materials combines elasticity, strength and stiffness.

■ Ductility : (malleable enough to be worked) able to be drawn out into wire or hammered into very thin sheets

: material that undergo plastic deformation before actually breaking

■ Malleability : (able to be shaped and bent) used to describe a metal or other substance that can be shaped or bent without breaking

: material that permits deformation without permanent fracture.

■ Brittleness : materials with low elastic limits and rupture under loads with little visible deformation

Thus, the cross sectional shape of a material relative to its specific properties are important when considering the relationship between span and deflection under loading.

External Properties of a Material

■ Dimensional Stability : as the material respond to changes in temperature and moisture content affecting its detailed construction to join with other materials.

■ Thermal Resistance : ability of the material to withstand water, moist and exposure to extreme weather conditions when used in constructing the exterior envelope.

■ Insulation : a material’s ability to transmit, reflect and absorb visible light and radiant heat

■ Durability : the materials density and hardness must be checked against tear, denting and abrasion including the cost required for maintenance.

:lasting for a long time, especially without sustaining damage or wear

■ Resistance : the ability of as material to resist combustion, withstand fire exposure and at the same time not produce smoke and toxic gases must be evaluated before using as a structural member or an interior finish.

■ Standard Shapes and Sizes : or stock dimensions may vary slightly according to manufacturer. They should be verified in the earlier design and planning phases to minimize wasteful cutting of materials.