Steel and Timber

Steel

Ordinary steel is an alloy of iron and carbon. Steel are classified as follows:

(i) Low carbon steel or mild contains less than 0.25 % carbon.

(ii) Medium carbon or medium steel with carbon content between 0.25 % - 0.70%.

(iii) High carbon steel containing carbon from 0.70 t0 1.5%.

>Steels are reinforced with concrete in order to have more compressive strength.

Tor Steel

Tor steel bar are twisted or torsioned deformed bars. Tor steel bars develop good strength between concrete and steel. They are used as reinforcements for slabs, lintels, beams, columns etc. Any deformed bar is hot rolled or cold twisted. Tor steel is cold twisted. They have longitudinal ribs in the form of continuous or discontinuous helix and have transverse ribs spaced nearly at uniform intervals. These ribs in developing higher bond due to interlock between steel and concrete. The yield strength is 415
N/mm^2. Higher yield strength is achieved by cold twisting. End hooks are not essential when torsteel rods are used.

Timber

>Wood is generally classified for construction as (a) Hard wood (b) medium hard wood and (c) soft wood.

>Medium hard wood is used for structure purpose like roof truss, making doors and window fabrication.

>Wood is graded according to natural defects present in timber like knots and sloping grains.

>Felled (freshly cut) contains lot of moisture.

>The process of drying the timber to remove moisture till it is ready to be used is called seasoning.

>The decay in Timber is called ‘rotting’.

>Plywood is a wood structure material formed by gluing 3 or more thin layers of wood together.