two way slab reinforcement

TWO WAY SLAB 

when reinforcement slab are supported by beam on all four sides and the load are carried by the support along the both directions. It is know as two way slab. In two way slab the ratio of longer span (L) to shorter span (B) is less than two. L/B < 2.

This type of slab are mostly used in the floor of multi-story building.

ONE WAY SLAB

One way is a slab which is supported by beam in two opposite side to carry the load along one direction. 

One-way slab are those slab with an aspect ratio in plan of 2:1 or greater, in which bending is primarily about the long axis.

So the slab is one way where L/B ≥ 2. It may be solid hollow and ripped.

CROSS SECTION

Application of one way slab

• Provides useful flat surface
• One way slab used when there is architectural limitation
• It is simplest design of slab design
• Main reinforcement placing is one way, so there is a little congestion than the two way slab.

CEMENT CONCRETE

Definition :-

The mixture prepared by mixing desired quantity of water in dry mix of cement (binding material, cement:fine aggregate,sand:course aggregate,pebbles or crushed stone). after setting it becomes harder than stone.

Reinforced cement concrete (R.C.C):-

When cement concrete used with mesh steel bars to achieve desired shape of structure. It is tered as reinforcement cement concrete.

Application of cement concrete:-

Same as mortar , the cement concrete used in any form shall be proportioned (mixing of binding material , fine aggregate , course aggregate) very carefully. This mix of cement concrete is denoted as X:Y:Z ( x=binding material that is cement y=fine aggregate that is sand and z=course aggregate that is crushed stone)

Standardization of concrete:-

As per BIS:456: 1978, concrete is designated in seven grades by [M x] , where ‘M’ stands for mix and ‘x’ indicates the specified compressive strength of that mixture after 28 days in K/N mm2.

Precast concrete :- 

Precast concrete refers to product which are factory made with high standard of finishing. These are brought to site and are ready to use directly with minor jointing. Some of the common product are:-

Concrete Building Block

Concrete blocks are gray in color and substantially free from crack and chips.the nominal dimension shall be 4”x8”x16”. concrete block are also used for block manholes.

Concrete Paving Block

Concrete paving block are generally used for paving for street and parking.

MORTAR

Definition :-

The paste prepared by mixing desired quantity of water, in dry mix of cement or lime (binding material ) and sand (fine aggregate). the sand is classified on the basis of its source in three types

I.e. pit sand , river sand , sea sand.

Types of mortar :- the types of mortar vary as per the composition as stated below.

Mixing proportion of binding material and fine aggregate for mortar

BRICKS

Quality of good Bricks:-

          Brick should be copper colored. Color should be uniform and bright.

          They should be uniform in size.

          It should be free from crack.

          When struck together it should produce ringing sound.

          They should be sufficiently hard.

          On soaking in water for 24hrs there should be no salt deposits seen on the block.

          If dropped from the height of one meters it should not be break in pieces.

SIZE:- in the most part of the in India the actual size of brick is 19cm x 9cm x 9cm, and nominal size is 20cm x 10cm x 10cm. The nominal size includes the joining of mortar between the bricks. Part of top surface of rick is lowered which is called frog.

Standardization of brick:-

As per BIS : 1077-1957, the minimum crushing strength of brick is 3.5N/mm2.

“A” grade bricks :- crushing strength between 7to 14 N/mm2.

“B” grade bricks :- crushing strength above 14N/mm2.

The color of brick varies due to com-positional difference in clay.

Shapes of bricks :-

       Bull-nose brick :- a brick moulded with a round end.

       Channel brick :- brick moulded in the shape of gutter or channel and are used for drain etc.

       Coping brick :- thickness of these bricks corresponds with that of wall on which coping is to be provided.

       Cow-nose brick :- a brick with double bull-nose end.

Hollow brick :- these are hollow from within and are also called cavity or cellular bricks.

Paving brick :- these bricks containing more amount of iron to provide more strength for   traffic loads.

Perforated brick:- these bricks contain cylindrical holes thus useful for light weight construction.

Substitute for brick :-

Concrete block

Fly ash brick

Sand lime or calcium silicate brick