Lecture No. 10: One Way Slab & Two Way Slab PDF

Mousl university 1st semester : Building Construction 2 Architecture department Date : xx / xx / xxxx Iraq Lecture no.10 one way slab & two way slab Building Construction 2 Assistant Teacher. : Adil Khalil  Concrete Slabs Slabs are an import...

Mousl university 1st semester : Building Construction 2 Architecture department Date : xx / xx / xxxx Iraq Lecture no.10 one way slab & two way slab Building Construction 2 Assistant Teacher. : Adil Khalil  Concrete Slabs Slabs are an important structural component where pre- stressing is applied. Slabs are used to provide flat and useful surfaces. TYPES OF SLAB ONE WAY TWO WAY GRIDOR SLAB FLAT WAFFLE PLATE SLAB &amp; FLAT SLAB One-way slabs are those slabs with an aspect ratio in plan of 2:1 or greater, in which bending is primarily about the long axis. If the ribs are provided in one direction only, the slab is classified as being one-way, regardless of the ratio of longer to shorter panel dimensions. So, the slab is one way where L/S ≥ 2. TYPES OF ONE WAY SLAB One way slab may be… SOLID HOLLOW RIBBED Two-way solid slabs A two-way solid slab curves under loads in two directions. Accordingly slabs supported on all four sides, and L/S < 2 are classified as two-way slabs. Bending will take place in the two directions in a dish-like form. Accordingly, main reinforcement is required in the two directions.  APPLICATION OF L/S RATIO In first figure slab is supported on two opposite sides only. In this case the structural action of the slab is essentially one way. In second figure there are beams on all four sides with a intermediate beam. Now if length to width ratio is 2 or greater, slab is one way even though supports are provided on all sides. LOADING OF ONE WAY SLAB When slabs are supported on two opposite sides only When supports are provided loads being carried by the on all sides most of the load is slab in the direction carried in the short direction perpendicular to the to the supporting beams and supporting beams. one way action is obtained.  LAYOUT OF ONE WAY SLAB APPLICATION OF ONE WAY SLAB One way slab may be used when there is architectural limitations. It is the simplest form of slab design. Main reinforcement placing is one way, so there is a little congestion than two way slab. ‫كثافة‬ One-way slab (simply supported slab) The following describe the way to reinforce a one-way (simply supported) slab. The structural frame consists of four columns, two beams and one slab "project: slabs10 " The one-way slab is supported by two beams. The example regards slab S1 which is 180 mm thick, its primary dimension is equal to 0.30+3.80+0.30=4.40 m and its secondary dimension to 8.0 m. The slab sits upon beams b1 and b2 which are supported by column pairs C2, C4 and C1, C3 respectively. Usually, when a slab sits upon a beam the support is considered to be pinned. The following figure is called carpenter’s formwork is the term given to moulds into which the concrete is poured. The wooden formwork is built on site out of timber. The formwork drawings are allocated for two specific uses: a) the creation of the formwork by the carpenter and thus it is called carpenter’s formwork draw-ing. b) the steel reinforcement implementation by the installer which is called installer's formwork drawing. It symbolically illustrates the structural frame of reinforced concrete.  What is two way Slab When the ratio of long span to short span is less than 2, then the slab is known as a slab spanning in two directions or two-way slab. If two beams are added under the free edges of the slab in the previous example, then the slab S1 becomes a two-way slab. The behavior of a two-way slab is similar to that of a one-way slab the only difference is that the former works in both directions. The reinforcement rules are also similar in both directions. The two-way slab S1 is supported by four beams "project: slabs20" Behavior of a two-way slab Types of two way Slab  conclusions Types of Slabs Solid slabs :- which are divided into – One way solid slabs – Two way solid slabs Ribbed slabs : - which are divided into - One way ribbed slabs - Two way ribbed slabs One-way solid slabs A one-way solid slab curves under loads in one direction only. Accordingly, slabs supported on two opposite sides only and slabs supported on all four sides, but L/S ≥ 2 are classified as one-way slabs. Main reinforcement is placed in the shorter direction, while the longer direction is provided with shrinkage reinforcement to limit cracking. Main reinforcement is placed in the shorter direction, while the longer direction is provided with shrinkage reinforcement to limit cracking.