Singly reinforced beam(Limit state method of design)

Different methods of design of RCC
1.Working Stress Method
2.Limit State Method
3.Ultimate Load Method
4.Probabilistic Method of Design
 
Limit state method of design

• The object of the design based on the limit state concept is to achieve an acceptable probability, that a structure will not become unsuitable in it’s lifetime for the use for which it is intended,i.e. It will not reach a limit state
• A structure with appropriate degree of reliability should be able to withstand safely.
• All loads, that are reliable to act on it throughout it’s life and it should also satisfy the subs ability requirements, such as limitations on deflection and cracking.
• It should also be able to maintain the required structural integrity, during and after accident, such as fires, explosion & local failure.i.e. limit sate must be consider in design to ensure an adequate degree of safety and serviceability
• The most important of these limit states, which must be examine in design are as follows      Limit state of collapse

             - Flexure

                       - Compression

             - Shear

               - Torsion

This state corresponds to the maximum load carrying capacity.

Types of reinforced concrete beams
a)Singly reinforced beam
b)Doubly reinforced beam
c)Singly or Doubly reinforced flanged beams
Singly reinforced beam
In singly reinforced simply supported beams or slabs reinforcing steel bars are placed near the bottom of the beam or slabs where they are most effective in resisting the tensile stresses.

LABORATORY TESTS on Mild Steel (Reinforcement Steel)

 
TENSILE TEST ON MS SPECIMEN
• Equipment required: Universal Testing Machine, Specimen and extensometer.
                                
• In a tensile test of mild steel specimen, usually a round or flat bar is gradually pulled in a testing machine until it breaks.
• Two points, called gauge points, are marked on the central portion. The distance between these points, before the application of the load, is called gauge length of the specimen.
• The Load is applied gradually and at regular interval of loads extension is measured.
• The strains corresponding to the recorded extensions are calculated by dividing the extensions by the gauge length, while the stresses are calculated by dividing the loads by the original area of cross-section of the specimen.
• Stresses so arrived at is called nominal stress to distinguish it from actual stress which is obtained by dividing the load at a particular instant by the area of the cross-section at that instant
 
• Limit of Proportionality(A):It is the limiting value of stress upto which stress is proportional to strain.
• Elastic Limit:This is the limiting value of stress up to which if material is stressed and released, strain disappears completely and original length is regained. This point is slightly beyond the LOP.
• Upper Yield Point(B):This is the stress at which the load is decreasing and strain increases. This phenomena is called Yielding of Material.
Stress=250kn/mm²
Strain=0.125%
• Lower Yield Point(C): At this stage the stress remains constant but strain increases for some time.
• Ultimate Stress(D): This is maximum stress the material can resist. At this stage C/S area at a particular section starts reducing very fast. This is called Neck formation. After this stage load resisted and hence the stress developed starts reducing.(370-400N/mm²)
• Breaking Point(E):The stress at which finally the specimen breaks is called breaking point.
Strain= 20-25%

MARINE PILING - PROCEDURE & COMPONENTS

Pile Foundations
Pile foundations are the part of a structure used to carry and transfer the load of the structure to the bearing ground located at some depth below ground surface. The main components of the foundation are the pile cap and the piles. Piles are long and slender members which transfer the load to deeper soil or rock of high bearing capacity avoiding shallow soil of low bearing capacity The main types of materials used for piles are Wood, steel and concrete. Piles made from these materials are driven, drilled or jacked into the ground and connected to pile caps. Depending upon type of soil, pile material and load transmitting characteristic piles are classified accordingly.
Classification of piles
Classification of Pile with respect to Load Transmission and Functional Behaviour.

• End bearing piles (point bearing piles)
• Friction piles (cohesion piles )
• Combination of friction and cohesion piles

Classification of Pile with respect to type of material. Timber

• Concrete
• Steel
• Composite Piles

Classification of Pile with respect to effect on the soil.

• Driven Pile ( Displacement pile)
• Bored Pile ( Non Displacement pile)

Classification of Pile with respect to Shore.

• On Shore ( Land Pile)
• Off Shore (Marine Pile)

Marine Piling
Marine piling work differs from land piling work in many respects.

• Distance from land
• Depth of water
• Hydrostatic pressure and buoyancy
• Underwater currents
• Wave and swells
• Tidal variation
• Wind and storm
• Cyclone
• Existing navigation and possibility of diversion etc.
• Marine Piling

Offshore Piling Works:
This kind of piling works are mostly carried out in construction of various marine structures like jetties, harbours, ports, wharfs and bridges on river/sea that are away from land.
Marine Piles can be installed by

• Tripod Rig.
• Rotary Rig ( Wirth Rig or Ordinary Crawler Mounted Hydraulic Rig)

Tripod Rig
Marine Piling
Different methods commonly used for advancing the bore holes.

• End on Piling Gantry ( Temporary movable gantry )
• Self elevated Platform ( Jack-up platform )
• Temporary fixed platform supported on temporary/ permanent piles.

Jack Up Platform with Bailer & Chisel

Temporary Movable Gantry with Bailer & Chisel

Temporary Movable Gantry with Bailer & Chisel

Basic Concepts for Civil Engineers for Interview and Campus preparation- Cement

The manufacture of cement consists of grinding the raw materials (calcareous and argillaceous stones consisting silica, alumina and iron oxide ) and mixing them intimately in a certain proportion. it is then burnt in a large rotary kiln at temeperature of 1500C, when the material sinters and partially fuses into balls known as clinker. The clinker is cooled and ground to fine powder with some gypsum added, and the resulting product is Commercial Portland cement.
The main Components of Cement are
 Lime - 63%
Silica - 22%
Alumina - 6%
Iron Oxide - 3%
Magnesium Oxide - 2.5%
Sulphur trioxide - 1.5%
Alkalies - 0.5%

 The lime, silica and iron oxide imparts strength to cement , while alumina gives quick setting property. The alkalies when in excess, causes efflorescence.

The Bougue's Components (Components of Cement Clinker)
Tri Calcium Silicate -C3S- 40%
Di Calcium Silicate - C2S- 32%
Tri Calcium Aluminate - C3A - 10.5%
Tetra Calcium Alumino Ferrite - C4AF- 9%

Basic Concepts for Civil Engineers for Interview and Campus preparation- Bricks

Stones

• Stones are geologically classified as Ingenious, Sedimentation and Metamorphic rocks.
• Chemically they are classified as Siliceous, Argillaceous(Clay or alumina), Calcareous stones
• Physically they are classified as Stratified and Un-stratified rocks. 

Bricks
The composition of Bricks are

• Alumina 20-30%
• Silica 50-60%
• Magnesium, manganese, lime, sodium.

Excess alumina in bricks may cause cracks and warp on drying.
Excess silica in bricks may cause brittle and weak.
Excess lime causes melting and distortion during burning process of bricks.
Presence of Alkaline salts causes efflorescence in Bricks
Classification of Bricks

• First class bricks – 20% of water absorption only when bricks are immersed in water for 24 hours and compression strength of 10.5 MN/sq.m.
• Second class bricks – 22% of water absorption only when bricks are immersed in water for 24 hours.
• Third class bricks – 25% of water absorption only when bricks are immersed in water for 24 hours and not properly burnt.
• Jhuma Bricks- Over burnt, Bluish or dark colour and irregular shape.

Size

Nominal size of Bricks are 19x9x9 cms

CPWD India – 23x11.5x7.5 cms.

Notes:

• The specific Gravity of bricks is 2-2.1
• In 1 cubic metre volume around 550 bricks are used