An overview of IS-1786 (1985) (HIGH STRENGTH DEFORMED STEEL) Section 2

Section 2

             The following test has to be conducted in test specimens as per IS code requirement.

1. Tensile Test
2. Bend Test
3. Rebend Test

 Tensile Test

                            

            As per code recommended for production of Plates, Sections ( Angles, Tees, Beams, Channels, etc) and Flats— One tensile test shall be made from finished steel for every 40 tonnes or part thereof rolled continuously from each cast, a separate test being made for each class of steel product ( namely, plates, sections, and flats ) rolled from a cast.

                 Where plates, sections or flats of more than one thickness are rolled from the same cast, one additional tensile test shall be made from the material in each class of product for each variation in thickness of 6 mm.

                   Bar’s ( Round, Square, and Hexagonal) — One tensile test shall be made from finished steel for every 40 tons or part thereof rolled continuously from each cast and for every class of product. When more than one diameter or thickness of the bar is specified, in additional the tensile test shall be made for each diameter ‘or thickness of the bar ordered, if so desired by the purchaser.

                the tensile test should follow as per IS -226 from the following table.The tensile strength, yield stress and percentage elongation of steel shall be determined from standard test pieces cut lengthwise or crosswise front plates and lengthwise from sections, flats and bars. The tests shall be carried out on Indian Standard test pieces prepared in accordance with IS: I608.

Table 1 -IS 226

An overview of IS-1786 [ HIGH STRENGTH DEFORMED STEEL] --Section -1

An overview of IS-1786    [ HIGH STRENGTH DEFORMED STEEL] - Section -1

                          The steel shall be manufactured by the method of open-hearth, electric, duplex,

basic-oxygen, or a combination of these processes. For manufacturing of steel following proportion of constituents should follow in order to reach their absolute strength.

                the nominal size of bar as follows - 4, 5, 6, 7, 8, 10, 12, 16, 18, 20, 22, 25, 28, 32, 36, 40,

45 and 50 mm, apart from this cross sectional dimension depends on manufacture and customers requirement and quality of material test conducted as per Indian Standard code provisions.

the following table shows cross sectional area and mass of the bars prescribed in IS-1786.

Proof stress, percentage elongation and tensile strength for all sizes of deformed bars/wires determined on the effective cross-sectional area are tabulated following categories.

Afflux or Backwater

Afflux or Backwater

              Afflux is the rise of water level on the upstream side of the bridge, caused by an obstruction across the channel and is the diffrence in levels of the water surfaces upstream and downstream of the bridge. Afflux is also caused when the effective lineal waterway of a bridge is less than the natural width of the stream immediately on the upstream side of the bridge. 

https://en.wikipedia.org/wiki/Kerala_backwaters#/media/File:Kerala_Backwaters_Sunset.JPG

The water way of any bridge is generally made less than natural waterway of the stream, for which guide banks or traininng banks are provided. the amount of afflux determined the top levels and lengths of the guide banks and also the free board.

cushions of pile heads

cushions of pile heads

              the top of a pile is damaged by the impacts of the blows, therefore, piles must protected by cushion of some resilience material whilst they are being driven, to absorb shocks with steam hammer a suitable driven head made of cast iron is provided to fit top of the pile.

 A thick packing of felt, bags of saw dust, gunny bags, old rags, ropes or such like material, is placed over the pile head and under a block of hardwood, which is placed on the top of the cast iron driving hood. The cushion should  not normally more than 75 mm thick but should give enough protection to the pile head and should not absorb too much of energy of the blow.

Damp-Proof Course

Damp-Proof Course

             one of the following specifications may be adopted for a damp proof course, According to the type of the construction and the nature of the ground.

• Two course of dense bricks in 1:3 cement mortar. Bricks should have a water absorption of not more than 4.5 percent. It is advantageous to leave the vertical joints unfilled moisture rises through the mortar joints.
• A Layer of well burnt bricks soaked in hot tar and pitch will suit for cheap class buildings

• Non-porous stone slab about 50 mm thick laid for the full width of the walls over a bed of cement mortar.
• Two layers of non-porous slate laid to break joints, each layer being bedded and set solidly in cement mortar 1:3
• 12 mm cement plaster 1:2 with some water -Proofing compound laid above the plinth masonry with one or two thick coats of hot coal tar applied over the mortar after the mortar has fully dried. Dry sharp sand should be sprinkled over the hot tar. Five percent of waterproofing compound used for standard mortar mix.

Thermometric Scales:

Thermometric Scales:

              Two thermometric scales are in common use, Fahrenheit and centigrade or Celsius. Temperature is measured in degree Fahrenheit or degrees Centigrade

1. Freezing Point of pure water or melting point of ice = 32 degree Fahrenheit
2. Boiling point of pure water=212 degree Fahrenheit = 100 degrees Centigrade
3. Human Temperature = 98.4 degree Fahrenheit  =37 degrees Centigrade
4. Cold Water temperature is taken = 45  degree Fahrenheit =7 degrees Centigrade

" 0 degree Fahrenheit is the melting point of a mixture of equal part of salt and snow "

To convert - degree Fahrenheit to degrees Centigrade

C = [5/9] ( F . -32)

F = [9/5] (C. +32)

       For most purpose mercury in glass thermometers are used . For recording the interior temperature of a dam, Thermocouples are used. 

       Stream as compared with water occupies 1646 times as much space. It is generally assumed that one cubic inch. 

Simple Field Tests to Distinguish Different Irons

Simple Field Tests to Distinguish Different Irons

              cast iron can be readily distinguished from wrought iron by its crystalline structure, by structure its want to ductility and its brittleness. If a piece of cast iron is struck with a hammer it breaks clean without bending and the fractured surface presents large grains of whitish gray and dark colour with black spots interspersed, while wrought iron when struck bends and then breaks and the broken surface presents an uneven thick fibrous appearance .

Heat and bending Test:

            cast iron cannot be bent when cold while wrought iron can be bent very easily and steel can be bent with some difficulty. cast iron breaks very quickly when heated while steel can be bent easily when hot.

Sound:

              Steel when struck gives a treble musical or sharp metallic ring like that of bell metal, wrought iron a note of a low pitch, while cast iron when struck gives a hollow sound.

fracture:

               A fracture in steel is granular in wrought iron fibrous and in cast iron crystalline in appearance.

Acid Test:

                Apply a drop of nitric acid on the iron to be tested and let it remain for a moment, and then rinse with water. There will be no perceptible stain  on wrought iron; a dark grey strain on steel ; and a black or brownish strain on cast iron, which is due to the presence of carbon.

The ASTM A262 Chart for Selection of Testing Practices

CORROSION OF STEEL IN R.C. STRUCTURES

CORROSION OF STEEL IN R.C. STRUCTURES

Repairs in Construction - A growing concern

  Bad construction practices

  Standards not adhered to

  Poor  maintenance

  Increasing pollution

SEM micrographs of microcracks propagating from a pore 

Deterioration of concrete due to corrosion results because of the product of corrosion – ferric oxide, brown in color – occupies a greater volume 9 more than 2 to 10 times) than steel and exerts substantial bursting stressed on the surrounding concrete.

SEM micrographs from the no-load specimen 

Internal voids

Pollution affects Durability

Contaminated Water       Chlorides

Effluents                           Chemicals

Soils                                   Sulphates

Vehicles                                     CO₂

CORROSION OF REINFORCEMENT IN CONCRETE

                Protection of the reinforcements from corrosion is provided by the alkalinity of the concrete, which leads to passivation of steel.  However, environmental influences and CO₂ in particular, will reduce the concrete’s pH value from 12.6 to 8.0, and thus remove the passivating effect.

•New steel is anodic to Old one

•Brightly cut one is anodic to un-cut steel

•Steel anodic to mill scales

•Highly stressed steel is anodic to unstressed steel

Stray direct current

•Stray direct current passes from them to electrolyte.

•Current arises from crane systems , embedded electrical conduits and improperly grounded equipments.

•Causes accelerated corrosion- Should be checked and corrected 

Differential environment

•Different levels of aeration ( oxygen content)

•Different salinities

•Corrosion occurs at locations of lower oxygen content- just below mean low tide level

Erosion corrosion

•Scouring action of sand

•Commonly found just above mud line of piles- riser chains of moorings

•High wind effect in sandy areas

Biological corrosion

•Marine organisms accelerate corrosion

•Creates differential oxygen levels

•Produces corrosive products for their metabolism

•Organisms remove protective layer on steel

colour Scheme for walls

colour Scheme for walls

there are only three primary colours - red, yellow and blue. All other colours are mixture of these three. There are warm colours and cool colours. Red, orange and yellow and warm ; violet, blue and green are cool. Exess of red or orange is upsetting, most uncomfortable to live with in hot climate. The coolness of blues and greens recall water, ice, snow and trees, white, pure greys and black are natural

Clour Terms;
A tint - is a colour plus white; a shade is a colour plus black:
A hue- is a colour plus a little of another colour that is close to it on the colourwheel
Tone - the intensity of colour, value refers to its lightness or darkness 
Dark values are called shades, lights values are tints.

Cool Colors:

1. Yellow Green
2. Green
3. Blue Green
4. Primary Blue
5. Blue Violet
6. Violet

Warm colours:

1. Red Violet
2. Primary Red
3. Red orange
4. Orange
5. yellow Orange
6. Primary Yeloow

Manufactured Sand ( M-sand)

Manufactured Sand ( M-sand)

Comparison

•        Environmental factors and shortage of good quality river sand has led to the invention of Manufactured Sand Also known as M Sand or Robo Sand

Parameters

•        Parameters M Sand/Process/Manufactured in the factory.

•        River Sand-Naturally available on river banks. M.Sand-Shape-Angular and has a rougher texture. Angular aggregates demand more water. Water demand can be compensated with cement content.

•       River Sand-Smoother texture with better shape. Demands less water.

           Need of the hour

•       The development of standards/specifications and incorporating in the BIS codes will reduce the pressure on using river sand. The standards and code specifications will assist to select and use the alternatives by the various stakeholders. Quality certification of the alternate aggregates and quality certification of the concrete manufacturing process plays a vital role in ensuring the durability of the concrete.

Some of the Alternatives to River Sand

 –    Manufactured Sand

–    Fly Ash/ Bottom Ash/Pond Ash

–    Copper Slag   –    Filtered Sand

–    Sea Sand, Slag Sand

–    Crushed Waste Glass

–    Recycled Aggregate/C&D Waste Aggregate etc..

IS 383-1970 (Reaffirmed 2007) recognizes manufacture sand as ‘Crushed Stone Sand’.

•        Crushed stone sand is produced by crushing boulders. Manufactured sand is produced by rock-on-rock or rock-on-metal Vertical Shaft Impactor (VSI) in which the process that produced alluvial deposits is closely simulated. Particle size reduction and achieving equidimensional shape is critical to get desired properties. If rock is crushed in compression lot of inherent properties exhibited by natural river sand are lost

Particle size and manufacture

•        Fine aggregates manufactured sand proposed to be used shall be produced from a Vertical Shaft Impact (VSI) crushers and shall conform to the requirements of Zone-II (in most of the cases) as per IS 383-1970 (Reaffirmed in 2007) and particles finer than 75 µm shall not exceed 15 %. Special efforts on the part of M-sand manufacturers (such as washing of sand by water or dry washing by air) is required to restrict particles finer than 75 µm to 15%. The global trend is to utilize dry classification solutions to produce manufactured sand. The dry separation process separates fine and coarse particles. This allows a reduced percentage of super fines in the manufactured sand, thereby meeting specifications and achieving quality products.

Sand for mortar

•        M-sand can also be used for making masonry mortar and shall conform to the requirements of IS 2116-1980 (Reaffirmed 1998) – “Specification of sand for Masonry Mortars”.

General Requirements:

1.    All the sand particles should have higher crushing strength
2.    The surface texture of the particles should be smooth
3.    The edges of the particles should be grounded
4.    The ratio of fines below 600 microns in sand should not be less than 30%
5.    There should not be any organic impurities
6.    Silt in sand should not be more than 2%, for crushed sand
7.    In manufactured sand, the permissible limit of fines below 75 microns shall not exceed 15%

Manufactured Sand Quality

1.    Sieve analysis
2.    Optical Microscopic Study to check the particle shape
3.    Workability (slump test by slump cone method)
4.    Cube test for compressive strength
5.    Tests for Silt and clay

Advantage of M – sand

•        The sand must be of proper gradation (it should have particles from 150 microns to 4.75 mm in proper proportion). When fine particles are in proper proportion, the sand will have fewer voids. The cement quantity required will be less. Such sand will be more economical. Demand for manufactured fine aggregates for making concrete is increasing day by day as river sand cannot meet the rising demand of construction sector. Natural river sand takes millions of years to form.

Size and Grading of Aggregates

•        IS 383 defines Fine Aggregates as aggregate most of which passes 4.75-mm IS Sieve and contains only so much coarser material as permitted in cl.4.3. [Cl. 4.3 Fine Aggregates -The grading of fine aggregates, when determined as described in IS: 2386 (Part I)-1963 shall be within the limits given in Table 4 and shall be described as fine aggregates, Grading Zones I, II, III and IV. Where the grading falls outside the limits of any particular grading zone of sieves other than 600-micron IS Sieve by a total amount not exceeding 5 percent, it shall be regarded as falling within that grading zone. 

Reference  - Lecture notes from 
Prof.A.R.Santhakumar
Former Professor and Dean (Civil Engg)
Anna University
Chennai.

Specific Gravity of soil Particles

Specific Gravity of Soil Particles:

          it is defined as the ratio of their density to that of water. The specific gravity of soil Particles may vary from 2.0 to 3.3, But usually is between 2.65 and 2.75. The usual soil weight (voidness) is between 2600 and 2700 kg/cu.m.

Types of soil	Specific gravity
Sand	2.65-2.67
Silt sand	2.67-2.70
Inorganic clay	2.70-2.80
Soils with mica or iron	2.75-3.00
Organic Soils	Variable but may be under 2.0

El Centro earthquake [ May 18-1940]

El Centro earthquake [ May 18-1940] 

The 1940 El Centro earthquake (or 1940 Imperial Valley earthquake) occurred in the Imperial Valley in southeastern Southern California near the international border of the United States and Mexico. It had a moment magnitude of 6.9 and a maximum perceived intensity of X (Extreme) on the Mercalli intensity scale. 

It was the first major earthquake to be recorded by a strong-motion seismograph located next to a fault rupture. The earthquake was characterized as a typical moderate-sized destructive event with a complex energy release signature.

It was the strongest recorded earthquake to hit the Imperial Valley, and caused widespread damage to irrigation systems and led to the deaths of nine people.

A surface rupture was formed during the earthquake of 40–60 km (25–37 mi), with a maximum, recorded displacement of 4.5 m (15 ft) close to the border. The sense of movement along the rupture was almost pure strike-slip, with no vertical displacement seen. During the 1979 Imperial Valley earthquake the same section of the fault ruptured on the US side of the border, but this time there was no sign of rupture on the Mexican side. 

The displacement pattern of the two earthquakes was very similar on the US side, suggesting that the Imperial Fault slips in discrete patches. Two of these patches are thought to have ruptured in 1940 but only the northern one in 1979.

Records of Burj Khalifa

Records of Burj Khalifa

• Tallest existing structure: 828 m (2,717 ft) (previously KVLY-TV mast – 628.8 m or 2,063 ft)
• Tallest structure ever built: 828 m (2,717 ft) (previously Warsaw radio mast – 646.38 m or 2,121 ft)
• Tallest freestanding structure: 828 m (2,717 ft) (previously CN Tower – 553.3 m or 1,815 ft)

• Tallest skyscraper (to top of spire): 828 m (2,717 ft) (previously Taipei 101 – 509.2 m or 1,671 ft)
• Tallest skyscraper to top of antenna: 828 m (2,717 ft) (previously the Willis (formerly Sears) Tower – 527 m or 1,729 ft)
• Building with most floors: 211 (including spire) previously World Trade Center – 110
• Building with world's highest occupied floor: 584.5 m (1,918 ft)
• World's highest elevator installation (situated inside a rod at the very top of the building)

• World's longest travel distance elevators: 504 m (1,654 ft)
• Highest vertical concrete pumping (for a building): 606 m (1,988 ft)
• World's tallest structure that includes residential space
• World's highest observation deck: 148th floor at 555 m (1,821 ft)

• World's highest outdoor observation deck: 124th floor at 452 m (1,483 ft)
• World's highest installation of an aluminium and glass façade: 512 m (1,680 ft)
• World's highest nightclub: 144th floor
• World's highest restaurant (At.mosphere): 122nd floor at 442 m (1,450 ft) (previously 360, at a height of 350 m (1,148 ft) in CN Tower)
• World's highest New Year display of fireworks.

Capillarity

Capillarity :

                  it is the ability of the soil to transmit moisture in all directions regardless of any gravitational force. Soil possess capillary action similar to a dry cloth with one end immersed in water. Water rises up through soil pores due to capillary attraction. the maximum theoretical height of capillary rise depends upon the pressure which tends to force the water into the soil, and this force increases as the size of the soil particles decreases. the capillary rise in a soil when wet may equal as much as 4 to 5 times the height of capillary rise in the same soil when dry.

1. Coarse gravel has no capillary rise; 
2. coarse sand up to 30 cm; 
3. fine sand and silts have capillary rise up to 1.2 m but dry sands have very little capillarity.
4. clay may have capillary rise up to 0.9 to 1.2 m but pure clay have low value.
5. in coarse-grained soils, the time required to reach the limit of the rise is much less than in fine-textured soils.  

Square measure or measure of surface

Square measure or measure of surface

[ British Units]*

144 sq.inches      = 1 sq.foot

9 sq.feet              = 1 sq. yard

301/4  sq.yards      = 1 sq.rod,pole or perch = 272 1/2  sq.ft.

40 sq.rods           = 1 rood = 1210 sq. yds.

484 sq.yards       = 1 sq. chain 

4 roods               = 4840 sq .yards = 160.sq. rods = 10 sq.chains

                           = 1 acre = 43,560 sq.ft.

640 acres            = 1 sq.mile

*An acre is the area of a square whose side is 208.71 ft.long. *

Nautical Measurements

Nautical Measurements

    A nautical or sea mile is the distance on the earth surface at the sea level of one minute of arc (1/60 of a degree) of longitude of earth at equator. 

              A nautical mile is taken equal to 6080.26 ft. or 1.1515 statute (or land ) miles-(5280x1.1515) by the British Admiralty, and 6086.07 ft. or 1.152664 statute miles by the US coast Survey Department. ( the statute or land miles being 5280 ft.)

          The international nautical mile is 6076.12 ft or 1852 meters, i.e. 1.15078 miles or 1.852 kilometer per hour.

          "knot" is a rate and not a distance and is used for expressing ship's rate of travel: 1 knot is one nautical mile or 6080 ft. per hour=1.1515 land miles (British Admiralty) per hour (or kilometers per hour.