STREET LIGHTING

Objectives of street lighting:

The objectives of street lighting are

1) Ensure that fast traffic moves safely,
2) Facilitates pedestrian movements,
3) Ensure that pedestrians and vehicle drivers recognize obstacles; and enhance security,
4) The first is only important for through routes. In residential areas, where traffic moves slowly, it will not be an important concern.

Definitions and description:

The lamp is the source of light, which converts electrical energy into radiation. The main types of lamps in use are:

1) Tungsten lamps (designated GLS): in which a small wire contained in a glass bulb is heated to a high temperature in a vacuum.

2) Fluorescent lamps (designated MCF and TL): in which ultra-violet radiation causes phosphor powder to glow inside a tube.

3) Discharge lamps: in which an electric current is passed through a mixture of gasses in a sealed tube. Examples are low-pressure sodium, high pressure sodium and high pressure mercury (designates SOX, SON and MBF or HPL-N respectively).

The lantern refers to the complete street lighting fixture, including the lamp and the pole or other means of raising it above the street

The luminous flux represents the quantity of radiation emitted by a lamp, measured in units of lumens.

The intensity of light by a lamp is measured in units of candelas.

The Luminance of a point on the road surface that is receiving light from a lantern equals the intensity of the light emitted by the lamp divided by the square of the distance of the point from the lamp.

It relates to the incident light falling on a surface and so is higher close to the lamp. It is measured in terms of lux (Lumens per square metre).

Another measure of the intensity of light is Luminance, which is a measure of the light reflected from the road surface. It is measured in candelas per square metre.

It is commonly used to assess lighting requirements for heavily trafficked roads and has limited relevance to the needs of low-income areas.

ANGANWADI BUILDING PLANS IN ANDHRAPRASEDHA

 

Credits: Architech Engineers, hyderabad

WASTE WATER TREATMENT

 Waste water and its characteristics:

The waste water  which is generated from 'kitchens, bathrooms, and other wash areas' is called "Grey water".
The waste water which is generated from 'Toilets' is called "Black water".

Grey water + Black water = Waste water

          In general, 80% of water used by the population comes out as waste water. If the water availability is 135 lpcd (Municipal+other sources), we consider 108 lpcd as the waste water generation. 

General characteristics of waste water is presented as below:

PARAMETER	HIGH	MEDIUM	LOW
COD Total	1,200	750	500
COD Soluble	480	300	200
COD Suspended	720	450	300
BOD	560	350	230
VFA (as acetate)	80	30	10
N total	100	60	30
Ammonia-N	75	45	20
P total	25	15	6
Ortho-P	15	10	4
TSS	600	400	250
VSS	480	320	200

What is Faecal sludge and septage?

The sludge produced by on-site sanitation systems like septic tanks is called "Septage".

The slude produced from pit toilets is called "Faecal sludge".

It is highly polluting than domestic waste water.

Faecal sludge quantity and quality

Supply based: It is estimated that 230 lts of Faecal Sludge is produced per capita per year.

Demand based: No.of septic tank emptying incidents X Capacity of the septic tank cleaning truck

Characteristics of Faecal sludge/septage is presented below:

Constituent All are units but for PH are in mg/l	Average
PH	1.5 - 12.6
Total suspended solids	12,862
Biochemical oxygen demand	6,480
Chemical oxygen demand	31,900
Ammonia-Nitrogen	97

 

Faecal sludge Management system (FSM):

Source: Bill And Gates Foundation

WORKABILITY OF CONCRETE !! SLUMP TEST ON CONCRETE

          Slump test on concrete is performed to check the concrete workability. A good workable concrete possesses good strength.

What is workability of concrete?

          Workability of concrete is defined as how easily concrete can be mixed, transported, consolidated, and placed in position in a homogenious state. Workability of concrete impacts concrete strength, quality, and therefore cost of labour for placing and finishing operations.

Methods of improving workability of concrete: 

• To increase the workbility we have to follow a few steps, they are:
• Increase water-cement ratio
• Using large aggregate
• Using well-rounded and smooth aggregate ratherthan irregular shape.
• By proper mixing time and temperature.
• By using non-porous and saturated aggregate.

The following tests are commonly used to check the workability of concrete, they are

1. Slump test

2. Compaction factor test

3. Kelly ball test

4. Flow test

5. K-Slump test

6. Vee-Bee consistometer test.

 

Reference: American Concrete Institute (ACI) Standard 116R-90 (ACI 1990b)

CALCULATION OF CEMENT, SAND AND WATER REQUIRED FOR PLASTERING

          Plastering is done to protect the wall or ceiling and also to remove surface imperfections caused by brickwork and to make the wall smooth for painting. 

          Plastering is done by using different materials like Cement, Clay, Lime etc., In this post we are discussing about cement plastering work. 

Calculation of Cement and Sand required or plastering:

          We have to remember some general points before going to plastering calculation, they are 

• Cement mortar ratio for wall plastering is 1:6, and for ceiling is 1:4. The ratios mentioned are volumetric ratios of cement and sand. (i.e., Cement:Sand = 1:6, 1 part of cement is mixed with 6 parts of sand for plastering).
• Plastering thickness should not be more than 12-20 mm including two coats.
• In two coat plastering work, the first coat of plastering is done with thickness 12 - 15 mm and this coat is called as "Primary Coating" (or) "Rough Coating".
• Second coating is done with 8 mm thickness, and this is called as "Secondary Coating" (or) "Finish Coat".

Steps involved in calculation of plastering quantities:

1. Calculate the wall area to be plastered in sqm (m²). Take assumption as 100 m².

2. Consider the ratio and thickness of plastering. (i.e., ratio 1:6 & thickness 12 mm).

3. Now we know the area of plastering and thickness, so by using this calculate the Total Volume of Plastering.

4. We know the Total Volume of Plastering and Ratio of plastering so we can calculate the Volume of Cement & Sand required individually.

Step 1 : Assumptions

Area of plastering = 100 m²,

Ratio of plastering = 1:6,

Thickness of plastering = 12 mm.

Step 2 : Volume of plastering

Volume of Plastering = Area of plastering X Thickness

                                        = 100 m² X 0.012 m = 1.2 m³ 

(Take 20% extra quantity, to fill joints & Wastage)

Step 3 : Find individual quantities of cement and sand required

Plastering Ratio = 1:6 

Total parts = 1+6 = 7

Quantity of cement required = 1.2 X 1/7 = 0.17 m³

Density of cement is 1440 kg/m³

Weight of cement = 1440 X 0.17 = 245 kg.

Quantity of Sand required = 1.2 X 6/7 = 1.03 m³

Density of sand is 1920 kg/m³ (It depends on moisture content)

Weight of sand = 1920 X 1.03 = 1978 kg.

Step 4 : Quantity of water required

Quantity of water required is 20% of Total dry material (Cement & sand)

Quantity of water = 20% (weight of cement + weight of sand)

                                 = 20% (245+1978) = 445 kg = 445 ltr

Like that we can calculate the requirement of cement, sand and water for any ratio and thickness of plastering work.