Hydroelectric power plants convert potential and kinetic energy of water into electricity.

In hydroelectric production, potential energy of water is created by the construction of large dams. The dams hold the water at a greater height than the water level at the turbines.

Water is the greatest contributor of renewable energy to the world electricity generating system.

The common unit of measurement used to indicate the installed capacity of a hydroelectric power station is Megawatts.

Types of hydroelectric power plants

Based of design, hydro electric power plants are broadly divided into 2 types;

1. Impoundment power plant
2. Diversion power plant.

In the impoundment type of power plant, All water coming into the plant is dammed. The dammed water creates the head needed to power the hydro plant.

In the diversion type, the water coming to the plant is partially dammed, some water is allowed to flow back into the river immediately while the rest is used to power the hydro plant.

Head and tail water

 In a hydro power plant system, the dammed water upstream is known as Head water and the water on the other side of the dam is known as Tail water. The difference between the top of the head water and that of the tail water is called pressure head.

Components of hydroelectric power plant

Trash rack; when water is coming fresh from the dam it needs to be cleared of big debris such as wood , plastic bags etc. the duty of the trash rack is to remove these.

Inlet gate; after water have been processed to remove debris, it then passed through the inlet gate. The inlet gate is used to regulate water flow into the turbines

Water conductors; water conductors are equipment used to convey water within the hydo electric power system. Example include; penstock, draft tube, scroll case, spill way, canals etc.

Penstock; the main pipe that conveys water to the turbine is known as penstock. It is a pressurized water conductor.

Spill way;  a spillway is a water conductor used to prevent overflow of dammed water

Runner; the runner is part of the turbine system and it rotates as water from the penstock passes through it at high pressure

Power house; the power house houses the turbine, electric generators, transformers and other electric generating equipment

Open air switch yard; when the electrical transmission equipment is installed in open air, it is called an open air switch yard.

How a hydroelectric turbine works

Water with high pressure head on the upstream side of the dam is lead through large penstock pipe. Before the water get to the turbine it passes through a scroll case. The scroll case is a large curved pipe that helps the flowing water to efficiently rotate the turbine. The turbine is connected to the generator through a shaft. so  as the turbine rotates, the connected generator also rotates  producing electricity.

Advantages of hydroelectric power plant.

1. It is a completely green process
2. It is a very efficient way of generating electricity.

Disadvantages of hydroelectric power plant

1. It is always necessary for settlement around the dammed area relocate. This is because water required to run hydroelectric plants is extremely large and dammed water will cause flooding of the settlement.

2. It is capital intensive. This is because the hydro dams constructed are extremely large.

Types of hydro power plants

1. Impoundment type power plant. This type of power plant utilizes a dam to impound large amount of flowing river water. The dammed water is the potential energy necessary to power the hydro plant. The different type of dams that could be used include; gravity, reinforced concrete, buttress, rock filled or earth dams.
2. Diversion type power plant( run of the river). In this case, the river water is partially dammed, only part of the flowing water is utilized to produce electricity.
3. Tidal water plant. This process works based on tidal action of water. it helps create a height difference on either side of the turbine, this pressure difference cause water to flow through the turbine rotating it.
4. Pumped storage power plant. This type of plant basically consists of very large reservoir of water held at a very high level. The stored water is then made to flow downwards through a penstock pipe to run the turbine and generate electricity. After reservoir is depleted, the water is pumped back again and the whole process is repeated. Pumped storage power plant is a type of standby power generator.Its acts as a supplement and is usually made available to the national grid during peak hours

Types of turbines

Broadly of two types;

1. Reaction turbine
2. Impulse turbine

The reaction turbine are pressure turbines. When water flow through this turbine, it creates a pressure differential which causes the turbine to rotate.

Impulse turbine are pressure-less turbines. It rotates due to the kinetic energy given to it by a jet of water as its hits the blades.

Types of turbine runners

There are many types of turbine runners, however, the 3 most commonly used are;

1. Kaplan runner
2. Francis runner
3. Pelton runner

Kaplan runners are types of turbine runners that can operate with medium to high water flows and efficient at low pressure heads. Kaplan runners are reaction  runners because the pressure difference of the water flowing through the blades causes it to rotate.

Francis runners  are reaction runners and can operate within a wider range of pressure heads than the Kaplan runners.

Pelton runners are only adequate for very high flows and operates within a narrower range compared to the Kaplan and Francis runners.

On a construction site it may become necessary to estimate the number of blocks required for the construction of a wall. To do it correctly you will need to read the construction plan or building plan and section drawing. From the building plan you will need to know;

1. The length of the wall
2. The height of the wall
3. The thickness of the wall
4. Window or door spaces within the wall unit.

In most cases, the thickness of the wall is not required unless the wall thickness is greater than the width or thickness of the block.

How to estimate the number of blocks using AREA METHOD

This method requires that you know the number of blocks required to construct 1m² of wall. For a normal block size of length 450mm, height 225mm, and width 225mm, with thickness of wall the same as the block, there is approximately 8 blocks per 1m². Simply put; 8 blocks per m² 

The above result was obtained practically, however other calculations report a value of between 8-10 blocks per m² .

How to practically obtain the number of blocks per unit area

You can obtain the result practically, look for an already constructed wall of similar type you want to build. The wall should still show the exposed block work, or is not yet rendered. Then with a builders square or builder’s level, draw a square of 1m dimension on the wall using a chalk or erasable material. The square you draw should have an area of 1m² .Next, count the number of blocks that fall within the square. The result you get is the number of blocks per square meter. This method works for any size of block or brick.

Now that you have the amount of blocks per m² , look at the building and section plan then calculate the area of the wall using the area formula of length x height .  From this wall area, deduct any area of door and window spaces. Finally multiply the wall area by number of blocks per unit area or per m² . (note the unit)

Formula for number of blocks required = (Area of wall) X (no. of blocks per unit area)

Simple example;

A wall of length 5m and height 3m will have an area of

5m X 3m = 15m²

Therefore number of blocks = 15m² X 8 = 120 Blocks.

How to estimate the number of blocks using DIMENSION METHOD

This method involve using the block dimensions to estimate the number of blocks required for a wall construction.

Lets assume you are required to estimate the number of blocks in foundation required to fence a plot of land. Block will be laid in stretcher bond. The height of wall in foundation being about 450mm. and we are to use block size of length 450mm, height 225mm, and width 225mm. The dimensions of the plot of land being 30m by 15m. Here is what you do;

Perimeter of plot of land;

2 X (30+15)m = 90m

Since the wall will be constructed in stretcher bond, you will just divide the perimeter of the plot of land by the length of the block;

90m / 0.45m = 200 blocks          ( note; 450mm is converted to m by dividing it by 1000)

This 200 blocks is the approximate number of blocks required for the 1^st layer in foundation.

Since the height of wall in foundation is 450mm, it means we will have 2 layers of blocks in foundation i.e. 450mm / 225mm (height of block) = 2

Hence total blocks required for foundation is 200 blocks X 2 = 400 blocks

Load combination.

The load combination for reinforced concrete design is 1.4G_k + 1.6Q_k where G_k and Q_k represent dead and imposed loads respectively. 1.4 and 1.6 is the factor of safety for dead and 1.6 is the factor of safety for imposed loads.

Other local combinations include; 1.2 G_k+1.2Q_k+1.2W_k where W_k represents wind load.

For full information on load combinations see table 2.1 page 9 of BS 8110 part 1, 1997.

In reality however, various load combinations of dead, imposed and wind loads should be considered. This is to ensure that the structure is designed for the worst possible case.

Load cases:

While it is ok to load all parts of the structure using 1.4G_k + 1.6Q_k­, it is also to be appreciated that theoretically, these loads can vary i.e from 1.0 G_k to 1.4 G_k and 0.0 Q_k to 1.6 Q_k, in the light of these, various load cases need to be considered to achieve an accurate design.

For example, assuming we are working on a 3 span beam with G_k of 25kN/m and Q_k of 10kN/m. It is good practice to consider the following load cases;

Case 1: loaded even spans with 1.4G_k + 1.6Q_k­ and odd spans with 1.0G_k.

Case 2: loaded odd spans with 1.4G_k + 1.6Q_k­ and even spans with 1.0G_k.

Case 3: All spans with 1.4G_k + 1.6Q_k­  

Each load case is analyzed for bending moments and shear forces.

Bending moment diagrams for each load case. (all values in kNm);

CASE 1. (Even spans loaded):

CASE 2. (Odd spans loaded):

CASE 3. (All spans loaded)

The results of load cases are then compared. So for any beam span, the highest value of bending moment and shear forces of the 3 load cases is taken for design.

Final Result.

Reference.

Mosley & Bungey, Reinforced concrete design. 5^th Ed. Page 30.

BS 8110 part 1, 1997.

Hello, today I am introducing to you an excel spreadsheet program specially created to help design one way continuous reinforced concrete slabs. A one way slab is a slab in which its length divided by its breadth is greater than or equal to 2. However, a slab with length/ breadth ratio of not less than 1.5  can still be designed as one way. The spreadsheet named RCC31 designs to BS 8110 and it is free. It was developed by the Reinforced concrete council and its been around for a while.

You can download this spreadsheet by clicking the link below.

https://drive.google.com/open?id=0BzV9-YpG96e7NDdIRVdMckNrZVE

How to use Excel Spreadsheet Program for One way slab design.

You can watch the video by clicking the link below to see how its works. https://www.youtube.com/watch?v=0tQFdL0LwqA

At the top of the spreadsheet is the title section. This is where you input title data for the slabs being designed. You can input names of the project and client as well as other title information.

Below it is the materials section where you can input material strength properties of concrete and steel. Including factors of safety.

In the span section you can set slab span and thickness, note the units.

Under loading pattern you set factor of safety values for dead and imposed load.

At the supports section, you can set 3 types of supports, including, kinife, cantilever and encastre.

A look at the loading section, and you will realize the spreadsheet can handle up to six slabs at once.You can input dead imposed and point loads n this section. Again note the units in which the loads should be provided.

Now all what I have explained so far is within the MAIN tab of the spreadsheet. To see the calculated span and support moments, click the ACTIONS tab.

To see calculated and design steel reinforcements, click the SPANS tab.

In the SPANS tab notice that top and bottom reinforcements are provided in the left right and center for each span designed. However in your detailing you can rearrange reinforcement for example, in each span you can pick the highest designed bottom reinforcement occurring either in the left, centre or right end and use as general for the whole span.

If design fails in maximum spacing ( max S), reduce size of reinforcement bar.

Civil engineering is a vast discipline with various subject areas. Common subject areas which a Civil engineer is required to have general knowledge of, is as follows;  

Surveying.

Surveying is the science of map making. To start any development activity, the relative positions of various objects in the area with respect to horizontal and vertical axes through a reference point is required. This is achieved by surveying the area. Earlier, the conventional instruments like chain, tape and levelling instruments were used. In this electronic era, modern electronic equipments like electronic distance meters (EDM) and total stations are used, to get more accurate results easily.

Construction Engineering.

Construction engineering is a professional discipline that deals with the designing, planning, construction and management of infrastructure such as buildings, highways, bridges, airports, dams, railroads etc.

Structural Engineering.

Structural engineering involves the application of maths and science to determine the appropriate type and sizes of component members required to build a structure. It involves structural analysis and Design. Structural analysis involves finding the internal stresses in components of a structure. It enables engineers understand the effects of load/stresses caused by gravity, the users of the structure, and the widely varying climatic conditions and ground conditions. Choosing appropriate materials for the structure as well as finding suitable sizes of structural components is known as structural design.

Structural engineering also involves analysis of various structures like buildings, water tanks, chimneys, bridges etc. And designing them using suitable materials like masonry, wood concrete, reinforced concrete, prestressed concrete or steel. A structural engineer should design safe and economic structures using mathematical optimization techniques.

Earthquake Engineering.

Earthquake engineering involves the study of occurrence, magnitude and behaviour of earthquakes forces and the design of structures that can resist them. It is also the study of behaviour of structures and geo-structures subject to seismic loading as well as protecting the society (the natural and man-made environment) from earthquakes by limiting the seismic risk to socio-economically acceptable levels.

Foundation engineering.

Foundation engineering involves the determination of suitable soil type and safe bearing capacities of soil suitable for foundation of buildings. It also involves the various studies required for design of pavements, tunnels, earthen dams, and canals as well as ground improvement techniques.

Quantity Surveying.

Quantity surveying deals with estimating what a construction project will cost. The determination of total cost of a construction project includes knowledge of material cost, labour cost, contract cost, contingency cost etc.

Quantity surveying also involves managing all costs relating to building and civil engineering projects, from initial calculations to final figures.

Fluid Mechanics.

Fluid mechanics involves the study of mechanics of fluids and flow characteristics in order to design and construct efficient hydraulic structures. Civil engineers are more involved in the mechanics and flow characteristics of water.

Irrigation Engineering.

Water is to be supplied to agricultural field. Hence suitable water resources are to be identified and water retaining structures are to be built. Identifying, planning and building water retaining structures like tanks and dams and carrying stored water to fields is known as water resources and irrigation engineering. Constructing canals, aqueducts and regulators form part of irrigation engineering.

Transportation Engineering.

Design of good roads involves the design of base courses, surface finishes, cross drainage works, road intersections, culverts, bridges and tunnels. Roads need suitable design of horizontal and vertical curves also. Railway is another important long way transport facility. Design construction and maintenance of railway lines and signal systems are part of transportation engineering. Design, construction and maintenance of harbours and airports are also the need of globalization era. For proper planning of these transport facilities traffic survey is to be carried out. All these activities constitute the transportation engineering.

Environmental Engineering.

 Environmental engineering is the application of engineering principles to improve the natural environment, to provide healthy water, air and land for human habitation and for other organisms, and to clean up pollution sites. It involves study of sources, causes, effects and remedial measures associated with air pollution, water pollution, land pollution and noise pollution forms, as well as supply of potable water to rural areas, towns and cities as well as disposal of waste water and solid waste.

Town Planning.

Town planning involves the design and regulation of the use of space that focus on the physical form, economic functions, and social impacts of the environment and the location of different activities within it.

New towns, cities and extension areas of existing cities are to be planned properly so that suitable communication systems, educational facilities medical facilities, shopping centres are provided along with residential areas.

Project Management.

Project management is the application of knowledge, skills and techniques to execute projects effectively and efficiently. Civil engineers are involved in managing construction projects from start to finish.

In addition to acquisition of general knowledge of all subject areas described above. The civil engineer by education and experience will go on to specialize in one or 2 of them. So it is not enough for one to say he is a civil engineer, he or she should also state subject areas of specialization in the field.

Retaining walls are designed and constructed to retain certain amount of soil at a particular location. Retaining wall must prevent any movement of soil it is designed to hold back so as not to cause damage to buildings properties nearby.

A good retaining wall must adequately resist sliding and overturning forces of the retained soil acting on it. To achieve this , the retaining wall must be designed to determine the correct size and amount of reinforcement required.

The design of retaining walls is very tedious and time consuming. However you can take advantage of this free retaining wall design SPREADSHEET to aid your design. It is a free spreadsheet created with Microsoft excel that designs retaining walls to BS 8110.

Credit goes to the Reinforced Concrete Council UK for making this spreadsheet free.

You can download  RETAINING WALL DESIGN WITH EXCEL SPREADSHEET HERE

You can also watch the video through this link; https://www.youtube.com/watch?v=3PF43tc41f4

How to use Retaining wall design with excel.

You enter data into cells with blue text.

In the first six rows of the spreadsheet you can enter name of project, client, date, job title and even logo.

From row 7 to row 21, you see a diagrammatic retaining wall explaining member dimensions and forces acting on it.

Row 22 to 26 you enter or edit retaining wall dimensions such as length and thickness of stem and base.

You enter material properties data such as strength and factor of safety for concrete and steel in row 27 to 32.

Enter soil properties data in row 33 to 41.

Lastly you enter load data in rows 43 to 53.

If data you have entered is ok, you will see design status read VALID in row 7.

Check the stability calculations by clicking the STABILITY TAB at the bottom of the spread sheet.

Required calculated Reinforcement for retaining wall can be viewed by clicking the DESIGN TAB. Similarly you can click the WEIGHT, Diagrams, Crackwidth and Notes TAB for more information.

To use excel spreadsheet to aid your design of pad footings you can read this POST