Civil Engineering Terms

Bridge definition

Bridge is a structure which covers a gap.

It is a structure carrying a path way or road way over a depression or obstacle.

Function

Generally bridges carry a road or railway across a natural or artificial obstacle such as river, canal or another railway or another road.
It is a structure corresponding to the heaviest responsibility in carrying a free flow of transport.
It is the most significant component of transportation system in case of communication over spacing and gaps. In short bridge is the key element in the transportation system.

Bridge controls the capacity of the system

If the width of a bridge is insufficient to carry the number of lanes required to handle the traffic volume, it will be a constriction to the flow of traffic.

If the strength of a bridge is deficient and unable to carry heavy trucks, load limits will be posted and truck traffic will be rerouted. Hence it controls both the volume and weight of the traffic carried by the transportation system.

Highest cost per mile of the system

Bridges are expensive. The typical cost per mile of a bridge is many times greater than that of roads. Since it is the key element of transportation system, so there must be balance between its cost and handling of future traffic volume and loads.

If the bridge fails, the system fails

The importance of a bridge can be seen by considering the comparison between the two main components of a highway system i.e. a road and bridge.

Suppose in a road there occurs deterioration and ultimately a crack, thus making a sort of inconvenience but it wont result in stopping of the flow of traffic. As traffic can pass or otherwise a bypass can be provided.

But in case of bridge its flow is completely stopped in case of failure of bridge. That is the reason it is often called

If the bridge fails the structure fails. As the function of structure could not be served at all.

Definition of Shoring

Shoring is the construction of a temporary structure required to support an unsafe structure.

Why Shoring is required ?

It is provided to get stability of a structure temporarily during construction, repair or alteration.

Such situations arises when

Stability of the structure is in danger due to removal of some defective portion of the structure.
There is unequal settlement during construction or in long run.
Alterations are to be done in the existing structure such as remodeling of walls or changing position of windows.
Alterations are carried out in adjacent building for remodeling or strengthening of foundation.

Installation of shores

It may be of timber or steel tubes. Sometimes both are used simultaneously. If timber is used its surface should be coated with preservative so that it may not get wet rot.
It is so designed on the basis of load it has to sustain and duration of load.
Shoring may be provided internally or externally depending on the case. In some cases they are provided on the both sides of the walls.
There is no time limit, it may range from weeks to years depending on the case.

The shores may be of the following types:

Raking or inclined shores

In this method, inclined members called rakers are used to give temporary lateral support to an unsafe wall.

Flying or horizontal shores

In this method, horizontal temporary support is provided to two adjacent, parallel partition walls of the two buildings where the intermediate building is to be pulled down and rebuilt.

Dead or vertical shores

In this method, vertical support is provided to walls, roofs, floors etc. when the lower part of the wall has to be removed for the purpose of providing an opening the wall.

Damp proofing course

A continuous water proof layer is provided above the ground level to prevent moisture to come up which is called damp proof course or simply DPC.

In order to prevent dampness in the building, damp proof courses DPC are provided at various points of entry of moisture into a building. At present, all building are provided withdamp proof courses. So the provision of DPC prevents the entry of moisture from walls, floors and basement of a building.

Causes of dampness in a building

Bricks have a porous structure and the pores are interconnected to form capillaries. As a result bricks suck dampness from the soil underneath and pump it to upper parts of the building under the action of capillary force.

Other causes are:

Rising of moisture from the ground.
Rain travel from wall tops.
Rain beating against external walls.
Condensation.
Poor drainage, imperfect orientation, imperfect roof slope, defective construction etc.

If there is any direct contact between the underneath soil and brickwork of super structure even for a very small part, whole of the building will be affected.

Effects of Damping

With dampness, mortar and concrete deteriorate, reducing the strength of the structure.
With time, plaster falls down and surface treatments like white washing and painting are damaged leading to unpleasant appearance.
Further these damp conditions are not good from hygienic point of view.

Characteristics of ideal damp proofing material

It should be perfectly impervious.
It should be durable.
It should be strong and capable of resisting superimposed loads coming on it.
It should be flexible, so that it can accommodate the structural movements without any fracture.
It should remain steady in its position when applied.
It should not be costly.

Materials used for Damp proofing

DPC to be provided in walls consists of 1.5 inch to 3 inch thick layer of P.C.C. (1:2:4) over which two coats of hot bitumen are applied. Sometime for load bearing walls, polythene sheet is also provided.

Materials commonly used for damp proofing are hot bitumen, mastic asphalt, bituminous or asphaltic felts, metal sheets, combination of sheets and felts, stones, bricks, mortar, cement concrete, and plastic sheets.

Things should be kept in mind while providing DPC

The top of DPC is made in level with the ground floor top of the building.
Damp proof course may be horizontal or vertical.
Horizontal damp proof course should cover the full thickness of walls excluding rendering.
DPC should be so laid that continuous projection is provided.
At junctions and corners of walls, horizontal DPC should be laid continuous.
Mortar bed supporting the DPC should be even and levelled and should be free from projections so that DPC is not damaged.
DPC should not be kept exposed on wall surface, otherwise it may get damaged during finishing work.
When a horizontal DPC (that of a floor) is continued to a vertical face, a cement concrete fillet of about 75 mm radius should be provided at the junction.

Deep foundation

When the depth of foundation is equal to or greater than its width, the foundation is termed as deep foundation.

The deep foundation are of the following types:

Pile foundation.
Pier foundation.
Caisson or well foundation.

1.Pile foundation

A pile is a long vertical load transferring member composed of either timber, steel or concrete. In pile foundation, number of piles are driven deep in the base of the structure.

The pile foundation is generally used when:

the soil is compressible.
soil is water logged.
and soil is made up type.

It is most suitable for bridges. Out of deep foundation types, pile foundation is the more commonly used in construction.

2.Pier foundation

In pier foundation, hollow vertical shafts are driven up to the hard bed. This hollow potion is then filled up with inert material such as sand or lean concrete.

Pier foundations are specially suitable for:

heavy structure such as fly overs in sandy soil or soft soil overlying hard bed at reasonable depth.

3.Caisson or well foundation

The open caisson called well is a box of timber, metal, reinforced concrete or masonry which is open at both at the top and at the bottom and is used for building and bridge foundation.

The well foundation is the most common type of deep foundation for bridges in India.

Definition of Shallow foundation

The foundation may be broadly classified as shallow foundation and deep foundation.

A foundation is said to be shallow if its depth is equal to or less than its width.

Types of shallow foundation

The shallow foundation are of the following types:

1.Spread footing

Spread footing is the one which transfer the super imposed load of the structure over the large area. Spread footing may be of the following types:

Single footing for a column.
Stepped footing for a column.
Sloped footing for a column.
Wall footing without steps and with steps.
Grillage foundation.

The base of first three types of foundation for a column is made of concrete.

When heavy structural loads from column are required to be transferred to a soil of low bearing capacity, the most economical foundation is Grillage foundation. The depth of such foundation is 0.6 to 1.9 m or 1.97 ft to 6.23 ft.

2.Combined footing

The common footing which is constructed for two or more columns is called combined footing.

The shape of combined footing is so proportioned that the center of gravity of the supporting area is in line with the center of gravity of the two column loads. The general shape of combined footing is either rectangular or trapezoidal.

Combined rectangular footing

A combined rectangular footing is provided where loading conditions is such that both the columns are equally loaded or the interior one carried greater load.

Trapezoidal combined footing

A trapezoidal combined footing is provided under any condition of loading.

3.Strap footing

When two or more footings are connected by a beam, then this is called strap footing.

It may be used where the distance between the columns is so great that a combined trapezoidal footing becomes quite narrow, with high bending moments.

4.Mat or raft foundation

A foundation consists of thick reinforced concrete slab covering the entire area of the bottom of the structure, is known as mat or raft foundation.

Where we use mat or raft foundation?

When the allowable soil pressure is low.
or the building loads are heavy.
and if the required area of the footing is more than half the total area of the structure, then it is more economical to use mat or raft foundation.

Construction Stages

Following are various stages in every construction work.

Conception or ideas of the owner concerning the project.
Study and evaluation.
Design, drawings and estimates.
Specifications.
Contractor realization or attainment.
Procurement of materials.
Construction and Super vision.
Utilization and maintenance.

Construction Team

Construction work cannot be completed by a single person. It requires a team of wokers with the specific duties.

Construction team includes:

Owner.
Engineer.
Architect.
Designer.
And Contractor or builder.

Responsibilities of Owner

The conception of idea for any construction work is the responsibility of the owner. He is both financer and beneficiary of the work.

Responsibilities of Engineer

The engineer is a professional man and is responsible for the safe design and construction of the work under his super vision. The field of activities of an engineer includes:

Designing.
Drawing estimation.
Approval of construction plans by the local development authority.
Tendering.
Supply of material as per contract.
Inspection of quality.
Inspection progress of work done by the contractor.
Measurement of work and,
Payment of work.

Engineer is also consulted by the architect regarding estimation etc.

Responsibilities of Contractor

Contractor is responsible for the material not supplied by the owner, organising, planning and execution of work as per given drawings and specifications laid down in the contract.

Softening of Water

Water treatment for the removal of water hardness or dissolved impurities from water, is known as softening of water.

Hard water

Water contains chlorides, sulphates and bicarbonates of calcium and magnesium is referred as hard water.

The hardness may be temporary or permanent.

Temporary hardness

The hardness of water due to carbonates and bicarbonates of calcium and magnesium is known as temporary hardness.

Temporary hardness may be removed by

boiling the water.
by adding lime water in the water. The process of adding lime water in water is known as lime process.

Permanent hardness

The hardness of water due to sulphates, chlorides and nitrates of calcium and magnesium is known as permanent hardness.

Permanent hardness of water may be removed by

lime soda process.
zeolite (silicate of sodium).
base exchange process (also known as cation exchange method).

The research process eight steps

1-Formulation of a research problem

This is the first and the most important step of the research process. It identifies your destination.

As in the absence of destination, it is impossible to identify the shortest route. In the absence of a clear research problem, a clear and economical plan is impossible.

If one wants to solve the problem, then it must be clear to him that what actually is the problem. It can be said that large part of the problem lies in knowing what one trying to do.

A research problem may take a number of forms, from the very simple to the very complex one. The way you formulate the problem determines every step that follows:

the type of study design that can be used.
the type of sampling strategy.
research instrument that can be used or developed.
the type of analysis that can be undertaken.

Hence you should give it considerable and careful thought at this stage.

It is extremely important to evaluate research problem in the light of the financial resources available, time available, your and your research supervisor’s expertise and knowledge in the field of study. It is equally important to identify any gaps in your knowledge of relevant disciplines, such as statistics, required for analysis. If you have a plan to use computer software then you must have sufficient knowledge of that.

2- Conceptualising a research design

An extremely important feature of research is the use of scientific methods. Research process involves systematic, controlled, valid and carefully established associations and causes that permit similar outcomes under the given set of conditions.

Research process also involves

identifying gaps in knowledge.
verification of what is already known.
Identification of past errors and limitations.

The validity of what you find largely rest on how it was found.

Main function of research design

Main function of research design is to explain how you will find the answers to a research problem.
The research design sets out the logic of our inquiry.

The research design should include the following:

The study design.
Logistical arrangements that you suppose to undertake.
Measurement procedures.
Sampling strategy.
Frame of analysis and time frame.

For any inquiry, the selection of an appropriate research design enable you to arrive at valid findings. A faulty design will result in misleading findings and is therefore wasting human and financial resources.

When selecting a research design it is important to ensure that:

It is valid workable, and manageable.

There are number of study designs. You need to be equipped with the most common ones. Select or develop the design that is most suited to your study. You must have strong reasons for selecting a particular design. You must be aware of its weaknesses and limitations.

3-Constructing a Research tool for data collection

Research tool may be defined as:

Anything that becomes a means of collecting information for your study is called a research tool or a research instrument. For example, observation forms, interview schedules, questionnaires, and interview guides are all classified as research tools.

Constructing a research tool is the first practical step in carrying out research process. You will need to decide how you will collect the data then you construct a research instrument for this.

If you are planning to collect data specifically for your research then you have to develop a research instrument or select an already developed one.

If you are using a secondary data (information already collected for other purposes), develop a form to extract required data.

Field testing a research tool is an important part. But as a rule, field testing should not be carried out on the sample of your study but on a similar population.

4-Selecting a Sample

The accuracy of your estimates largely rest on the way you select your sample. The basic objective of any sampling design is to minimise the gap between the values obtained from your sample and those prevalent or dominant in the population.

The underlying theory in sampling is that, if a relatively small number of units is scientifically selected, it can provide a fairly true reflection of the sampling population being studied.

Sampling theory is guided by two principles:

Avoidance of bias in selecting sample.
the attainment of maximum precision for a given outlay of resources.

There are three categories of sampling design:

Random sampling designs.
Non random sampling designs.
Mixed sampling designs.

There are many sampling strategies within the first two categories. You need to be equipped with these sampling designs to select the one most appropriate for your study. You need to know the strength and limitations of each. You also need to know the situations in which it can or it cannot be applied in order to select the most appropriate design. The type of sampling strategy you use also determines your ability to generalise from the sample to the total population and the type of statistical tests you can perform on the data.

5-Writing a research proposal

Before writing a research proposal, you have done all the preparatory work. Next put everything together in a way that provides adequate information. This will give information about your research report to your research supervisor and others.

This overall plan tells a reader about your research problem and how you are planning to investigate, and is called a research proposal.

The main function of research proposal is to detail the operational plan for obtaining answers to your research questions. It ensures readers of the validity of methodology adopted to obtain answers.

Universities and other institutions may have different requirements about the contents of research proposal. Requirements may also vary within an institution, from discipline to discipline or from supervisor to supervisor.

A research proposal may tell you, your supervisor and the reader the following things:

What are you proposing to do.
How you plan to proceed.
Why you selected the proposed strategy.

A research proposal must contain following information about your study.

A statement of the objectives of the study.
a list of hypothesis, if you are testing any.
the study design you are proposing to use.
the setting for your study.
the research tool you are planning to use.
information on sample size and sampling design.
information on data processing procedures.
an outline of the proposed chapters of the report.
the study problems and limitations.
the proposed time frame.

6-Collection of Data

Having formulated a research problem, developed a study design, constructed a research instrument and selected a sample. Now you collect the data from which you will draw influences and conclusions for your study.

Many methods could be used to gather the required information. As a part of research design, you will decide the procedure through which you want to collect the data.

At this stage you actually collect the data.

For example, depending upon your plans, you might commence interviews, mail questionnaire, conduct group discussions or make observations. Collection of data by any method may involve some ethical issues as well.

7-Processing of data

The way you analyse the information largely depends on two things:

the type of information: descriptive, qualitative, quantitative or attitudinal.
the way you want to write your report.

There are two broad categories of report: quantitative and qualitative. The difference is more academic than real. Because in reality you need to combine quantitative and qualitative skills. But there are some only qualitative and some only quantitative studies.

In addition to qualitative and quantitative distinction, it is equally important for data analysis that you want to analyse it manually or by a computer.

If your study is purely descriptive, you can write your report on the basis of your field notes, manually analyse the contents of your notes, or use a computer program such as Nudist or Ethnograph for this purpose.

If you want quantitative analysis, it is also necessary to decide:

upon the type of analysis required. For example frequency distribution, cross-tabulations, regression analysis, factor analysis or analysis of variance etc.
how it should be presented.
variables to be subjected to these statistical procedures.

8- Writing a research report

Writing the report is the last and for many, the most difficult step of the research process. This report informs the world of

what you have done.
what you have discovered.
and what conclusions you have drawn from your findings.

If you are clear about the whole research process, you will also clear about the way you want to write your research report. Your report should be written in academic style and be divided into different chapters and sections based upon the main theme of your study.

Definition of Concentrated or Point load

A load acting at a definite or specific point of a beam is known as point load or concentrated load.

That is called concentrated because that load is focusing on a single point.

Uniformly distributed load

The load that is acting on a beam in such a way that each unit length is loaded to the same extent, is known as uniformly distributed load.

It may be expressed as Kg/meter or lb/ft. It is abbreviated as U.D.L.

Uniformly varying or Gradually varying load

A load which is acting on a beam in such a manner that it varies uniformly on each unit length, is known as uniformly varying or gradually varying load.

Triangular load

If the load is zero at one end and increases uniformly to maximum at the other end, then this type of load is known as triangular load.

Definition of Overhanging beam

A overhanging beam may be defined as:

A beam having its end portion extended beyond the support, is known as overhanging beam. It may be overhanging on one side or on both sides.

Fixed beam

A beam whose both ends are fixed is known as fixed beam.

Continuous Beam

A beam supported on more than two supports is known as continuous beam.

Ozone Layer

Ozone layer is the region of the atmosphere, that is earth’s natural sunscreen, since it filters out harmful ultraviolet rays from sunlight before they can reach on the surface of our planet and cause damages to human and other life forms.

Ozone Layer is present in the upper and middle region of the stratosphere.

Units

The total amount of atmospheric ozone is expressed in terms of Dobson Units (DU).

Each Dobson Unit is equivalent to a 0.001 mm thickness of pure ozone at the density it would possess if it were brought to ground level (1mm) pressure.

Ozone Concentration

Normal amount of overhead Ozone at temperate latitudes is 350 DU. Because of stratospheric winds Ozone is transported from tropical towards polar region. Tropical is the region of the earth surrounding the equator. So there is less amount of Ozone protecting you if you are living closer to the equator. Ozone concentration in the tropics usually average 250 DU. Whereas in sub polar regions it is about 450 DU except where holes appear. There is also some seasonal variation in ozone concentration.

Creation of Ozone in Stratosphere

In the stratosphere, intensity of UV-C photon is much less as the oxygen lying above it filters most of it. High energy UV-C radiation strikes on oxygen molecule and causes it to split into two free oxygen atoms in the stratosphere. Since the concentration of Oxygen molecules in the stratosphere is large, the fewer oxygen atoms formed as a result of decomposition are more likely to collide with these oxygen molecules to form tri atomic oxygen molecule called Ozone.

This reaction is the source of all the Ozone in the atmosphere. During daylight, Ozone is constantly formed by this process. The rate of Ozone production depends upon:

Amount of UV light.
Concentration of Oxygen molecules at the given altitude.

Above the stratosphere, air is so thin that most of the oxygen exist in atomic form because of sufficient amount of UV and it does not support the formation of Ozone. On the other hand, below the stratosphere where there is sufficient amount of Oxygen molecule, sunlight is devoid of the high energy UV radiation. Therefore the most suitable conditions for the ozone production are in the upper and middle portion of stratosphere where both the factors are present in the reasonable ratio.

Most of the Ozone is located in the region between 15 and 35 km, known as Ozone layer or Ozonosphere.

Hole in Ozone Layer

The destruction of ozone molecules by CFCs seems to cause a seasonal reduction in ozone over Antarctica called the Ozone hole.

Green house Gases

By their percentage contribution to the green house effect on Earth the four major green house gases are:

water vapor.
carbon dioxide.
methane.
ozone.
CFCs.

Carbon dioxide

During spring and summer

CO2 highly removed from air during spring and summer due to Photosynthesis in plants.The carbon dioxide captured by the photosynthesis is no longer free to function as a green house gas or as any gas. Because it is packed away in the polymeric form, typically the cellulose that gives wood its mass and bulk.

The carbon that is trapped in this way is called as free carbon.

That is why it is suggested to plant more and more trees. As they tend to clean air by fixing carbon dioxide. On one hand removal of carbon dioxide from the air causes a cooling effect on the other hand the enhanced transpiration from the surface of the leaves further reduces temperature.

During fall and winter

However the biological decay of plant material, very reverse of this reaction occurs in fall and winter replace the withdrawn CO2. The annual fluctuation in the carbon dioxide concentration are due to the growth in spring and summer that removed carbon dioxide from air and decay cycle in fall and winter that increases the concentration of carbon dioxide.

Some scientists suspect that the rate of photosynthesis increases as the amount of CO2 and air temperature increases. However, there is no doubt that atmospheric concentration of CO2 is increasing which is resulting from burning of fossil fuels for cooking, cleaning, heating, cooling, washing, drying, transporting and manufacturing.

Much of the increase in carbon dioxide concentration is due to the combustion of fossil fuels mainly coal, oil and natural gas.

On average, each person is responsible for the release of about 5 metric tons of carbon dioxide from carbon containing fuels each year.

Some of this release is direct in the form of exhaust gases when vehicles are driven.

While some of this is indirect for example,

when energy is used to produce and transport goods.
to heat and cool factories, classrooms and offices.
produce and refine oil.

A significant amount of CO2 is added to atmosphere when forest are cleared and the wood burned in order to provide land for agricultural use.

About half of the CO2 emission currently find a sink. Much of it is removed from the atmosphere by dissolution in seawater. It is also important to remember that rising global temperature tends to increase the temperature of oceans as well. Due to this ability of upper layer of oceans to absorb CO2 may be decrease. Because the solubility of gases in water decreases with increasing temperature.

Water Vapors

Water molecules, always abundant in air, are the most important green house gas. Although on a per molecule basis, it is less efficient absorber than is CO2.

H2O in form of liquid droplets in the clouds also absorb thermal IR. However such clouds reflect some incoming sunlight both UV and visible back into space.

It is not yet clear that the additional cloud cover produced by increasing water content will have a net positive or net negative contribution to the global warming.

Clouds over tropical region including Pakistan are known to have a net zero effect. However, those in northern latitudes produce a net cooling effect since their ability to reflect sunlight is more than their ability to absorb IR.

CO2 absorb maximum light in 14- 18 um on the other hand water vapors absorb maximum light in 4-8 um ranges. Only IR light from 8-13 um that escaped the atmosphere efficiently.

This portion of spectrum which is passing unhindered is called a Window.

Methane

Other trace gases which are capable of absorbing thermal IR will lead to additional global warming, that is called as enhanced green house effect.

Particularly serious are the green house gases which absorb IR in the Window region. Since the absorption by water and CO2 is already so great that there remains little such light for trace gases to absorb. Important trace gas whose concentration is small but ability to warm air is great, includes methane, the next most important green house gas.

Sources of methane production

Increased food production.
fossil fuel use and forest clearing.
When the plants decay under water logged conditions as in wetlands such as swamps and bogs.
Anaerobic decomposition of organic matter in garbage in landfills.

In some communities methane is collected from landfills and used to generate heat rather than being allowed to escape into the air.

The biogas plants though not extensively used in Pakistan but are successful wherever experimented.

Nitrous oxide

N2O, 270 times more effective than CO2 on a per molecule base, causing global warming. N2O is naturally produced during nitrogen fixation as a byproduct of biological denitrification and is artificially produced through the same reaction due to use of ammonia and nitrate fertilizers for agriculture purposes.

Green house effect

The redirection of thermal radiation towards the earth is called Green House Effect.

The green house effect is the rise in temperature that the earth experiences. Because certain gases in the atmosphere trap heat energy from the sun. These gases do not let it escape while the light is transmitted unimpeded.

Green house gases are comparable to the roof of a green house, thus the effect created by them is known as green house effect.

The term green house effect in ordinary usage simply means the rise of temperature by several degrees as a result of the build up of Carbon dioxide and other green house gases in the atmosphere. Many scientist believe that such global warming has been underway already. This is largely responsible for temperature increase of about 2/3 of degree Celsius that has occurred since 1860.

Definition of Wall

A wall is a structure that defines an area, carries a load, or provides shelter or security.

There are many kinds of walls:

Defensive walls in fortification..
Walls in buildings that form a fundamental part of the superstructure or separate interior sections, sometimes for fire safety.
Retaining walls, which hold back earth, stone or water.
Walls that protect from oceans (seawalls or rivers levees).
Permanent, solid fences.
Border barriers between countries.

Green Walls

A green wall is a wall partially or completely covered with vegetation that includes a growing medium, such as soil. Most green walls also feature an integrated water delivery system. Green walls are also known as living walls or vertical gardens.

Difference between Green wall and Green facades

It is useful to distinguish green walls from green facades.

Green walls have growing media supported on the face of the wall, while green facades have soil only at the base of the wall (in a container or in ground) and support climbing plants on the face of the wall to create the green, or vegetated facade.

Green walls may be indoors or outside, freestanding or attached to an existing wall, and come in a great variety of sizes.

Roof

A roof is part of a building envelope, both the covering on the uppermost part of a building or shelter which provides
protection from animals and weather, rain, but also heat, wind and sunlight; and the framing or structure which supports the covering.

Characteristics

The characteristics of a roof are dependent upon the purpose of the building that it covers.
The available roofing materials.
The local traditions of construction and wider concepts of architectural design and practice, may also be governed by local or national legislation.
In most countries a roof protects primarily against rain.
A verandah may be roofed with material that protects against sunlight but admits the other elements.
The roof of a garden conservatory, protects plants from cold, wind and rain but admits light.

Definition of Green roof

A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane.

It may also include additional layers such as a root barrier and drainage and irrigation systems. Container gardens on roofs, where plants are maintained in pots, are not generally considered to be true green roofs. Rooftop ponds are another form of green roofs which are used to treat grey water.

Types

There are two types of green roof.

Intensive roofs, which are thicker, with a minimum depth of 12.8 cm, and can support a wider variety of plants but are heavier and require more maintenance.
Extensive roofs, which are shallow, ranging in depth from 2 cm to 12.7 cm, lighter than intensive green roofs, and require minimal maintenance.

The term green roof may also be used to indicate roofs that use some form of green technology, such as a cool roof, a roof with solar thermal collectors or photovoltaic panels. Green roofs are also referred to as ecoroofs, vegetated roofs, living roofs, green roofs and VCPH (Horizontal Vegetated Complex Partitions).

Construction Process

Construction process is the process of creating and building infrastructure or a facility.

Difference between manufacturing and construction

It differs from manufacturing as, manufacturing typically involves mass production of similar items with out a specific purchaser and construction is typically done on location for a known client. Construction as an industry is 6 to 9% of the gross domestic production of developed countries. Construction starts with planning, design and financing and continues until the project is built and ready for use.

Large scale construction is a feat of human multitasking. A Project manager normally manages the job, and a construction manager, design engineer, construction engineer or project architect supervises it. For the successful execution of a project, effective planning is essential. Those involved with the design and execution of the infrastructure must consider the zoning requirements, the environmental impact of the job, the successful scheduling, budgeting, construction site safety, etc.

Three sectors of construction industry

In general, there are three sectors of construction.

Building construction is usually further divided into residential and non-residential.

Infrastructure is often called heavy/highway, heavy civil or heavy engineering. It includes large public works, dams, bridges, highways, water/waste water and utility distribution.

Industrial includes refineries, process chemical, power generation, mills and manufacturing plants.

Simple levelling

When it is required to find the difference between two points which are visible from a single position of level. Then the method used is simple levelling.

Suppose A and B are two points and the level is set up at approximately midway between them, suppose at O. After the instrument is correctly levelled, the telescope is directed toward the staff held vertically on A and focused. Reading at which Horizontal hair of the diaphragm appears to cut the staff is taken. Ensure that bubble of the level is in center. Then the staff is held vertically on B. Again reading is taken at point B from point O. Let the respective readings on A and B be 2.350 and 3.315 . The difference between these readings give the difference of level between A and B which is equal to 3.315 m – 2.350 m = 0.965 m

If the reduced level of A is 100 m, then we can find the reduced level of B.

Height of instrument at O = R.L of A + 2.350 m

Height of instrument at O = 100 m + 2.350 m = 102.350 m

R.L of B = 102.350 m – 3.315 m = 99.035 m

Note

When the point is lower, the staff reading is greater. When the point is higher, the staff reading is smaller.
The bubble must be in center while the readings are being taken.
If the true difference of level between two points is required, then level must be set up exactly midway between them.

Differential levelling

This method is used in order to find the difference between two points which are far apart or if the difference in elevation between them is too great or if there are obstacles in between them.

Principles of Surveying

Followings are the principles of surveying which should be kept in mind while determining the relative positions of points on the surface of earth:

To work from whole to part

Working from whole to part is done in surveying in order to ensure that errors and mistakes of one portion do not affect the remaining portion. First step in the extensive surveys such as topographic surveys, is to establish a system of control points with high precision. For the horizontal control, the points are established by triangulation or precise traversing. To do this by triangulation, the area to be surveyed are divided in to large triangles. These triangles are surveyed with greatest accuracy. These large triangles are further divided in to small triangles which are surveyed with less accuracy. The object of this system is to prevent the accumulation of errors, and to control minor errors.

On the other hand if we work from part to whole, small errors are magnified in the process of expansion of survey. These errors become uncontrollable at the end.

Fix the positions by two independent process

To fix the positions of new stations by two independent process. The new stations are fixed from points already fixed by linear measurements, angular measurements or by both linear and angular measurements.

Definition of Coffer Dam

Coffer Dam is a temporary structure constructed in a river, lake etc for excluding water from a given site (where the construction is to be start) to enable the building operation to be performed on dry surface.

It may be made of earth materials, timber or steel sheet piling or a combination of these. Some of the common types of coffer dams are as follow:

Cantilever sheet pile coffer dam: This dam is suitable for small heights.
Braced dam: These are economical for small to moderate heights.
Embankment protected dam: There is no height limit for embankment type coffer dam.
Double wall dam: These are suitable for moderate heights.
Cellular dam: These are suitable for moderate and large heights.

FRAME STRUCTURE

A rigid frame structure is one made up of linear elements, typically beams & columns, which are connected to one another at there ends with joints that don’t allow any relative rotations to occur between the ends of the attached members, although themselves may rotate as unity.

In frame structure, the main loads are transferred to the foundations via the structural frame. The external skin serves to provide wide weather protection and aesthetic quality. The rigid joints that are made between vertical and horizontal members should be rigid enough to enable a framed structure to carry significant lateral loads. This joint rigidity impact a measure of stability against lateral forces.

PREFERENCE OF CONCRETE FRAMED STRUCTURE

Reinforced concrete framed structures are best suited to resist repeated earthquake loading. Repeated earthquake loading which require a high amount of resistance and ductility. Ductility is the ability of structural member to bend in response to earthquake induced forces awhile simultaneously continuing to support the loads it was designed to carry.

Framed structures have greater flexibility.
The greater joints rigidity, which enables the frame structure to resist lateral loads, & continuity of concrete frames, gives them more versatility.
Economical.
Aestheticism.

STRUCTURE

A structure is one in which the members are arranged in such a way that the weights, loads & forces are transmitted to the foundations by the cheapest means consistent with the intended use and nature of the structure.

There are two types of structures:

Masonry Structures.
Frame structure.

MASONRY STRUCTURE

In typical masonry construction, the main loads are transfer to the foundations via the internal load bearing wall. The external skin serves to provide weather protection and aesthetic quality.

In masonry structure, there is heavy reliance on the skills of the site worker and on wet trades, e.g. brick laying, plastering etc. Quality control is highly dependent upon the labor used and the quality of supervision on site.

Value Engineering

As an engineering function, Value Engineering uses a process of function cost analysis to identify features that can be changed to reduce cost without affecting the quality of the facility.

Value Engineering is also known as function analysis of Value Analysis. Ideally, it is applied during the design process, and not after the submission of bids.

Objectives and Goals

The main objective is to reduce project cost, without reducing the quality.
Cost reduction can be achieved by taking advantage of the existing streets and utilities, or the prevailing winds and available solar heat.
There may be cost savings in removing unneeded features such as insulation in walls and roofs in unheated spaces.
There may be value in simply changing the shape of the sewer pipe from round to oval, based on availability of the specific type.
The required depth of excavation may be reduced as a result of change.
Value Engineering changes should produce a facility that still performs the same functions as it did before the change was made.
The value of the facility should remain undisturbed without cost savings

Flaky particles

The particles whose least dimension is less than 0.6 times the mean size dimensions.

Elongated particles

The particles whose greatest dimension is greater than 1.8 times the mean size dimension.

Mean size of aggregates

Mean size of aggregates is defined as the mean of two seive sizes, between which the particle is retained.

Mean size = (Passing sieve size + Retaining sieve size)/2

Flakiness index

The percentage by weight of flaky particles present in a given test sample.

Elongation index

The percentage by weight of the elongated particles present in a given test sample.

What is construction management ?

The act, manner or practice in which a construction executive oversees, supervises or controls the organized process.

System execution of a construction project.

The focus of construction management is the planning and control of resources within the framework of project.

Resources of Construction

The construction resources are :

Time.
Money.
Equipment.
Technology.
Materials.
People.

Four M’s of construction

These four M’s of construction are also the resources of construction.

Manpower.
Machines.
Materials.
Money.

Construction management includes:

How these resources are used in the construction project.?
Co-ordination of these resources to perform a system execution of project.
Organize resources into activities.
Perform activities in a logical sequence.