Difference between End Bearing Piles and Skin Friction Piles.

upto a certain extent after which it again reduces. Terzaghi’s and Meyerhof’s theory of Bearing Capacity are mostly used for the geotechnical design of foundations.

A pile in civil engineering & construction is basically a long cylinder of a strong material either concrete or steel that may be casted at site or driven or pushed into the ground to act as a steady support for the structures built on top of it.

Cases to Use Pile Foundation

Following are the cases in which pile foundation is recommended :-

1. When there is a layer of weak soil at the surface. This layer cannot support the weight of the building, so the loads of the building have to bypass this layer and be transferred to the layer of stronger soil or rock that is below the weak layer. 
2. When a building has very heavy concentrated loads, such as in a high rise structures, bridges or water tanks. 
3. Subsoil water level is high so that pumping of water from the open trenches for the shallow foundation is difficult or uneconomical. 
4. Large fluctuations in subsoil water level that may cause sinking foundation in case of shallow foundation. 
5. Structure is situated near river bed, where there is a danger of scouring action of water. 
6. The top soil is of expansive nature. 
7. 
   

End bearing piles and friction piles are basic two types of pile foundation mostly used throughout the worlds. 

End Bearing Piles 

These piles are used to transfer the load through water or soft soil ground to a suitable hard bearing stratum.

End bearing piles are used to transfer load through water or soft soil to a suitable bearing stratum. Such piles are used to carry heavy loads safely to hard strata. Multi-storeyed buildiare invariably founded on end bearing piles, so that the settlements are minimized.

End bearing piles are typically driven through soft soil, such as a loose silt-bearing stratum underlain by compressible strata. Remember this factor when determining the load the pile can support safely.

Friction Piles

These piles are used to transfer to a depth of a friction load carrying material by mean of a skin friction along the length of piles.  Friction piles are used to transfer loads to a depth of a friction-load-carrying materials by means of skin friction along the length of the pile. Such piles are generally used in granular soil where the depth of hard stratum is very great.

Some piles transfer the super-imposed load both through side friction as well as end bearing. Such piles are more common, especially when the end bearing piles pass through granular soils.

Friction piles are used in the soil of fairly uniform consistency and the tip is not seated in a hard layer, the load carrying capacity of the pile is developed by skin friction.  The load is transferred downward and laterally to the soil.

FIRE RESISTING PROPERTIES OF COMMON BUILDING MTERIALS

Fire resisting properties of common building materials such as stone, brick, timber, cast-iron, glass, steel and concrete are mentioned below.

1. STONE

The stone is a bad conductor of heat. But it suffers appreciably under the effects of fire. The stone is also liable to disintegrate into small pieces when heated and suddenly cooled. Granite explodes and gets easily disintegrated in case of a fire. Limestone is easily crumbled even by ordinary fire. Sandstones of compact composition with fine grains can generally stand moderate fire successfully without the formation of serious cracks.

2. BRICKS

It is found that bricks are not seriously affected until very high temperature of 12000C to 13000 C are reached. This is due to the fact that a brick is a poor conductor of heat. If the type of mortar and quality of workmanship are good, brick masonry generally offers good resistance to fire. However, a brick has its own structural limitation for use in buildings.

3. TIMBER

As a general rule, structural elements made of timber ignite and get rapidly destroyed in case of fire. Further, they add to the intensity of fire. But timber used in heavy sections may attain a high degree of fire-resistance because timber is a very bad conductor of heat. This is the reason why time is required to build up sufficient heat so as to cause a flame in timber. In order to make timber more fire resistant, the surfaces of timber are sometimes coated with certain chemicals such as ammonium phosphate and sulphate, borax and boric acid, zinc chloride, etc. such a treatment on timber surfaces retards the rise of temperature during fire. The timber cam also be made fire-resistant by the application of certain paints on its surface.

4. CAST IRON

This material is rarely used as structural material at present. This material flies into pieces when heated and suddenly cooled. Hence, when this material is used in construction, it is covered either by brickwork of one brick thickness or any other fire resisting material such as concrete.

5. GLASS

This material is a poor conductor of heat and its expansion due to heat is small. Cracks are formed I this material when heated and then suddenly cooled. Reinforced glass with steel wire is ore fire-resistant than ordinary glass and it can resist sudden variation in temperature without the formation of cracks. Wired glass, even if it breaks, keeps the fractured glass in its original position.

6. STEEL

Steel is a good conductor of heat and hence, it is rapidly heated in case of fire. It is found that steel loses its tensile strength with the increase in heat and the yield stress of mild steel at 6000C is about one-third of its value at normal temperature. Hence, under intense fire, the unprotected steel beams sag, the unprotected steel columns buckle and the structure collapses. Steel completely melts at a temperature of 14000C. It is also found that if the surface paint is not specially made fire-resistant, it assists in spreading the flame on the surface and thereby it adds to the intensity of fire.

If steel plate or sheet form is fixed to framework, it becomes affective is resisting the passage of flame. Such construction is widely adopted in manufacturing fire-resisting doors and windows.

7. CONCRETE

Concrete has got very good fire resistance. The actual behaviour of concrete in case of fire depends upon the quality of cement and aggregates used. In case of reinforced concrete and prestressed concrete, it also depends upon the position of steel. Larger the concrete cover, better is the fire resistance of the member.
There is no loss in strength in concrete when it is heated up to 250°C. The reduction in strength starts if the temperature goes beyond 250°C. Normally reinforced concrete structures can resist fire for about one hour at a temperature of 1000°C. Hence cement concrete is ideally used fire resistant material.

HOW MANY TYPE OF STONE TEST

There are various kinds of lab and field tests available for building stones or rocks. These stone or rock tests are generally performed to determine the physical quality of stone materials used for construction work. Few tests such as Acid test may be performed to determine the chemical quality of building material or stones. Many of the known building stone & rock tests are explained briefly below:

. Hardness test

• Hardness is the resistance of a stone to indentation, rebound or scratch.
• It is tested by a pen knife with the aid of Moh’s scale of hardness.

Minerals	Moh’s Scale	Hardness test
Talc	1	easily scratched with the thumb-nail
Gypsum	2	scratched by the thumb-nail
Calcite/ Marbles	3	not scratched by thumb-nail but easily cut by knife
Fluorite	4	can be cut by knife with greater difficulty than calcite
Apatite	5	can be cut only with difficulty by knife
Orthoclase/ Feldspar	6	can be cut with knife with great difficulty on thin edges
Quartz	7	not scratched by steel, scratches glass
Topaz	8
Sapphire/ Corundum	9
Diamond	10

. Crushing test

• Three cube samples of size are cut and placed in water for 72 hours.
• They are tested in crushing test machine with loading 13.7 N/mm2 per minute.

3. Transverse strength test

• A specimen of the stone whose length is ten times its depth is placed on wedge-shaped supports near its ends. A vertical load applied at the centre is gradually increased until failure occurs. The transverse strength, called the modulus of rupture, in MPa is computed as

Where,

W = breaking load applied at the centre in N,

L = distance between the supports in mm,

b = width of the specimen block in mm and

d = depth of the specimen block in mm

• Transverse strength tests are usually made on specimens of 25mm square in section. The approximate values for ordinary stone are: Granite 10 – 17.5 MPa; limestone 3.5 – 20 MPa and sandstones in the range 4 – 15 MPa.

4. Impact test

• For toughness
• A steel hammer of 20 N is allowed to fall axially in the specimen.
• The blow at which the specimen breaks represents the toughness of the stone.

5. Fire resistance test

• The stone which is free from calcium carbonate can resist fire.
• Presence of calcium carbonate can be detected by few drops of dilute sulphuric acid which will produce bubbles.

6. Attrition test

• To determine the rate of wear of stones employed.
• Also known as abrasion test and is carried out in Deval’s Attrition Testing Machine.

7. Acid test

• Kept in solution of 1% H2SO4 or HCl and checked for deposits on surface.
• The stones having high percentage of lime content exhibit efflorescence when subjected to action of acids.

8. Porosity and water absorption test

• The porosity of the commonly used stones varies from 0 to 20%.
• The percentage of water absorbed by an air dried stone when immersed in water for 24 hours is termed as absorption of stone (air dry basis).
• A good building stone must absorb less than 5% water and those stones that absorb more than 10% of water should be rejected.
• Sandstones should not absorb water more than 10%, 17% in case of limestones and 1% in granites of their volume when dipped for 3-4 hours.

9. Smith’s test

• This test indicates the presence of earthy matter.

10. Crystallization test:

• To determine the durability or weathering quality of the stone.
• A sample of stone is immersed in solution of sodium sulphate at room temperature and dried in hot air.
• The process of wetting and drying is carried out for two hours; the difference in weight if any is recorded. Little difference in weight indicates durability and good weathering quality of the stones.

DANGERS ON THE CONSTRUCTION SITE

When you are exposed to any type of construction work, whether you are renovating your home or are in the business, safety should be the premiere concern. Construction sites are filled with danger and a common place for injuries so taking the right preventative measures will ensure the safety of all those concerned as well as the finishing of a project on time, safely and successfully.

1.       Make sure all employees and anyone that has access to the construction site wears proper protective materials. That includes hard hats, safety goggles, work boots, and proper attire. Make sure anyone that will be around the construction area is trained to look for dangers like loose nails, unsturdy ladders, and power tools. Construction sites are not playgrounds and children should not running around them without adult supervision.

2.       Debris and scattered materials can be the sneakiest forms of danger on a construction site. Make sure that the staff keeps the debris and trash to an absolute minimum and that everyone’s area is cleaned prior to leaving for lunch or for the day. Things like debris, loose wires, and garbage can lead to accidental injury even when people are not actually working.

3.     Protecting equipment will help keep it in the best condition for usage. Bad equipment creates a bad product as well as encroaching on the time a project takes to finish. Make sure tools and larger forms of equipment like bulldozers and cement trucks are updated and maintained. Exposed hoses are easy victims of construction site overlooking, but if they are ruined, it can prove time-consuming and disastrous to fix. Instead cover your hoses with a hose protector such as the ones seen on nayakcadd.blogspot.com. Having precarious equipment can put every person in the vicinity in danger at well as well as exposing you to liability.

QUALITY CONTROL AND SAFETY CONCERNS IN CONSTRUCTION

Quality control and Construction Safety represent increasingly important concerns for project managers.

Weak quality control leads to defects or failures in constructed facilities, thus result in very large costs. Even with minor defects, re-construction may be required and facility operations impaired. Increased costs and delays are the result. In the worst case, failures may cause personal injuries or fatalities. Accidents during the construction process can similarly result in personal injuries and large costs. Indirect costs of insurance, inspection and regulation are increasing rapidly due to these increased direct costs. Good project managers try to ensure that the job is done right the first time and that no major accidents occur on the project.

As with cost control, the most important decisions regarding the quality of a completed facility are made during the design and planning stages rather than during construction. It is during these preliminary stages that component configurations, material specifications and functional performance are decided. Quality control during construction consists largely of insuring conformance to these original design and planning decisions.

While conformance to existing design decisions is the primary focus of quality control, there are exceptions to this rule. First, unforeseen circumstances, incorrect design decisions or changes desired by an owner in the facility function may require re-evaluation of design decisions during the course of construction. While these changes may be motivated by the concern for quality, they represent occasions for re-design with all the attendant objectives and constraints. As a second case, some designs rely upon informed and appropriate decision making during the construction process itself. For example, some tunneling methods make decisions about the amount of shoring required at different locations based upon observation of soil conditions during the tunneling process. Since such decisions are based on better information concerning actual site conditions, the facility design may be more cost effective as a result.

With the attention to conformance as the measure of quality during the construction process, the specification of quality requirements in the design and contract documentation becomes extremely important. Quality requirements should be clear and verifiable, so that all parties in the project can understand the requirements for conformance. Much of the discussion in this chapter relates to the development and the implications of different quality requirements for construction as well as the issues associated with insuring conformance.

Safety during the construction project is also influenced in large part by decisions made during the planning and design process. Some designs or construction plans are inherently difficult and dangerous to implement, whereas other, comparable plans may considerably reduce the possibility of accidents. For example, clear separation of traffic from construction zones during roadway rehabilitation can greatly reduce the possibility of accidental collisions. Beyond these design decisions, safety largely depends upon education, vigilance and cooperation during the construction process. Workers should be constantly alert to the possibilities of accidents and avoid taken unnecessary risks.

RISKS IN CONSTRUCTION PROJECTS

Risks in construction projects may be classified in a number of ways. One form of risks classification is as follows:

1. Socioeconomic factors
   • Environmental protection
   • Public safety regulation
   • Economic instability
   • Exchange rate fluctuation
2. Organizational relationships
   • Contractual relations
   • Attitudes of participants
   • Communication
3. Technological problems
   • Design assumptions
   • Site conditions
   • Construction procedures
   • Construction occupational safety

The environmental protection movement has contributed to the uncertainty for construction because of the inability to know what will be required and how long it will take to obtain approval from the regulatory agencies. The requirements of continued re-evaluation of problems and the lack of definitive criteria which are practical have also resulted in added costs. Public safety regulations have similar effects, which have been most noticeable in the energy field involving nuclear power plants and coal mining. The situation has created constantly shifting guidelines for engineers, constructors and owners as projects move through the stages of planning to construction. These moving targets add a significant new dimension of uncertainty which can make it virtually impossible to schedule and complete work at budgeted cost. Economic conditions of the past decade have further reinforced the climate of uncertainty with high inflation and interest rates. The deregulation of financial institutions has also generated unanticipated problems related to the financing of construction.

TYPES OF COLUMN FAILURE:

TYPES OF COLUMN FAILURE:

Columns are the most important parts of a structure. They transfer loads of the structure to the surrounding soil through the foundations. So we need to build strong columns, otherwise, failure will occur.

Columns are built with two building materials, concrete and steel. Before designing the columns, civil engineers should calculate total stress due to live and dead load of the building. When the applied stress exceeds the permissible stress (calculated) the structure will fail.

In this article, different types of column failures are discussed.

COMPRESSION FAILURE:

When columns are axially loaded, the concrete and steel will experience some stresses. When the loads are greater in amount compared to the cross-sectional area of the column, the concrete and steel will reach the yield stress and failure will be starting without any later deformation.

In this type of failure, the material fails itself, not the whole column. This type of failure mostly occurs in shorter and wider columns. To avoid this, the column should be made with sufficient cross-sectional area compared to the allowable stress.

2. BUCKLING FAILURE:

Buckling failure generally occurs in long columns. Because they are very slender and their least lateral dimension is greater than 12. In such condition, the load carrying capacity of the column decreases very much.

The columns tend to become unstable and start buckling to sideward even under small loads.That means the concrete and steel reached their yield stress for even small loads and start failing due to lateral buckling.

This type of failures can be avoided by not constructing long columns of slenderness ratio greater than 30