civil techniques

Footings

abbu riyaz 1 May, 2023

Footings designs to resist the shear force causes by imposing loads. Footings constructs in open space and known as open foundations. It provides with natural slopes on all sides. It employs for a depth up to 5 m. The base of the structure enlarges or spreads to provide individual supports. These type of foundations provides for the structure of moderate heights built on the dry ground.

Types of footings

Wall Footing
Isolated footing
Combined footing
Inverted footing
Continous footing
Cantilever footing
Grillage footing

1. Wall Footing

Footings are of simple or stepped on wall footing. The base course of the footings is of concrete or other material. These footings employ only for simple structures. It has one projection beyond the width of the wall on sides. The width of the concrete base is equal to twice the width of the wall. In single footings, the brick footing is widely employing.

2. Isolated or column footing

It uses to support individual columns. It is in step or has a projection in the concrete base. In heavy loads, steel reinforcement provides in both directions in concrete bed. An offset of 15 cm provides on all sides of the concrete bed. In brick masonry, offset is of 5 cm on all sides in regular layers.

3. Combined footing

A combined footing supports more columns in a row. The combined footing is of rectangular shape if both the column carry equal loads. In unequal loads it of trapezoidal shape. It is rigid and resisting on the homogeneous soil.

4. Inverted arch footing

Inverted arch footing use on the soft soil to reduce the depth of foundation. Loads above an opening transmit from supporting walls through inverter arches of soil. In this type of footing, the end columns are stable enough to resist the outward pressure causing by arch section.

5. Continuous footings

In this type of footing, a single continuous R.C. slab provides a foundation of more columns in a row. It is suitable for locations liable to earthquake activities. This prevents differential settlements in structure. To have a better stability deeper beam constructs in between columns.

6. strap or cantilever footing

It consists of more individual footings connects by a beam known as a strap and known as cantilever footing. This type of footing uses where the distance between the column is greater. It serves to transfer column loads on the soil with equal and uniform soil pressure.

7. Grillage footing

This type of footings uses to transmit heavy loads from steel columns to the soils having low bearing power. This type of arrangements avoids deep excavation. And provides a necessary area at the base to reduce the intensity of pressure. Grillage footings are of roll steel joists and name as grillage beams to providing in single or double tires.

civil techniques

Scaffolding types

abbu riyaz 1 May, 2023

There are many scaffolding types. Scaffolding is a temporary structure to support the original structure and workmen. And use as a platform to carry on the construction works. Types of scaffolding vary with the type of construction work. Scaffolding is of timber or steel. It is stable and strong to support workmen and other construction material place on it.

Scaffolding Types in Construction:

Following are types of Scaffolding in construction:

Single scaffolding or brick layer’s scaffolding.
Double scaffolding.
Cantilever scaffolding.
Suspended scaffolding.
Trestle scaffolding.
Steel scaffolding.
Patented scaffolding.

1. Single Scaffolding or bricklayer’s scaffolding.

Single scaffolding use for brick masonry and called as brick layer’s scaffolding. This is most commonly employs in the construction of brickwork. Single scaffolding consists of standards, ledgers, putlogs. Standards drive into the ground at a distance of about 1.5 m to 2 m apart. And about 1.2 m away from from the wall to construct. The standards connect to each other by ledgers placing at right angles. It secures in position with rope lashing.

2. Double Scaffolding:

Double Scaffolding is stronger so its use for stone masonry. The formwork is similar to single scaffolding. This type of wall is completely independent of walls and no holes are drill in the wall to support putlogs. To make it more strong rakers and cross braces use.

3. Cantilever Scaffolding:

cantilever scaffolding employes where it is not possible to fix the standards into the ground. In this, scaffolding the standards supports by series of needles. And these needles pull out through holes in the wall. It provides on side of a busy street without obstructing the traffic on the road. It is important in the construction of multistorey and industrial buildings.

4. Suspended Scaffolding:

These Scaffolding types are suitable for light steel frame construction, maintenance work like painting, pointing, distempering, etc. In this type, standards don’t rest on the ground.

The working platforms suspend from rooftops by means of wire ropes and chains. And there is a mechanical arrangement to raise or lower the platform.

5. Trestle Scaffolding:

In this scaffolding types, the working platforms support on tops of mobile devices like movable tripods and ladders. These employes for work inside the room, like paintings, repairs etc., up to a height of 5m.

6. Steel Scaffolding:

The steel scaffolding is similar to timber scaffolding in which wooden members replace by steel tubes. And rope lashings replace with couplings and screw-nuts. Steel tubes fix with steel couplers and fittings. It is very easy to construct or dismantle and has greater strength, durability, and fire resistance. It gives more safety to workers.

7. Patented Scaffolding:

Patented scaffoldings are of steel. And equip with special couplings and frames. It is readymade scaffolding and available on the market. In this type of scaffolding, a working platform arranges in brackets and adjustable to a level.

civil techniques

Scaffolding

abbu riyaz 1 May, 2023

Scaffolding is a temporary structure uses in building operations to support platforms for workmen. And helps with structural materials, and materials required during construction of high rise buildings. It uses for above height of 1.5 meters. This temporary scaffold is useful in building construction, repairs, demolition, maintenance and repair works.

It sets one or both sides of the wall according to needs. It sets one side of wall or buildings for ordinary works. For major quality works scaffold to sets on both sides of walls. The height of the scaffolding is adjusting according to the work.

Components of scaffolding

Standards
Ledgers
Braces
Planks
Put-logs
Guard boards
Toe-boards

Standards: These are vertical members of the scaffolding.

Ledgers: Ledgers are horizontal members at right angles to the standards and parallel to the wall.

Braces: Braces are members fix diagonally to the standards.

Planks: They forms the horizontal platforms for supporting men, materials, and appliances.

Put-logs: These members place on horizontal members at right angles to the wall.

Guard boards It uses at working level to guard against materials.

Toe-boards Toe-boards place parallel to the ledgers and using for protection at high levels of the working platform.

These components/members of the scaffold are secure by means of rope lashings, rails, and bolts.

Advantages of scaffolding

The first advantage of using scaffold is to complete the work task safely.

Easily installs and complete various work tasks without hassle.

With scaffold, the worker can reach many meters high as possible.

It provides large space to keep your construction tools and more usable workspace.

LIghtweight and cost-effective.

It is easier for workers to maintain their balance on a flat platform than on a ladder step.

Provide access to difficult places when buildings are constructs and reduce time to complete work.

civil techniques

Retaining Walls

abbu riyaz 1 May, 2023

Retaining walls

Retaining wall prevents the earth from sliding or eroding away. And to resist the material pressure of the material that it is holding back. It constructs with heavy blocks, angled stones, offset cinder blocks, wood or reinforced concrete frames backfilled or filled with the well-graded stone designed to create the geological resistance or mass required to counteract the earth pressures and surcharge loading. And also, anchor into the ground with steel I beam vertically inserted into the ground and reinforced with concrete and linked in between with planks or reinforced, Pre-fabricated concrete blocks.

Types of Retaining wall

Classification of retaining walls:

Following are the different types of retaining walls based on the shape and the mode of resisting the pressure.

Gravity wall-Masonry or Plain concrete
Cantilever retaining wall-RCC (Inverted T and L)
Counterfort retaining wall-RCC

1. Gravity wall – Masonry or Plain concrete

Gravity retaining Wall constructs of concrete, stone or brick masonry and are thicker in section. The geometry of these walls also helps them to maintain the stability. Mass concrete walls are suitable for retained heights of up to 3 m. The cross-section shape of the wall affects by stability, the use of space in front of the wall, the require wall appearance and the method of construction.

2. Cantilever retaining wall-RCC (Inverted T and L)

A cantilever retaining wall is one that consists of a wall which connects to the foundation. They are the most common type engages. Cantilever wall rest on a slab foundation. A cantilever wall holds back a significant amount of soil. It consists of a stem, toe slab, and heel slab.

3. Counterfort retaining wall-RCC

counterfort types adapted to larger heights. It consists of a stem, toe slab and heel slab as in case of cantilever retaining wall. But it also consists of counterforts are a regular interval which divides the stem. The stem with the combination of counterfort behaves like a tee-beam with varying width. The stem and heel slabs are effectively fixed to counterforts so that the stem bends horizontally between the counterforts due to lateral earth pressure. Thus the thickness of stem and the heel slab is considerably reduced due to the reduction of the moment due to fixity of these slabs between counterforts.

civil techniques

Pile Driving Equipment

abbu riyaz 1 May, 2023

Pile Driving Equipment

Pile Driving Equipment uses to drive piles in the weak soil for providing strong grip to foundations. The process of forcing a pile into the ground is pile driving. The piles drive vertically into the earth.

The equipment required for pile driving is as follows

Pile frames
Pile hammers
Leads
Winches and
Miscellaneous.

1. Pile frames

The pile frames are generally of steel having a height varying from ten to twenty-five meters and more. Pile frames are light and easy to transport. It consists of platforms for supporting drivers, engines, winches, etc.

2. Pile hammers

The function of hammers is to impart energy to drive the pile into the soil. These hammers guides between two steel members known as leads. Heavy conventional hammers drive pile by an impact. Vibratory hammers evolve as to avoid noise pollutions by driving piles by vibration.

3. Leads

Leads employ to guide hammers and piles. For drop hammers, fixed leads are uses. Leads are movable and adjustable as per use. Leads are more convenient.

4. Winches

Winches require for lifting the hammer and pile. These are of a light type with a single drum or heavy type with a double or triple drum. And it fits with reversing gears. Drop hammers, pneumatic hammers, winches operate by diesel, petrol, and electric engines. For steam hammers, use steam-power winches to lift the hammer and pile.

5. Miscellaneous

The other equipment requires for the process of pile driving are pile extractors, followers, jetting equipment, steam engines, air compressors.

pile extractors are for pulling piles from the ground after its impaction to a connection of reinforcement to foundations.
followers are connecting pieces of wood or steel between hammer and top of a pile. It is to transmit energy from the hammer to pile in underwater pilling.
jetting equipment is necessary to discharge water jets at high pressure to assist driving piles into sand or fine gravel.

civil techniques

Causes of Cracks in concrete structures

abbu riyaz 1 May, 2023

Causes of Cracks in concrete structures

There are many Causes of Cracks in concrete structures, they are

Thermal movement
The permeability of concrete.
Corrosion of Reinforcement
Creep
Moisture Movement
Structural design and specifications
Poor Construction practices.
Improper maintenance

1.Thermal movement

All materials expand on heating and contract on cooling. The thermal movement depends on temperature variations, dimensions, a coefficient of thermal expansion and physical properties of materials. The external exposed to direct solar radiation and the roof subject to thermal variation is liable to cracking.

Remedial Measures:

Thermal joints avoid by expansion joints, control joints and slip joints.

2.The Permeability of concrete

Concrete permeability controls by factors like water-cement ratio, water hydration, curing, air voids, micro-cracks and continues exposure to thermal variations.

3.Corrosion of Reinforcement

Concrete provides protection to reinforcing steel. Steel will not corrode as concrete around it is impervious. And does not allow moisture or chlorides to penetrate within the coverage area. A properly designed and constructed concrete is initially water-tight. The reinforcement steel protects by a physical barrier of the concrete cover having low permeability and high density.

Remedial Measures:

Increase the concrete cover with proper materials like plastic, concrete, readymade cover blocks, etc., instead of using stones and wood pieces. Increased concrete cover over the reinforcing bar reduces corrosion.

use concrete with low permeability.

4.Creep

Concrete subjected to loading exhibits a slow time-dependent deformation known as creep. Creep increases with increase in water and cement content, water-cement ratio and temperature. It decreases with increase in humidity of surrounding atmosphere and age of material at the time of loading. Use of admixtures and pozzolanas in concrete increases creep. Amount of creep in steel increases with rising in temperature.

5.Moisture Movement

Shrinkage occurs in all building materials that are cement/lime based. Heavy aggregate concrete shows less shrinkage than lightweight aggregate concrete.

Materials with pores in the structure in the form of intermolecular space expand on absorbing moisture and shrink on drying. These movements are cyclic in nature and causes by increase or decrease in inter pore pressure with moisture changes.

Remedial Measures:

Shrinkage cracks in masonry minimize by avoiding the use of rich cement mortar in masonry.

Plastering of masonry after proper curing.

6.Structural design and specifications

Cracks in concrete forms due to poor structural design and specifications. At the starting of design first, consider the environmental conditions existing around the building site. It is important to determine the type of foundations, the type of concrete materials use in concrete. And the grade of concrete depending on chemicals present in groundwater and subsoil. Closely spaced of reinforcement steel bars due to inadequate detailing causes segregation.

precautions while designing

specification for concrete materials and concrete.

Proper quality and thickness of concrete cover around the reinforcement steel.

proper reinforcement layout and detailing

7.Poor Construction practices

Construction should design and supervise only by civil engineers or persons having proper knowledge and experience in construction practices. People without construction knowledge are engaging nowadays to supervise construction works and to carry out construction works.

Lack of good construction practices due to ignorance, carelessness, greed or negligence.

For a healthy building, it is necessary to ensure good quality materials selection and good construction practices.

Some of the main causes for poor construction practices

Using poor quality materials
improper selection of materials
cheap and nonstandard materials
improper concrete mix
Inadequate control on various steps of concrete products such as batching, mixing, transporting, placing, finishing and curing
Inadequate quality control and supervision causing large voids(honeycomb)
Improper construction joints between
Addition of excess water in concrete and mortar mixes.
Poor quality of plumbing and sanitation materials and practices.

8.improper Maintenance

Buildings should maintain at regular interval of time properly to avoid damages. Attend Leakages as earliest as possible before corrosion of steel inside concrete starts. The external painting of the building helps in protecting the building against moisture and other chemical attacks. Necessary water-proofing and protective coating on reinforcement steel or concrete.