Cavity Wall

A cavity wall or hollow wall consists of two separate walls called leaves or skins with a cavity or gap in between. The cavity wall construction is an effective method of damp prevention, in which the main wall of building is shielded by an outer skin wall, leaving a cavity between the two. The cavity wall are often constructed for giving better insulation to the building. It also prevents the dampness to enter and acts as sound insulation.

The cavity extend vertically all along the height of the wall, except at the openings, where it is discontinued. The cavity should terminate near coping in case of flat roods with parapet walls and up-to or near eaves level in case of sloping roof. In the foundations, the cavity should start near the ground level or 150 mm below the D.P.C level.

TBM ( Tunnel Boring Machine ) in Nepal

TBM is going to be used in the Bheri Babai diversion multi project for the first time in the history of Nepal.

This project aims to divert the water from Bheri river to Babai at the rate of 50 cubic meter per second for facilitating 80,000 bighas of land Bara and  Parsa district. Also, it is designed to produce 48 MW of hydroelectricity.

In this project, tunnel of 12 km should be constructed which is very difficult by drill and blast method. Hence, this TBM is bought from China, Shanghai. Its cost is 2.5 arab and its size is 200m long and cutting diameter is 5.06 m. It will take about 1 months for assembling which has been started by early September, 2017.

If this TBM can be used in further tunneling projects, Nepal will have rapid development in roads, canals and underground metro in future.


Photo Gallery

Assembly going on

TYPES OF FOUNDATION

Generally, there are two types of foundation.

1) Shallow Foundation

Some of its example are:

a) Spread Footing

b) Combined Footing

c) Strap Footing

d) Raft or mat Footing

2) Deep foundation

Some of its example are :


a) Pile foundation

b) Pier Foundation

c) Well Foundation

Method of design of RCC Structutres

1) Working Stress Method  (WSM) 

This method  is also know n as modular ration method or elastic methods. It is most popular and commonly used method for the design purpose. In this m,ethod the moment nad forces actin on a structure are obtained from the actial values of service loads but the stresses in concrete and the reinforcing steel are restricted to onlt a fraction of their true strenght in order to proved an sadquate safety factor. A factor of safety of 3n in concrete and 1.78 to 1.80 in steel is generally adopted.

2) Limit State Method 

This method is also known as plastic method. In this method, the structures is designed to withstand safely all loads liable to act on it throughout its life. It should also satisfy the serviceability requirements such as prevention of excessive deflection, excessive cracking and excessive vibration. The acceptable limit for the safety and serviceability requirements before failure occurs is called limit state.

3) Ultimate Strength Method 

This method is also known as load factor method. In this method of design, the true margin of safety is accurately known. The ultimate strength procedure is based upon the results obtained from the experimental investigation depicting the true behavior of the structures.

Flow lines and Equipotential lines

The flow net in the seepage of water through a soil medium is a network of flow lines and equipotential lines. The flow net is used to determine the seepage flow, hydro-static pressure, seepage pressure and exit gradient. A flow line or stream line in a seepage through a soil medium is defined  as the path of particles of water through a saturated soil mass. The equipotential line in a seepage  through a soil mass is defined as the line connecting the points of equal head of water. The direction of seepage is always perpendicular to the euipotential lines. The flow lines and equipotential line are intersecting lines at 90 degree to each other.

* The portion between any two successive flow line is known as flow channel. The potion enclosed between two successive equipotential line and successive flow line is known as field.
* The discharge (Q) passing throuh a flow net for isotropic soil is given by :

Q = KH * Nf/Nd

K = A constant
H = Total Hydraulic Head causing flow
Nf = number of flow channels
Nd = Number of potential drops

TOP 10 UNIVERSITIES OF USA

Here is the list of top universities of USA. (By clicking on 'click', you can visit there websites)

1. Massachusetts Institute of Technology (MIT) (click)

Location: Cambridge, Massachusetts

World Ranking: 1

2. Stanford University (click)

Location: Silicon Valley

World Raking: 2

3. Harvard University (click)

Location: Cambridge, Massachusetts

World Ranking: 3

4. California Institute of Technology (Caltech) (click)

Underpinning

The underpinning is an arrangement of supports provided underneath the existing structures without disturbing its stability. The underpinning is required in the following situations:

1. When a building wit deep foundation is to be constructed to an existing buildings.

2) when the settlement of existing foundation has taken place, resulting in serious cracks in the  wall.

3) when the basement is to be provided to an existing building.

4) when the existing foundations are to be deepened so as to rest them on soil of higher bearing power.

The underpinning may be carried out by the pit method or pile method.

Classification of Bricks

The bricks are classified as under:

1. First Class Bricks
These bricks are well brunt having smooth and ecen surface with perfect rectangualr shape and uniform reddish colour. These bricks should not absorb water more than 20% of its own dry weight after 24 hours of immersion in water. It should have a minimum crushing strength of 10.5 MN/m^2

2) Second Class Bricks
 These brikcs are slightly over brunt having rough surface and nor perfectly rectangular in shape. These bricks should nor absorb water more than 22 percent of its own dry weight after 24 hours immersion in water.It should have a minimum crushing strength of 7.5 MN/m^2

3) Third Class Bricks
These bricks are not brunt in the kiln and hence these are soft and can be easily broken. These bricks should not absorb water more than 25 percent of its own dry weight after 24 hours immersion in water.

4) Jhama / poor Bricks
These bricks are over brunt with irregular shape. These bricks are dark and bluish colour.

The standard size of the bricks are 19 cm * 9 cm * 4 cm
The specific gravity of brick is about 2 .
the number of bricks required for 1 cubic meter of brick masonry is 562.

Difference between Triangulation vs. Trilateration

Triangulation

In this process, all the angles and 1 baseline distance are measured in the field of a triangle.
With the help of these measurements the side lengths are computed on the basis of measured angles applying sine law.

Trilateration

In this process, all the sides of  a triangle are measured in the field.
With the help of these distance, the angles are computed applying cosine law.

Stress Strain Diagram for Mild Steel

The stress- strain diagram for a mild steel specimen under tensile test is shown in Fig. We see that from O to A is a straight line which represents that the stress is proportional to strain. It is thus obvious that Hook's law holds good up-to point A, which is called elastic limit. When the material is stressed beyond this limit (i.e point A), the strain increases more quickly than the stress. The points B and C are called the upper yield point and lower yield point respectively. The stress corresponding to point D is called Ultimate Stress. After the specimen has reached the ultimate stress, a neck is formed which decreases the cross-sectional area of the specimen. A little consideration will show that the stress (or load) necessary to break away the specimen at point E is less than the ultimate stress. The stress corresponding to point E is called Breaking Point.

Some of the formula are shown in the figure below: