Dampness is one of the most common problems in buildings and can cause a wide range of serious problems. It is therefore important to be aware of the potential causes of dampness and the methods of preventing it.
Types of Foundation
Foundation is an important part of building structures. Followings are the types of foundation:
- Shallow Foundations
- Spread Footing
- Strip Foundation
- Combined Footing
- Strap Footing
- Raft or Mat Foundation
- Deep Foundations
- Pile Foundation
- Pier Foundation
- Caisson Foundation
Bulking of Sand
Bulking of sand means an increase in volume. Fine aggregate (i.e., sand) increases in volume when they possess some moisture.
This volume increase is not due to the increase in the volume of the individual sand particle in the presence of moisture. It is due to the formation of a thin film of water around the aggregate or sand particles. The thickness of this film goes on increasing with more moisture. That is, the volume of sand mass continues to increase with moisture content. This increase in volume varies 20-30% (vol. basis) depending upon the fineness of sand. The finer particles will undergo a greater increase in volume. After a certain percentage of water (5-8%, also depends on the fineness of sand), the volume of sand starts decreasing with the further increase in water and eventually, the increased volume completely vanishes, and at this moment, the volume occupied by sand becomes equal to the volume of dry sand.
Bulking of sand effects water-cement ratio and also the proportioning of aggregate.
This volume increase is not due to the increase in the volume of the individual sand particle in the presence of moisture. It is due to the formation of a thin film of water around the aggregate or sand particles. The thickness of this film goes on increasing with more moisture. That is, the volume of sand mass continues to increase with moisture content. This increase in volume varies 20-30% (vol. basis) depending upon the fineness of sand. The finer particles will undergo a greater increase in volume. After a certain percentage of water (5-8%, also depends on the fineness of sand), the volume of sand starts decreasing with the further increase in water and eventually, the increased volume completely vanishes, and at this moment, the volume occupied by sand becomes equal to the volume of dry sand.
Bulking of sand effects water-cement ratio and also the proportioning of aggregate.
Types of Bricks for Construction Work
Bricks are a clay made rectangular unit used for different building construction works. There are different types of bricks used in construction. They are:
- Based on Quality
- First Class Brick
- Second Class Brick
- Third Class Brick
- Based on Building Process
- Unburnt Bricks
- Burnt Bricks
- Over Burnt or Jhama Brick
- Based on Manufacturing Method
- Extruded Brick
- Molded Brick
- Dry pressed Brick
- Based on Raw Materials
- Burnt Clay Brick
- Fly ash clay Brick
- Concrete brick
- Sand-lime Brick
- Firebrick
- Based on Using Location
- Facing Brick
- Backing Brick
- Based on Weather-resisting Capability
- Severe Weather Grade
- Moderate Weather Grade
- No weather Grade
- Based on Uses of Brick
- Common Bricks
- Engineering Bricks
- Common Bricks
Advantages and Disadvantages of White cement
The strength of white cement is lower than that of ordinary Portland cement. It is not liable to cause staining because it has low content of soluble alkalis. It is four times costlier than ordinary Portland cement.
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Advantages and Disadvantages of Reinforced Concrete
Reinforced concrete, as a construction material, is widely used in many types of structures. For economic execution of structure, Reinforced concrete is the best choice for designers.
The advantages of reinforced concrete
- It has a relatively high compressive strength;
- It has better resistance to fire than steel;
- It has a long service life with low maintenance cost;
- In some types of structures, such as dams, piers, and footings, it is the most economical structural material;
- It can be cast to take the shape required, making it widely used in precast structural components. It yields rigid members with minimum apparent deflection.
The disadvantages of reinforced concrete
- It has a low tensile strength of about one-tenth of its compressive strength;
- It needs mixing, casting, and curing, all of which affect the final strength of concrete;
- The cost of the forms used to cast of concrete placed in the forms;
- It has a low compressive strength as compared to steel (the ratio is about 1:10, depending on materials), which leads to large sections in columns of multistory buildings;
- Cracks develop in concrete due to shrinkage and the application of live loads.
Poisson's Ratio for Materials
Definition:
Poisson's Ratio is the ratio of the transverse to the longitudinal strains under axial stress within the elastic range. It is a negative ratio.
Compression Flange of Beam or Girder
Definition
The widened portion of a beam or girder, such as the horizontal portion of the cross section of a simple-span T-beam, which is shortened by bending under a normal load is known as Compression Flange.
In a continuous floor beam under gravity loading, the laterally un-braced bottom flange is subjected to compressive stresses (Compression Flange) near the interior support(s). To prevent lateral buckling of the flange, this region must be adequately designed.
Related Question:
- What is compression flange?
- Why compression flange is important?
- Which portion of beam or girder is known as Compression Flange?
- Why compression flange must be adequately designed?
Slender Beam
The Slender beam can be defined as the beams in which the spacing of the lateral support to the compression flange or face is more than 50 times the least width of the flange or face.
Since lateral support equal to a minimum of 2 percent of the total (internal) compression in the compression flange is usually considered adequate, and may often be satisfied by simple friction of separate floor materials transmitting the load to the beam, the beam slenderness problem will be encountered only rarely in routine design. It may arise in design of long span upturned roof beams or in the design of thin deep panels used as spandrel beams. Such spandrels are often precast and added to the frame as simply supported beams with a span equal to the column spacing and width of the compression flange as little as 4 inch.
When a slender beam condition arises, the simple solution is to provide lateral bracing within the spacing limits, thus eliminating the condition. Where lateral bracing is impracticable, the load capacity must be reduced.
**Hansel. William, and Winter. George, "Lateral Stability of Reinforced Concrete Beams", ACI Journal, 56(Sep.1959), 193-214.
** Sant. J., and Bletzacker. R. W., "Experimental study of Lateral Stability of Reinforced Concrete Beams", ACI Journal, 58(Dec. 1961), 713-736.
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