Month: September 2011

Septic Tank Design for an Office Complex

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Septic Tank Design Calculations | Building Construction

In the previous article, we discussed in detail the calculations that are to be carried out for the design of a Septic Tank for 3bhk, 2bhk and 1bhk homes.

In this article, we will move forward with our discussion on the Septic Tank calculations for an Office Complex.

First question that is likely to occur to your mind would be, “How are Septic Tank Design calculations for an Office Complex different from that of a Residence?”

Let us first answer this question before we move forward with the calculations.

Residences are structures which are occupied with families living, eating and sleeping there. Let’s take an example of a person who regularly goes to an office for his job.

Let’s have a look at his Daily schedule:

  • He wakes up in the morning.
  • Takes a bath, uses a toilet.
  • Has his breakfast after which he washes his hands. Apart from him using the services in the house, his family members also use the same.
  • He leaves for his office. After he reaches the office, he wouldn’t take bath which consumes the maximum amount of water which turns into sewage water after use.
  • His usage of toilet and bathroom would be minimum. Hence, it is important to understand the logic behind the Septic tank calculations.

Calculations for an Office Complex with 8000 employees

As per thumb rule;

Quantity of sewage to be considered for an Office Complex is to be calculated on the basis of the capacity of the Office.

Now, we are calculating the Volume for the Septic Tank required for an Office Complex with 8000 employees.

Hence, quantity of sewage to be considered per person should not be less than 20 gallons.

Office Complex = 8000 persons

Total quantity of sewage = 8000*20 = 1,60,000 gallons

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Septic Tank Design Calculations | Building Construction and Design

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How to design a Septic Tank?

A Septic Tank is a small scale sewage treatment system used in areas which have no connection to the main sewage pipes that are provided by the Local governments or private Corporations.

In this article, we will detail out all the calculations that are to be performed to get the required volume of a Septic Tank with the help of examples.

Schematic Diagram of a Septic Tank
Schematic Diagram of a Septic Tank

We would begin with a small scale example so that your concept of Septic tank design is clear.

Here are the thumb rules to be kept in mind which will help you in calculating the volume of a Septic Tank.

For a three bedroom house:

The quantity of sewage considered for a three bedroom house should not be less than 900 gallons.

For a two bedroom House:

The quantity of sewage to be considered for the design of Septic Tank should not be less than 700 gallons.

For one bedroom unit:

The quantity of sewage to be considered for the design of a Septic Tank should not be less than 550 gallons.

Let’s begin with an example of a three bedroom residence.

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Thumb rules for designing a Column layout | Civil Engineering

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Guidelines to be followed for making a column layout

In this article, we will go through the essential thumb rules to be followed for giving a column layout. Of-course columns have to be designed in accordance to the total forces acting on the structure, but apart from that, it is essential for every Civil engineer and Architect to remember a few thumb rules so that they are prevented from making mistakes.

You can hire me for your structural design need. Contact me.

Three thumb rules to be followed are as follows:

  1. Size of the Columns
  2. Distance between Columns
  3. Alignment of columns

Minimum Size of RCC columns

The size of the columns depends on the total load on the columns. There are axial loads and lateral loads. Large beam spans induce bending moment not only in the beams, but also in columns which are pulled by the stresses in the beams. It is important to use advanced structural design software like ETabs or Staad pro. I highly recommend every structural designer learn these software. The thumb rules are for general designing in very small projects.

For this general thumb rule, we will assume a structure of G+1 floors high, using standard 6″ walls.

Minimum size of an RCC column should not be less than 9” x 12” (225mm x 300mm) with 4 bars of 12 MM Fe415 Steel.

These days the minimum I use in my projects is 9″ x 12″ (225 mm x 300mm) with 6 bars of 12 MM Fe500 steel. You can never go wrong with strong columns. I also recommend use of M20 grade concrete for the structure (ratio 1 part Cement : 1.5 parts Sand : 3 parts Aggregate with 0.5 parts water by volume). I recommend use of 8 MM stirrups at a distance of 150 MM center to center throughout the length of column.

This setup of 9″ x 12″ RCC columns is safe for G+1 Floors. There are a lot of other considerations, but this is just a thumb rule.

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Causes of Foundation Damage | Moisture

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Foundation Damage caused due to Moisture absorption

In my earlier articles, we discussed some of the important causes of foundation damage.

Getting a clarity on the subject helps you prevent your structure from further damage or any damage that might happen in future. We have also discussed “how analysis of foundation damage is to be carried out”.

In this article, we will discuss in detail the foundation damage occurring due to Moisture. This element is also responsible for foundation damage and if ignored or left unnoticed can cause severe damage resulting in structural failure.

Types of foundation damage can be classified as follows:

Erosion

  1. Natural rock
  2. Brick

Rot

Insects

Moisture damage

  1. Frost wedging
  2. Salt bloom

Settlement in the ground

  1. Groundwater lowering
  2. Limited bearing capacity of the ground (land)
  3. Excavations performed below the foundations and poor quality of backfill
  4. Increased load on the ground leading to failure
  5. Damage to the neighbouring houses
  6. Increased load
  7. Damage (by removing) to the neighbouring houses
  8. Horizontal movement occurring in the ground

Frost heave/adfreezing

Alum shale

Let us move on with the discussion on damage caused by moisture to the foundations.

Moisture damage

In older buildings, the walls were covered with clay and lime as mortar. These building materials are moisture absorbent. The walls do not undergo severe damage as long as the lime and clay walls are not treated with any other building material.

For example:

In an old building where the plastering has been done using lime and clay suffers from some chipping and damage. This calls for locals repairs which are to be done to maintain the aesthetics of the structure.

Since, cement mortar is a modern material and is available in abundance, the repairs are done with Cement mortar.

Before initiating such tasks, it is to be remembered that the coefficient of expansion of different materials is different. When cement mortar is used as a repair material over lime mortar, due to different moisture absorption properties and coefficient of expansion, the combination does not work very well.

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