Foundation Damage and Retrofitting

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Causes of Foundation damage leading to Retrofitting

In one of my previous articles, we discussed various steps in which the survey of the foundation has to be done in order to be considered for retrofitting.

In this article, we will discuss various reasons or causes for the damage of the foundations.

Cracks in foundation
Cracks in foundation

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. Uneven depth of the bedrock (varying bearing capacities of the soil in the same patch of land)
  4. Excavations performed below the foundations and poor quality of backfill
  5. Increased load on the ground leading to failure
  6. Damage to the neighbouring houses
  7. Increased load
  8. Horizontal movement occurring in the ground

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Specifications for RCC Construction | Building Estimating and Costing

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In my earlier articles, I have discussed types of specifications and various purposes for which specifications are to be given. Most of the constructions of various types of buildings are RCC constructions. In this article, we are going to discuss in detail about the specifications that are to be necessarily given for carrying out RCC (reinforced Cement Concrete) constructions.

RCC specifications
RCC specifications

RCC Specifications

  • Shuttering shall be done using seasoned wooden boards of thickness not less than 30mm.
  • Surface contact with concrete shall be free from adhering grout, nails, splits and other defects.
  • All the joints are perfectly closed and lined up.
  • The shuttering and framing is sufficiently braced.
  • Nowadays timber shuttering is replaced by steel plates.
  • All the props of approved sizes are supported on double wedges and when taken out, these wedges are eased and not knocked out.
  • All the framework is removed after 21 days of curing without any shocks or vibrations.
  • All reinforcement bars conform IS specifications and are free from rust, grease oil etc.
  • The steel grills are perfectly as per detailed specifications.
  • The covers to concrete are perfectly maintained as per code.
  • Bars of diameter beyond 25mm diameter are bent when red hot.
  • The materials proportion should be as per the specifications of the concrete.

Number of Cement bags required for a specific cement concrete ratios

  • For cement concrete of ratio 1:1:2(1 cement:1sand/coarse sand:2graded stone aggregate) require 11no bags of 50kg.
  • For cement concrete of ratio 1:1.5:3 require 7.8no bags of 50kg.
  • For cement concrete of ratio 1:2:4 require 6 no bags of 50kg.
  • For cement concrete of ratio 1:3:6 require 4.25no bags of 50kg.
  • For cement concrete of ratio 1:4:8 require 3.2 no bags of 50kg.
  • For cement concrete of ratio 1:5:10 require 2.50 no bags of 50kg.
  • For cement concrete of ratio 1:6:12 require 2.25 no bags of 50kg.

New trends in the Color schemes and Materials of Design

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New Trends in the choice of Color schemes

The new trends in Furniture design has brought a concept of new choice of color schemes depending on the type of ambiance to be created. Along with maintaining the aesthetic aspect, new materials and new lighting techniques have also come up.

Two trend streams emerge; one following the ‘international’ look of pale sophistication, with beiges, creams and white, offset by stark black. A parallel stream throws into focus the bright new color palette with the nouveau chic fuschia, lime green, aubergine and aqua.

Trendy furniture Design
Trendy furniture Design

The trade and architect community notice a bifurcation in usage with designers selecting the former for more elegant, more ‘serious’ spaces such as offices, or for general use spaces such as lounge areas in hotels, while residential spaces, use color to project the personality of the owners. The bright colours give a happy office look. Finance and Insurance offices are serious and very professional offices can have lighter colors that add richness to the space whereas other offices could use shades of yellow and light brown.

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Types of Ranging | Chain Surveying

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Methods of Ranging in Chain Surveying | Guide to Surveying and Levelling

In measuring a survey line, the chain has to be laid out on the ground between the stations.

If the line is short, the chain could be put in alignment easily but if it is long or the end station is not clearly visible, then intermediate points has to be established in line with end points to know the directions of the line by ranging.

Types of Ranging

There are two types of ranging:

  1. Direct ranging
  2. Indirect ranging

Direct ranging

Direct ranging is possible when the stations are intervisible.

Ranging is done by eye-judgement. Ranging rods are erected vertically beyond each end of survey line.

The surveyor stands 2m beyond the ranging rod while the assistant folds the ranging rod vertically in the intermediate stations.

The ranging rod is held roughly in line by the thumb and fore-finger.

The surveyor directs the assistant to move the rod to the left or right until the three ranging rods appear to be in a straight line.

To avoid errors due to the ranging rods not being vertical, the lower end of the rod are cited for alignment.

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Numerical Examples for Errors in Chain Surveying

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A practical Example for Calculation of the True Area of the field | Errors in Chain Surveying

In my previous article, we studied how to measure true distance considering the Errors occurring in Surveying.

Correction formulas to be kept in mind (for incorrect length of Chain)

True distance = L’/L*measured distance

True area = (L’/L)2*measured area

True Volume = (L’/L)3 * measured volume

Where, L’ = incorrect length of chain

L = correct length of chain

The chain was tested before starting the surveying and was found to be 20m. At the end of surveying, it was tested again and was found to be 20.12m. The area of the plan of the field drawn to a scale 1cm = 6m was 50.4sqm. Find the true area of the field in sqcm.

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Chaining on Sloping Ground | Guide to Surveying and Levelling

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Chaining on Sloping Ground | Surveying and Levelling

There are two methods for determining horizontal distance on sloping ground.

  1. Direct Method
  2. Indirect Method

Direct Method of Chain Surveying

This method is also known as “Stepping Method”.

The horizontal distances are directly measured by the process of stepping.

Procedure

A path of chain or tape is stretched out from ‘P’.

The path length of chain or tape depends on the steepness of the ground.

The follower holds the zero end of the chain at ‘P’ and directs the leader at P1 to be in the line of PQ and stretch the chain or tape above the ground in horizontal line.

Direct Method | Chain Surveying
Direct Method | Chain Surveying

The leader then transfers the point ‘P1’ to P2 on the ground by means of plumb bob or dropping a pebble or an arrow,

Now the followers take the new position ‘P2’ and directs the leader to move forward and stretch the tape or chain in a line of PQ.

Now the followers take the new position ‘P2’ and directs the leader to move forward and stretch the tape or chain in a line of PQ and the new position is P3.

Again the leader transfers the point P3 to P4 on the ground as done earlier.

This process is repeated till the point Q is reached.

Horizontal distance PQ = S1 + S2 + S3 + S4 + S5

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Development in Structural Systems in Postmodernist Period

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Evolution of Structural Systems in Postmodernism

Before 20th century, there were three great developments in structural systems.

Bulk Active structure is classified as followed:

  1. Post and lintel
  2. Arch system

Dome and vault construction (either in the form of bulk, employing plastic materials i.e. concrete, hardening into a homogeneous mass or the thrust type, in which the loads are received and counterbalanced at definite points; steel-glass skeleton system.

 

St. Peter's Dome
St. Peter's Dome

 

After World War II, the analysis of building types provides information behind each of the greater styles. This can easily be understood that it was not merely a trend, but a period of serious and required experimentation directed toward answering the needs of a specific way of life. In the era, most of the construction work was dominated by sustainable building design, construction and using materials in ways that minimize toxic production methods and in using natural sunlight for energy and natural air movement and water for cooling, climate, methods of labour, available materials, and economy of means thus impose their dictates.

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Guide to Design of Simple Beam | Design of Steel Structures

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Design of Simple Beam

A member carrying loads perpendicular to its axis is defined as a beam.

For a simple floor beam, I-sections are used.

M/I = (sigma) /y

M = (I/y)(sigma)

I/y = Z (section modulus)

Therefore, M = z(sigma)

When beams are loaded, bending stresses are developed at all sections.

The bending stresses developed in beams can be determined by the equation theory of simple bending.

For laterally supported beams, the permissible bending stress in tension as well as in compression should not exceed (sigma)bc or (sigma)bt = 0.66fy

For laterally unsupported beams, the permissible stress in bending compression is calculated by using tables from the the IS code book (IS:800).

Load carrying capacity of the Beam

From structural steel tables for the given beam, the section modulus (Zxx) is obtained.

Depending upon whether the beam is laterally restrained or unrestrained; the value of permissible stress in bending compression ((sigma)bc) is calculated.

The moment of resistance of the beam is found out.

MR = Zxx .(sigma)bc

Equating the moment of resistance to the maximum bending moment equation, the total load (w) the beam can carry is calculated.

Practical Problems related to Construction on Site | Building Construction

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General Construction Problems on Site

Getting fine aggregate free from dust, clay, salts etc.

  • Silt clay and silt (sizes below 70M)
  • (sizes below 4-5M)
Practical Construction Problems on site
Practical Construction Problems on site

Being small, they absorb lot of water. Water available for cement hydration is less, leaves pores. Clay and silt affect the gel formation. As it does not participate in gel formation, denser cone is not formed. Durability is reduced.

Clay particles tend to flocculate due to cohesion and under stress, may tend to break resulting in voids, therefore weak concrete. These clay particles coat the coarse aggregate, thus presetting the bond between the coating of cement and coarse aggregate. This seriously affects the strength.

Therefore, sand containing silt and clay should be summarily rejected or through washing of sand but expensive.

Quality of water

  • Many it is hard water that is available at site. For food concreting job, it requires portable soft water, as the salt contents in hard water may affect the gel formation.

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Underwater Lighting Techniques | Aqua Architecture

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Under water lighting deals with the lighting systems placed inside water entities like swimming pools , fountains , etc , and some times even in smaller areas like Jacuzzis . This aspect of lighting mainly depends on the various physical properties of water ( refraction , reflection etc of stand still and moving water). Under water lighting also deals with the effects of lighting placed above water , on and in water.

Figure showing a water fall lit from beneath showing the ‘Glowing steps ‘ effect
Figure showing a water fall lit from beneath showing the ‘Glowing steps ‘ effect

Under water lighting also deals with the effects of lighting placed above water , on and in water.

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