• Error in design or construction
• Modification of structural system
• Seismic Damage.
• Structural Cracks
• Corrosion due to penetration honeycomb.
PROBLEM IN CONCRETE COLUMN
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| Column Problem |
PROBLEM IN CONCRETE SLAB
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| Slab Problem |
RETROFITTING
* It is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes.
* The retrofit techniques are also applicable for other natural hazards such as tropical cyclones, tornadoes, and severs winds from thunder storms.
Objective of Retrofitting
- Retrofitting is the seismic strengthening of existing damaged or undamaged structures.
- It is an improvement over the original strength when the evaluation of the building indicate that the strength available before the damage walls insufficient and restoration alone will not be adequate in future quakes.
Configuration of Building
1. Modification of Plan
Majority of school buildings have simple design, most of them are rectangular with length to width ratio less than three. Then ext preferred shapes are elongated rectangle or L-shape. Other shapes also exist. The design of the buildings can be improved by separating wings and/or dividing it in parts as shown in fig.
To balance the stiffness of the building design, some existing openings may require elimination, reduction in size or even construction of new openings. Similarly, as in new building construction, there should be limitation on openings. Total openings in a buildings hall not exceed that specified in section
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| Modification Shape of Building 1 |
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| Modification Shape of Building 2 |
2. Elevation Improvement
School building in general is simple in construction though there remains some problem of stiffness distribution in vertical direction. As the construction process has been incremental, upper storey could have less covered area than lower one making building look like terrace that may lead to rotational effects. The problem can e solved through not necessary either by demolition of upper part or construction of the uncovered areas.
Improving Earthquake Resistance of wall Structure
Earthquake resistance of a masonry building can be improved by increasing the strength ,
*Reducing the length of existing walls
*Reducing the existing Opening
*Changing the location of Opening
In some cases even constructing new opening if the openings in opposite face.
Some Method
- Inserting Internal Cross wall
- Strengthening Existing wall with buttressing
Honey comb in Column & Beam
Honeycomb are void spaces and cavities left in concrete mass on the surface or inside of the concrete where the paste of cement could not reach. These look like honey bees nest. It occurs due to improper vibration and workability of concrete are main causes of honeycombs in concrete
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| Honey comb in Tie-Beam |
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| Honey comb in Column |