Introduction: be induced internally due to thermal

Introduction:  Settlement? ?in a structure refers to the distortion or disruption of parts of a building due to unequal compression of its foundations; shrinkage or undue loads being applied to the building after its initial construction.?Some settlement is quite normal after construction has been completed, but unequal (differential) settlement may cause significant problems for buildings.  Cracks are developed whenever stress in the component exceeds its strength. Cracks are classified in to structural and non structural categories. The structural ones are due to faulty design, faulty construction or overloading which may endanger safety of buildings. The non structural cracks are due to internally induced stresses. Depending on width of crack, these are classified. Stress in a building component could be caused by externally applied forces, such as dead, live, wind or seismic loads, or foundation settlement or it could be induced internally due to thermal movements, moisture changes, chemical action, etc.  cracks may have any direction depending on the direction of tensile strain. At a specific location in a wall, beam, column, cracks have the same direction. These cracks which appear on both sides of the structural elements have similar patterns in all floors with intensity decreasing at higher floors.    Foundation Settlement observed in ODF Type 3 residential complex: Site Factor: Black cotton soil,the observed differential settlements is mainly due to the black cotton soil under the foundation.Chemically black soils consist of lime, iron, magnesium, alumina and potash but they lack in nitrogen, phosphorus and organic matter. The montmorillonite crystals which constitute the black cotton soil are not tightly bound hence water can intervene causing the clay to swell.     Based on the Foundation crack pattern, reason for the cracks can be identified ? Vertical foundation crack pattern:    Location: ?Ground Floor.  Width: ?2.5cm  Generally Vertical foundation cracks usually develop during the first few years after construction finishes, as the building settles and the concrete finally cures. They typically start as hairline cracks that progressively open up. ? Diagonal Crack Patterns in Building Foundations Location: ?First floor  Width: ?3cm   Diagonal cracks which emanate from the corners or windows, openings, or other changes in the shape of a wall (or slab) are called reentrant cracks and are a form of shrinkage crack and are usually the result of stress built up at the corner. ? Horizontal Crack Patterns Location : ?first floor  width :?4 cm  The most common cause of horizontal cracks in concrete block foundation walls is excessive unbalanced soil pressure. This type of movement will have horizontal cracks that may occur near the center of the wall or nearer to the top of the wall.   Conclusions: B?uildings are no longer safe for human residence, foundation movements are too high. Crack width has crossed the limit provided by the IS for the human residence.Proper site exploration is required before constructing on this type of soil


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