REPAIR

[Audio] REPAIR The main purpose of repair is to bring back the architectural shape of the building so that all services start working and the functioning of building is resumed quickly. Repair does not pretend to improve the structural strength of the building ..

[Audio] The action will include the following: Patching up of defects such as cracks and fall of plaster. Repairing doors, windows, replacement of glass panes. Checking and repairing electric wiring. Rebuilding non-structural walls, compound walls, etc. Re-plastering of walls as required. Relaying cracked flooring at ground level. Decoration – white washing, painting, etc. Checking and repairing gas pipes, water pipes and plumbing services..

[Audio] RESTORATION It is the restitution of the strength of the building had before the damage occurred. The main purpose of restoration is to carry out structural repairs to load bearing elements. Some of the approaches are stated below: Removal of portion of cracked masonry walls and piers and rebuilding them in richer mortar Addition of reinforcing mesh on both face of the crack wall, holding it to the wall through spikes or bolts and then covering it suitably Injecting epoxy like material, which is strong in tension into the cracks in walls, column, beam and footing..

[Audio] RETROFITTING Retrofitting is the seismic strengthening of existing damaged or undamaged buildings. It is an improvement over the original strength when the evaluation of the building indicates that the strength available before the damage was insufficient and restoration alone will not be adequate in future quakes..

[Audio] MASONRY CONSTRUCTION ASPECTS FOR EARTHQUAKE RESISTANCE A) PLAN OF A BUILDING The building as a whole or its various blocks should be kept symmetrical about both the axes. Asymmetry leads to torsion earthquake and is dangerous. Simple and regular shapes behave better during earthquake than shapes with many projections. If longer lengths are required two separate blocks with sufficient gap 25 to 40 mm in between should be provided. The projection in plan shall not exceed L/3 or B/3 in length or width respectively. Length of block in plan should not exceed 3B..

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[Audio] MASONRY CONSTRUCTION ASPECTS FOR EARTHQUAKE RESISTANCE B) MASONRY MORTAR As per IS : 4326-1993, buildings are classified into A to E categories, According to earthquake resistance, as under : BUILDING CATEGORY DESIGN SEISMIC COEFFICIENT A 0.04 to less than 0.05 B 0.05 to 0.06 C More than 0.06 and less than 0.08 D 0.08 to less than 0.12 E 0.12 and More.

[Audio] The proportion of masonry mortar shall not be poor than (1:6) cement-sand. BUILDING CATEGORY MASONRY MORTAR A Cement-sand 1:6 or Lime-Cinder 1:3 or richer B, C Cement-Lime-Sand 1:2:9 or Cement-sand 1:6 or richer D, E Cement-sand 1:4 or Cement-Lime-sand 1:1:6 or richer.

[Audio] MASONRY CONSTRUCTION ASPECTS FOR EARTHQUAKE RESISTANCE C) WALL DIMENSION AND BUILDING HEIGHT For single storey building, wall thickness shall not be less than 1 brick (190 MM) For Three storey building, wall thickness in ground storey shall not be less than 1 1 brick and in the upper floors wall thickness shall not be less than 1 brick. Wall thickness shall not the less than 1/16 of the distance between two cross walls. The floor height shall not exceed 3.0 m. BUILDING CATEGORY MAXIMUM NUMBER OF STOREYS A, B, C 3 D 2.

[Audio] D) WALL OPENING In walls the size of opening shall be small and located in the middle of the wall. Opening Shall be located at minimum distance of ¼ into height of opening from the inner corner. This distance shall not be less than 60cm. Total length of openings in a wall shall not exceed : One Storey Building = 50% of the distance between two cross walls. Two Storey building = 42% of the distance between two cross walls. Three Storey building = 33% of the distance between two cross walls. The horizontal distance between two nearby openings shall not be less than 0.5 x height of opening and not less than 60cm. The vertical distance between two openings shall not be less than 0.5 x Width of opening and not less than 60cm. If above criteria are not satisfied, the opening shall protected by 2-8mm diameter of bars..

[Audio] E) MASONRY BOND For getting sufficient strength masonry work shall be carried out in proper bond with vertical joints in one vertical line in the alternate courses. First of all wall shall be constructed for 60cm height at the corners, than central portion of wall shall be constructed. At the junction of two walls, toothed joint shall be provided..

[Audio] E) HORIZONTAL BANDS PLINTH BAND- Plinth bands are provided when soil is soft or uneven in their properties. This band also acts as DPC LINTEL BAND- This is most important band and will in corporate in itself all doors and window lintels. It must be provided in all storeys in buildings. The reinforcement of lintels should be provided extra. ROOF BAND- This band will be required at eaves level of trussed roofs and also below or in the level with such floors which consists of joists. GABLE BAND- Masonry gable ends must have the triangular portion of masonry enclosed in a band, the horizontal part will be continuous with the eave level band..

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[Audio] MATERIAL FOR REPAIR OF CRACKS Material for Repair:- Cement Slurry Cement Mortar Epoxy Resin Polymer Modified Cementious Products (PMCC) 4.1) Polyvinyl Acetate Styrene Butadiene Rubber Acrylics.

[Audio] Requirements of and ideal Repair Materials:- An excellent bonding material. A very good repair mortar which provides excellent waterproofing and resistance to carbon dioxide penetration apart from having bonding property. Temperature compatibility of the repair material with the material of existing structure, which is being repaired. If distress is due to corrosion of reinforcement a proper surface cleaning and application of a suitable corrosion inhibiting material is a requirement. If waterproofing treatment is waterproofing system is required. necessary for rehabilitation, application of good.

[Audio] REPAIR OF BRICK MASONRY Sealing of cracks by epoxy resin injections. Repairing brick work with Epoxy mortar or Cement mortar. Installing Ferro-cement plate at corner. Rebuilding Portion of a wall. Stitching Method of Repairing Cracks..

[Audio] 1. Sealing of cracks by epoxy resin injections. If cracks are reasonably small the technique to restore the original tensile strength of the cracked element is by pressure injection of epoxy. The procedure for repair is as follows : The external surfaces are cleaned of non structural materials. Plastic injection ports are place along the surface of the cracks on both sides of the member and are secured in place with an epoxy sealant. The c/c spacing of these ports may be approximately equal to the thickness of the element. After the sealant has cured, a low viscosity epoxy resin is injected into one port at a time, beginning at the lowest part of the crack in case it is vertical or at one end of the crack in case it is horizontal. The resin is injected till it is seen flowing from the opposite sides of the member at the corresponding port. The injection port should be closed at this stage and injection equipment move to the next port and so on..

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[Audio] 2. Repairing brick work with Epoxy mortar or Cement mortar. For cracks wider than about 6 mm or for region in which the concrete or masonry is crushed a treatment other than the injection is indicated. The procedure for repair is as follows : The loose material is removed and replace with any of the materials like expansive cement mortar, quick setting cement or gypsum cement mortar. Where found necessary, additional or shear or flexural reinforcement is provided in the region of repairs. This reinforcement could be covered by mortar to give further strength as well as protection to the reinforcement. In areas of very sewer damage ,replacement of the member or the portion of the member can be carried out..

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[Audio] 3. Installing Ferro-cement plate at corner. To repair the cracks at the corners of a wall, wire mesh G-14 (2mm wire, 25mm x 25mm mesh) is fixed with bearing of 500 to 600 mm on either side of crack. The wire mesh is covered by rich mortar..

[Audio] 4. Rebuilding Portion of Walls If the stone masonry is severely damaged due to earthquake, the portion of wall or entire wall is dismantled and new masonry wall is constructed. At the time of repair, the roof must be supported temporarily..

[Audio] 5. Stitching Method of Crack Repair Stitching method is used for repairing wide cracks in masonry walls and slabs. The Various steps are : Drill holes on either sides of the cracks. Chaze a groove between the holes drilled. Fix u-shaped M.S. bar in the holes and groove transverse to the cracks. Grout the holes using epoxy grout or other non-shrink grout. Finish the hole and groove with epoxy mortar..

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