E-COURSE
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VULNERABILITY ATLAS
OF INDIA

  From the Desk of Executive Director

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RAT TRAP BOND BRICK WALL
 
System Components
 
Initial Cost Structure
 
 
 
 
 
 
 
 
 
 
 
  
 
Local Economy Component = 23%
23 mm thick load bearing wall in rat trap bond brick masonry using cement mortar (1:6) and class I bricks 
Design Example : Wall For A Two Storeyed Building With Rcc Roof
 
 
Load on the Wall         = 40KN
Length of the Wall       =3m
One end continuous and the other end discontinuous
Effective length            = 0.9 x 3 = 2.7m
 
(Table 5 : Section VI : 4 NBC)
Thickness of the wall    = 0.23m
Effective thickness       = 0.15m
 
(Table 6 : Section VI : 4 NBC)
Height of wall              = 3m
Effective height of wall = 0.75 x 3 = 2.25
 
(since roof is RCC)
Area of cross section   = 3 x 0.15 = 0.45 sqm
Slenderness ratio         = Min (2.25/.15,2/7/.15) = 15
Stress reduction factor  = .78 (Table 8: Section VI : 4 NBC)
Compressive stress    = 44/.9 = 0.1 N/sqmm.
Permissible compressive stress   = 0.273 N/sqmm
Hence Safe at 23 cm thickness
 
 
 
 
 
 
 
 
 
 
Critical Factors
 
1.  Curing
2.  Quality of Bricks
3.  Not used for buildings having more than two floors
4.  Quality of sand
5.  Availability of skilled mason
Tools Used
 
1.     Trowels            5. Shovel
2.     Plumb bob       6. Baskets
3.     Thread                         
4.     Pans  
DO’S
 
DON’T’S
 
1.  Curing should be done for seven days
2.  Cavity should be broken after six layers
3.  Brick should be completely soaked in  
     water before using for masonry
4.  Mortar should be used within 30 minutes  
     of adding water to the mix
5.  Brick bats should be used at corners and   
     T - Junctions
 
 
1.    Find sand should not be used for
 masonry
 2.  Mortar should not be left in cavities
 
Construction Process
 
 
 
 
 
 

 
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