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Design of Concrete Anchor Blocks

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STATIC ANALYSIS & DESIGN OF PIPE ANCHOR BLOCK FOUNDATION

DESIGN OF PIPE ANCHOR BLOCK 

FOUNDATION GEOMETRY & SKETCH        

Length of the Pipe Block        L= 1800mm      
Width of the Pipe Block        B= 1800mm      
Length of the Pipe Block Foundation   L= 3100mm      
Width of the Pipe Block Foundation’   B= 3100mm      
Depth of the foundation block below H.P.P  = 2000mm      
Height of Foundation block above H.P.P   = 500mm      
                 
Height of the Pipe         h= 1500mm(Avg ht assumed)
Depth of Raft            = 600mm      
Conrete , Fck              30N/mm2     
Reinforcement grade            500N/mm2     
Anchor Block

Thrust  blocks  or  anchor  blocks  are  required  on  all  unrestrained  pressure  pipelines  at  locations where thrust forces caused by internal pressures act upon the sides or ends of  pipelines.

 

Pipe Trust Block Foundation & Reinforcement Drawing
Click here to download the Drawing and Excel design calculation sheet
 WEIGHTS OF FOUNDATION & PIPE                     
                                        
  Weight of concrete foundation (Wf)     = ( 1.8 * 1.8 * 1.9 ) * 25 – Pipe 1.2Dia) + raft weight     
   (Pipe 1.2m dia Detected from conc wt)    = 9.7kN            
                                        
  Operating weight of Pipe Anchor Block, (WD)  = 240.00kN            
                       .                
                                        
  Total weight of Foundation system, Py     = 9.7 + 240             
  \                 = 249.70kN            
  Pipe Lever arm for moment         = 0.65m            
                                        
  Piping Horizontal Loads (Input from Piping Stress)                  
  Fz                 = 260kN            
  Fx                 = 25kN            
  Lateral Force dut to trust     Fz                      
  (Piping load              = 260kN            
  transverse direction of the block )                         
  Moment due to lateral Force    Mx1  = 260 * 0.65             
                     = 169.00kNm           
                                        
  Longitudinal Force due to unbalanced forceFx                  
      = 25kN            
                                        
                 Mz1  = 25 * 0.65             
                     = 16.25 kNm           
                                        
                                        
 CHECK FOR OVERTURNING ABOUT X-X AXIS                    
                                        
  During Normal Operation:        Without Wind/Seismic                  
                              

 
         
  Overturning moment about xx,MOT= Mx1                     
                = 169.00kNm             
                                        
  Restoring moment about x-x, MRx= ( Py x ( B/2 ) )                 
                =

 
(249.7 * (3.1 / 2 )   

 
            
                = 387.04kNm          
  Factor of safety,     MRx / MOT = 387.04 / 169                  
                = 2.29            
                >  1.2              
                         Hence Safe          
                                        
 CHECK FOR OVERTURNING ABOUT Z-Z AXIS                      
                                        
  During Normal Operation:                 

 
         
                                        
  Overturning moment about z-z,MOT=

 
Mz1        

 
            
                = 16.25kNm             
                                        
                                        
  Restoring moment about z-z, MRz= ( Py x ( L / 2))                 
                = (249.7 * (3.1 / 2)                
                = 387.035kNm             
  Factor of safety,     MRz / MOT = 387 / 16.25                  
                = 23.9               
                >  1.2                
                    

 
  
 

   Hence Safe          
 CHECK FOR SLIDING ALONG X-X- AXIS                       
                                        
  ‘Passive resistance due to soil in X direction                     
   1/2 x 3 x 18 x D^2 x B    = 348.75 kN                
  Resisting Force       = ( n * Py)                   
                = 0.3 * 249.7                  
                = 74.91kN         
  Sliding Force        = Fx + 0.5*V                  
                = 25.00kN         
  Factor of safety against sliding  = 74.91+348.75 /25                
                = 16.95            
                > 1.4             
                         Hence Safe          
                                        
 CHECK FOR SLIDING ALONG Z-Z- AXIS                       
                                        
  During Normal Operation:                           
                                        
  Passive resistance due to soil in Z direction                     
  1/2 x 3 x 18 x D^2 x B     = 348.75kN                 
                                        
  Resisting Force       = ( n * Py)                   
                = 0.3 * 249.7                  
                = 74.91kN            
  Sliding Force        = Fz                     
                = 260.00kN            
  Factor of safety against sliding  = 74.91+348.75 /260               
                = 1.6               
                > 1.4   Hence Safe          
  CHECK FOR BASE PRESSURE                         
                                        
    Soil weight      =160.524kN                   
    Bearing pressure on soil, s =P/A + Mx/Zx + Mz/Zz                 
             Max Pressure  =81.8kN/m2                  
             Min Pressure =3.7kN/m2                  
                                        
    Allowable SBC      < 237kN/m2  Hence Safe         
                                        
                                        
   CHECK FOR REINFORCEMENT                      
                                        
  Thickness of the foundation Raft,    t = 0.6m            
                                        
   Structural Design of the Base Slab:                           
                                        
   Cantilever projection beyond the face of the     0.650m            
         Column, l = (D – Dp) / 2                      
                                        
   BM at the face of the Column ,M                         
   Mu = M x FOS x 9.807           194.095 kNm / m         
   Effective depth of Raft slab required = sqrt(Mu / (3.45 x Lr) =0.237 m           
   effective depth              550.000 mm          
   Mu                  0.642 N/mm2          
   bd2                                
   From SP 16, percentage of Steel required    0.151 %           
                                        
   Area of Steel = cm2 / m           832.680 mm2           
   Gross Area                550000.000 mm2           
   Minimum steel =0.06% of Gross area =    330 mm2           
   Hence area of steel to be provided = MAX ( Astreqd, Astmin) =832.680 mm2           
    Provide     12Dia100c/c                   
   Provide 12 Tor at 100 mm c/c bothways at bottom                           
                                        
  Area of Reinforcements provided:                       
  At top        12mm @150mm c/c (Both X & Z Direction)         
  At bottom       12mm @100mm c/c (Both X & Z Direction)         
  Intermediate Reinforcements12mm @150mm c/c                 
  Vertical bars     12mm @150mm c/c                 
  Side Reinforcements  12mm @150mm c/c                 
                                        
   CHECK FOR UPLIFT                            
   Uplift presure    = (3.1 x 3.1 x 2 ) x 10    192.2kN            
                                        
   Downward Force  =           410.22kN            
   (Dead Weight of Foundation with Pipe Contant )                     
            =           2.13             
                                        
                  2.13 < 1.2    Hence Safe      

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