Doubly Reinforce Section Design

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Design of doubly reinforced section using eurocode 2

• Section 250x400
• fck = 25N/mm2  fyk = 500N/mm2
• Design Moment 175kNm
• d' = 50mm

 find K
M/bd^2fck  = 175*10^6/(250*(350^2)*25)
                   = 0.229>Kbal = 0.167
therefore compression reinforcement is required
         x        = 0.45d
                   = 0.45*350
                   = 157.5mm
         d'/x     = 50/157.5
                   = 0.317 < 0.38
therefore compression reinforcement yeild
then   fsc     = 0.87fyk
Compression reinforcements
        A's     = (M-0.167*fck*bd2)/(0.87*fyk*(d-d')
                  = (175*E6-0.167*25*250*350^2)/
                      (0.87*500*(350-50)
                  = 1337mm2
Tension reinforcement
     Zbal       = d(0.5+(0.25-Kbal/1.134)^0.25)
                  = 350*(0.5+ (0.25-0.167/1.134)^0.5)
                  = 287
    As          = 0.167*fck*bd2/(0.87*fyk*z 
                       + A's
                  = 0.167*25*250*350^2/(0.87*500*287
                            + 1337
                  = 2361mm