RF-CONCRETE Members – Online Manual Version 5

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RF-CONCRETE Members – Online Manual Version 5

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9.2.6.2 State I (uncracked)

State I (uncracked)

When determining the cross-section properties, we take the available steel area into account. The missing area of concrete in the zone of rebars is neglected. Recalculating the centroid of the ideal cross-section is not necessary because the reinforcement is symmetric with the same edge distances on top and bottom side.

The following distances for the Steiner component (parallel axis theorem) are the direct result:

  • ac = 0 cm
  • as1 = 8 − 2.5 = 5.5 cm
  • as2 = 5.5 cm
Moment of inertia

Iy,I = b · h312 + 2 · As1/s2 · a22 · αe = 100 · 16312 + 2 · 6.22 · 5.52 · 26.33 = 44 041 cm4 

Ideal cross-section area

AI = Ac + As ·αe = 16 · 100 + 12.44 · 26.33 = 1927.5 cm2 

Crack moment Mcr

We assume that the cross-section cracks when the tensile strength fctm in the most external fiber is reached.

σ = McrI · zct = fctm 

Mcr = fctm · Izct = 0.22 · 44 0418 = 1 211 kNcm = 12.1 kNm 

Steel stress σsrI and steel strain εsrI for crack moment

σsr1,I = fctm · 5.58 · αe = 2.2 · 5.58 · 26.33 = 39.82 N/mm2 

εsr1,I = σsrEs = 39.82200 000 = 1.991 = 0.199  

Notional steel and concrete stress for effective moment M = 17.64 kNm

σs1 = MI · zs1 ·αe = 176444041 · 5.5 · 26.33 = 5.77 kN/cm2 = 57.7 N/mm2 

σc = -MI · zcc = - 176444041 · 8 = - 0.32 kN/cm2 = -3.2 N/mm2 

Curvature for uncracked section (state I) (1/r)z,I = (1/r)I

1rz,I = ME · I = 0.017647594.9 · 4.4041 · 10-4 = 5.283 · 10-3 m-1 

Results of RF-CONCRETE Members
Figure 9.23 Detailed results for state I

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