Concrete Formwork Design

What is Concrete Formwork?

Concrete Formwork is the structure, usually temporary, used to contain poured concrete and to mold it to the required dimensions and support until it is able to support itself. It consists primarily of the face contact material and the bearers that directly support the face contact material.

Notation for Concrete Formwork

f_el = Mold plate bending strength [MPa]
f_ebk = Primary support beam bending strength [MPa]
f_eik = Secondary support beam bending strength [MPa]
f_kl = Mold plate shear strength [MPa]
f_kbk = Primary support beam shear strength [MPa]
f_kik = Shear strength of secondary support beam [MPa]
GK = Safety factor
p = Pressure on the formwork due to fixed and live loads [MPa]
E_l =Plate modulus of elasticity [mm ² ]
E_bk = Primary support beam modulus of elasticity [mm ² ]
E_ik = Secondary support beam modulus of elasticity [mm ² ]
A_l = Plate cross-sectional area [mm ² ]
A_bk = Primary support beam cross-section [ mm ² ]
A_ik = Secondary support beam cross-sectional area [mm ² ]
I_l = Plate section moment of inertia [mm ⁴ ]
I_bk = Primary support beam section moment of inertia [mm ⁴ ]
I_ik = Secondary support beam section moment of inertia [mm ⁴ ]
S_l = Plate section moment of inertia [mm ³ ]
S_bk = Primary support beam section moment of strength [mm ³ ]
S_ik = Secondary support beam section moment of strength [mm ³ ]
b_l = Formwork plate width
L_bk = Primary support beam spacing
L_ik = Secondary support beam spacing
N_d = Fastener tensile capacity or strut axial compressive capacity

How to Design Concrete Formwork with Detailed Calculation?

Concrete formwork Design and carrier formwork scaffolding design calculation is below:​

The characteristic value is the Concrete formwork components' modulus of elasticity and strength. For the strength value, GK = 2.0 is accepted.

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• Primary Beam Interval, L_bk , Secondary Beam Interval, _Lik , Prop Interval, L_d , Rod Interval, L_b

• Primary Beam Intervals according to the selected plate thickness in slab formwork boards, beam bottom and top formwork boards, and column or shearwalls side formwork, L_bk ,

f_el= Formwork plate bending strength [MPa]

f_kl= Formwork plate shear strength [MPa]

GK = Factor of safety

p = Pressure acting on the formwork due to fixed and live loads [MPa]

E_l= Plate Modulus of Elasticity [mm²]

A_l= Plate sectional area [mm²]

I_l= Plate section moment of inertia [mm⁴]

S_l= Plate section moment of strength [mm³]

b_l= Formwork plate width

For slab and column-wall formwork, b_l= 1000 mm. In the beam lower formwork plates, b_l is taken as the width of the beam.

• Secondary Beam Intervals according to primary support beam dimensions to be used in slab, beam, column, and shear wall formwork, L_ik ,

f_ebk= Primary support beam bending strength [MPa]

f_kbk= Primary support beam shear strength [MPa]

GK = Factor of safety

p = Pressure acting on the formwork due to fixed and live loads [MPa]

E_bk= Primary support beam modulus of elasticity [mm²]

A_bk= Primary support beam cross-sectional area [mm²]

I_bk= Primary support beam section moment of inertia [mm⁴]

S_bk= Primary support beam section moment of strength [mm³]

L_bk= Primary support beam interval

• Rod Intervals to be used in column, shearwall, and beam side formwork, L_b

f_eik= Secondary support beam bending strength [MPa]

f_kik= Secondary support beam shear strength [MPa]

GK = Factor of safety

p = Pressure acting on the formwork due to fixed and live loads [MPa]

E_ik= Secondary support beam modulus of elasticity [mm²]

A_ik= Secondary support beam cross-sectional area [mm²]

I_ik= Secondary support beam section moment of inertia [mm⁴]

S_ik= Secondary support beam section moment of strength [mm³]

L_ik= Secondary support beam interval

N_d= Rod tensile capacity or prop axial pressure capacity

• The props of the slab formwork will be on each secondary support beam. Prop Intervals, L_d

f_eik= Secondary support beam bending strength [MPa]

f_kik= Secondary support beam shear strength [MPa]

GK = Factor of safety

p_d = Pressure acting on the formwork due to fixed and live loads [MPa]

E_ik= Secondary support beam modulus of elasticity [mm²]

A_ik= Secondary support beam cross-sectional area [mm²]

I_ik= Secondary support beam section moment of inertia [mm⁴]

S_ik= Secondary support beam section moment of strength [mm³]

L_ik= Secondary support beam interval

N_d= Rod tensile capacity or prop axial pressure capacity

• The props of the beam formwork will be on each secondary support beam.

f_eik= Secondary support beam bending strength [MPa]

f_kik= Secondary support beam shear strength [MPa]

GK = Factor of safety

p_d = Pressure acting on the formwork due to fixed and live loads [MPa]

E_ik= Secondary support beam modulus of elasticity [mm²]

A_ik= Secondary support beam cross-sectional area [mm²]

I_ik= Secondary support beam section moment of inertia [mm⁴]

S_ik= Secondary support beam section moment of strength [mm³]

L_ik= Secondary support beam interval

N_d= Rod tensile capacity or prop axial pressure capacity

• In column or shearwall formwork, at least one level of support should be used to carry the wind loads calculated according to 1.2.2.

• Wind effects are taken into account in the support design.

• The Ƥ_d value used to determine the Prop Interval, L _d, varies according to the sequential use of the scaffoldings. The total number of stories (n) where the props are used sequentially, starting from the ground story, is entered as user-defined.

• If the number of primary beam, secondary beam, rod, or prop is 2, the interval values ​​are reduced by multiplying by 0.8.

• When calculating the prop interval, the total load (nG+Q) that will affect the props is increased by 10%.

• Prop interval for slabs,

• Prop interval for beams,