Continue to timber formwork design, hi-ribbed formwork usually used in large shape concreting.
Review of capacity of hi-ribbed
1) Check design span of hi-ribbed
Refer to previous concrete pressure checking, design concrete pressure imposed on falsework is 24.97 kPa.
or equivalent depth of concrete pour = 24.97 / 24 = 1.04m (say 1.5m)
From manufacturer's design manual, recommended vertical support spacing is 0.40m for depth of pour = 1.5m
Obviously, provide 300mm vertical supports span for hi-ribbed falsework is adequated, OK!
2) Check T32-300mm in vertical support spacing for hi-ribbed
Inclined tie bar (T12) support = 600 mm c/c in horizontal and vertical spacing (for conservative, say 1000mm in horizontal spacing)
Design concrete lateral pressure = 24.97 kPa
Design strength of T32 re-bar, fy' = 0.87*fy = 400.2 MPa
Section modulus of T32 re-bar, Zx = 3.14*32^3 / 32 = 3217 mm^3
Sectional area of T32 re-bar, A = 3.14*32^3 / 4 = 804 mm^2
Moment capacity of T32 re-bar, Mc = fy'*Zx = 400.2 x 3217 = 1.287 kNm
Shear capacity of T32 re-bar, Vc = fy'*A = 400.2 x 804.2 = 321.9 kN or 0.6Vc = 193.1 kN
Design shear, V = 3.75*1.4 = 5.24 kN < 193.1 kN, OK!
Design moment, M = 1/10*7.49*10^2*1.4 (for continuous span) = 1.049 kNm < 1.287 kNm, OK!
Design shear, V = 3.75*1.4 = 5.24 kN < 193.1 kN, OK!
Design moment, M = 0.188*2*3.75*0.6*1.4 = 1.18 kNm < 1.29 kNm, OK!
3) Check T12 inclined tie bar
Spacing of tie bar, S = 600 mm c/c in horizontal and vertical spacing
Design concrete lateral pressure = 24.97 kPa
Inclination of tie bar = 45°
Design tensile load on tie bar, T = 24.97*0.6*0.6*1.4 / cos45° = 17.80 kN
Sectional area of T12 re-bar, A = 3.14*12^2 / 4 = 113 mm^2
Tensile of bar, ft = 17798 / 113 = 157.37 N/mm^2 < fy' = 400 N/mm^2, OK!
Review of capacity of hi-ribbed
1) Check design span of hi-ribbed
Refer to previous concrete pressure checking, design concrete pressure imposed on falsework is 24.97 kPa.
or equivalent depth of concrete pour = 24.97 / 24 = 1.04m (say 1.5m)
From manufacturer's design manual, recommended vertical support spacing is 0.40m for depth of pour = 1.5m
Obviously, provide 300mm vertical supports span for hi-ribbed falsework is adequated, OK!
2) Check T32-300mm in vertical support spacing for hi-ribbed
Inclined tie bar (T12) support = 600 mm c/c in horizontal and vertical spacing (for conservative, say 1000mm in horizontal spacing)
Design concrete lateral pressure = 24.97 kPa
Design strength of T32 re-bar, fy' = 0.87*fy = 400.2 MPa
Section modulus of T32 re-bar, Zx = 3.14*32^3 / 32 = 3217 mm^3
Sectional area of T32 re-bar, A = 3.14*32^3 / 4 = 804 mm^2
Moment capacity of T32 re-bar, Mc = fy'*Zx = 400.2 x 3217 = 1.287 kNm
Shear capacity of T32 re-bar, Vc = fy'*A = 400.2 x 804.2 = 321.9 kN or 0.6Vc = 193.1 kN
Design moment, M = 1/10*7.49*10^2*1.4 (for continuous span) = 1.049 kNm < 1.287 kNm, OK!
Design moment, M = 0.188*2*3.75*0.6*1.4 = 1.18 kNm < 1.29 kNm, OK!
3) Check T12 inclined tie bar
Spacing of tie bar, S = 600 mm c/c in horizontal and vertical spacing
Design concrete lateral pressure = 24.97 kPa
Inclination of tie bar = 45°
Design tensile load on tie bar, T = 24.97*0.6*0.6*1.4 / cos45° = 17.80 kN
Sectional area of T12 re-bar, A = 3.14*12^2 / 4 = 113 mm^2
Tensile of bar, ft = 17798 / 113 = 157.37 N/mm^2 < fy' = 400 N/mm^2, OK!