모두CBT
아래 단면을 가진 철근콘크리트 기둥의 최대 설계축하중(ϕPn\phi P_nϕPn)은? (단, fck=30 MPaf_{ck}=30\,\mathrm{MPa}fck=30MPa, fy=400 MPaf_y=400\,\mathrm{MPa}fy=400MPa)
21,425 kN21{,}425\,\text{kN}21,425kN
17,958 kN17{,}958\,\text{kN}17,958kN
12,958 kN12{,}958\,\text{kN}12,958kN
15,425 kN15{,}425\,\text{kN}15,425kN
띠철근 기둥의 최대 설계축하중:ϕPn=ϕ⋅0.80[0.85fck(Ag−Ast)+fyAst]\phi P_n=\phi\cdot0.80\left[0.85f_{ck}(A_g-A_{st})+f_yA_{st}\right]ϕPn=ϕ⋅0.80[0.85fck(Ag−Ast)+fyAst], ϕ=0.65\phi=0.65ϕ=0.65Ag=700×1800=1,260,000 mm2A_g=700\times1800=1{,}260{,}000\,\mathrm{mm^2}Ag=700×1800=1,260,000mm2, Ast=2×3210=6,420 mm2A_{st}=2\times3210=6{,}420\,\mathrm{mm^2}Ast=2×3210=6,420mm20.85×30×(1,260,000−6,420)+400×6,420≈34,534 kN0.85\times30\times(1{,}260{,}000-6{,}420)+400\times6{,}420\approx34{,}534\,\mathrm{kN}0.85×30×(1,260,000−6,420)+400×6,420≈34,534kNϕPn=0.65×0.80×34,534≈17,958 kN\phi P_n=0.65\times0.80\times34{,}534\approx17{,}958\,\mathrm{kN}ϕPn=0.65×0.80×34,534≈17,958kN
띠철근 기둥의 최대 설계축하중:ϕPn=ϕ⋅0.80[0.85fck(Ag−Ast)+fyAst]\phi P_n=\phi\cdot0.80\left[0.85f_{ck}(A_g-A_{st})+f_yA_{st}\right]ϕPn=ϕ⋅0.80[0.85fck(Ag−Ast)+fyAst], ϕ=0.65\phi=0.65ϕ=0.65
Ag=700×1800=1,260,000 mm2A_g=700\times1800=1{,}260{,}000\,\mathrm{mm^2}Ag=700×1800=1,260,000mm2, Ast=2×3210=6,420 mm2A_{st}=2\times3210=6{,}420\,\mathrm{mm^2}Ast=2×3210=6,420mm2
0.85×30×(1,260,000−6,420)+400×6,420≈34,534 kN0.85\times30\times(1{,}260{,}000-6{,}420)+400\times6{,}420\approx34{,}534\,\mathrm{kN}0.85×30×(1,260,000−6,420)+400×6,420≈34,534kN
ϕPn=0.65×0.80×34,534≈17,958 kN\phi P_n=0.65\times0.80\times34{,}534\approx17{,}958\,\mathrm{kN}ϕPn=0.65×0.80×34,534≈17,958kN
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