Dimension
[σ]kokam = 10 MPa; [τ]kokam = 4,5 MPa
1. Mmax = 119,88 kN/m; Q = 4,70 kN ; N = 104,78 kN
σ = M/W ≤ [σ]; W = M/[σ] = 119,88 kN/m / 10 MPa = 1198800 kgxcm / 100 kg/cm2 = 11988 cm3
W = b x h/6; h =√W x 6/b; b - 30 cm
h =√W x 6 / b = √11988 x 6 / 30 = √2397,60 = 48,97 cm; h = 50 cm
F = b x h = 30 x 50 = 1500 cm2
Wx = b x h2/6 = 30 x 502 / 6 = 12500 cm3
σ = M/W + N/F ≤ [σ]; σ = 1198800 kgxcm /12500 cm3 + 10478 kg / 1500 cm2 = 103,63 kg/cm ≈
≈ 10 MPa ≤ 10 MPa
Ix = b x h3/12 = 30 x 503 / 12 = 312500 cm4
Sx = b x h2/8 = 30 x 502 / 8 = 9375 cm3
τ = Q x S / b x I ≤ [τ]; τ = 470 x 9375 / 30 x 312500 =4406250 / 9375000 = 0,47 kg/cm2 ≈
≈ 0,05 MPa ≤ 4,5 MPa
2. Qmax = 54 kN; Nmax = 108 kN; M = 0 kN/m;
σ = N/F ≤ [σ]; F = N/[σ] = 108 kN / 10 MPa = 10800 kg / 100 kg/cm2 = 108 cm2
F = b x h; h = F/b; b - 10 cm
h = F/b = 108 / 10 = 10,80 cm; h - pieņēmu 15 cm
F = b x h = 10 x 15 = 150 cm2
σ =N/F ≤ [σ]; σ = 10800 kg / 150 cm2 = 72…
