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Deflection control by span to effective depth ratio
Basic span/depth ratio with the modification factor for tension steel, checked against the ratio provided. Reference: IS 456:2000 Cl. 23.2.1, Fig. 4.
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# Data
L := 5.5 m
d := 450 mm
b := 300 mm
f_y := 415 MPa
A_st.req := 1050 mm^2
A_st.prov := 1206 mm^2
# Modification factor
f_s := 0.58*f_y*A_st.req/A_st.prov = MPa
p_t := 100*A_st.prov/(b*d) =
k_t := min(1/(0.225 + 0.00322*f_s/(1 MPa) + 0.625*log10(p_t)), 2) =
# k_t follows the curve of Fig. 4 (a fitted expression), limited to 2.
# Check
ratio_basic := 20
ratio_allowed := ratio_basic*k_t =
ratio_actual := L/d =
ratio_actual <= ratio_allowed =How to use this example
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