Video from my You tube channel

Subscribe to My You tube channel

Example 2: Design of rectangular beam(SI units)

Design a rectangular beam for a 10-m simple span to support a dead load of 20 kN/m (not including beam weight) and a live load of 30 kN/m. Use ρ = 0.01415, fc'= 28MPa, and fy= 420 MPa, and concrete weight is 23.5 kN/m3. Do not use the ACI thickness limitation.

assuming beam weight=10/kn/m
dead load for beam=10+20=30kn

b*d^2= Mu/(Ф*ρ*fy(1-ρ*fy/(1.7*fc')))/Mu
assuming Ф=0.9

b*d^2=2.243x10^8=   400 mm × 749 mm
                                                   450 mm × 706 mm                                                    500 mm × 670 mm

selecting 500 x 800 (d=680mm)

Beam weight=0.5*0.8*23.5=9.4 kn/m this less than assumed so ok

As= ρ *b*d=0.01415*500*670=4811mm2

use 6#32 in two rows, As=4914mm2

now checking if Ф=0.9 is valid

a=4914*420/(0.85*28*500)=173.43 mm
β1=0.85 for fc'=28 Mpa
C=a/β1=204 mm

εt=(0.003*d/c)-0.003=0.007>0.005    ok

checking Ф*Mn>Mu
Ф*Mn=0.90*4914*420*(680-174.43/2)=1,101,093,395.22>Mu   ok


Popular posts from this blog

Field density test-sand cone method

Example 1: Design of one-way slab

Determinate and indeterminate structure

Pile cap

Zero force member for truss

Flakiness Index and Elongation Index of Coarse Aggregates

Tributary area(Loading)

Types of structure

Equations of Equilibrium In Structural analysis

Cracking moment