economic section

Solution to Problem 543 | Floor Framing

Problem 543
A portion of the floor plan of a building is shown in Fig. P-543. The total loading (including live and dead loads) in each bay is as shown. Select the lightest suitable W-shape if the allowable flexural stress is 120 MPa.
 

For Girders (G - 2) | Solution to Problem 542

For Girders (G - 2)

542-girder-g2.jpg$S_{required} = \dfrac{M}{f_b} = \dfrac{120(1000^2)}{120}$
$S_{required} = 1000 \times 10^3 \, \text{mm}^3$
 

For Beams (B - 3) | Solution to Problem 542

For Beams (B - 3)

542-beam-b3.jpg$M_{max} = \frac{1}{8}(20)(62)$
$M_{max} = 90 \, \text{kN}\cdot\text{m}$
 
$S_{required} = \dfrac{M_{max}}{f_b} = \dfrac{90(1000^2)}{120}$
$S_{required} = 750 \times 10^3 \, \text{mm}^3$
 

For Beams (B - 2) | Solution to Problem 542

For Beams (B - 2)

542-beam-b2.jpg$\Sigma M_{R2} = 0$
$6R_1 = 20(4) + 10(2)(5) + 15(4)(2)$
$R_1 = 50 \, \text{kN}$
 
$\Sigma M_{R1} = 0$
$6R_2 = 20(2) + 10(2)(1) + 15(4)(4)$
$R_2 = 50 \, \text{kN}$
 

For Girder (G - 1) | Solution to Problem 542

For Girder (G - 1)
542-girder-g1.jpg$S_{live-load} = \dfrac{M}{f_b} = \dfrac{40(1000^2)}{120}$
$S_{live-load} = 333.33 \times 10^3 \, \text{mm}^3$
 

Solution to Problem 542 | Floor Framing

Problem 542
Select the lightest W shape sections that can be used for the beams and girders in Illustrative Problem 537 of text book if the allowable flexural stress is 120 MPa. Neglect the weights of the members.
 

Solution to Problem 536 | Economic Sections

Problem 536
A simply supported beam 10 m long carries a uniformly distributed load of 20 kN/m over its entire length and a concentrated load of 40 kN at midspan. If the allowable stress is 120 MPa, determine the lightest W shape beam that can be used.
 

Solution to Problem 535 | Economic Sections

Problem 535
A simply supported beam 24 ft long carries a uniformly distributed load of 2000 lb/ft over its entire length and a concentrated load of 12 kips at 8 ft from left end. If the allowable stress is 18 ksi, select the lightest suitable W shape. What is the actual maximum stress in the selected beam?