Engr 426 steel structure

ENGR 426 - Spring 2020 San Francisco State University Instructor: S. Günay

Homework 5 (Due: 4/14/2020) Question 1 Determine the elastic section modulus and the plastic section modulus for a W36×330 modeled as three rectangles forming the flanges and the web. Compare the calculated values to those given in the Manual.

Question 2 Determine the plastic neutral axis and the plastic section modulus for a WT15×45 modeled as two rectangles forming the flange and the stem. Compare the calculated values to those given in the Manual.

Question 3 Using the dimensions below, determine the plastic section modulus for an HSS8×8×1/2 modeled as four rectangles forming the flanges and webs. Compare the calculated value to that given in the Manual.

Question 4 Determine the lightest-weight W-shape to carry a uniform dead load of 1.8 kip/ft plus the beam self- weight and a live load of 5.4 kip/ft on a simple span of 32 ft. Consider full lateral support and a compact section. Use A992 steel and Table 3.2 of the Manual (15th edition).

Question 5 A 36 ft simply supported beam is loaded with concentrated loads 16 ft inwards from each support. On the left side, the dead load is 8.0 kips and the live load is 18.0 kips. On the other side, the dead load is 4.0 kips and the live load is 9.0 kips. Self-weight of the beam can be ignored. Lateral supports are provided at the supports and the load points. Determine the least-weight W-shape to carry the load. Use A992 steel, Cb = 1.0 and Table 3.10 of the Manual (15th edition).

Question 6 For the beam, loading and steel grade in Question 5, check if a W21×62 will be sufficient considering the correct Cb. Do not use Table 3.10 and work the problem with calculations.

Question 7 (Bonus) An A992 W16×31 is used on an 18 ft simple span to carry a uniformly distributed dead load of 0.95 kips/ft and a live load of 1.9 kips/ft. Self-weight of the beam can be ignored. Using Cb = 1.0, determine the locations of lateral supports in order to provide enough strength to carry this loading.

16’ 16’ 4’