Question

ENGR 426 Steel Structures (3) Spring Semester 2019 Dr. Pong School of Engineering San Francisco State University Page 2 45%) 1 RL= 10 PL 500 PLf (including Self were ut ) Io' A992 stee Foll (aterol supp。 LRFD Considerine ounly benol Design: tha liut-erzut W-shap beur Wanbr gut-weigt

Answer 1

GIVEN DATA Properties of Steel section Span of beam, 20 ft Ud Dead Load W D0.5 kip/ft W11.2 kN/m Live Load 10 kips Dead Load Live Load 10 kips CALCULATIONS 50 ksi Yield stress of steel W 1.2 wD +1.6 w 2.52 kip/ft Factored Load (udl), Factored Load (concentrated), Pu = 1.2 PD+ 1.6 PL 28 kips Maximum factored moment, 8 28.00 x 2.52 x 20 x20 /4 266 ft-kips Assume "compact section" that is As Ap or both the flange and the web Design strength of beam is Taking Therefore, required plastic section modulus is 266 x 12 0.90 x 50 70.93 n2 Select section such that Z>Z (required) Beam Section W 18x 40 z, 78.4 in 3 Plastic section modulus b,/2tf5.73 h/t w= 50.9 Width/thickness ratios Check for compact section 65 9.191 ок 2t 640 90.51 1 OK

Hence, the section is COMPACT Design strength of beam × 50 /12 ft-kips 0.9 x 78.4 294.00 ft-kips> 266 ft-kips Mu Hence, SAFE