4 A W14x30 tension member with no holes and Fy 50ksi is subj

4. A W14x30 tension member with no holes and Fy 50ksi is subjected to unfactored tension influences of Po 80k and P 100k and unfactored moment load influences of Mox 10 kft and Mu 12kft. Is the member satisfactory in LRFD if Lb 12 and Cb 1.0? (Hint: factor load demands, then determine design strengths of tension on gross section and moment. Use Chapter H to combine axial and moment)

Solution

tension capapcity of w14x30 = 398 kips

moment capacity of W14x30 for unbraced length of 12\' is given by 177-[(177-110)/(14.9-5.26)]*(10-5.26)=144 kip-ft

LRFD tension demand on member = (1.2*80)+(1.6*100)=256 kips

LRFDmoment demand on member = (1.2*10)+(1.6*12)=31.2 kips

The interaction check is , (256/398)+(8/9)*(31.2/144)=0.835<1

section is adequate