LRFD Calculation Questions-Please Help!!!

Structural Layout Vignette and Multiple Choice

LRFD Calculation Questions-Please Help!!!

Postby AJD » Mon Jan 01, 2018 2:46 pm

I am struggling with some aspects of LRFD design for steel. Ballast only shows the Allowable Stress method, but NCARB states that they use LRFD for steel. I have the following questions. Can anyone please help shed some light on them?
1) Are the loads that are provided on the exam (for steel LRFD) already factored or must we calculate the factored load before we begin calculations?
2) When calculating the moment in steel do we use the figure for Z (plastic section modulus) or S (section modulus)?
AJD
 
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Re: LRFD Calculation Questions-Please Help!!!

Postby AJD » Mon Jan 01, 2018 9:59 pm

Thank you Coach. I have read some of Mike’s notes, but not all yet. I’ll dig deeper now and see if I can make sense of it.
AJD
 
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Re: LRFD Calculation Questions-Please Help!!!

Postby AJD » Mon Jan 01, 2018 10:41 pm

I understand conceptually the differences between ASD and LRFD. What I do not understand is during the exam will they give us the required information to solve the problem or are we to assume certain aspects of the problem? For example, if we are given a simply supported steel beam and asked to size the beam for a given load, will NCARB give us figures for Dead Load and Live Load and which combination of factors to use or do we just assume 1.2DL + 1.6LL? Any guidance is appreciated.
AJD
 
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