LRFD Load Combination
LRFD Load Combination
(OP)
I have a roof perimeter beam subjects to loads on vertical and laternal directions.
Vertical load: L, D, W1(upward)
Laternal load: E, W2(to the wall)
Considering 1.2 D + 1.6 Lr + 0.8 W and 0.9 D +/- E,
1) how can I fit the vertical W1 and laternal W2 to the first equation?
2) am I supposed to ignore the directions (vertical, laternal) of D and E, and plug into the second equation?
Thanks for help
Vertical load: L, D, W1(upward)
Laternal load: E, W2(to the wall)
Considering 1.2 D + 1.6 Lr + 0.8 W and 0.9 D +/- E,
1) how can I fit the vertical W1 and laternal W2 to the first equation?
2) am I supposed to ignore the directions (vertical, laternal) of D and E, and plug into the second equation?
Thanks for help






RE: LRFD Load Combination
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: LRFD Load Combination
vertical loads: 1.2D + 1.6 Lr + W1
lateral loads: O D + 0 Lr + W2 (don't forget lateral loads may be transferred through bending and axial, depending on the structural layout)
RE: LRFD Load Combination
RE: LRFD Load Combination
Do you mean I can seperate the analysis in two parts,
Part 1, analysis vertical load only and check the bending, shear..... on vertical-dir
Part 2, analysis laternal load only and check the bending .... on horizontal-dir
and size the members based on both analysis?
RE: LRFD Load Combination
The design equations depend on the materials you are using. You'll need to review your material code documents (AISC for steel, NDS for wood). They all have many chapters explaining how to evaluate strength in tension, compression, bending, etc.
RE: LRFD Load Combination
I have a rectangular steel building with concrete shear wall core (at the center within steel structure) which supposes to resist all lateral forces. When I do the steel beam and column analysis, do I need to consider earthquake and wind load?
RE: LRFD Load Combination
All the things you have been asking require some critical thinking about a structure as a whole and can't be adequately evaluated with only a beam calc or two. Additionally, the model codes have some stringent requirements for connections which you'll need to become familiar with.
It would be best to find a mentor at your office who can provide you with step-by-step help and check that you are on the right track.
RE: LRFD Load Combination
If correct, 1.2D + 1.6Lr + 0.8W could become 1.2D + 1.6Lr + 0.8(W1 + W2). uplift wind pressure and horizontal wind pressure act simultaneously. for the second equation, 0.9D +/- E, that could depend on the direction of your seismic. most often if you are working with 3D model, +X, -X, +Z and -Z direction is consider; that is 0.9D+EQ+X, 0.9+EQ-X, 0.9D+EQ-Z AND 0.9D+EQ-Z are consider.
RE: LRFD Load Combination
RE: LRFD Load Combination
Each load combination should include ALL applied wind loads whether they are vertical or horizontal.
The analysis may be done in each direction separately (or all at once if you use a 3d program) and the results are (as jenDL says) combined into an interaction equation.