Your Design Journal entries this week should highlight your design thinking and analysis results that influenced your decisions about:
- the sizes of the three critical beam test case framing elements
- any special structural challenges
- how you expect the computed beam sizes will affect the space available for your HVAC design elements in the next module
First test: long beam below the South terrace
For now, I only used a dead load (hosted line area load) to model the slab of the terrace, because there won't be too much movement (no live load for now). DD of -0.04kip/ft.
I get the following results: instability because slenderness ratios are too high but the efficiency ratio is fine at only 0.20. Not sure how to fix the slenderness ratio issue. The efficiency ratio means that I could size the beam to be smaller?
Second test: long beam in exhibition room on 2nd floor
DD of -0.05kip/ft because both the concrete deck for the roof + green roof (13pounds/sqft)
There seems to be an issue here, probably related to material parameters in the first place.. the efficiency ratio is way above 1 so the beam is probably undersized anyways.
Third test: Structural truss below second floor
Boundary conditions on structural walls (fixed at bottom)
Load on truss due to second floor right above: -0.04kip/ft
Deformation is the following:
Forces: in z direction - because of trusses are made of small beams, the diagram is pretty complicated + I get forces on the ax-axis too. It's not symetric which is interesting
Fx values are way higher than Fz values. I am not sure why there is a lack of symmetry, with a peak to the left of the diagram.
Code check on the bottom beam gives:
Code check on the upper beam gives:
It seems like both of them are way undersized. Surprisingly the upper beam should be bigger than the bottom one? I would have thought the contrary.
Out of curiosity, I checked the intermediate beams within the truss structure, and they were all fine, probably even oversized because their efficiency ratios averaged around 0.20. I think it's because all beams (both the two main ones and the small ones) are W12x26. I thought structural trusses would be designed with bigger beams for the top and bottom one, and smaller ones in the middle? Wonder if it's normal.
Impact on HVAC equipment:
I already thought the structural elements took a lot of place, and made it tricky especially in open areas like my atrium. If I need to upsize most of them, or add columns, it might affect the room left for HVAC equipment and end up affecting useable space.