WR1

Back to the basics, Just faced this issue where a retaining wall (assume it singly reinforced section) had very less capacity with provided As. However, when calculated the stress, it was found out to be less than modulus of rupture and hence safe. Why is the discrepancy and when one should use the ultimate design? I understand the reo will start working only after Mcr has reached (cracking moment).

It's simply V12 or V21 contours.

When you remove the steel stress at top, your concrete columns become cantilever giving you 'satisfactory' or increased reo because of unbraced length. When you put in the steel structure, concrete columns become braced and hence less effective length. I would not consider steel members to brace top story concrete columns.

Wondering if there is any quick drag and drop kind of parametric tools for drawing of common structural temporary works which are also quick to use for structural engineers? Have tried Revu, Cad, Sketchup, Edraw etc. Not talking about full fledged drafting CAD softwares. For example brackets, props, bolts etc which you can drag/drop and change dimensions? Any suggestions? Libraries?

Why is there no bearing check guidance for circular hollow sections in Australian steel code AS4100? or any other code. Is this check not required for CHS?

I was referring to ACI 350-06 Appendix I (Working stress method) which limits fs to 20ksi or 0.33fy if fy=60ksi.

Please refer to response above your post. It contains a very good document from StucMag. My reasoning is also based on the same document.

I think it is upto you to consider the lateral resisting system that you want to design for. It all comes to down to rational lateral resisting system concept. Then you can always refer to applicable building codes to suit certain conditions and 'design checks'. The most important thing is the concept i.e. engineering judgement instead of following crude building codes. You could consider resisting 25% of lateral loads by the frame and rest of it by shear walls, or you could consider using lateral system to resist 100% of lateral loads. It's entirely upto you.

You have to make sure, load cases, section properties etc are same in both etabs models. Then export both files one by one to SAFE and import in SAFE. There is one caveat however if there are spectra loads present in ETABS. In that case, you will have to make sure that importing acceleration data is matches from 2 ETABS models to 1 SAFE model.

Mumtaz, Ít all comes down to engineering judgement. Would you draw a wider strip if there is a point load? Obviously no. The codes allows L/4 strip widths for uniform loads. Obviously you will get more moment/m for a wider strip as compared to a less wider strip around moment concentrated elements like walls or columns.

What do you mean it does not take the negative values? As far as I can recall there are four load cases with positive and negative directions. Please elaborate your question.

Please post the question here. I can't help preparing models for you but if you do have a specific question, please feel free to post in the relevant section of the forum. This post will be deleted after 3 days.

See the code e.g. UBC-97 to calculate amplification factor Ax. Max Ax = 3.0. This Ax you will multiply by 5% (0.05) and input in response spectrum cases/static earthquake cases. To calculate Ax, you need maximum and average story displacements at CM. You can export this data from ETABS Tables to EXCEL for static earthquake cases (Don't use spectrum cases for this). Once in EXCEL, you will see column named 'Ratio'. This will be Max/Avg displacement. Sort this out to find values more than 1.2. These are the locations you need to amplify torsion. After checking which stories you need to amplify torsion in, use the amplified torsion value for e in response spectra cases.

I'd like to add here that ACI report on punching; in examples, use bi axial moments but they are shifted from column center to centroid of critical punching perimeter (in this way, they are reduced in magnitude). However in PCA Notes (in main chapter of punching) they mention not to take biaxial moment at the same time. Another issue; in PCA Notes (in one of the edge columns punching example), they just take Axial force to check the extent of parameter upto where punching reinforcement can be terminated. They don't use Axial+Moment, they use only axial force for this.

Good point.

I believe strength formulas are calculated based on the standard cylinder strengths given in ACI. That's how you design it. Now, if you want to test the concrete with whatever the dimensions or shape, it has nothing to do with actual building being constructed or the formulas used in the design.

I don't see at the moment any thing positive except a mere monopoly show. This being said without any research on them as I don't even want to. It's just my perception without even knowing what's going on. Other members please participate.

For moment reversal, uplift etc.

f'c in design (e.g. in ACI) corresponds to standard cylindrical strength at some specific days. If they are cubes or cylinders of other dimensions, you could convert them to standard cylinder for design.

These points are automatically generated with support on them. They are created because of wall meshes and are okay.

Nice finishing. I think they are shrinkage cracks, not structural.

0.28% rebar looks okay to me. R is 6.5, what else you expect?

There's a whole lot of discussion on the topic. PCA notes, mention it, to not use biaxial moments for punching. SAFE takes biaxial moments. If you check the punching manually with moment in 1 direction, it should be okay. Analyze in both directions but dont combine moments. Others suggested moving the water tank. I'd like to further add to this, to add a beam between columns, a stiff one, to ignore punching all together and save in raft thickness.

I won't be increasing to 30" for a house. I'd rather prefer putting small punching reinforcement under column (it's like a beam with stirrups).

If the stress is over the allowed limit and is distributed on a large area as shown in your image, then it is not called 'stress concentration' locally. You need to increase the soil capacity.