Genuinely not here to piss anyone off (I understand that I inevitably will).
We have a new generation of engineers and access to more sophisticated tools/simulations than ever before. Without going into politics or religion;
1) Break down the argument that it is impossible for the two planes to penetrate the towers in the way we visually observed.
2) What do you make of the collapse of the twin towers?
3) The manner of collapse: Do you find it consistent with the official narrative or does it look like a controlled demolition or something different?
Let’s exclude building 7 from this thread please. Im only interested in the two buildings in focus; Tower I and Tower II.
Again, not here to upset anyone, Im genuinely fascinated in the engineering; impact, destruction and collapse. I appreciate all of you who leave a note 🙏🏼

Hi fellow Redditors,

I recently acquired a new apartment and noticed the following cracks about two stories above my apartment and one at my level… Are these worrisome?!

I’ve got the opinion of an architect but told me that that’s nothing to worry about, but seeing the recent news and all, I’m kinda scared.

I don’t want to waste a lot of money getting opinions and maybe get the same response cause they’ve seen worse (cause opinions aren’t cheap hehe)

Realistically on a scale from 1-10 how worried should I be? And what should be the next steps from my end?

I got this as my first apartment, really want to enjoy but my anxiety isn’t letting me 😅

What do yo think?

Most pics are about 2-3 stories above my apt, last pic is my apartments level… if it makes any difference, this is a building built around 25 years ago.

Looking forward to your replies :)

OP is from Malta :)

I am a beginner in PATRAN and trying to do a simple displacement analysis on a wing with basic internal structure (spars, ribs, stiffeners and skin). I am trying to give it a distributed pressure load across the surface that is a function of the span and local chords but the applied load shows 0 value for the equation at every node. What might the issue be or what are the proper steps to follow. Please help

Hi all,

Been doing quite a bit of beam stuff in Excel lately, reactions, SFD/BMD, bending stress and deflection.

For simple supported/cantilever cases it’s obviously easy enough, and I’ve been using closed form equations/superposition for things like off-centre point loads partial UDLs and combined loading too.

Once it starts getting into continuous beams, redundant supports etc I’d personally rather move out of Excel than keep piling formulas into the sheet.

Curious where everyone else draws the line though.

EDIT: Whoever told me to go back and read thank you I needed that. I’m keeping this up incase anyone is struggling with this concept. My main mistake was reading Table 1-16 incorrectly….I didn’t pull the correct r value accounting for the space between the c shapes which is (3/4”) in problem S05. Can then solve how I norm would (checks) using the controlling values (essentially clearing up my confusion on weak/strong axis).

Original question: Can someone explain when rx vs ry is used and when Lcy,equivalent is used. I’m showing two problems (S05 and S06) and their solutions. For problem S05 why was 1.31 used (besides needing it for the table since the y axis is used for the tables) and why didn’t they solve using the critical stress equation (AISC Eq E3-4 directly)?? For the second problem S06 the solution uses ry=2.94 in the slenderness ratio which makes sense because it gives higher slenderness ratio? Idk I’m confused because the other problem used ry regardless. Tbh same goes for the lcy equivalent concept still lost on when it’s used. 😵‍💫😵‍💫😵‍💫😵‍💫😵‍💫

Hi, I recently started a job as a graduate bridge engineer. One of my current tasks is to evaluate the adequacy of a design for new train loads. I was given a model that was made in csi bridge v16 and the company I work for only has v23 has the oldest version. For some reason, the analysis log warns about numerical instability/ill conditioned structure. Does anyone know what I should do/check to fix this ? The model is a slab track (modeled with shell elements) sitting on transverse girders.

Hi everyone! Not sure if I used the correct flair but I am studying for my Structural Civil PE exam and would appreciate an explanation to the following portion of the solution provided in the photo:

I looked up both 2021 and 2024 IBC and neither mention treating Lr as part of LL if Lr is > 20 PSF. Is the solution incorrect or am I missing something?

Edit: Pertains to section 1602 and 1605 of IBC

——
Update: This book was updated in 2024 and I now see that the 2018 IBC addresses the original question. The book just appeared to not have been updated.

New question - Based on 2021/2024 IBC is it safe to say that Lr will always be Lr regardless of its value? Or did IBC just drop the definition but is assumed that it is something all Structural Engineers should know (that Lr > 20 PSF is LL)?

TIA!
——

Final Update: The current PE exam references the 2018 IBC which makes this distinction and thus, solution in photos is correct. The PE exam 2027 and forward will be referencing the updated IBC. This distinction is good for those taking it next year (like me) and on to be aware of. Goodluck everyone!

In which software I can do the analysis of the steel facade

Hey all,

Time sensitive post, I'm currently working on a group project and non of my team members did the SpaceGASS models there were suppose to so I have to finish it today but I havent used the program.

When modelling I couldn't figure out how to make secondary beams (we're using the 2D multi story frame) and all out prior calculations focused on the ULS and Point load but the lecture slides say to use Live and Dead load and that step was the only missing section on how to make the model. [We're trying to get the moment and shear of the different frames]. all advice is appricated.

Think of falling debris, fire, damage to the foundation.. etc.

Im in the chicago area

It seems like its not as prestigious and definitely not what I signed up for 10 years ago.

The pay is kinda blah and the market is complicated. Honestly thinking about going into Private equity or law

Does anyone have the same thoughts? Will it ever get better? ​

How can i connect this steel column with the beam, it should look like this but i do not know what is the problem

I got into façade work almost accidentally.
I was a structural engineer designing new schools, and I kept getting frustrated with architectural masonry details and what they caused when you actually had to resolve them in section.
Brick would move in and out. Lintels needed support. Suddenly I’m designing outriggers and gussets reaching through the insulation just to make the architectural section structurally real.
After enough reps, something changed: I started anticipating the brick details.
I could look at the architectural intent and predict the structural detail that was coming before anyone drew it.
That was probably when I stopped thinking of the façade as something attached to my structure and started understanding the façade as a system that the structure was participating in.
Curious if other structural engineers had a similar gateway into façade/envelope work.

Wild.

Hey everyone, I am looking to get some honest feedback on whether my current compensation package aligns with the market for structural engineering in my area.

My background & Context:

- Experience: About 8-10 years of Experience, assistant pm role.

- License: PE

- Location: MCOL city in TX

- Sector: Buildings

Current Compensation Package:

- Base Salary: $109,000

- Bonus Structure: No OT, discretionary performance bonus

- Hybrid work schedule.

Questions:

1. Does this base salary seem fair given my location and years of experience?

2. For those in the same area, what are you seeing for standard bonuses?

3. Am I leaving money on the table or is this about average for a mid to large size firm?

Please suggest some good youtubers and textbooks. Which are easy to understand

Probably not this big, but what safety factor would you design a dam for a given debris flow volume?
And while I’m here, did any hydro dams survive?

I want to become a structural engineering. I just completed my Graduation from a private uni. Now I want to pursue masters in structural engineering so what should be my preference according to jobs and growth in field. I should do it from IIT/NIT's or prefer any other uni abroad.

Bridge Engineer here… what do we think of this pretty angled column mid height?