ETABS Life Saving Hacks: Hacking Model Instabilities

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You should be able to find this file

Howdy everyone こんにちは!

I’m sure you missed my structural engineering blogs. Lately I’ve had the transition from chasing the limelight to settling and basking in anonymity and a quiet life.

But hey let’s get down to business shall we?

So, after modelling the entire geometry, had all the loads applied, entered the correct load combinations and then you get the annoying notice that there are instabilities which is why the results won’t show the specx and specy calculations, and deadlines’ looming, how irritating can that be?!

Yep, instabilities can be a pain in the ass and they’re not easy to spot. But it does not mean it’s impossible to have an instability free model. So how do we start to trouble shoot?

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What I mean in item number 1 below
  1. First, we need to set the “Advanced SapFire Options” tab to Solver Options→Standard Solver and it’s corresponding Analysis Process Options→GUI Process. This will give you a detailed output on certain points where there were lost computational accuracies in the analysis. If you can find anything about negative stiffness or if the values exceed 11.0 digits, zero in to the location because that’s exactly the area that causes the instability. In the example above, the problem is the diagonal value of the matrix which turned zero. If the diagonal value of a matrix turns zero, then there is instability (you can refer to structural analysis textbooks to verify this).
  2. Very near joints. If you are using manual mesh, this is no problem. You can just merge the points and that mostly solves the issue. But if you’re having this problem and you are using auto mesh, then it’s a little bit harder to tweak. Generally, you can slightly alter the meshing and the geometry or reshape somewhere to get this right. By the way, this can also happen to walls that you manually meshed.
  3. End releases. If your columns for example are pin supported at the bottom, and say you applied end moment releases at the bottom of the column as well, this would cause instability because of the redundancy. If you intend to have zero bending moments at base, then applying a pin support would be enough and needs no further member end releases.
  4. Disjointed members. This normally produces very high displacement values. You can pinpoint this by animating the model and looking for those “insanely huge” displacements that are out of the ordinary. A big help would be by looking at the Modal Participating Mass Ratios table and animate at the mode of the peculiar period.
  5. Pdelta. This is a bit harder to explain because it has something to do with the framing which is of course a case to case basis. Sometimes it means stiffening a relatively flexible part of the building.

I hope I made myself clear with these. And as I recognize that it is very hard to put every imaginable scenario there is to writing this, I welcome your queries which I’ll try to answer if I can. Just look for my email address on the right side and send your ETABS model and queries about what’s causing the instability and I’ll point it out free of charge tomodachi (ともだち) just for you!

So don’t be disheartened to see that instability. Where you cant solve it yourself, ask for help. Never hurts to ask the knowledgeable dude out there. The important outcome of this is, if you are able to master the art of trouble shooting you are one step ahead in doing sensibility checks which is indispensable.

So stop pouting when you see that instability. Just find it. And I would like to give you the same advice I’ve been getting while studying Nihongo:

がんばってください ! (Keep at it!)

Fault Finder

Pero ang West Valley Fault ay di biro.

At utang na loob, wag na wag kang magtatanong kay Master Hans Cua dahil hindi ka kayang isalba ng sinasabi niyang lucky color at number.

west valley.jpg

Mag-public service na muna tayo.

Who is at fault? Tayong nasa Metro Manila at karatig lalawigan ng Rizal.

Lilinawin ko lang yung title. Ang fault na tinutukoy ko ay ang kinatatakutan at ang hinog na hinog nang  West Valley Fault na maaring magdulot ng sinasabing “the big one,” ang lindol na siyang magiging sanhi ng malaking pinsala sa mga imprastraktura sa NCR.

At ang fault finder naman ay isang website galing Phivolcs kung saan ay naka-superimposed ang mga tukoy nang mga faultlines sa google map.

Eto yung link: http://faultfinder.phivolcs.dost.gov.ph/

Ang kailangan lang gawin ay I-double click ang lugar kung nasaan ang bahay nyo at voila! Bibigyan kayo ng sukat kung ilang kilometro ang pinakamalapit na fault line sa inyo.

At syempre, kung mas malapit ka sa isang faultline ay mas vulnerable ang bahay mo, buhay mo at ng pamilya mo. Mabuti na yung 10 kilometers ka kalayo kesa kapitbahay mo lang yung fault line!

Kaya kung sakaling ikaw ay isang tambay na walang ibang magawa kundi mangulangot at pumindot ng mouse at keyboard, o di kaya ay isa ka ring Pilipino expat sa ibayong dagat gaya ng mga kaututang-utak ko dito sa wordpress ay panahon na para kumunsulta sa mga tulad kong structural engineer na magpapatibay sa bahay nyo dahil kami ang lubos na nakakaintindi at nakakaunawa pano gawin ito.

Kaya kung may bahay kang milyones ang halaga sa Green Meadows (screen grab ko sa taas) sa Quezon City sa tabi ng C5 kung saan mismo dumadaan ang West Valley Fault, ang maipapayo ko sayo ay ibigay mo na lang sa akin ang titulo ng lupa’t bahay mo.

Joke lang brad. Pero ang West Valley Fault ay di biro.

At utang na loob, wag na wag kang magtatanong kay Master Hans Cua dahil hindi ka kayang isalba ng sinasabi niyang lucky color at number.

Conspiracy Theory

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Photo from pinterest.com

Unless you’re a child or you are honing your craft then predictability is a necessity. Otherwise, being predictable has its own evil.

And this includes a predictable thought process.

I for one am a slave to this. And so this challenge of thinking the unthinkable get’s me out of my own created circle once in a while like a restart button to an unresponsive pc. Just like in the following conspiracy theories:

  1. The war in Mindanao, specifically in Marawi City is a way of the political enemies of President Duterte to get him dethroned – with the hand of US in the background.
  2. Or, can be a way of the president and his cronies to get something out of it, like the liberation of the whole Mindanao in exchange of something. Feel free to fill in the blanks.
  3. There is already a cure for cancer and all terminal diseases but they chose not to reveal it because of commercialism.
  4. Why can’t the Arab countries unite when they all basically have the same faith that forged an empire still as powerful as today? Some say that CIA is wreaking havoc to the existing foreign relations in the Middle East.
  5. Why is Africa left out in terms of development? Some say that Europeans are at work here because Africa also has a lot of oil reserves that can dictate the world market, much like the Middle East.
  6. The collapse of the Twin Towers on 9/11. As an engineer, I believe that the building being pulverized while crashing down is not the “correct” behavior. Only controlled demolition employing explosives can do that.

The list goes on and of course you can start adding to this from rationalizing that the behavior of your pesky neighbor is linked to the ISIS, to the belief that the Illuminati is leading the world to a who-knows-where destination.

But remember, this is meant only for mental calisthenics and not for anyone to be a self-made cynic. Believing that something good will come out of people and situations are still the best way forward.

And the strange thing is, when you think of it that way, the universe seems to conspire to make it happen THAT way.

Now that’s a conspiracy theory that rocks.

“I’ll Be Better Off Without You “

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Photo from gettyimages.com

It was my son’s first day in grade school when I took a day off from work and accompanied him to show my support.

I had been a witness on that one day of his struggle to adjust to his new schedule – from waking up early to throwing up inside the school service due to motion sickness.

I felt pity for him. I even told myself that if and only if I can give him, in one single shot, all the things I learned in life up to this very moment, I would’ve done it right away.

After a couple of days though, he seemed to have fairly adjusted to his routine. He is tired but I see that he’s happy. And one early morning when we’re both dressed, me for work and he to school, he told me something that got me thinking:

“Dad, please don’t accompany me to school anymore.”

I was stunned thinking that he’s saying that he’ll be better off without me though I know that he didn’t mean to shut me off entirely. I am happy that he realizes the value of experiential learning at a very tender age. Atta boy!

It’s still kinda sad to hear though. But it’s that kind of sadness that I have to live with and be happy about anyway.

If by Rudyard Kipling

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from glasbergen.com

Sharing to you all a great, great advice from Rudyard Kipling. Which part of it resonated with me? ALL OF THEM.

Happy weekend everyone. ‘Till the next piece of me.

じゃあまた

Gishi
技師

 

If

Rudyard Kipling

If you can keep your head when all about you
Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you,
But make allowance for their doubting too;
If you can wait and not be tired by waiting,
Or being lied about, don’t deal in lies,
Or being hated, don’t give way to hating,
And yet don’t look too good, nor talk too wise:

If you can dream—and not make dreams your master;
If you can think—and not make thoughts your aim;
If you can meet with Triumph and Disaster
And treat those two impostors just the same;
If you can bear to hear the truth you’ve spoken
Twisted by knaves to make a trap for fools,
Or watch the things you gave your life to, broken,
And stoop and build ’em up with worn-out tools:

If you can make one heap of all your winnings
And risk it on one turn of pitch-and-toss,
And lose, and start again at your beginnings
And never breathe a word about your loss;
If you can force your heart and nerve and sinew
To serve your turn long after they are gone,
And so hold on when there is nothing in you
Except the Will which says to them: ‘Hold on!’

If you can talk with crowds and keep your virtue,
Or walk with Kings—nor lose the common touch,
If neither foes nor loving friends can hurt you,
If all men count with you, but none too much;
If you can fill the unforgiving minute
With sixty seconds’ worth of distance run,
Yours is the Earth and everything that’s in it,
And—which is more—you’ll be a Man, my son!

Tesbun

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Photo from dreamstime.com

Mahal kumusta ka na?!

Ansakit naman ng biro ng tadhana

Na makitang buntis ka na

Ngunit para sayo ako ay masaya

Pero mas masaya sana

Kung ako ang naging ama

Subalit ngayon ay iinumin ko’ng aking mga luha

Kung sana noo’y di ako naunahan ng kaba

Nung ika’y malaya pa

Malamang tayo ang itinadhana

Pero ngayon ay huli na

At wala na’kong magagawa pa

Kundi ibulong sa sarili ko ang “mahal kita”

At tanungin ka ng “kumusta?”

FUCK THE SOULMATE MENTALITY!

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Photo from ebay.co.uk

Love is like a heart-shaped jigsaw puzzle made up of two pieces. And due to the novelty of our experiences, each puzzle piece have intricate, unique patterns that can fit perfectly to only one piece.

But what people fail to realize is that  it’s not just a trial and error fitting spree. It involves the painful process of refining the edges, cutting an edge to accommodate the other piece, and extending some parts to fill the gaps of the other.

The interesting thing is, this gap that we’re trying to fill in order to piece together this puzzle, is dynamic. Such that, the patterns change in our lifetime and thus the process of cutting, welding, and grinding are perennial processes necessary to keep the love puzzle in perfect fit.

Moral of the story? FUCK THE SOULMATE MENTALITY!

Backride

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My kind of girl. Photo from hdopenroad.com

Adda kam nga sangapamilya iti ruar ti balay mi iti maysa nga malem idi limmabas ni kuya Dan, kaarruba mi, nga naka-motor. Iti likudan na ket kalubbun na ni baket na nga ni ate Bel nga adda nga tarin-backless ti badu na ta dandani makita amin a duri nan.

Nalukmeg diay baket, ket inturtured ku nga haan nga makapugsu ti katawak diay pannakakitak diay bukut na.

“Puunay diay badun ate Bel-en,” kunak ken baket nga adda met nga sikikita. “Bale adda kimmut diay bukut na!”

Kasla kam la madupuy nga nagkatkatawa ti naimas ken awan uni na a katawa

Independence Day Daddy Blues

“Mommy, mommy! Ibinili ako ni Daddy ng sunglasses, ang ganda wala akong makita!”

Face palm.

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Well deserved. Lebron’s one hell of a player and deserves no less credit. This championship is hard earned and that’s what makes this victory very sweet indeed! (AP Photo/Marcio Jose Sanchez) Photo taken from sports.abs-cbn.com

Mas madilim na sunglasses, mas ok para sa akin.

Yun ang tangi kong pamantayan sa pagpili ng proteksyon sa mata. Naapektuhan ng ilang taon nang pagtatrabaho sa harap ng computer ang mga mata ko kaya eto, nai-stress na masyado sa maliwanag.

Madalas madaling araw pa lang tuwing umaalis ako ng bahay at may kalaliman narin ng gabi ako nakakauwi kung kaya, kung tutuusin ay di ko na kailangan ng shades. Pero nitong mga huling araw ay nadadalas na akong masinagan ng araw pag-commute kung kaya na-excite akong magka sunglasses ulit.

Kaya nitong Lunes na holiday ay pumunta kami ng anak ko sa DIY upang bumili ng shades. “Yung pangwelding” ang deskripsyon ko sa sales lady. Nawili ako sa pagpili at hangang hanga ako sa kakayanan kong mamili ng shades. Balot na balot yung shades at di mo pwedeng buksan para isuot. Pero di na bale, alam ko ang pinipili ko. At dark nga yung nabili ko gaya ng gusto ko. I’m the man!

Nang makalabas na kami matapos kong bayaran yung shades ay agad ko itong kinuha para isuot.

Putik!

Wala akong makita kapag nasa lilim na yung tinitignan ko! Badtrip, pormatiks yung hitsura pero pangwelding ata talaga yung nakuha ko.

Habang nasa tricycle kami ng anak ko ay tuwang-tuwa siyang pinag-aagawan namin yung shades. Pero sobrang panghihinayang ko sa pinangbayad kong kulang-kulang dalawang daan.

Nang makatulog na ang panganay ko ay saka lang naikwinento sakin ni boss yung excitement ng anak niya nang makauwi kami. Tawa ng tawa si boss.

“Mommy, mommy! Ibinili ako ni Daddy ng sunglasses, ang ganda wala akong makita!”

Face palm.

Konswelo ko nalang na may natural humor yung bata, mana sa mommy nya…

Giving while expecting something in return is manipulation in disguise. – Angmamangenhinyero

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