Answer to Quora question, "What is 'spectral acceleration' in structural analysis?"

Quora's bots asked me to answer the above question, and below is my response. What do you think of my response? Did it answer the question? Is there anything incorrect with what I said? How would you have answered the question? Let me know in the comments.

"What is 'spectral acceleration' in structural analysis?"

Presentation(s) on observed wind damages due to Typhoon Yolanda

I have made about three presentations now on the same topic above. One is at the UPD-ICE* Forum on Earthquakes and Typhoons (Jan 2014):

It's risky to miscommunicate risk

In a previous post, I asked that we take caution how we communicate a certain risk. That example talked about the location of the "Valley Fault System," previously called the Marikina Fault, which obviously presents a certain disaster risk. One problem was that risk wasn't quantified then -- how close should one be to the fault lines to be at risk? It wasn't very clear, but people could readily assume that if they are clearly not along the fault lines, they should be safe. If they're not sure, they should consult PHIVOLCS (not PHILVOLCS, by the way), who can provide information on distance of a certain property from the nearest fault line.

Metrology is not the same as meteorology #didyouknow

I know that the word "meteorology" is difficult to pronounce and sometimes even spell. But some, whether unintentional or otherwise, pronounce it like "metrology," or its descriptive form "meteorological" as "metrological." It might be all right, because not so many people know about metrology, and even some spell checkers think it is a misspelling. But in fact, this is how it is defined:

Damping in buildings for wind-resistant design based on a stick-slip model

I am posting a download link to a copy of my dissertation here for those of you who are interested.

Title:

DAMPING IN BUILDINGS FOR WIND-RESISTANT DESIGN BASED ON A STICK-SLIP MODEL

Abstract:

Damping is said to be one of the most important parameters in the wind-resistant structural design of buildings. But, damping is also known to have high uncertainty, which leads to low reliability in the design. Current estimation formulas and early research on structural damping, particularly, are associated with stick-slip mechanism. But these current models have only shown this qualitatively. In the end, these models fitted formulas to databases of full-scale experimental data. This dissertation therefore aims to quantitatively study the stick-slip mechanism itself to derive a theoretical expression, and finally, to apply the derivation to actual physical structure data to illustrate that stick-slip damping is indeed a valid model. The study starts from a very simple one-degree-of-freedom (1DOF) system with one stick-slip component (1SSC), to a more complicated 1DOF system with a large number of SSC (NSSC). The study also briefly touches on the damping of SSC inside MDOF systems. The study of MDOF with NSSC systems is necessary because actual physical structures are such.

Your house is not along the faultline. What now?

[Image from tulisanes.wordpress.com]

A friend linked to this blog article:

http://tulisanes.wordpress.com/2012/04/03/is-your-house-standing-on-an-earthquake-faultline

Obviously, the author has good intentions, although he is seemingly not an engineer (or maybe still a young engineer?). The impression I'm getting though is that the article is suggesting to check whether your house/property is along one of the published faultlines. If it is, you're obviously in danger. But it might also give the impression that if you are a good distance away, you probably shouldn't worry.

In the eye of Super Typhoon Yolanda

Well, not exactly. But pretty close -- this is a 12-minute compilation of videos taken by the folks at iCyclone.com of STY Yolanda's fury right in Tacloban City.

WARNING: You are risking your life when you try to do this. Technically, the city should have been evacuated already. When authorities (e.g. PAGASA) warn of an impending storm, follow their instructions! You might say that they been "wrong" before... But it's because this is nature we're talking about. No one can very accurately predict nature. We can only prepare for the worst.

Do we need to increase the code-required minimum design wind speed now after Yolanda?

The answer to this question is NO, there is no need to provide NEW wind load code requirements for higher wind speeds.

Response to students' questions on NSCP 2010 wind loading provisions

These are actually in the comments, but I thought I should promote them to a full post. The first asks about leeward wall pressures:

Are the values for the Leeward wall pz really constant with elevation?

Response to a reader question regarding using the NSCP for estimating wind loads on irregular shapes

A reader asked:

How would you evaluate the pressure coefficients for structures with irregular polygon shapes. An example would be those structures with a plan shape resembling the letters "W" or "K." Most of the pressure coefficients in the code are for uniform cross-sections such as circle, rectangle, square, and so on. I have my own approach on this (mostly based on engineering judgement), but I would like to hear first on a wind load aficionado, such as yourself.

2013-2014 1st Sem CE 197 Final Grades

Another semester has gone. I feel that this class has learned things that they wouldn't have otherwise been taught, and yet there is a lot more to know. Even I am still learning! What I did was I only penalized those who did not follow instructions, such as rounding off, etc., or those who did not even try at all. That said, complaints will not be entertained. These grades are final.

Response to a reader question on the damping estimation formulas in NSCP 2010 Section 207

A reader asked,

Equations 207-38 & 207-39 equate damping to 0.016/h and 0.23/h, respectively. However, Equation 207-40 equates damping to 0.007/n, in which h = height of structure, and n = natural frequency of the structure. Are Equations 207-38 & 207-39 correct, or should h be replaced by n?

Another NSCP 2010 Erratum

This one is actually a question asked by a former student.. from back in 2010! She says:

I came across with Method 1 - Simplified Procedure, and in Equation 207-2, pnet=lambda*Kzt*w*pnet9, where pnet9, as given in the definitions, is the net design wind pressure for Exposure B at h=9m and Iw from Figure 207-3. I turn to Figure 207-3, and in the label of Figures 207-3 it states that it is "pnet (Exposure B at h=10m with Iw=1.0 and Kzt=1.0)". My question is if the Figure 207-3 is already the net design wind pressure (pnet) or is it the pnet9 (net design wind pressure)? Also, if the values are for a 10m high building or 9m high building?

Some NSCP 2010 Section 207 Errata

If you have been using the NSCP 2010 wind loading provisions (Section 207), you have probably noticed already many typographical and other errors. I have only started to look at it more deeply recently, and here are some I noticed (and that readers have also pointed out):

Take Home Quiz ;-)

Note: This was updated on 9/17/13 at 8:00 PM.

This is a take home quiz that I gave my students 10 13 days to complete on their own. To encourage independent work, I based the parameters they were going to use on their "student numbers." If you are a practicing structural engineer, go ahead and choose from the values listed below and try to answer the questions yourself.

Presentation at the 2013 ASEP Wind and Earthquake Engineering Seminar, Cagayan de Oro City

The 2013 ASEP Wind and Earthquake Engineering Seminar was held on August 16 to 17, 2013 in Cagayan de Oro City.

Presentation in front of ~2,000(?) Civil Engineering Undergrads at the 2013 National CE Symposium

The event was held on September 6, 2013 at the University Theater, University of the Philippines, Diliman, Quezon City, and organized by the UP Association of Civil Engineering Students. I introduced the many different facets of wind engineering to these civil engineering undergrads from around the country. I think I did okay. :-)

An example problem on wind load calculation according to NSCP 2010 ;)

A 20-meter-high square-plan five-storey building with flat roof and 4m-high floors, located in Makati CBD, has sides of 10 meters length each, and a large open front door on the first floor that is 2m x 2m in dimension. Assuming that G = 0.85 and that torsion is negligible,

1. Show how this maybe is an open, partially enclosed, or enclosed building.
2. Determine the internal pressure coefficients.
3. Determine the external pressure coefficients for the design of main girders and shear walls.
4. Determine the base reactions due to along-wind loads acting on the front wall of the building.

Demonstration of base-isolated versus conventional building under "earthquake" / ground motion #video

Nice visualization/demonstration.

IBM to donate supercomputer to PAGASA

The DOST announced that IBM will donate a supercomputer to PAGASA. The meteorological agency will purportedly use it with more advanced modelling software to account for general climate conditions in the country for the next 5 to 10 years, and to improve their weather forecasting, being able to anticipate typhoons up to 7 days before it might affect the country as opposed to the maximum 3 days advanced forecasting they are able to do with current resources.