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):

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.

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.

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):

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.

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.

Presentation at 2013 PICE National Midyear Convention

On June 28, 2013, I went to Subic Bay to present a paper entitled "How to estimate 'site-specific wind loads?'" at the 2013 National Midyear Convention of the Philippine Institute of Civil Engineers. It is essentially a more formal paper version of an article I posted here on this blog earlier. The full video of the presentation is below. (Note: The slides are in English but the presentation itself is in Filipino.)

Detroit DIYer cooks up stronger, lighter steel... shames scientists?

Read this article on Engadget from back in 2011 first.

The non-(civil-)engineers, of course, are in high praise for the "little guy" one-upping the "big guys" (i.e. the scientists). Because, sure, stronger and lighter steel is good. And faster production time.

But hey, a DIYer discovering something is also almost effectively a scientist. An accidental one, maybe. But yeah, journalism is about sensationalization, so, framing it like he's "one of us" and not one of those stupid people who studied for years to get a PhD and did whatever else in his career who can't even discover this thing -- that's good for a journalistic publication. Touches people's emotions, certainly.

Response to a Reader Question... from 2007! About Billboards.

The e-mailer asked:

I was wondering if we could discuss billboards of the flexible type? I am a BS Geography student finishing my thesis right now and trying to find resource persons or key informants.

My thesis is about the hazards the billboards pose to human life and property. In line with my recommendations part, I wanted to seek alternatives on billboards, if not alternatives for the laws for it. Since I see that billboards can not really be wiped out, due to its economic contributions to the LGU or National government, your concepts are deemed vital.

The initial plan I have in mind is to interview you RE solutions we could make if and when billboards can not be banned totally.

Billboards proved to be something that can affect adversely the lives and properties of people. As a social scientist, I saw it very interesting to tackle but not really focus on the technical aspects of it. Flexibility is understood as a solution to the social problem.  

I replied:

Wind-Induced Vibrations Damage Pedestrian Bridge

"The first cable-stayed bridge in Minnesota——a 686 ft dedicated bicycle and pedestrian crossing over a busy six-lane road in Minneapolis——was greeted with fanfare when it opened in 2007. But on February 19, 2012, two of the cables detached from the Martin Olav Sabo Pedestrian Bridge when the cable diaphragm plate holding them to the main pylon fractured and a portion of the plate fell to the ground... A new report has determined that wind-induced vibrations caused the failure of a cable diaphragm plate."

Framework for structural damping predictor models based on stick-slip mechanism for use in wind-resistant design of buildings

Article to be published in the June 2013 issue (Vol. 117, pp. 25-37) of the Journal of Wind Engineering and Industrial Aerodynamics. It was published online on 12 May 2013. Co-authored by yours truly and my former PhD supervisor at Tokyo Polytechnic University and current International Association for Wind Engineering president, Prof. Yukio Tamura.

Abstract:

On stick-slip phenomenon as primary mechanism behind structural damping in wind-resistant design applications

Article published in the April 2013 issue (Vol. 115, pp. 121-136) of the Journal of Wind Engineering and Industrial Aerodynamics. It was published online on 5 March 2013. Co-authored by yours truly and my former PhD supervisor at Tokyo Polytechnic University and current International Association for Wind Engineering president, Prof. Yukio Tamura.

Abstract:

Not the smartest thing I've heard from a relatively very senior structural engineer... [UPDATED]

Talking to a group of wind engineers, a structural engineer with years of experience in structural design said:

"Can't you people reduce the wind loads? The columns on core walls in our 400-meter tall or higher buildings are 1.5 meters thick wide. These are too big."*

I've said it before, but I'll say it again: experience does not equal expertise.

---
* Note: This is not a verbatim quote.

How do we get "Site-Specific Wind Loads" in the Philippines?

I was asked this question, and here is how I would answer it.

In the structural engineering community especially in my home country, the interest and knowledge in earthquake engineering and earthquake-resistant design has grown rapidly over the past two decades especially after the 1990 Luzon Earthquake. Some of the recent "buzz words," if I may use that term, in the community are "site-specific seismic hazard assessment," and "performance-based seismic design."

Amplitude-dependent model of structural damping in buildings based on stick-slip mechanism for use in wind-resistant design

On February 9, 2013, I successfully "publicly" defended my PhD dissertation on the topic mentioned above. I will soon be posting the full dissertation manuscript once it is final. I requested my friend to take a video of the whole presentation, including the question-and-answer portion at the end, as well as closing remarks by my PhD supervisor. The video is shown below.

"High-rise" and "tall" buildings, and the 10 worst collapses in history

Image from Wikipedia

What makes medical practice better? The fact that doctors have made a ton of fatal mistakes that has cost lives. And they learned from those mistakes. That's pretty much how it is for civil engineers, and particularly in this case, for structural engineers. If you think doctors and engineers know everything and can't make mistakes, you're thinking wrong. Doctors and engineers and other professionals are researching, discovering, and learning new things everyday.

Anyway, check out this list on bestonlineengineeringdegree.com of the 10 worst high-rise building collapses in history. If in case the link stops working, you can try this Google-cached copy of the webpage: