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Critical Threshold by Taner Aksel

Taner Aksel As our world is approaching critical thresholds and may have already passed some, it is getting more urgent for concerned people to understand what really is happening. As human species, we keep forcing the world towards an unsustainable path which will eventually lead to a collapse. Nature is giving numerous signs that indicates this is actually happening right now. Most people do not comprehend what these signs mean because they are not aware. Nature is the biggest teacher if you can observe it. Through different media it gives clues as to what could happen in the future if certain paths are continued.

I completed my master’s thesis on dynamic behavior of structures in 1993 at University of Cincinnati, OH, USA. I tested two old steel bridges and found their resistance to earthquakes. After graduation I started my own engineering company and sold software that design structures. Years passed by and I had almost forgotten about my graduate research. Then the US mortgage crisis occurred in early 2008, which then turned into an economic crisis and quickly spread to all over the world. I was reading an article about this crisis on NewYork Times web site and saw a graph of average house prices in last 20 years. This graph resembled so much to the graphs I was obtaining during my research on dynamic behavior of structures that I started reading the article more closely. Then I realised, not only the graphs were similar but also the behavior was very similar – the behavior that causes structures to collapse under earthquakes is similar to the behavior

of masses of people leading to economic crises. This realization led me to further research about what other systems would exhibit similar behavior and finally led me to ‘climate change’. There seemed to be similar behavior patterns in dynamic systems. So initially let me explain how structures behave under earthquakes. Understanding this behavior will shed light into others. Just like every living being having a unique DNA that defines that creature, structures also exert a unique behavior when an external force such as an earthquake acts upon them. With nondestructive dynamic testing, structural engineers can identify this behavior and get crucial information on how a structure will respond to an earthquake – whether it would fail and collapse.

In order to identify the dynamic behavior of a structure, engineers  install sensors at critical locations of the structure; apply an external force and then capture the structure’s response from the sensors. Engineers place a ‘dynamic actuator’ as the external force, at a critical location on the structure. This ‘dynamic actuator’ is really a huge hammer and it is controlled by a computer.  This hammer is lifted  up with a command on the computer, let go and the structure is hit with it. At that moment the structure’s response is captured from the sensors. Since each earthquake is different, the applied external force has to simulate every possible earthquake wave. There is a simple solution to this.

Initially the hammer is lifted up and let go every few seconds or so and slowly the speed is increased. From slow to fast hammering of the structure, almost every possible earthquake wave is thus simulated. Of course, the full response of the structure is also captured. In the end, engineers get 2 sets of data from each location they put sensors at – the displacement and the acceleration datasets of that location. When these data are plotted, something like below graph is obtained. The green data are the displacements and the pink are accelerations on logarithmic scale. Left hand of the graph is the beginning of the test – when the hammer  hits slowly on the structure. Right hand of the graph is when the hammer hits very fast.

Interestingly, the structure does not follow a linear response.  At certain times the response suddenly jumps. This happens when the structure gets into dynamic resonance. It is like this: you are hitting the bridge with the hammer 2 times per second, of course the bridge is shaking but you can still stand and move on the bridge. Then you give a command on the computer screen and increase the speed of the hammer to hit the bridge at 2.1 times per second. Right at that moment, the bridge starts shaking more. You increase the hammer speed to 2.2 times per second and the bridge starts shaking violently – you can not stand on the bridge any more. Increase the speed to 2.3 and the shaking starts dying. At 2.4 shaking has really subsided. But then at another moment, say at the speed of 4.3 you get another violent shaking.

So the peaks on the above graph are when these violent shakings occur. The log acceleration graph shows this more significantly. Each peak on this graph signifies moments at which this structure would exhibit dynamic resonance – violent shakings. If an earthquake wave at the same speed as these resonances occur would hit the structure, then you would get these violent shakings and the structure could collapse.


What really happens and how do these violent shakings occur? Engineers can view each sensor’s response on the computer screen. When initially the hammer is hit slowly, the response of each node on the structure is somewhat chaotic – some nodes are shaking to left & right, others  up & down. As the hammer speed is increased and dynamic resonance modes are approached, something interesting starts happening – all members of the structure start moving in the same direction. Because they are moving in the same direction, they enforce each other’s behavior and the movement accelerates. Very quickly it starts shaking violently and it gets impossible to stand on the structure.

Each peak on the below graph indicates a unique dynamic behavior of the structure. You may notice that at some peaks only some parts of the structure are excited. At these peaks, most of the structure is shaking normally whereas some part of it shakes violently. These are called local modes. On the left is a single, significant peak where all members of the structure shake in the same direction. This is called the fundamental mode because it is the most critical resonance mode. If this mode is excited during an earthquake, surely the structure would shake violently, get damaged and maybe collapse. Structural design engineers try to circumvent exciting this mode by arranging the design of the structure so that no earthquakes could excite structure at this mode.

So not all peaks have the same importance – there is one peak which is very significant and others that are less significant. In between the peaks are valleys where the structure would shake just a little but nothing serious. Once the structural engineers receive this data, they can guess which peaks would be excited during any kind of earthquake and then guess if the structure’s members would fail or not.

In year 2000, London would have a new pedestrian bridge on Thames River – the Millenium Bridge. During opening day more than 2000 people rushed on top of bridge and the bridge started shaking violently. The same day it was closed and after serious scrutiny if was realised that this bridge’s dynamic behavior under masses of people walking on it was not taken into account in the design stages. A herd of people’s regular walking speed caused the bridge to shake sideways. As shaking increased, people tried balancing themselves, and as more people tried doing this, the shaking increased further. People’s same collective behavior caused an unexpected response of the bridge.

The graph below is the one that I had encountered while reading the NY Times article. During 1987 to 1997, average house prices in the US were more or less the same. Then the prices started increasing with an exponential rate. On the increasing side of the graph are exclamation marks – that is when experts warn of an impending crash – they say this exponential increase in prices is not sustainable and it will crash. However at that time nobody seemed to care and it crashed.

The reason people do not care is because as exponential behavior starts occurring, more and more people start benefiting from it. Towards the peak, so many millions of people are benefiting from it that they they influence more of each other and not many question what is actually is happening. MIT professor Andrew Lo calls this behaviour ‘herding’ – people act as a herd and cause the behavior to increase erratically. During normal times people invest on different things and decide independently. However once there is an increasing trend, more people start investing in the same manner and cause the beginning of an exponential behavior – towards a crisis. Below graph shows many peaks/economic crises in last 100 years.

Warren Buffet likens the behavior that led to the mortgage crisis to Cinderella story, here are his words:  “The line separating investment and speculation, which is never bright and clear, becomes blurred still further when most market participants have recently enjoyed triumphs. Nothing sedates rationality like large doses of effortless money. After a heady experience of that kind, normally sensible people drift into behavior akin to that of Cinderella at the ball. They know that overstaying the festivities—that is, continuing to speculate in companies that have gigantic valuations relative to the cash they are likely to generate in the future—will eventually bring on pumpkins and mice. But they nevertheless hate to miss a single minute of what is one helluva party. Therefore, the giddy participants all plan to leave just seconds before midnight. There's a problem, though: They are dancing in a room in which the clocks have no hands. "

So as the peaks are reached, there is also a misleading sense of everthing going pretty well.

I had realised that collective behavior of structures at dynamic modes during an earthquake resembled very much the collective behavior of people causing economic crises – they led to exponential increases which would eventually end up with a crash of the system. I knew that exponential increases were not sustainable and I knew about the exponential increase of human population. This definitely would have domino effects on many other systems, so I researched on other exponential increases. Below are some facts I found out about:

There seemed to be an exponential increase in almost everything I looked at but the most worrisome was global temperature increase. Below graph correlates the increase in fossil fuel use with global temperature increase.

There has been an exponential increase in all types of fossil fuel consumption since the 1950’s.

And fossil fuel consumption leads to increase in green house gas concentrations in the atmosphere which leads to greenhouse effect and thus to climate change.

So at the end of my research I had arrived at ‘Climate Change’. And climate change had an effect on natural disasters:

Climate change was causing sea levels to rise even faster than the scientists were predicting.

And if business as usual, global temperatures would continue rising exponentially:

Obviously all this exponential increase would eventually lead to a collapse, I could see this and obviously many other people saw this too, but still things were getting worse; nothing significant was being done to avert climate change, why?

One reason is Warren Buffet’s Cinderella story – most humans are participants in climate change and they have a false sense of comfort with all the conveniences that the fossil fuel industry provides – they do not want to give up the comfort and the convenience – and as the peak is approached it seems there is no end to new conveniences that are provided for humans – party getting better towards the end!

Another reason is climate change does not follow a linear trend – that is, it is not always ever increasing – or so it seems. Some years at certain parts of the world all seems normal and  may even be colder. So people ask, ‘where is the climate change?’

Climate change dynamics are also very similar to structures’ behavior.

Remember the dynamic test: an external force is applied on the structure and the structure is excited, first the speed of applied force is slow and then it is  gradually increased. Since the  1800’s when humans first started consuming fossil fuels, green house gasses  (GHG) started increasing in the atmosphere. The external force in structure testing  is the big hammer and the external force causing climate change is fossil fuel consumption. Just like structural engineers increasing the speed of hammer during testing, humans are increasing rates of GHG’s in the atmosphere. Engineers increase the speed of hammer to be able to simulate all possible earthquake scenarios and reach to all peaks – dynamic modes that could damage or collapse the structure . As humans are increasing GHG’s, it is as if we are trying to hit the peaks where damage to environment and maybe collapse would occur. Remember in dynamic testing, at some peaks only parts of the structure would shake violently. This is what is happening right now in our world. Tornadoes in the US, flooding in Pakistan, Thailand, extreme draught in Africa, extreme heat waves in Europe, etc… all are local peaks that occur every now and then in the time scale as we continue forcing the world systems. But just as in the structure testing – between the peaks are valleys where all seems to be normal – so people get a false sense of normalcy until when another peak is approached. And the unfortunate thing is, we can not know if this peak would be a local one or the big/fundamental one that could cause a global collapse. One thing is for sure, if we continue forcing the world as is, we will eventually reach the fundamental peak and we will not realise this until very late.

At the base of all these exponential increases are these major factors:  exponential increase in human population and consumption of world’s resources unsustainably. Unless these issues are addressed, the paths only lead to  collapse.
Humans need to comprehend what is really happening and collectively change their current unsustainable behavior towards a sustainable life. With current technologies, accumulation of knowledge we humans could do much better. A sustainable life is possible.

After the end of my research, I wrote a book named ‘Critical Threshold’ and at the same time started researching on sustainability. I knew what the problem was and I was also part of the problem. I had to first stop being the problem and change my lifestyle. My research led me to ‘permaculture’. Permaculture is ‘sustainable living systems design’. Its ethics were identical to mine so I quickly identified myself with permaculture. In permaculture ‘problem is the solution’. Permaculture’s directives:  Stop being the problem. Take your own and your childrens’ responsibility on your shoulders and act – change your life to a more sustainable one. Take care of the earth, revitalize dying soils, generate resilient ecosystems that could also produce food for people in abundance…

Permaculture is actually the vast collection of knowledge from our ancestors on how to live sustainably on any piece of land on earth – be it the desert or the tundra. Permaculture is not the only solution to sustainability, but it is a very good one to follow.

With guidance of permaculture, I first changed my lifestyle, my home and garden. Now I am building a 100% sustainable farm & research center for sustainability in the hope of reaching out to as many people as I can and show that sustainable living is possible, is much healthier and is much more comforting.

I am ready to share all knowledge and information and would like to collaborate more with all of you so that there may be hope for a sustainable world. Only together there may be a chance…


Taner Aksel

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