Arguments
Doubling down: Researchers investigate compound climate risks
Posted on 6 January 2020 by Guest Author
This is a re-post from Yale Climate Connections by Daniel Grossman
It was a grim day in Moscow on July 25, 2010. The English-language Moscow Times reported that the Russian capital had broken the 1936 temperature record for July: 98 degrees Fahrenheit.
That month, the city, where air conditioning was (and still is) rare, was an average of 32 degrees Fahrenheit hotter than a normal July.
Plumes of smoke rising from peat bogs burning in the distance wafted through Moscow’s central Presnensky district. The newspaper reported that “grass has dried down to straw,” and trees were dropping leaves and dying from dehydration.
The mega heatwave – since designated eastern Europe’s hottest episode in 500 years – affected an area as large as Mexico. By the time it abated it had caused 55,000 deaths from respiratory failure and other disorders caused by heat and air pollution from wildfires. It had destroyed one-third of Russia’s grain harvest.
Jakob Zscheischler, a senior scientist at the Climate and Environmental Physics group at the University of Bern, calls the 2010 incident a quintessential compound climate event, a weather disaster intensified by the combined effect of two or more factors. In this case, a heat spike reinforced by a prolonged drought produced the second most deadly heatwave in history after the western European heatwave of 2003. Climate change could make compound events more likely, Zscheischler says.
When it rains … it often really does pour
Researchers generally study the intensity and likelihood of heatwaves, droughts, and other adverse climate incidents in isolation, as if the incidents were independent phenomena that don’t interact with each other. Radley Horton, a Columbia University climate science professor, who had helped organize the world’s first international workshop on compound events, says that such phenomena are often not independent at all and that assuming they are can lead to unreliable results. “Relying on climate models to look at single variables could understate the risk because of the way these extreme events interact,” he said in a phone call.
Research on the 2010 Russian heatwave illustrates how taking more than one factor into account can improve estimates of the likelihood that an adverse event will recur, and of the degree to which climate change can be held responsible for it.
Though climate scientists have generally analyzed the incidence of drought and elevated heat in isolation, they have known for decades that the two phenomena go hand in hand, each making the other worse. The causal connection between them is easily explained by the well-known relationship between air and moisture in the soil, an effect called land-atmosphere feedback.
When temperature increases so too does the amount of water evaporating from the ground. Even if precipitation remains unchanged, soils become drier – a defining characteristic of drought – when temperature goes up, reducing the availability of moisture for forests, crops, and urban gardens. By the same token, soil moisture regulates regional air temperature. Wetter soil absorbs more heat. So unseasonably low rainfall dries soil and raises temperature.
When six plus three equals 13?
Authors of several papers have studied the Russian heatwave as a compound event with land-atmosphere feedback. Authors of a 2016 publication concluded that climate change increases the likelihood of a devastating heatwave by a factor of six. Low soil moisture increases the likelihood by a factor of three. The combined effect of drought and climate change raises the probability of such a heatwave by a factor of 13.
Another compound event attracting close attention is the combined impact of ocean surge and river flooding on coastal cities. Surge temporarily increases sea level when high wind pushes water against the shore. River flooding occurs when heavy rain swells waterways.
Either surge or river flooding alone can swamp a city, threatening large losses of property and life. In 2011 Hurricane Irene caused $15 billion in damage, much of it caused by raging rivers swollen by intense rainfall. In 2012, in contrast, it was storm surge that made Superstorm Sandy one of the most costly natural disasters in U.S. history. High tide in New York was nine feet above normal, inundating entire neighborhoods, flooding subway lines, and shorting out parts of the electrical grid.
When the surge of Sandy meets the rainfall of Irene …
Horton advises that disaster planners consider the possibility that a future storm could combine the offshore surge of Sandy with the heavy rainfall of Irene. Prevented by elevated tides from draining into the ocean, rivers in flood would overrun the coast at their mouths. A 2015 analysis of weather records concluded that simultaneous ocean surge and heavy rainfall has become more common at major coastal cities of the contiguous U.S. “That combination could potentially lead to greater risk and loss of life,” Horton said.
Researchers at the recent Columbia University workshop distinguished between several varieties of compound events (sometimes called correlated extremes). Not all are incidents enhanced by multiple factors occurring in synchrony such as drought-enhanced heatwaves or surge exacerbated by rain.
Another kind includes episodes occurring roughly simultaneously but far from each other. The El Niño weather pattern is a well-known example of how atmospheric conditions can change all at once in places separated by great distances. During an El Niño, drought descends on the Amazon and the U.S. Pacific Northwest, while heavier rains fall in the southeastern U.S. and British Columbia. Researchers have identified other climate phenomena, connecting far-flung parts of the world by often-poorly understood “teleconnections.” Could such events cause previously unanticipated problems? Researchers are striving to better understand and answer that question.
In a world dependent on far-flung shipments of food, fuel, and manufactured goods produced in and shipped through a small number of key centers, simultaneous climate disasters could create widespread economic and humanitarian disaster. For instance, Horton worries that drought and high heat could cause crop failure in the breadbaskets of the Ukraine, central Europe, and the U.S. “You could see big changes in crop prices and big implications on food security, and potential repercussions in terms of conflict and migration as well.”
Recent research justifies Horton’s concern. Authors of one paper published last March have teased out relationships between adverse growing conditions in the world’s top wheat-growing regions. Among other findings, they noted a suggestive relationship between hot, dry periods in the E.U. and Australia. And authors of a paper published in June 2018 concluded that global warming will dramatically increase the likelihood that the world’s four top maize producing regions will have simultaneously climate-related crop losses.
More questions now than answers = more research to come
Jane Baldwin, a postdoctoral fellow at Princeton University, is studying another kind of compound event made up of a repeated series of short, extreme incidents. She wonders if a succession of short temperature spikes, each too brief to fit the definition of a heatwave, could be as deadly as a longer spell of high heat officially designated as a heatwave. Last April she and several colleagues at Princeton published a paper showing that climate change is increasingly the likelihood of such short extremes of heat. “We should be thinking if having multiple heatwaves in sequence matters,” says Baldwin. She’s continuing her research with epidemiologists to find out.
Geoscience professor Michael Oppenheimer, at Princeton, says he thinks the Columbia University conference – which he helped put on – “signaled a broad interest in compound events in the climate community.” Zscheischler, who has written prominent papers on compound events in Nature Climate Change and Science Advances, says that so far researchers have raised more questions about the subject than they have answered. But, he added, “I’m sure there will be a lot of research in the next couple of years on the topic.”
Combining the impact of climate events makes sense. Structure design codes have required that for decades.
An example is the need to combine the weight of ice collected on a high-tension power line with the increased wind force of a strong wind blowing on the larger diameter feature (increased because of the ice). The required cable and support tower design is substantially impacted by that combination.
The difficulty in investigating the 'combinations of climate impact' should have been a justification for more aggressive action to reduce the rate of climate change impacts until the severity of the consequences was better understood.
A knowledgable person in a more advanced nation today would not try to build a building with new materials or a novel structural system without very thoroughly investigating and understanding its behaviour, and proving it would be safe under a massive diversity of combined potential impacts.
Why is the future of humanity on this planet continuing to be be significantly geo-engineered by current day actions of the 'supposedly most advanced people in the supposedly most advanced nations' without the consequences being 'very well understood'?
Any person claiming it's OK to carry on doing whatever is popular and profitable needs to be challenged to answer why that is morally acceptable.
How difficult are these structure design codes to formulate!??!
bozzza,
Not sure what the question is, but here is an attempt to clarify.
A signficant structure design challenge is accurately identifying things like the worst case climate events that a structure could face. Rapid climate change makes that very difficult to do, and raises doubts about every already built structure.
And proving the reliable performance of all the materials and shapes and connections has been constantly improved through the efforts of countless institutions around the planet.
But the need for a structure to be safe is not compromised by a desire to carry on doing something questionable just because it was popular or profitable. Things that were dicsovered to be unsafe or harmful stopped being done and are corrected.
Designing structures for combined events is not too complicated. You design a structure to withstand a certain snowload, and then the structure has to be designed to withstand a certain wind load, on the basis that it is also sustaining the designed maximum snow load at the same time.
The climate problem is the inverse of this, but harder to work out.
This insidious combined cimate effect is what needs to be front and centre of discussions aimed at the public, not the arm waving, highly speculative apocalyptic stuff that many people will scoff at.
Actually designing structures to withstand combined effects can get quite complicated at times.
Some structure design is incredibly complex. Dynamic response is a very complex behaviour to evaluate. But the real issue is 'not doing something when there is uncertainty regarding the potential for negative consequences'.
Some of the most complex design is dynamic response of a structure with partially yielding elements of a structure system (parts stressed beyond their elastic behaviour). That includes seismic and blast resistance design (things I have personally done). And that complex dynamic system response gets combined with the understanding that lateral motion of a structure is amplified by vertical loads acting concurrently on the off-set structure (the vertical load is no longer straight down a support column).
My main point remains. The knowledge that the combination of effects of climate change are not yet well understood should have been enough to cause the leadership of the highest impacting people to dramatically reduce their impacting while pursuing the required expanded awareness and improved understanding. That is what they would expect to happen in Structure design, even though a flawed structure design would only affect a tiny portion of the global population, and have almost no effect on generations in the distant future.
The real problem is the fatally flawed of belief that the 'power of innovation' requires anything that is competing for popularity and profit to be allowed in the competition before the potential negative consequences are well understood. Competitive consumerism, especially the Patent/Copyright systems and related limited time period for benefiting from owning patent/copyright protection, tempts people to try to get away with harmful and unsustainable activity (because it is easier and cheaper than the alternatives).
Harmful unsustainable developments can be seen to be defended if they become popular and profitable. The demand is that evidence of it being harmful 'must be very certain', with higher certainty of unacceptability required the more popular and profitable it is. In some people's minds that has quickly gotten to the absurd point where no amount of evidence will 'meet the demanded level of proof' (on many issues, not just fossil fuel abuse). The 'learning resistant people' who enjoy benefiting from the popular and profitable activity, or developed a liking for an incorrect understanding, can claim that any evidence is Fake and demand that any presentations of information on the issue be 'Balanced or Moderate' which means 'Compromised'.
Compromising expanded awareness and improved understanding of how harmful something may be may seem appealing to the Kumbaya types who just want 'everyone to get along and let everyone live the way they want'. That attitude has its place, when no profit or personal benefit at the expense of others is involved. But that attitude would never cut it in Structure design. And it certainty should not apply to the issue of the future disaster creating potential of the popular and profitable fossil fuel abuse.
Everyone's actions need to be governed and limited by the avoidance of creating harmful impacts on others, even if that means having to forego potential personal benefit because of uncertainty regarding the acceptability of an activity.
OPOF
“A signficant structure design challenge is accurately identifying things like the worst case climate events that a structure could face. Rapid climate change makes that very difficult to do, and raises doubts about every already built structure.”
I realize what you are trying to say but I don’t think you understand the process that engineers use to determine the loading on a structure. Structures are not designed for the worst case climate event that a structure could face. In the US wind loading is divided into hurricanes that occur along the gulf and eastern coast, and storms that occur in other locations. Hurricanes are based on 1200 year probability and storms are based on 700 year probability. A 5000 year hurricane or storm COULD occur. However it has been agreed that the code design probabilities are a reasonable value that allows structures to be built without costs being unreasonable. In addition, structures are divided into 4 risk categories which determine a risk factor for a structure. Category 1 is for structures that represent low risk to human life like agricultural buildings. Category 2 which is everything not in the other categories. Category 3 which represents substantial risk to human life. Category 4 which includes essential facilities (hospitals, fire stations, etc). Basically the risk factor changes the design hurricane or storm probability.
Rapid climate change is dangerous. However changes in maximum wind speeds for hurricanes and storms are not enough to raise doubts about existing structures.
As a retired structural engineer, you guys brought up a subject I used to have to deal with. To begin with, why do you guys assume we put up safe buildings? Steel moment frame buildings built at the end of the 19th century have proven to be more durable to earthquakes than ones built in the late 20th century. The build environment has suffered from faster/cheaper while design fees keep falling. Commercial building codes no longer have structural design info because the codes are written by people with high school educations. Welcome to deregulation.
Look into the neoliberal race to the bottom and the rise of authoritarian governments as a response to the resulting destruction of the middle class in the west. You will begin to see why we aren't going to fix anything (including a looming climate disaster) until it's too late. (Neoliberal economic theory called neo-conservative in America. Remember Bush and the neo-cons? The reason we invaded Iraq.)
@7, Hank, we know how to design safe buildings, we just don't. Did you see the pictures of a town in FL destroyed by a hurricane? Did you read about the one house that survived because the owner wanted a stronger house?
Last years hurricane that stalled over the Bahamas is a peek at what is to come. Hansen, Et Al (2015) talks abut Atlantic storms 10x worse than today's during the last interglacial, with temperatures only 1C warmer than we are.
@ 8 & 9, dkeierleber
I have to disagree with you on every statement. As a Registered Professional practicing Structural Engineer I have no idea where you get your information.
Out of the millions of building that are erected in the US there have been relatively very few failures. Of those failures, only a small percentage are due to improper design. That’s not an assumption, that’s a fact. That shows we DO put up safe buildings.
Buildings built at the end of the 19th century were not based on codes since they didn’t exist. There was also almost no knowledge of seismic loading or how to resist that loading. They were simply built very conservatively. That said you didn’t provide any references that show they have performed better than more recent structures. Seismic design is very complicated and every occurrence allows engineers to study the results of current design practice. It is known that buildings designed with the more recent codes perform better than previous designs.
Building codes DO ABSOLUTELY have structural design information. Otherwise they would have no purpose. Today’s codes have probably 10 times the amount of design information as in the past. That’s just an estimate on my part based on the size of the codes. In addition they have extensive commentaries that explain how and why each formula should be used. I served on the ASCE committee for Design of High Voltage Substations a few years ago and I can assure you it was not written by people with only high school educations. Out of about 40 representatives there were several PhD’s, including the lead, along with probably 20 graduate engineers with masters degrees. There may have been a few industry representatives without college degrees but they were only there for guidance in specifying materials that might be unavailable and other minor advice.
The buildings destroyed in the Florida town you mentioned are a testament to design codes. Residential buildings are seldom designed by an engineer. The one that was standing was reinforced concrete construction and WAS designed by an engineer for 250 MPH winds. After that the codes in Florida were changed so that an engineer must sign off on residential designs and the design wind speeds were increased. That doesn’t agree with your statement that codes are being affected by deregulation.
I am a strong believer that we are failing future generations by not addressing climate change. I am in favor of laws that decrease the amount of CO2 were a putting in the atmosphere. Storms will be worse and we need to account for that. But I don’t think unrealistic claims that storms will be 10X worse are helpful to our cause.
Hank,
I am a Structural Engineer with 40 years experience, including participation in design code update processes. But I am Canadian with experience in many other nations, including the USA.
I share your understanding of structural design, and sort of agree that dkeierleber has offered an unfounded opinion. However, dkeierleber is correct about the harmful influence of competition for profit.
The A36 grade of steel was a decent material for seismic design before 'recycling of steel became common'. It had fairly reliable performance values allowing it to be used for the 'designed to yield first' components of a structure. However, 'recycled steel meeting the crude criteria of A36' often ended up being a much stronger steel than expected. It was those 'over-strong A36' parts of seismic structures that led to the tragic failures that resulted in the USA belatedly updating its steel material specifications and design codes. That delay of update could be seen to be a protectionist action by the USA profit interests (related to dkeierleber's correct concern) to keep imported steel out of the USA because, though imported steel was based on better specifications, it wasn't A36.
Now on to the climate condition point you made @7:
I am well aware of what you refer to, and agree that wind forces 10X worse are a long way off. But I would state that inland wind speeds could increase to levels currently thought to only happen near a coastline. And in some nations, like Canada, the regional design requirements are based on the history of local conditions rather than the less location-specific (cruder) USA approach of generalized climate conditions.
I would add that your comment misses the need to design for climate related things like ice accumulation during freezing rain events and 'maximum accumulated snow loading'. Climate change can increase the amount of accumulation of freezing rain, and introduce it to regions that previously never had that type of event. And climate change can result in more snow falling. And a warmer snow event will also be wetter heavier snow.
So there are many aspects of building design that can end up being exceeded as climate change alters the nature of regional climate events.
As a final note about coastal wind speeds, did you notice that this year there was a storm near the USA coast with wind speeds that were well above the threshold of Category 5, high enough to warrant consideration of adding a Category 6?
@10, Hank, very happy to see your reasoned response. I have a fondness for engineers and engineering but I’m not sure where you’ve been working.
There were about 30 steel moment frame buildings in SF at the time of the ’08 quake. Around 20 were still in service in 2000 when CA had just finished extensive repairs to a lot of more modern steel moment frame buildings. The problem with the newer buildings was that the moment connection was too stiff. The older buildings had riveted (likely) connections. For a while we had creative solutions for that joint but those all went away when the same prescribed welded connection was again approved. It is supposedly now safe because we have a new alloy and new rules on how to make the full pen weld between the beam flanges and the faces of the column flanges. We’ll see what happens in the next big one.
Older buildings generally had the steel frame protected by masonry which made a pretty durable joint. It was an accidental benefit of engineers realizing that steel needed protection from fire. Engineers forgot that some time ago. Tell an engineer he should be responsible for protecting his structure and you will have an angry engineer. Engineers can’t be bothered to get a bigger portion of the design fees.
I read a paper in the Structural Journal, some years ago, that claimed steel buildings could not fail due to a fire. This despite the fact that we lost a steel building to fire in 9-11 (the third collapsed building). The paper was based on tests done in England in the 1970s but 9-11 showed that fire loads are much higher now, esp in office occupancies. The journal paper was arguing for performance based codes. Do some research on how well that’s worked for the Chinese.
Hurricane Andrew was a wakeup call to the insurance industry. Whole subdivisions were leveled due to shoddy construction practices. Roofs without hurricane clips had partial failures that let in water, turning particle board sheathing to mush. The response, instead of requiring better construction practices and better code enforcement, was to completely change how wind loads were calculated and applied, especially to low, gable roof buildings. That was likely the beginning of the end for the UBC (Uniform Building Code).
The UBC grew from a small, easy to understand book, with design standards for the common building materials, to 3 large volumes in 1994. The last UBC was 1997. Since then the same private industry has produced the International family of codes. The design standards in the UBC were written by prominent engineers who sat on the industry boards and advisory groups. IBC language is voted on in conventions of code officials. The minimum requirement for a building official is a high school diploma (It’s in both the IBC and IRC). After the IBC, structural design info moved out of the code book. You now have to get the current ASCE 05 for loads, the AISC for steel design, etc. At least the AISC now makes a passing mention about fire protection of steel members.
Over the years a system of weighted design has been suggested. I’m sure it’s now being used. The idea is to set a level of design standards to match an expected level of performance for given events. Instead of being an option for building developers to choose, it’s being incorporated into codes based on occupancy (I think). Part of the problem in the built environment is that nobody has a building built for them. Developers put up the cheapest, fastest building they can and then sell it. What’s worse is that many buildings are sold piecemeal. Condo projects will never have any defects corrected or be demolished because they are building ownership by a bunch of building owners, none of whom are very knowledgeable about buildings.
You are probably fed up with me by now but I still think that it’s frightening to think that buildings built to standards of 1890 are structurally better than buildings built to current standards. Of course, then there are the old clay brick buildings (I did a fair amount of seismic upgrades to those).
Hank, I also share many of your views, but the truth on this thing is possibly more nuanced. I'm a semi retired Architect, involved in the design of both housing and highrise construction in New Zealand.
Our building codes are quite detailed on everything including structure. There was a massive earthquake in Christchurch recently and modern buildings survived better than older brick masonry buildings and concrete framed buildings, as you would expect.
However there are huge caveats around all this. dkeierleber has a point to some degree. Our codes are minimal codes, so for example earthquake and fire codes target only life safety, not property damage. This is because of neoliberal thinking that constantly aims to minimise building codes.
As a result although modern highrise buildings and timber farmed houses survived the earthquake and not many people were killed, these structures suffered considerable damage and many had to be demolished and rebuilt. The bottom line is the codes are pretty minimal, and neoliberal ideology is definitely involved. I dont have time to go into all the details, but I know this for a fact.
@11 OPLF
Nice to see engineers are represented here and concerned about climate change.
I am only familiar with the US codes. I do know that in the 1980’s steel mills started suing more modern production processes that resulted in steels specified as A36 had a higher yield strength of around 50 ksi are more. As a result the beam to flange weld metal at the joints became under-matched which may have contributed to excessive strains at the joint. The Northridge earthquake in 1994 resulted in several studies that were initiated by AISC and the AWS over the next few years which revealed the problem. Soon after the codes were changed to address this and numerous other issues. I did not realize there was ever a delay in updating any codes due to protectionist actions. However I’m always eager to learn so would appreciate any documentation you know of regarding this.
I graduated in 1971 and have worked in 5 different industries, transmission lines, railroad bridges, large satellite antennas, consulting engineering, and high voltage sub-stations. Maybe I’ve just been lucky but I have never been asked to compromise any design based on costs or any other factor. I have of course been asked if a less expensive product could be substituted for some part but only if it checked out to meet code requirements. The only thing close to this was a somewhat humorous experience when I was going over a part with some people in the shop. One of the welders stated he had built many of these and the plate was too thicker than needed. I handed him my pin and stated “Ok just write that on the drawing and sign and date it”. He didn’t make any more comments.
I certainly realize the need to stay on top of changing weather and agree with you that areas can experience changing environmental requirements. I believe the engineers on the committees that write and revise the codes in the US do track extreme weather events and take this into account. Living in the South ice and snow are not usually controlling conditions so I’m not as familiar with those types of loading. With the exception that even in the South, ice on wires combined with wind can control the design of supporting structures.
Concerning your final note. The US code does not consider hurricane categories. Instead it has wind maps that specify the wind speed at locations throughout the US. At this time the highest wind speeds are 180 MPH along the Gulf Coast. I don’t think any hurricane has hit the US with those wind speeds. I would also point out that the highest wind speeds in a hurricane are limited to near the eye of the storm. In addition for most structures the maximum wind speed must attack the structure from one specific direction for the structure to be fully loaded to the design load. That reduces the likelihood that a structure will be fully loaded in a hurricane. But as I said, structural loading is statistical in nature. So there is always the risk that any storm could exceed the design loading on a structure. We just want to lower that risk to an acceptable number.
@12, dkeierleber
You have stated before that buildings built to standards of 1890 are structurally better than buildings built to current standards. Yet you have not provided any evidence of that. Nor have you stated what standards you are talking about in 1890.
If you are talking about residential buildings you are correct that SOME developers build the cheapest and fastest they can. If you are talking about commercial and industrial buildings that is something different. Commercial and industrial buildings as well as other structures in the US require they be designed and certified by a professional engineer. Only a very small number of structural engineers would risk their license by designing a building that does not meet code requirements. That is evidenced by the small number of structural failures in the US.
The three US building codes were combined into the International Building Code in 1994 so other countries that do not have the resources for research could adopt it as their own code. Structural design has never moved out of the code book. The three original codes also referred to AISC for steel design and the other codes for concrete, aluminum and wood. They also used the wind speed maps that were based on ASCE 7. The IBC is primarily a fire code that specifies ASCE 7 and the material codes for the structural loading and design sections. I don’t know where you get the idea that those codes are written by individuals that only have a high school education. They are written mostly by engineers with advanced engineering degrees.
@13 nigelj
Nigelj I can only speak for the US but I have researched the European codes since we sell around the world and their codes are very similar. There is a very logical reason buildings are designed to just prevent the building from collapsing during a high seismic event and it has nothing to do with neoliberal ideology.
The forces on a building during a seismic event are a function of the building mass. The mass of a building results in loadings that are up to 8-10 times the forces due to extreme wind pressures. Therefore a building that is designed for extreme wind at $200/sq ft would be $1000/sq ft if designed to the same requirements. Just a foundation to support the additional weight would be massive. For the billionaires this might be acceptable, however a developer that was investing in a building for rent would never be able to find any clients. Therefore the tradeoff is a building that is safe for humans but at risk of having to be rebuilt or even destroyed if a high seismic event happened. This type of risk happens every day in the stock market.
With the committee that was writing the design code I served on there was never a discussion of trying to minimize the code requirements. There was lots of discussions about how to assure the code produced structures that were safe and operational. Structural engineers are the most sued engineering profession in the US. That’s not because they are incompetent or because they try to cut corners. It’s because structural failures are usually much more expensive, not to mention lethal, than designs in the other engineering professions. We lose a lot of sleep hoping we didn’t divide by 2 instead of multiplying by 2.
Hank @16, thank's for the comment and I do understand there has to be a sensible compromise between code requirements on property protection versus cost. However it appears the buildings in the Canterbury earthquake suffered more damage than buildings in Japan and other places subject to the same forces. I recall discussion in our media on this but I can't find anything using google. I can tell you earthquake codes were reviewed.
It looks like our codes are weighted a long way towards lowest cost. However I doubt that has anything to do with the engineers on the committees that develop codes. In my experience structural engineers in NZ are very commited to tough building codes, I've worked with plenty of these guys. Several times they have recommended going above code.
However heres another couple of examples where ideology combined with cost cutting appears to have intruded. Our building code was revised in 1995 and the fire code was changed from something that included both safety and a mild level of property protection to just safety. And the construction code was changed removing the requirement for treated timber framing and metal flasings around windows etc, and this lead directly to an expensive leaky homes crisis.
Insulation requirements were downgraded to a bare minimum. During all this the government of the day was promoting deregulation, austerity, freedom of choice, lower costs, etc the whole neoliberal paradigm. These definitely look to be factors in the changes Ive mentioned.
While you dont want to over regulate and cause massive expense, these three examples of downgrading the code were stupidity and a disaster. As a result, the code was revised yet again, and insulation requirement was increased and we went back to treated timber etc around 2005.
Hank @14,
I have seen foreign clients demand that their buildings in Canada be designed for less loading than the Canadian code (some claiming the USA code is Universal). The basis for their demand was that they did not believe that the code load was justified and as the client they thought they could dictate the design requirements (like they apparently could in other nations that did not require Registered Professional Engineer's to be gate-keepers against desires for things to be cheaper or done quicker).
And there have been cases of structure failures because of a lack of proper maintenance. In some cases the owner sought out an inspector who would deem everything OK like the Elliot Lake shopping plaza collapse (some people love being able to find someone who will say what they want to hear). Many bridges, including in the USA, are becoming disasters waiting to happen.
And a recent pedestrian bridge collapse while under construction in Florida is a dire warning about New Design. The video of the NTSB meeting is enlightening. That bridge was designed and built as an example of a quicker cheaper way to build bridges.
Regarding the delay in the USA updating their structural steel from the A36 standard: The delay I am referring to was not a delayed response to the identified tragedy of Northridge. I am referring to the fact that the old lower-strength A36 specification was very slow to be upgraded to the higher-strength more stringent specifications that were implemented for basic Structural Steel around the planet long before the problem of continuing to use that old lower quality specification was exposed by Northridge.
The change of structural steel production from raw-iron to recycled steel was the cause of the problem. A36 was written in those old days of raw production when contaminants in recycled steel did not need to be restricted by the A36 specification. Exactly why the USA failed to investigate the potential risks of continuing to use the A36 specification when recycled steel production began is a mystery I do not have an answer to. What I am aware of is the history of USA protectionist actions like the continued use of Imperial Units which delayed and limited the competition from foreign producers (but also limiting the ability of USA made products to be exported if their production did not go metric - the USA coming up with its own Railway Rail Spacing is an earlier example). That resistance to stop using Imperial can also be argued to be 'simple resistance to change'. But it is almost certain that there is more to it than just a resistance to change. I presume, in a similar way, the delay of updating the A36 was also more than just 'resistance to change' (which relates to dkeierleber's correct observations of the potentially serious negative consequences of pursuits of popularity and profit).
And that protectionist profit-motivated resistance to correction (that can also easily be popular) can be seen in the actions of certain factions in the USA and other nations as they fight against the corrections of unsustainable creation of negative consequences that are identified by the improved understanding of climate science.
The science is clear that total global impacts exceeding a 1.5C increase of global average surface temperature is unsafe (harmful) for future generations. There is fairly well understood significant negative consequences due to that amount of warming, And beyond 1.5C warming there are significant uncertainties regarding how much more negative things will be.
There is virtually no chance that there will be Positive Future Impacts of warming beyond 1.5C. And since perceptions of wealth today are so heavily based on unsustainable activity there is serious doubt about today's wealth continuing to exist in the future.
A correction to Sustainable Development, not just the rapid ending of fossil fuel use, is urgently required. Resistance to that required correction is seriously detrimental to the future of humanity. And the reality that change/correction resistance can be so powerfully fuelled by desires to Protect Developed Perceptions that are popular and profitable is a serious threat that humanity needs to figure out how to Govern and Limit.
The uncertainty regarding the severity of negative consequences of combined climate change impacts is more reason to more rapidly pursue Sustainable Development and all the changes and corrections of current incorrect over-development that are required.
There was some controversy about future storms going to be "10X worse" (mentioned first dkeierleber, #9) and Hank at #10 said that claims of storms 10X worse is unrealistic and unhelpful and then OPOF, #11, said "I [...] agree that wind forces 10X worse are a long way off". But "worse" is not a SI-unit or in any way rigorously formally defined. I don't think what was meant from the beginning was 10X windspeeds. I tried to find the paper by Hansen 2015 to look for mentioning of 10X worse storms but didn't really find it. I did find this:
"increment [...] as much as 10-20%. Such a percentage increase of wind speed in a storm translates into an increase of storm power dissipation by a factor ~1.4-2, because wind power dissipation is proportional to the cube of wind speed " (mentioned in "Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations that 2°C Global Warming is Highly Dangerous", Hansen et al, 2015).
So wind power increases much faster than linear with wind speed. I can imagine then that damages also increases faster than linear with wind power. So it is not completely unreasonable to to foresee future storms to be 10X as destructive, "destruction" measured as cost of damages.
Ignorant Guy @19, Good Point.
Defining how bad climate change consequences will potentially be should not be expected to be restricted to "Specific Units of Measure". Like attempts to perform economic evaluations, many things cannot, and should not, be expected to be fully Quantifiable. What can be quantified can be when it is reasonable to do so, along with all of the unquantifiable considerations.
Things being 10x worse is indeed a murky point.
The fundamental related understanding is that it is unacceptable for any individual to act in a way that potentially creates negative consequences for another individual. That understanding involves many unquantifiable considerations. And it does not allow a trade-off where one person decides it is OK to have negative impacts on another because they 'mathed it out and overall it is Good (they figure that their benefit exceeds the harm they think they do to others)'.
What is actually important is to stay focused on: Any negative consequence inflicted on future generations, or Other current day people, due to a lack of correction of harmful unsustainable ways of living is simply Unacceptable.
In spite of the fact that it is a distraction to discussion of how much worse things will be due to human caused climate change there is some merit in those things being discussed, even extreme potential consequences. Structural engineers have to consider possible effects that are not covered by Code Minimum Requirements (at least responsible ones do that - including considerations of safety of construction of their structures).
I am aware of the cube relationship for wind. A 10x increase of maximum wind force requires more than doubling the wind speed. So I suggest that is a 'long way off'.
However, I did not mention that how far into the future that worse condition is is actually not a relevant factor. The future of humanity on this planet is potentially more than a billion years. It does not matter how much later that worse condition is caused by harmful unsustainable activity (some economists incorrectly believe that such future costs can be Discounted, when they incorrectly also believe that they can quantify all aspects of this issue for Their analysis).
However, on the point of Hansen's concerns, the following 2017 Washington Post article, "Ancient storms could have hurled huge boulders, scientists say – raising new fears of rising seas" refers to a study that suggests that the dramatically worse impacts that were part of what Hansen was expressing concern about (boulders being moved by waves) could happen with lower wind speeds.
Some scientists and commentators are talking about a need for category 6 hurricanes here and here.
We have millions of buildings designed to resist certain wind strengths. With more frequent winds above what the buildings are designed to withstand, you get more damage overall, and this is where we are heading. Given the lifespan of buildings is typically 50 years minimum and often considerably more, a lot of buildings will be at risk, particularly housing. Strengthening these structures will be an expensive pain in the proverbial.
OPOF @ 18
As I’ve said I can’t speak for codes in other countries. In the US the IBC has been legislated in all 50 states and anyone demanding those laws be broken are subject to prosecution. Clients I have dealt with did not even know the code enough to know what the design requirements were.
My argument has mainly been with dkeierleber’s comments that building built previously were structurally better than today and that today’s codes are written by people with high school education. That is simply not true.
As for structural failures because of a lack of proper maintenance you are absolutely correct. In the US, ASCE has been warning for years that our infrastructure is being poorly maintained. They give a grade every year and for the last several years it has been a D-.
It certainly appears the pedestrian bridge you referenced had design problems. That doesn’t mean the design codes are responsible for engineers that don’t follow the code. And quicker and cheaper does not mean the structure is not safe. We have been lowering the cost and time to build structures for years with better materials and manufacturing technology. It is an engineer’s job to design the most efficient structure that meets all safety requirements.
Maybe you don’t have an answer to why the US failed to investigate the potential risk of the A36 specification is because it’s very difficult to predict potential risk. As they say 20/20 hindsight is always correct. But being able to predict the future is difficult. I just did a search for structural failures and they happen all over the world including Canada.
Resistance to change is not limited to the US. All countries and most individuals struggle with change. I have no idea why railway rail spacing has anything to do with this. Railway rail spacings are different in multiple countries around the world. And profit-motivated resistance to correction is present in all countries, not just the US.
I completely agree with you about the dangers of 1.5C increase. We are on the same side about the need to rapidly end fossil fuel use. I don’t know what you have done but I’ve put in solar panels and changed out my A/C units to more efficient units which dropped my average electrical bill from $350/month to $136/month. But that’s a different subject from saying the structural codes are written by high school graduates.
Ignorant Guy @ 19
I don’t know where you found a 10-20% increase in wind speeds but I would be interested to see a link. Here is a link to a study on global warming and hurricanes. (I may not have inserted the link so it can be one-clicked so I included the text)
study
https://www.gfdl.noaa.gov/global-warming-and-hurricanes/
That study showed a 4% increase in wind speed per degree Celsius increase. For a 2C increase that would be an increase in wind speed of 108%. Wind power dissipation may well be as you say proportional to the cube of wind speed but structures are based on wind pressures which are a function of the wind speed squared. That would be an increase in pressure of 17%. The 10x comment was made by dkeierleber during a discussion of designing safe buildings. I don’t think I was being unreasonable in assuming he was referring to wind pressures in that discussion since wind pressures are how buildings are loaded. Right now the design code requires in southern Flordia a building to be designed for 180 MPH for risk category II and 200 MPH for risk categories III and IV. A 10x increase in pressure would change that to 570 MPH for risk category II and 630 MPH for risk categories III and IV. I do think that is harmful to the cause of those that think there is a climate crisis. Right now the Glacial National Park is taking down signs that state the Glacial will be gone in 2020. I don’t know what was behind them putting those signs up to begin with but as you can imagine the deniers are having a field day with it.
As for 10x the cost of damages you may be right although that still seems to me a very high bar. For everything I’ve read the damages are usually due mostly to flooding, not so much wind. My understanding is that rising sea levels, flooding, and heat & drought will be more costly than increased winds.
Nigelu @ 21
Right now in the US the design wind for risk category II buildings along the coast is based on a 1200 year storm and for the interior a 700 year storm. The design wind for risk category III and IV buildings along the coast is based on a 3000 year storm and for the interior a 1500 year storm. If you were in charge of the design codes, what wind rating would you have engineers design structures?
Also do you think it is reasonable to have agricultural structures such as diary barns designed to different standards than say fire stations?
I’m not trying to be argumentative I’m just trying to get a feel for how much decreased risk the general public might be willing to pay for.
Hank @22,
We substantially agree. And one of my links was to a structural problem in Canada. And there are indeed many other cases of structure failures in Canada.
The root cause of many of the structural problems around the world (poorer quality of design, materials, construction, or maintenance) is economic systems developing desires to get things that are cheaper and quicker (more profitable). Professional Engineers have to stand firm against those pressures, not allowing the 'protection of the public and the environment from harm' to be compromised by any 'economic considerations', or they are unprofessional (an engineer cannot responsibly evaluate 'potential for profit' against a reduction of level of safety against harmful consequences - just as it is inappropriate for economists to compare the lost opportunity of people today with the harm their pursuit of opportunity will do to future generations, especially inappropriate when they discount those future costs).
A side consequence of pursuit of profit is 'protectionist actions' attempting to protect a pursuit of profit from challenges or corrections. And the current USA leadership, and other national leadership like it, is acting in a protectionist manner with actions resisting the corrections required to limit the future climate change consequences.
An early example of USA protectionism is the designation of a unique rail spacing that kept British rail equipment from being imported. The resistance to the use of metric units is a more recent example. And it is likely that protectionism was a major factor in the USA still using A36 steel specifications long after most of the rest of the world had updated to better 44 ksi material specification for general structural steel.
And the change of steel production to 'recycling of steel', with the potential for different material compositions than steel made from pig-iron, happened long before the tragedy that exposed that the A36 standard written for pig-iron production of steel was dangerously out-dated compared to other long-established structural steel production specifications.
Hank @22,
In my comment @25 I should have included that when Canada had a Conservative Party as Leaders it also acted "...in a protectionist manner with actions resisting the corrections required to limit the future climate change consequences". And Canada's Provincial leadership, like USA State leadership, also is heavily skewed to Right-Wing Conservative leadership acting in protectionist ways to resist the corrections required to limit climate change impacts on future generations (and resisting other corrections required to achieve the Sustainable Development Goals).
And a similar observation can be made of what is happening in Australia.
The correlation of New Right-wing Conservatives (not the same as the environment protecting and helpful to Others Conservatives of years ago), and resistance to expanded awareness and improved understanding and the application of that learning to develop sustainable improvements for the future of humanity is a tragic global phenomenon.
Hank @24, buildings in New Zealand also have to withstand something like 1000 year storms from memory. We don't get hurricanes, the worst tends to be tropical cyclones occasionally with very severe gales, so category 2 wind speeds typically. Data on regional zones and maximum limit state wind speeds here.
www.level.org.nz/site-analysis/wind/
Making housing resistant to every conceivable threat with near zero damage would probably lead to houses being built like concrete bunkers. The public would never put up with that, and neither would I.
However let's take an increase in wind pressure of 17% as you mentioned. This doesn't sound too horrendously severe. I agree much of the global warming threat comes more from flooding etc. Anyway upgrading the code for a 17% increase in pressure sounds like a bit of extra wall and roof bracing and more fixings, so not a huge increase in cost. Our public look like they would be ok with that from discussion I have seen on this sort of thing especially if it was phased in. They are quite safety conscious types in the main, except for the libertarian fringe. But they wouldn't wear big changes to the code and huge cost burdens.
Yes its reasonable to treat agricultural structures differently from fire stations. It's just commonsense. I'm 99% sure we do that. To be honest as an Architect I leave most structural stuff to the engineers, although I do know how to do basic beam calcs etcetera. The only structural stuff I do is light timber frame prescriptive code stuff, so I'm a bit hazy on some of the wind design load criteria details.
You get an insight on what the public will bear from the earthquake issue. The Christchurch earthquake was a wake up call, especially as a lot of old brick masonry buildings failed (no surprise there). As a result there were proposals to change the code so that older buildings have to be upgraded to improved earthquake resistance, although not as much as new buildings. People have generally gone along with this as a whole quite well, but there were complaints about costs so the original scheme was downgraded a bit, and owners have been given more generous time frames to upgrade. Some information below on the final proposals. Makes sense to me.
www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11446301
Hank @ 23
The 10-20% increase in wind speeds was mentioned in the paper by Hansen et al that I referenced. (And I see now that I got the year wrong. 2016, not 2015.) Hansen et al themselves referenced this to Emanuel, 1987, 2005, which I haven't read. I got the link to the Hansen piece from a net search. This:
https://www.atmos-chem-phys.net/16/3761/2016/acp-16-3761-2016.pdf
Tried-to-make-clickable-link
The "10X worse" was first mentioned here by dkeierleber @ #9, and dkeierleber attributed that to Hansen.
What Hansen really meant I don't know. I didn't find the right reference.
My real point was that "10X worse" is so vague that we can't really say anything about how reasonable it is without more details. 10X worse what? Wind speed? Wind pressure? Wind power? Number of buildings damaged? Cost of damages? Number of people injured?
I can imagine this (speculation - I don't build houses): If a collection of buildings are designed to stand for a certain wind pressure and they are exposed to a storm with a lower wind pressure then none are damaged. If they are exposed to a storm with a higher wind pressure lots are damaged. So there will be a threshold effect. As soon as a building has been damaged the amount of damage will depend on the total energy dissipated into the damaged building. That will be about proportional to the wind power X the duration of the wind. Thinking about it like that "10X worse" is not too far-fetched.
Ignorant Guy @28, J Hansen talking about 10X worse wind speeds may have been referring to 'superstorms' in earths past. Theres some paleo evidence for these huge storms. Research paper here.
nigelj @29
You link to the exact same paper as I did.
I never said that Hansen specifically mentioned "10X worse wind speeds". Did you find "10X worse wind speeds" in that text?
"Worse storms" are not necessarily storms with higher wind speeds. Storms with more precipitation are also "worse".
If we anticipate a certain worst case level for a bad storm and build our infrastructure to withstand such storms with only small damages then a storm with only slightly higher wind speeds and only slightly more precipitation could cause significantly more damage. And so it could be "10X worse".
I repeat again: My point was _not_ that Hansen ever said we would see storms with 10X wind speeds. My point was that if anyone says that we may encounter storms that are "10X worse" that claim is too vague to be immediately rejected as unreasonable.
Ignorant Guy @30, oops I didn't read your link for some reason. Sorry. No it doesn't mention 10X but "if" Hansen said 10X that article may be what he had in mind. I recall mention of these super storms pushing quite huge boulders up beaches, which suggests high wind speeds affecting the oceans.
I find it a bit hard to see how 'slightly' higher wind speeds and 'slightly' more precipitation being ten times worse. Granted the two effects combine, but 10X seems intuitively seems like its stretching things.
The problem seems to me more that that the IPCC reports might be underestimating how bad storms will get. Thats a whole other subject and space doesn't allow, but theres numerous discussions on the IPCC low balling some things. But without a correct estimate its hard to develop codes.
And for the record I believe its wise to have quite high building code standards, so not done on the cheap. But there are limits to this, because eliminating all damage would make building costs astronomical. Its a balancing act.
A better way to make the point of my comment @20 may be to state that the objective of the current day population should be for the accumulated result of everyone's actions to be an improvement that lasts into the future, making the future better for humanity. And the supposedly more advanced or more fortunate a person is the more helpful they should be required to be in order to maintain their status.
While debating how much worse the future is being made, the important thing to remember is that the discussion is all about things being Worse. Fossil fuels cannot be burned forever, so any perceived benefit from fossil fuel use has no future. The only exception is the temporary transitional use of fossil fuels to kick-start sustainable development in the few remaining regions that are still in extreme poverty.
Looking reasonably holistically at any future that is the result of GHG emissions continuing to accumulate beyond today's levels exposes that the future, on the whole, is being made Worse. How much worse the future becomes is a direct function of how high the accumulated total impacts become. And less corrections of the harm creation today makes things worse. And a continuation of the attitude that there is some way to justify making the future worse will undeniably create a much worse future, potentially worse than the worst that has been conceived so far (and that is not an extremist claim).
A serious correction is required to end the cycle of making-up excuses for continuing to act harmfully. One of the worst excuses is believing that history proves that industrial materialistic consumerism always makes things better. An even worse excuse is believing that any challenges created can be overcome by the brilliance of innovative developments.
Things could become much worse than the conditions potentially created by RCP8.5 by 2100. The future of humanity should continue well beyond 2100. And hopefully those future people will not have to deal with an even worse future after 2100.
As shocking as some of the potential futures for humanity may appear to be, they are still potential futures, especially if less correction happens today, or the next day, or the next day ....
I will admit that I may be defensive about my profession after practicing and experiencing it for 50 years but I hope I can still be objective. I think we are all on the same team of trying to prevent climate change deniers from spreading their false and damaging message. However....
One of the things I have consistently found is that climate change deniers use bits and pieces of scientific research and twist it into the opposite of what the research found. If they can convince the public that they know as much about climate change as the scientists because the data is just simple to understand, then they have accomplished their mission. One of the things I have learned in my limited research into climate change is that what can appear simple on the surface is very complicated when digging down into the details, something that deniers take advantage of every day. In my experience the same is true of all technical professions so in the end I ask and defer to the opinions of peer reviewed published material as explained by the authors. So I think that ironically the same thing is happening in this debate.
Nigelj has stated this:
“However let's take an increase in wind pressure of 17% as you mentioned. This doesn't sound too horrendously severe. I agree much of the global warming threat comes more from flooding etc. Anyway upgrading the code for a 17% increase in pressure sounds like a bit of extra wall and roof bracing and more fixings, so not a huge increase in cost.”
In effect you have decided that you know enough about the statistical analysis of wind speeds, the application of that analysis to structures, the development of risk factors the economics of risk and the risk to the public among many other things that makes you an expert in how the structural codes should be changed. Yet you have pretty much admitted you have no expertise in any of these areas. And it appears you assume that the professionals that produce these codes are either not aware of environmental changes and how they affect the design of structures or they are deliberately ignoring those changes because of political pressure or greed. Pretty much exactly what climate change deniers are saying and using against climate scientists.
From what all of you have said it seems you have some if not a fair amount of structural training. If so you should know that the design of structures are limited by the yield strength of the material for wind design in most cases. This is far from the “failure” of a structure unless you consider the “failure” of a structure to be some limited permanent deflections of the structure. This is evidenced by the success of seismic designed structures to prevent the total collapse of structures which exceed the wind forces by a large amount. In other words there is almost always a large amount of redundancy in structures due to many factors that are not considered in design. So rarely is this a matter of risk to public safety, but to economic risk.
I am by all means in favor of requiring structures to consider human safety first and economy risk second. However there is no way codes can be written to cover all possible risks. My company and some of the companies I have worked for have multiple standard products they sale. The costs of upgrading all those products by a 17% increase in wind pressure would include a massive amount of redesign (I’m not sure everyone realizes the amount of time and work that goes into designing a large structure), the replacement and/or modification of millions of dollars of tooling required for the existing structures and the amount of published marketing material that would need to be replaced. This is not just adding some bracing. Existing structures would be grandfathered in with a new code but sales of new structures have to meet the new codes. If the experts decide an increase is necessary I will be leading the cause to get it implemented. But I’m not in favor of unnecessary feel good changes that can have unintended consequences.
I am all in favor of public pressure to create changes in public policy when it is obvious the government is ignoring public safety. I think that is pretty evident with climate change when you look at heat waves, drought, floods, rising seas, the consensus of climate scientists, etc. Of course structures do fail for many reasons. But I have not seen, nor has anyone here presented any evidence of an increase in structural failures due to increased wind pressures.
Hank @33
"In effect you have decided that you know enough about the statistical analysis of wind speeds .....etc... and many other things that makes you an expert in how the structural codes should be changed. "
I never claimed that. I was simply tossing some ideas around sparking some discussion.
You are the expert, so roughly how much cost would upgrading the code to cope with an increase of 17% of wind pressure add to 1) a typical timber framed house and 2) typical highrise building?
Maybe its too high to be feasible. Like I said I believe in tough codes, but its always a balancing act between toughness and what the public can reasonably afford. I dont see where we differ - you tell me.
"And it appears you assume that the professionals that produce these codes are either not aware of environmental changes and how they affect the design of structures or they are deliberately ignoring those changes because of political pressure or greed. Pretty much exactly what climate change deniers are saying and using against climate scientists. "
Please stop putting words in my mouth. I have already said the exact opposite above "It looks like our codes are weighted a long way towards lowest cost. However I doubt that has anything to do with the engineers on the committees that develop codes....( I explained my reasons)"
The codes in NZ do appear to set lower standards than some other countries. This is not my opinion, the issues has been raised by various experts after the Canterbury earthquake. The question is why. I think its probably political in origin but I doubt it reflects badly on engineers.
Politicians or bureaucrats sometimes have the last say on approving building codes. This is not the venue to pontificate in detail on all this, other than to say this is a very different thing to denialists claiming politicians write or approve climate science (which they dont). You are comparing apples and oranges.
However bureaucrats do sign off the IPCC report summary for policy makers, so that is something to bear in mind. Evidence suggests the language in this report got watered down a bit in one of the reports. Very likely became likely etcetera.
You are taking things personally as an attack on structural engineers. Nothing could be further from the truth. I have lots of respect for engineers. You have taken things completely the wrong way.
The discussions of how buildings are designed are interesting.
Flood damage is expected to be worse in the future because AGW causes harder rainfall. It has been recently reported that most nuclear power plants are not designed to withstand the most severe anticipated floods. While there are not many nuclear power plants it occured to me that much infrastructure like drinking water plants, sewage plants, airports, chemcal facilities and other heavy industry are located near rivers or the ocean (where sea level rise is also a problem). There were reports of many facilities being flooded by Harvey in Texas.
I am not an engineer but it occured to me that if nuclear plants are not designed to withstand expected flooding many other industrial facilities will also not be designed to withstand high floods.
Do the engineers here have any comments on how major infrastructure will be affected by increased flooding?
Nigelj @ 34
I am educated in the science of structural design. I am no expert in determining what loading should be applied to a structure in order to balance risk to economy. As you said structures are designed on the basis of a 50 year life. Although some are used longer we have to put some limit on a design time. The study I link too stated a 1 to 10% increase in intensity for a 2C warming with the probability that the strongest storms will be less frequent. That will probably be 2100 if we don’t change our direction which is 80 years from now, long past the design life of a structure. Taking the largest estimate way past the life of a structure with a decreased probability of frequency for structures we know the failure limit is way past the design limit just seems to need further study, which I’m not qualified to do. You can say you are just tossing around ideas but I can promise you ideas like this tend to be spread around the internet by those saying engineers are derelict for not preparing for the future by their disregard for climate change. Just like the opposite side says climate scientists are irresponsible for being alarmists.
I wasn’t putting words in your mouth. I was using my words to say it ‘appears’ you are saying the professionals aren’t doing their job.
“It looks like our codes are weighted a long way towards lowest cost. However I doubt that has anything to do with the engineers on the committees that develop codes”. What? How can the codes be weighted towards lowest cost without the engineers who write the codes being responsible? As I have said before I can only speak for the US codes. But in the US the politicians and bureaucrats have zero input in the development and revisions to the structural design codes. In the US the government has legislated the material design codes to be the law which they didn’t have to do. Although I doubt any engineer would design any differently even if they weren’t the law. But there have been so many lawsuits regarding damages when a structure fails I would imagine the politicians are afraid not to legislate those laws. In addition no insurance company would insure a structure not certified by a Professional Engineer.
If I have taking things the wrong way then I apologize. But it still seems to me that it would be better if the experts are not second guessed in social media at least until there is evidence they are not doing their job. And saying our building codes are weighted towards lowest cost without evidence is doing exactly that. It’s certainly your right to do that, at least in America, but that’s what is being done to climate scientists and I’m opposed to that also.
Michael @ 35
Michael that is a very good observation. Engineers are definitely concerned about how flooding is affecting structures. The three most recent code revisions have increased the attention and detail in every revision regarding how to design for flooding in the US. This is a case where the increased flooding has been documented by research. And as flooding is becoming more intense engineers who write the codes have more detailed loading requirements. Also insurance companies are becoming more involved in specific requirements for design as they often employ engineers or consult with engineers on the subject.
michael sweet @35,
The 'flood concern' is a valid one. And it allows a clarification to be made regarding structural performance.
In addition to structure design which need to account for rain ponding on roofs, I have designed surface run-off systems. These systems get designed for events that are based on historical weather data for a region. And there is a level of safety against that design failing to perform so that the design will withstand events that exceed the maximum expected design condition. What that means is that if climate change increases the severity of rain events there is an increased likelihood of the system failing to perform adequately. The system becomes less safe than the desired safety level of the design.
Updated design requirements will result in 'new designs' meeting desired safety standards. But anything designed base on the previous requirements will become 'less safe'. There is no way of arguing around that. It is the reality. Existing surface run-off systems all become less safe if the weather conditions they may experience become more severe.
The same applies to structure performance. The design codes establish a minimum factor of safety against performance failure. The factor of safety is a combination of increasing the expected forces on the structure (factors greater than 1.0 are applied to that loads) combined with reducing the structure resistance values (factors less than 1.0 are applied to material resistance properties). Updated design requirements establishing higher design loads will result in new designs having the desired safety. But structures designed to the previous requirements will be less safe, they will have an increased chance of a failure of performance.
And as I have stated in other comments, there is no real value in discussing exactly how much less safe things are going to become. Many structures are still standing many years beyond a '50 year design basis'. The fact that human caused climate change is making almost all existing structures and surface run-off systems 'less safe' should be sufficient to motivate responsible leaders of society to rapidly correct the incorrect activities that are making things 'less safe'.
Hank @36,
"The study I link too stated a 1 to 10% increase in intensity for a 2C warming with the probability that the strongest storms will be less frequent."
Ok that changes the complexion a bit. My understanding is research is suggesting a higher frequency of the strongest storms. For example its interesting that numbers of category 5 hurricanes seem to have increased as below. Some people are suggesting we need category 6 hurricanes. And this is why I was concerned about the whole wind speed thing.
www.wunderground.com/education/webster.asp
Anyway I agree it all needs further investigation, and that current code standards in America look good, and theres no point in a panic over design reaction.
“It looks like our codes are weighted a long way towards lowest cost. However I doubt that has anything to do with the engineers on the committees that develop codes”. What? How can the codes be weighted towards lowest cost without the engineers who write the codes being responsible? "
My understanding is our structural building codes in New Zealand are designed to some extent by a committee process that includes not just structural engineers, but builders, representitives from building research organisations etc and the code has to be approved by politicians at the end of the day. It just sounds quite different from your system. Engineers do the detail work, but it appears other parties have some input. We are also not as litigous as you guys. Not saying our system is better than yours, the opposite could well be true. Anyway you can see there are several input factors that could be aiming for minimising costs and standards rather than the engineers.
"If I have taking things the wrong way then I apologize. "
Apology accepted.
"And saying our building codes are weighted towards lowest cost without evidence is doing exactly that. "
I was talking about New Zealand! I thought that was reasonably clear. Sorry for any confusion.
Nigelj @ 39
Nigelj I have seen you post at different climate blogs and agree with you almost 100% of the time. I do not think you would intentionally disparage engineers. However I do think in this case you un-intentionally created an impression that engineers have been derelict in their duty to protect the public by not addressing climate change. It appears some of the differences in our understandings is due to living in different countries with apparently different systems of producing design codes. It may also due to my frustration in trying to defend scientists against climate change deniers who continuously accuse climate scientists of fraud and deception. Regardless this is the last I will comment on this subject.
BTW I have seen you post on realclimate (I assume you are the same person). I sometimes post there under the name of TPaine.
OPOF @38
“The same applies to structure performance. The design codes establish a minimum factor of safety against performance failure. The factor of safety is a combination of increasing the expected forces on the structure (factors greater than 1.0 are applied to that loads) combined with reducing the structure resistance values (factors less than 1.0 are applied to material resistance properties).”
In the US the factors of safety you mentioned (we call them load factors) have been reduced to 1.0 for wind. The wind speed maps were then increased to compensate for the load factor reduction. This now produces a procedure where the design wind speed is the actual wind speed the structure is designed for without yielding instead of a lower wind speed with a safety factor. I like this change as it seem more transparent to our customers. In other word what you are told is what you get.
Hank @40, yes I might have unintentionally done that. For the record I don't see any evidence engineers have been derelict in their duty protecting the public from climate change, and other threats. Theres something a bit weird going on where I live, but I suspect it reflects entirely on other parties not engineers. I have worked with dozens of engineers, enough to get a general view and ok its anecdotal, but In New Zealand they push for high standards and treat the codes with respect. I wont bring up the issue again either.
That said we have to be able to "talk about stuff" even if its contentious, and not get too defensive. It just needs us all to be clear on exactly what we mean and have the evidence.
Yes I comment on RC and I recognise your name.
Hank @41,
That change of the way the US code works that you mention will result in the same reduction of safety as the climate conditions get worse that I have mentioned.
The reality remains, everything already built is less safe as the climate conditions become more severe. Even things designed to the updated requirements will become less safe as the climate conditions become more severe. Admittedly, there is potentially an over-statement of the design requirements that will make new designs even safer under current conditions. But how significant the over-statement is and how much climate change impact continues to be created will determine if and when the over-statement is no longer an over-statement, after which time the design level of safety becomes less than the desired minimum as climate changes continue to be increased.
Does the code identify how much it is over-stating the design requirement and indicate the related amount of global warming that the over-statement is expected to be valid for? Is it good for 1.5C, 2.0C, 3.0C warming? And if it claims to be good for anything beyond 1.5C warming I would really be interested to see the basis for being so certain about that. Everything I have seen appears to indicate that significant uncertainties exist if there is more than 1.5C warming.
OPOF @ 43
OPOF I obviously didn’t explain how the wind charts are made very well. I’ll try again. In the 2005 version of the code the wind charts were made from 25 year, 50 year, and 100 year storms for the different risk categories. A 50 year storm has a 2% (1/50) probability of occurring at a location every year. The probability of a 50 year storm occurring over the 50 year design life of a building is 67%. This is of course way too large a risk. So the code applied a 1.6 load factor to the calculated wind pressure which in effect changes the 50 year storm to a 700 year storm. The risk of a 700 year storm occurring at a location over the 50 year life of the building is about 3% (That’s about right but I haven’t looked at the numbers in a while). That is what the code considers acceptable for a category II risk.
Now the 2010 version of the code (and later versions) change the wind maps to show the wind speed of a 700 year storm and eliminated the load factor (or changed it to 1.0). Of course the wind speeds increased but that way everyone can see exactly what wind speed we are designing too, not the wind speed that is increased by a load factor for design.
The speed that is calculated for a 700 year storm for a specific location is based on past data. Every time a revision is issued the wind speed will probably be slightly different because there are 5 more years of data to include in the calculations. The study I linked estimated maximum global wind speeds between 1% and 10%. But that is global, not local. The maximum local wind speed for a specific location might be larger or smaller or the same as in the past. It’s the difference between climate and weather. In addition the maximum wind speed at a specific location will not be the wind speed of a 700 year storm, except by chance, since the wind speed of a 700 year storm is a statistical value base on probability of that storm occurring in any year. So those values are not based on trying to predict maximum future wind speeds, since as you said it is very uncertain, but on trying to establish risk.
As to the reduction of safety for a structure, it will depend on the location of the structure. If it is located where the 700 year storm wind speed is increasing there will be some increase in the risk. If it is located where the 700 year storm wind speed is decreasing there will be a decrease in the risk. It’s like insurance companies know how long the life expectancy is for each age group but they don’t know how long an individual will live. And that life expectancy for each age changes with time, depending on general health habits and other factors of the group.
Hope that helps
Hank @44,
I have worked with many international design codes and am well aware of the basis for wind design and other climate condition design requirements.
I understood what you presented. That is why I replied.
Climate change will result in many regional climate conditions that are more severe than historical records. As a result of the increases of extreme events every item design based on the less extreme history will become less safe than intended. Reread all of my comments with that new awareness and uunderstanding.
OPOF @ 45,
“I have worked with many international design codes and am well aware of the basis for wind design and other climate condition design requirements.
I understood what you presented. That is why I replied.”
Your questions about whether the code claims to be anything beyond 1.5C and your interest in seeing the basis for being certain made me think you did not understand how the code determines design wind speeds. That was the reason for my explanation.
“Climate change will result in many regional climate conditions that are more severe than historical records. As a result of the increases of extreme events every item design based on the less extreme history will become less safe than intended. Reread all of my comments with that new awareness and uunderstanding.”
That is pretty much what I stated when I said some structures will be at more risk and some will be at less risk depending on the location. The only difference which is somewhat technical is the engineers I know consider a structure to be either safe or unsafe for a specific loading. If a loading shows the structure to be higher than the point of failure (not the design wind but similar to seismic loading), then the structure is considered unsafe. But it’s not considered less safe because it is at a risk of being loaded with a higher wind speed loading.
Hank,
Engineers I know share the understanding that any structure that does not meet code minimum design requirements is an unsafe structure based on the new code requirements.
The fact that increased levels of minimum requirements in a code update are not required to be applied to already built items, because of the cost, does not change the reality that the structure just meeting the older lower design standard is unacceptable based on the updated code. And in Canada any modification of an existing structure must include all modifications required to meet the current code requirements. And if the updated code requirements become significant enough then older buildings will be declared unable to continue to be used without upgrades.
So as I have tried to consistently say, increased risk of failure is the reality being created by rapid climate change. And any attempt to establish a design requirement in anticipation of rapid climate change faces the challenge of establishing certainty regarding how severe the future design requirements will become.