The collapse of the 12-story condominium on an oceanfront in Miami Beach, Fla. last week has raised concerns among structural engineers.Experts say such unplanned collapses are very rare in modern structural design history. Engineers and planners want to know what caused the June 24th collapse of Champlain Towers South, Surfside, Fla. 16 people have been confirmed dead and over 140 are still missing. There is no immediate explanation for this disaster. Experts speculate about structural damage, corrosion of reinforced concrete buildings foundations or stabilizing bars.Structural engineers design buildings that can withstand forces and hazards like gravity and weather. Engineers regularly update their design methods, often as a result of technological advancements or lessons learned from past failures. Nearly all of the U.S. building stock isn't new. Champlain Towers South was built in 1981. These buildings could face loads and other dangers that the designers didn't anticipate, such as those related to climate change.Before rescue operations are concluded and possibly multiple investigations into the cause of the Surfside collapse, policy makers, structural engineers and leaders may need to wait to gain useful insights into building codes and designs to avoid similar disasters in the future.Scientific American spoke to Benjamin W. Schafer (structural engineer, professor, and director, Ralph S. OConnor Sustainable Energy Institute, Johns Hopkins University) to learn more about the long-term impact of the Champlain Towers South tragedy on building designers.[An edited transcript follows.]What are the reactions of structural engineers to the collapse at Champlain Towers South in Champlain Towers?Buildings don't fail often. The field is very conscious of the need to learn from failures that do occur, especially if there isn't an obvious, large-scale, or external precipitating event we didnt account. The field was challenged by collapses that occurred in the late 1970s or early 1980s. These included the Kemper Arena roof and walkway collapses at Hyatt Regency Hotels in Kansas City. This led to changes in construction methods and computerized structural analysis. We have a long history of investigating the causes of earthquakes and changing our field to respond. The most concerning thing about the latest Florida disaster is that our early theories about what happened don't give us much information about what to do differently. This is a corrosion issue. The number of buildings with corrosion problems in the U.S. would be very low if this was the case. If it is a foundation problem, we may be able to determine the cause and then proceed from there. Many uncertainties were not considered when Champlain Towers South was designed in 1981.Are the potential corrosion of columns, rebar and reinforced concrete likely to need to be carefully examined?100 percent. This is an older concrete structure with salt exposure and flooding. A building will eventually fall if there is too much corrosion. You may still be wondering, "Why now?" Why now? Corrosion can be slow and long-lasting. There will come a time when it is too much. One wonders if there is another factor that can trigger this?What will be the impact of rescue, recovery and any other follow-up activities at this location?If it weren't for the human tragedy, this level of debris would pose a serious problem that will last several months. This is a complex project, even if you don't try to understand the failure.The U.S. building stock is aging, so could we expect a rise in the severity and number of events such as the Surfside building falling?Our infrastructure is vital and must be protected. Experts have known this for over 40 years. After a massive fracture in a beam caused by a beam, a major bridge linking Memphis, Tenn. and Arkansas, Interstate 40, had to be closed last month. These types of incidents will continue to occur more often. These examples won't be all caused by us neglecting our infrastructure. But many will. Climate change is not helping. We have a lot of infrastructure already in place, and it is important that we continue to invest in this development.We were also in unfamiliar territory in that we saw demands on buildings we didn't anticipate. It could be a climate-change-induced flood demand where flooding occurs once a year, when we wouldn't have expected it. Or more frequent, higher-speed windstorms. The environment in which buildings live is the environment in which they are designed. They are designed for this environment.What are you going do when you have an area with low snow loads and suddenly you get a storm in the South? Although rare snow events are rare, we still design roofs using historical records. We are more vulnerable to hurricanes. Heat waves are longer. As structural engineers, it is a challenge to keep up with these changing demands.Gravity is gravity at the end of it all. Understanding the fundamental forces that drive a building is possible with greater precision these days. We can also track what happens when a building fails much better than in previous decades. However, we must be able to estimate the needs.What past events and failures led to the design of modern buildings being altered?Many of them were caused by earthquakes. California's 1994 Northridge earthquake changed the way we think about building in earthquake-prone regions. Four people were killed when a gas stove explosion in a residential building named Ronan Point in 1968, [England] destroyed 22 stories of the building. This event was the start of increased concern about building collapses. The Grenfell Tower fire spread from London's facade to the entire building in 2017. This is having an enormous impact on the design of facades. Because we don't yet fully understand the problem, there is a lot of interest in Surfside, Fla.'s particular failure.How is it possible to investigate a large building fall such as this?Investigators will collect all calculations and drawings from the original design. The investigators will then be able to compare the drawings and calculations with the records of the final construction. They will then assess the condition of the building at the moment of collapse. This might include taking samples from the debris of the building and testing the precollapse strength and durability of concrete and rebar. There has been much speculation regarding the condition of the Champlain Towers South columns. Investigators will do their best to determine the initial state as well as any corrosion or degradation. The building will be subject to modern computer simulations by investigators. This will allow them to determine how it can withstand the demands made against it according the codes that were in place at the time. They will also compare the performance of the building to current codes. This will give them an idea of whether or not the building was designed in a way that would make it vulnerable to failure. They will then create scenarios using all the information to find plausible scenarios that are consistent with the failure. They will test, simulate and analyze these scenarios to determine if they are possible.Is there a future for cities like the one depicted by Kim Stanley Robinson's New York 2140? The science fiction novel depicts a Manhattan post-climate disaster. Residents live in skyscrapers with waterproofed foundations, and commute by watercraft on a continuously flooded street grid.He suggests that we could keep all of our infrastructure intact and magically protect its bottom with current technologies to repair concrete that is suddenly exposed to salt water. This is probably impossible. Most of our infrastructure is underground. Unusable underground infrastructure can lead to underwater infrastructure. A building without power, water, and sewer service is not safe for people to live in.Today's structural engineers will see a lot of adaptations to buildings and infrastructure. Some areas of high wealth will be affected by flooding and then they can move because they have the capital. How will we deal with the inequality of mass movement from our population centres, which already have large inequalities?
