Riding the Wave of the Future

Let's say someone wanted to put a building somewhere in a body of water. They have a few options. One, wait a million years and hope a volcano forms a new island. Two, drain all the water. Three, fill the body of water with something solid. Or four, use a Very Large Floating Structure.

Problem with Option One: Millions of years is a very long time to wait.
Problem with Option Two: If the body of water is the Pacific Ocean, it will be hard to drain.
Problem with Option Three: See Problem with Option Two.
Problem with Option Four: Nothing as bad as the other three.

So what exactly is a VLFS?

Photo: US Navy Mobile Offshore Base Website

According to UH civil engineering professor Dr. Ronald Riggs, "A VLFS refers to a structure that is typically so large that it cannot be considered a rigid body, like a ship or an offshore oil platform. If you think of a large airport or a floating mobile offshore base, the structure becomes too big to be considered rationally a rigid body and so you have to take into account the structural dynamics, elasticity, and the flexibility of the body."

VLFS can be placed into different categories. "You can separate VLFS in terms of types of hull. One would be a barge-type of hull, which would be like a floating box. Another would be a semi-submersible type of hull, where you have a submerged pontoon supporting columns," Dr. Riggs said. "You can also classify them on whether they are mobile or not mobile. A mobile offshore base (MOB) would likely look quite different than a floating civilian airport, which was meant to stay at one location and probably not feasible to move around."

Dr. Riggs combined his research efforts with UH Ocean and Resources Engineering professor Dr. Cengiz Ertekin, to provide information that will help further the development of VLFS. Dr. Riggs handled mostly the research dealing with the structural engineering of VLFS, while Dr. Ertekin focused on the hydrodynamic effects. These two also co-organized the First International Workshop on Very Large Floating Structures in 1991.

Discussions about VLFS-type of structures have been around for decades. There were plans to build refueling stations for commercial aircraft. However, these proved to be unnecessary as the technology in aircraft allowed for long-range flight. Today, there are many planned uses for VLFS, but there are two in particular that stand out.

One major proposal for the VLFS was a floating civilian airport, which has been looked at for many years. In the last few years, Japan was looking at the option of creating a floating airport. There is talk about projects at Kansai International Airport in Osaka Bay and in Tokyo Bay because of the problems with Haneda and Narita airports being overcrowded. "Because of Japan's population density and the fact that the country is crowded around the coastal region and the cost of land in Japan, I think a civilian floating airport in Japan would be the most likely place for one to be built," Dr. Riggs said.

Another major idea for VLFS, which was looked at in depth over the last several years was a mobile offshore base (MOB). "The United States was interested in the idea of having a large mobile floating base that could be relocated anywhere in the world. It could be placed in international waters, where it wouldn't be subjected to other country's national laws, regulations, and restrictions," Dr. Riggs said.

Photo: US Navy Mobile Offshore Base Website

Other proposed uses for VLFS include a mining operation on a large floating platform and other processing type of applications like waste processing. Another application that has been talked about is the creation of a floating port for really large tankers and cargo ships that are too large for a land port. The ships would dock to the floating offshore port, unload their cargo onto smaller vessels, and then these smaller vessels would take the cargo in from there.

However, the most interesting application for VLFS has been the Freedom Ship. It will be a 4,500-foot long (almost a mile long), 750-foot wide, and 350-foot tall vessel that will sail continuously around the world. According the Freedom Ship's website, it will contain residential space, a library, schools, a hospital, an extensive shopping mall, banks, hotels, restaurants, casinos, and a small plane airport on the top deck.

Dr. Riggs and Dr. Ertekin's research led them to solving fluid and structural dynamics problems that these very long structures would face. Their research for the U.S. Navy helped gain a better understanding of how multi-module structures would respond and behave in waves, which in turn will help engineers design a more intelligent structure.

The duo also developed a computer program, which made the evaluation of alternative conceptual designs easier. "That program was developed and handed over to the Navy and they've been recently using it for a floating causeway, which is basically a very long pier," Dr. Riggs said. "They wanted a floating causeway in locations where there weren't any other approaches to get materials from ship to shore. We got good feedback for that particular product."

So are VLFS the wave of the future? Just like the waves in the ocean, Dr. Riggs admits the interest in VLFS has its ups and downs. However, as the population increases and land becomes more expensive and scarce, VLFS could someday be the best option.





 

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