Krylov Center will bring the Crimean Bridge to Yekaterinburg

In December 2018, the 100+ Forum Russia will host a thematic session dedicated to the construction of the Crimean Bridge across the Kerch Strait. We have prepared an interview with Sergey Solovyov, Deputy head of the Department of Hydroaerodynamics at the Krylov State Scientific Center. The head of scientific support for the construction of the Crimean Bridge tells how full-scale tests of the arches of the Crimean Bridge were carried out in the wind tunnel, the aerodynamic stability of the arches, as well as other cable-stayed bridges, were studied, wind and snow loads on stadiums, airports, high-rise buildings and other unique structures were studied.

What was the difficulty of transporting the arches of the Crimean Bridge? How did your research center participate in this operation?

- The arches of the Crimean Bridge were assembled on the shore, then they were loaded onto pontoons and towed to the installation site on supports. The main difficulties, firstly, are that the arches are massive and overall, each weighing about 6,000 tons and 229 meters long. Secondly, the shallow depths of the Kerch Strait are commensurate with the draft of the pontoons, so transportation took place through a channel only 120 meters wide. Thirdly, there is a strong wind in the strait, current and waves, which can carry the transported structure beyond the boundaries of the channel aground.

To date, such operations for the sea transportation of bridge structures have never been carried out. Considering all these difficulties, the designers of the Crimean Bridge turned to us at the Krylov Center for experimental mathematical modeling, as we have experience in carrying out similar work for the transportation of drilling platforms.

In this work, we had two main goals: to determine the maximum values of wind, current and waves, as well as their combinations, under which safe towing of arches is possible. Determine the schemes of construction and composition of the tow warrant.

At the first stage, we experimentally determined the exact values of the wind effect on the surface part of the transport system consisting of tugs, pontoons and the arch itself, as well as the hydrodynamic loads on the underwater part. The wind load was determined in a Landscape wind tunnel for all possible wind directions, while the effects of the atmospheric boundary layer were taken into account, and hydrodynamic forces were determined in the experimental pool.

At the second stage, a mathematical model of the movement of the transport system for the training complex was developed. As initial data, experimental data obtained in a Landscape wind tunnel, an experimental pool, as well as initial data on wind, current, and waves characteristic of the Kerch Strait were loaded into the developed model.

After that, various options for a tow warrant were checked at the training complex. Based on the simulation results, the weather restrictions under which safe transportation is possible were determined. We have checked three possible options for a tow warrant, and for each of them there are 12 cases of the most unfavorable combinations of weather conditions. As a result of the work, an important result was obtained: the operation cannot be performed at a wind speed of more than 10 m/s, otherwise there is a risk of an emergency. The composition and construction scheme of the tow warrant, which is capable of carrying out a transport operation, was also worked out.

Determination of wind loads on the transport system

Are there any analogues of the Krylov State Scientific Center in Russia or abroad?

- Not in Russia, there are research centers abroad similar to ours, but with much narrower specialization and experimental capabilities. The Krylov Center was founded in 1894, and employs about 3,200 people, of whom more than 350 have academic degrees. Thanks to our professional team and the presence of a unique experimental base, the scientific center is considered a world leader in shipbuilding science. We have 97 unique experimental stands, half of them have no analogues in the world.

Tell us about the Landscape Wind Tunnel. What projects have it been used for testing, and will you present them at the 100+ Forum Russia as examples for your reports?

- The Krylov Center has a complex of seven wind tunnels, and the "newest" of them is a Landscape Wind Tunnel. It is a specialized installation for determining wind and snow loads on unique structures. There are only five such installations in the world, and it is the only one in Russia.

There are many aircraft-type wind tunnels in Russia, they have a short open working part and therefore are not suitable for testing architectural objects. The landscape wind tunnel has a working length of 18 meters, so we can simulate the boundary layer of the atmosphere. The width of the working part is 11 meters, and this allows for research of unique dimensional structures on large models, on a scale of 1:50 or 1:100. The climate control system maintains the set temperature of the air flow in the working part of the wind tunnel. The turning circle, on which the model of the object under study and the surrounding landscape is installed, allows you to simulate all possible wind directions. There is a coordinate device for moving measuring probes and measuring wind speed in pedestrian areas of residential areas.

The installation scheme is a landscape wind tunnel. Longitudinal section

After putting the Landscape Wind Tunnel into operation, Russian designers no longer apply abroad, but conduct aerodynamic research here. Over the past two years, we have conducted research on 23 unique objects in the air tube, including high-rise buildings, large-span bridges, stadiums, airports, and shopping malls. I will make reports on some of them at the forum.

Our customers are mostly domestic designers, but we also receive requests from foreigners. In 2017, we completed work for customers from Europe, China, and Japan, and at the moment we are working with a design bureau from Italy. I will tell you about the project of a large-span cable-stayed bridge and its aerodynamics for a customer from Europe in a separate report at a forum in Yekaterinburg for the first time.

Text: Victoria Pivovarova