A new foundation system has taken root in a tower project in Virginia Beach. The system, created by Austrian Spinnanker, mimics the roots of the trees to create a stable base with relatively low impact compared to conventional concrete foundations. The Spinnanker system is being installed for the first time in the United States in the Nautilus observation tower in the landing project of Cala Owl.
The foundation’s work began in January and the tower is scheduled to open in time for the Day Memorial weekend.
The Tower Observation project was conceived by Outdoor Venture Group, an adventure park owner, operator and builder with features such as string courses, climbing areas and trees platforms. The company, which owns and operates the adventure park in Virginia Aquarium, had long planned to create a new attraction in an adjacent place of 38 hectares. Initially, it was considered to build a tower that could be used for Ziplines, but then decided to go in a different direction, says Bahman Azarm, founder and CEO.
“People like the idea of the Salt towers [for ziplines]But many people are too scared, “he says.” I made some visits throughout Europe to determine what kind of product would work well and found that in Europe they began to build what they call the observation towers about a decade ago. People went essentially to these outside centers where these towers had incredible views. It was an experience that anyone could enjoy. “
Located in a strongly wooded place on the edge of Virginia Beach’s Owl Cala, the natural place presented important challenges. The team needed an ecologically responsible solution that caused a minimum disruption to an environment -sensitive area. In addition, access to the site was restricted to a single pedestrian bridge with a capacity of 1 tonnes, so heavy equipment and large pieces of materials could not be used. The team soon determined that traditional specific foundations would not be a viable option, which led the team to consider the Spinnanker system, according to Azarm.
A Spinnanker crew tested the site, climbing steel reeds to a circular base, similar to those used at the base of the lookout tower.
Photo courtesy Group Venture Outdoor Venture
Rooted with rods
The basis of the foundation system uses a circular steel base plate with 12 threaded holes. Double dual galvanization steel rods: up to 12 meters long with a diameter of ¾ in. The threaded holes of each base are designed in various angles, so that when the rods are loaded on the floor, they extend into a cross pattern like the roots of a tree.
Peter Okonek, CEO of Spinnanker, says the system can be used in a wide variety of soil conditions. The rods have some flexibility, so that if found with rocks during the installation, they can change the direction, as would be a tree root.
“From our calculations, with each slight bend in the wand, we increase the load capacity,” he says.
He says that the rods can also pierce the smoother types of rock and, under certain conditions, could act as a rock nail.
“With each light flexion on the wand, we increase the load capacity.”
– Peter Okonek, CEO, Spinnanker
The Spinnanker System has been used in Europe for more than a decade, mainly for applications such as type cables in utility towers. However, Okonek says the company has recently expanded its abilities to include larger structures. For the Nautilus lookout tower, the foundations should withstand an 115 -foot steel structure 80 feet wide. The design of the tower has a spiral road of 7 feet wide, built with an open steel roof, which rises to the tower in a circular pattern to a slope of up to 5 degrees. The tower also includes steel stairs and railings.
The Spinnanker anchoring system was designed with the ability to withstand 150 tons of strength in 12 anchor points. At each anchor point, the team used a series of prefabricated concrete modules that each had four spinnanker anchors. As a modular solution, the crews install as many sections of concrete as needed at each anchor point. For the Nautilus tower, three modules were used at each inside and two in the outer points.
Soil tests and analysis showed that each cane should be driving about 25 feet deep to meet the capacity requirements. Since the site is in a mile in the Atlantic Ocean, the structure also had to be able to withstand hurricane strength winds of up to 170 miles per hour. Prior to the construction, Spinnanker sent a team to install an anchor and take a shot.
Okonek says Spinnanker also designs its anchors to consider soil erosion or other problems over time. “We can always lose up to 10% of the bar (capacity) installed and fulfill security,” he says. “If we have twelve reeds of 6 meters, this is 72 meters of rod installed. Thus, we can lose seven meters in total and yet the anchor provides you the same results.”
Although the system has never been used in the United States, its career in Europe impressed Danny Speight, President of Speight, Marshall and Francis in Virginia Beach, who served as a structural engineer. He says that the concept makes sense in situations where traditional concrete steps cannot be placed.
“When you think about it, they act as prefabricated foots that are tied,” says Speight. “It’s very outside the thought box, but that’s what you needed for this project.”
A spiral route 7 feet wide leads to an open roof, raising visitors to the view of a bird over the natural environment.
Image Courtesy Group Venture Outdoor
Fast installation
To install each anchor point, the soil was excavated higher than several inches deep at each point, and then filled with gravel. The modules were then placed using a skid, leveled and tied. A United States crew formed by the system installed the rods by means of highly modified hand -powered hand drills. A total of about 1,900 reeds were installed for a period of two weeks in January.
Okonek states that one of the main advantages of the system is that it is the “immediately” load. “We have a lot of construction [projects] Where we do the foundations in the morning and in the afternoon, [a construction crew] Return with a crane to set up [structure] on top. “”
“It’s very outside the thought box, but that’s what you needed for this project.”
—Danny Speight, Speight, Marshall and Francis
Although the Spinnanker system helped meet many of the challenges of the project, access to the site remained a problem throughout the project. Given the limited capacity of 1 tons of the pedestrian bridge, which was the only access to the site, all materials had to be limited. The whole tower and the foundation system had to be prefabricated without cutting in place. The structural elements were limited to 12 feet in length and were linked as needed. The area of the project’s disposition was in a parking lot at almost half a mile away.
“It took a week just to solve -everything,” says Azarm, “like all the nuts and screws and pipes and where they go and where everything is adapted, etc.”
He says, at first, the team thought he should use a skid to transport all materials. Ultimately, the team was able to use carts to remove most of the materials in the site.
Once the foundations were in place and materials were ordered, up to eight people were able to build the tower in four weeks. With the complete structure, the team is putting the touches on the tower and the league in the existing adventure park. When opening the weekend of the Day Memorial, visitors will have the option of walking from the tower through rope bridges that pass through the trees marquee and will connect to other parts of the park.
The technology of the pre -deployed Foundation is modular, so that several elements can be joined to create anchor points.
Image Courtesy Group Venture Outdoor
Future Applications
Azarm says he was impressed with the speed and simplicity of the Spinnanker system. “It was so easy for these people to design it for us, which was a surprise to me,” he says. “Now that this structure is over, it really is trusted in what types of structures are possible.”
Okonek says the company is about to release a more robust system that uses a higher -pair capable machine that can pierce bars up to 1½ inches in diameter, twice the diameter of the current bars. He claims that the most robust system would be able to manage significantly higher loads and open opportunities.
“For example, we receive dozens of temporary bridge applications after a disaster,” he says. “With this new device, we can create much larger foundations.”
Okonek says about 25% of Spinnanker’s business are temporary structures. In addition to quickly installing the system without the need to cure concrete foundations, the system can also be eliminated with a minimum impact, according to him.
“The rods are drilled simply and there is nothing left,” he says.
For now, Okonek is cautiously optimistic that Spinnanker could be widely accepted in the United States, acknowledging that it could take time for customers to pilot the system and demonstrate their concept in the national market. “The nautilus tower is very important to us,” he says.
