Knickei: Sports Egg for Halstenbek
In the 1990s, a small town in Germany decided to build something very special. They wanted a new sports hall, but not an ordinary three-field hall like every other town has. They wanted something spectacular, a building that would make headlines and be remembered. The famous Knickei from Halstenbek undoubtedly achieved this goal, although not as intended. But more about that later.
The hall, with a dome made of glass and steel, was supposed to be mostly underground. Only the glass steel dome in the shape of an egg lying on its side was to be visible from the outside. A truly interesting construction project, especially for a small town. And yet, Halstenbek's Knickei belongs in our “Failed Construction Projects” section. Why? You'll find out in a moment. First, let's dive into the history of the Knickei.
Knickei: Design of Very Special Sports Hall
Let's start our story of a building right at the beginning. In 1992, the decision was made to build a new sports hall on the former site of a tree nursery. The whole thing was to cost about 5 million marks.
The city council held an urban planning ideas competition to find bold, courageous architectural companies to take on this task. The winner of the competition was a self-supporting steel structure designed by André Poitiers and his architectural company, Poitiers & Partner, based in Rellingen, Germany. The goal was to give the center of Halstenbek a whole new look.
Thus, the idea was to come up with a familiar shape—an egg—in a futuristic design. The city turned to a renowned engineering office from Stuttgart with high hopes of being able to implement this design. Everything would be fine.
Although a very pro-green political party proposed a conventional sports hall as an alternative, the city decided to stick with the sports egg. It made this decision even if the costs were to more than double, as the political party feared. By 1994, the time had come, and the much-anticipated development plan No. 51 was finally approved. This meant it was time to get started with the Knickei project.
Start of Construction of Knickei: One Big, Expensive Egg
The skeptics were right, and the construction costs rose to 9.7 million marks as early as 1995, when work began on the Knickei. But that wasn't all. The architects' and engineers' fees and various furnishings totaled another 2.6 million marks, which really pushed up the cost.
The city had to pay a total cost of 12.3 million marks for the building. But that wasn't the end of it. A revised cost calculation in 1996 bumped up the construction costs to a total of 15.6 million marks, which was more than three times the originally planned budget for the sports hall.
First Crack in Knickei: Self-Supporting Structure
The self-supporting steel dome in the Knickei soon caused problems. Problems so serious that they gave the Knickei von Halstenbek its name (dented egg). But what exactly is a dented egg? In short, it's a slightly damaged egg, like one with a small dent in the shell.
Normally, a cracked egg can't be sold, but it can be processed industrially. But how can we draw a parallel to a building here? Let's find out now.
This was the first problem with the Knickei…
A few problems arose pretty early in the construction phase. On the cold night of February 5, 1997, the first construction disaster occurred. The steel mesh dome of the half-finished sports hall partially collapsed. What happened?
The night before, the scaffolding struts supporting a part of the metal dome had been removed. The metal struts of the 45-ton (49.6-US ton) structure smashed through the timber working platform when it collapsed, causing several million marks' worth of damage to the Knickei.
Fortunately, it happened at night, so none of the 20 workers were hurt. The engineering office said that the dome collapsed because of a strong storm, and the structure just couldn't withstand the weather.
In fact, the weather service data show something different. That night, the wind was blowing at 8 Bft (19.6 m/s; 43.8 mph). That's just a strong breeze, not even close to a storm. So was there a structural fault in the Knickei after all?
The city hired an expert to get to the bottom of it. The expert's report said that the collapse was caused by weather conditions and assembly errors on the Knickei, but there were no fundamental structural issues. Well, the city had to put its trust in an expert.
…but the second problem followed soon.
The city decided to spend more money and rebuild the hall roof. It turned out that the actual stresses in the steel mesh did not correspond to the engineering office's theoretical calculations of the Knickei. After all, it couldn't be a structural error!
To make sure the stress on the Knickei was evenly distributed, the workers stretched seven steel cables across the entire width of the dome. Therefore, the calculated load-bearing capacity was reached. So was all well now and the Knickei of Halstenbek lived happily ever after? In fact, the end came sooner than expected.
Just a few months later, the self-supporting dome roof collapsed again. Maybe the structural engineers were to blame? In order to clarify the matter once and for all and to ease the minds of the taxpaying residents of the town, the municipality of Halstenbek applied to the Itzehoe district court to initiate proceedings for the preservation of evidence to clarify what led to the collapse of the Knickei. So a new expert opinion was required.
Knickei Structural Engineering: Second Expert Report
The results of the second expert report were shocking. There were considerable deficiencies in the structural design. First of all: Yes, the Knickei structure is a highly challenging structure. It was a shell structure that had been separated into a structural grid.
Such structures are extremely sensitive in terms of tolerances, and the assembly is also a challenge. A steel construction company needs a lot of experience for this. One small mistake is enough to turn a sports egg back into a dented egg.
One of the issues, if not the primary one, was the connection of members. The engineering office likely assumed them to be rigid in the structural analysis. However, only semi-rigid connections were used in the construction. They vibrated somewhat like cables when subjected to loads.
In such a sensitive structural system, this quickly leads to a stability problem. The connections should probably have been considered as springs in the structural analysis. However, the structural engineers failed to identify this structural error.
The stiffness of the nodes in the steel mesh structure was clearly overestimated, and the fasteners between the steel struts of the 950 connection points couldn't even reliably bear the calculated load of 100 kg/m² (0.14 psi).
In addition to these completely miscalculated structural analysis, the old parts from the first collapse were reinstalled without thoroughly checking whether they were already damaged. In addition, various assembly errors had likely been made on the Knickei.
The end of the tragedy was that the engineers responsible for the structural analysis, the test engineers, and the glass construction company were to blame for the second collapse. But how did things continue with the Knickei? They didn't, at first.
Spoiled Knickei: Mold in Ruined Building
The lawyers of the affected companies, insurance companies, and the municipality of Halstenbek spent months negotiating to consider a possible claim for damages.
The structural engineering office refused to co-finance a second reconstruction of the Knickei, and the civil proceedings to start the action for damages got underway—but this could still take some time.
In 2000, fungal spores were detected on the floor of the Knickei sports hall. So what was to be done? Until the court case was settled and it was clear what to do next with the Knickei, the best thing to do was to keep the ruins as safe as possible.
To prevent the mold from spreading further, something had to be done. The hall ventilation and heating measures led to daily maintenance costs of about 520 marks.
Third Chance for Knickei?
As the Knickei ruins were slowly deteriorating, several discussions were held about rebuilding the dome. This time, the city was determined to get it right. New companies were commissioned with the structural analysis, structural testing, and assembly of the Knickei.
In 2001, the municipality decided to rebuild the sports hall, but only if they could make some structural improvements to the roof skeleton and a stronger roof arch. And the cost of the new Knickei? Meanwhile, it continued to rise. It's a losing battle to keep a vacant building economically viable in the long term.
But the people of Halstenbek didn't want to stand by and watch the misery of the Knickei. They collected a total of 2,199 signatures to hold a referendum on the future of the Knickei. Just 1,300 would have been enough. However, the local authority said the petition wasn't valid, for no good reason.
State of Knickei Project
The construction site at Knickei had been idle for 39 months. Only the mold fungi felt particularly at home on the hall floor, as they were almost as big as mushrooms. The cleanup work hadn't been done yet. It was pretty quiet around the Knickei.
At a meeting with residents, the local council said that about 78% of the building structure was still undamaged. Thus, the Knickei would still be worth 7.3 million marks.
Referendum Against Knickei: Second Attempt
Meanwhile, the referendum process moved on to the second stage, with the case now before the administrative court. In 2002, the court ruled in favor of the people of Halstenbek, who had been watching their tax money go to waste for too long. So there was to be a referendum on the Knickei.
So, how did people feel about rebuilding and finishing the moldy sports hall? On September 22, 2002, 50.7% of the 10,675 Halstenbek voters voted to rebuild and finish the Knickei, while 49.3% voted against.
So the citizens had decided: The Knickei should live! And not just because of the mold. This was followed by more questions. Should the roof be reinforced more? Should a different structure be used? After the local elections in 2003, however, the decision was made to rebuild the Knickei exactly in the same way as it was when it collapsed twice before.
New Concept, New Luck?
In November 2003, the Knickei concept was revised slightly. A slightly elevated shape and more stable steel beams were agreed. The city started with a functional tender for a general contractor, which was a good move.
Not long after that, though, they put the Knickei project on hold and started over. Why? The planned completion costs were another €4.5 million. The city changed its mind and put out a new tender for the budget of €2.5 million, with a freely selectable roof shape.
However, the value of the Knickei debris had long since dropped. The entire building could be sold to an investor for the price of one euro. So, what was going to happen next?
Knickei Dispute
Meanwhile, a new petition was launched. This time, there were 2,713 signatures, which meant the local authority said the petition could go ahead in November 2004.
However, the municipality of Halstenbek objected to this declaration of admissibility by the municipal supervisory authority. This prevented the referendum from being held. The municipality only dropped its objection after filing an injunction with the administrative court.
In 2005, something happened that could have prevented many problems from ever arising. All the parties involved met at a round table, with a mediator on hand, to try to find a common solution that everyone could agree on for the Knickei.
The discussions continued for two months, but no resolution was reached. They all had to go back to court. This led to more lawsuits being filed against each other for months.
Knickei with Glaring Effect
Meanwhile, the Knickei caused more issues. We all know that glass reflects sunlight. This was especially problematic with a glass dome that was only half-broken and had thousands of intact panes.
This caused some of the neighboring houses to experience something of an annoying glare. The local authority only responded to complaints after legal proceedings before the Schleswig Administrative Court. So, in the autumn of 2004, the panes were sprayed with a gray matte paint. Problem solved? Not exactly. By the summer of 2005, the paint on the Knickei was peeling off again.
Demolition of Knickei: Yes, No, Maybe!
At around the same time, the moment had finally come. On July 18, 2005, the local council made the final call to tear down the hall and build a new conventional three-field hall. So that was it, then?
Actually, more was to come. On August 15, 2005, the mayor used his right of veto and personally suspended the decision of the municipal council. On December 11, another referendum was held. This time, 71% of Halstenbek's residents voted against rebuilding the Knickei. Nobody could oppose it.
On January 30, 2006, the final decision was made to tear down the old hall and start over with a new one. The city was already looking for a general contractor for the new building and paid €200,000 to get the demolition done. On March 20, 2007, the Knickei demolition was finished and the site was filled with gravel.
After Knickei
As it turned out, more was to come legally. On April 17, 2007, the Schleswig Higher Regional Court said that the Stuttgart engineering office could be sued for damages. The proposed settlement said that the engineers should pay 80% of the damage caused to the building, and the costs of the proceedings.
They finally settled the case in September 2008. The insurance company of the structural engineering office paid the municipality €2.3 million in compensation. It's probably just a drop in the ocean.
From December 2007 to September 2008, a conventional nine-meter-high (29.5-foot) sports hall with three fields was built on the former Knickei site. The total cost of the failed Knickei in Halstenbek project came to €9.4 million. After all the deductions, the company had to settle for €7.1 million—a truly sad result.
What should have been done differently with the Knickei?
Probably the most important issue of the Knickei was the lack of proper structural analysis. Correct structural design would have saved not only materials, but also time and money. From a structural point of view, it is essential for an engineering office to have enough experience to be able to implement such a project. The Knickei is a great example of this.
Another point is independent expert opinions, and it's better to have one too many than one too few. In the case of the Knickei in particular, where the weather conditions on the day of the collapse didn't match the assertion of the expert opinion, it would have been advisable to at least obtain a second opinion on the first opinion.
It's also important to think about all the different aspects when planning supporting structures. This also includes any glare caused by sunlight reflecting off the glass. We all know how powerful reflected sunlight can be, as we saw with the car-melting Walkie-Talkie in London.
In large construction projects in particular, cooperation between the various parties involved is essential for successful construction. This includes not only open communication, but also admitting mistakes in a timely manner in order to minimize (consequential) damage: both financial and material. Long court proceedings are extremely counterproductive while mold is growing in the ruined building.
Of course, today's structural design capabilities are completely different from those of the past. Today, engineers can calculate their projects using modern structural analysis software, such as RFEM and RSTAB. Furthermore, helpful tools exist for simulating environmental influences, such as snow and wind loads. The Steel Connections add-on by Dlubal would obviously have been an advantage here. Such extensive possibilities did not exist more than 25 years ago.
Nowadays, we should use all the resources available to us for the construction of our buildings—including our common sense–so that construction projects can continue to be realized economically and, above all, safely in the future.
