New ECB Buildings
In the spring of 2010, spannverbund received the contract for the construction of steel structures for two buildings: a T101-04 steel skyscraper and a T101-05 steel central market hall.
The steel structure of the tower can be divided into two main components. The first of these includes the bilateral reinforcement and connection of two high-rise towers with braces, transfer platforms, bridges, stairs, balconies, and concrete-steel connection elements(a total of about 3,000 tons of steel). The second component consists of steel structures on the high-rise heads with steel roofs as well as the constructed Council Chamber (a total of approximately 400 tons of steel).
We saw possibilities for optimization primarily during the installation and development of the struts and their wall connections, but such options were also present during the final design stages of the transfer platforms, and fire protection.
The question of how elements 38 meters in length and 120 tons in weight could be installed between the towers with heights of 150 meters was one of the main problems we had to solve. In order to achieve this result, spannverbund developed a cost-effective installation concept that eliminated elaborate scaffolding. Our concept also resulted in minimal time needed for crane operation, an extremely important factor in high-rise construction.
The planning of this installation concept naturally required an extended amount of time and innovation. In order to transport the subcomponents of the struts to their unique mounting positions and to allow the cranes more articulated and independent movement, it was necessary to sometimes ascertain and graphically produce three-dimensional concepts of the tandem strokes of the construction cranes.
One particularly intriguing challenge was the construction of the strut connections to the concrete walls. Due to the curved and sloping walls with columns of similar shape behind them and the inclined core staircase of the north tower, the geometry of the two towers twisted and shifted at each phase of construction, causing the location of the strut connection points to change constantly. The high-to-transfer tensile and compressive forces as well as the large tolerances ruled out connections via screw. We therefore developed a construction method that allowed for length and angle adjustments.
The two towers are additionally linked by the supports of the transfer platforms, which also shifted position in every phase of construction. The high tensile and compressive forces of the beams, the necessary tolerances, and the rotation of the beam ends under alternating stresses of the platforms posed unique issues that required further research and conceptualization, including the development of special forms of bearings. Bolt connections were not possible because of the tolerances. The use of locally-adapted, rigid welded construction wouldn’t work because of the twisted shape of the support structure. And given the large number of fittings, local welding work would have delayed the construction schedule. Therefore, we opted for a quick-to-install and re-adjustable solution.
The final work on the high-rise head presented a further challenge. The antenna mast towered over the northern high-rise tower by 16 meters and extended the total building height to 201 meters. To avoid dangerous assembly work at this altitude, it was necessary to execute the completion of the mast elements and the mounting of the antennas on the ground. The precast parts of the steel truss mast, totaling 30 meters in length, had to reach their sky-high installation point without complication or damage to the building's painted exterior. A transporter was specifically built for this purpose, which also provided increased support on the ground after unloading.
Our solutions made it possible to install the antennas, lightning protectors, and the lighting of the entire cabling at a comfortable working height. Because the mast foundation was fixed to a bogie, the antenna mast was able to be mounted in a simple manner. After the structure had been released from the bogie, it was pulled onto the roof of the north tower in one piece and bolted onto the concrete ceiling.
Steel-Construction Central Market Hall
Within the central market hall, there are significant steel structures in three major areas: the conference area, the staff restaurant, and the entrance structure with the connection to the historically protected arched roof. Of particular structural noteworthiness is the truss structure, which forms the conference area and supports various ceilings over large spans.
A structure of thick-walled, welded, and hollow sections was conceived to suit these parameters, which had to be protected with an impact-sensitive, flame-retardant coating.
We also engineered an alternative composite structure that had the same rigidity as the originally tendered structure. The segments were completely prefabricated and bolted on site.
The casing of the nodes was welded in a way that achieved a sharp-edged, smooth surface. This was then coated with gray aluminum paint used throughout the building.
For the insertion and installation of bulky, large, and heavy steel parts through the wall openings of the Central Market Hall and beneath the huge, arched roof, logistics had to be planned in detail. In some places, the components were moved with two assembly cranes. In certain instances, the cranes themselves could only be transported in and out of the hall in parts.