The Olympic Hall in Munich has a monitoring system to check the loads applied and their distribution over the lighting gantries. This was solved with measurement technology from HBK.
The variations in the load on the lighting gantry cause the supporting beam to deform, with the deformation being transferred to the transducers via the metal holders. TypeSLB700A strain transducers from HBK are used here.
MX840A modules from the HBK QuantumX data acquisition system are used as the amplifiers. A total of four amplifiers transmit the measurement data with an interposed fiber-optic link to a type CX27 gateway module, acting as a central measurement node.
HBK catman®AP software runs on the server in the computer center, and is used to configure and perform load monitoring.
After all the components and systems were installed in spring 2010, the load-monitoring system was calibrated. To do this, different loads of up to three tons were attached at different points on the gantries. It was then possible to achieve the planned measurement accuracy of 2% of the load or 100 kg for smaller loads.
As far as the Olympiahalle arena is concerned, the load monitoring system has now become an advantage for the location. Some concert promoters are tending to start major concert tours in Munich. If the lighting technology has complied with the strict system in Munich, other hall operators can obviously rely on the information provided by the concert promoter.
One focus is modern timber construction with its new possibilities such as load-bearing structures made of cross-laminated timber, board stacks, high-strength beech or wood-concrete composites.
During the Olympic Games in 1972, the Olympiahalle arena was home to the gymnastics and handball competitions, but now, it mainly stages concerts and other major events. Lighting is a great extravagance for promoters, particularly with major concerts.
The Olympiahalle arena has four lighting gantries available, running from east to west under the tented roof, from which promoters can suspend their technology. These four lighting gantries are statically determinate and are attached to the two main girders that run from north to south. These are also statically determinate, and are suspended by steel cables in the stanchions, that also support the tented roof.
The transition between the main girders and the suspension cable is resolved by a threaded spindle, 80 mm or 110 mm in diameter, that runs through the supporting beam. There is a needle bearing between the spindle and the supporting beam, which prevents the spindle being subjected to bending stress in the north-south direction. Similar mobility from west to east was not planned for its earlier use and so was not provided.
The entire structure of main girders, lighting gantries and fixed lighting, sound and video technology, weighs in total around 350 tons and because of the cable suspension, it behaves similarly to a swing. Unevenly distributed loads in the west-east direction, which is the rule in concerts for the majority of the technology, because the stages are arranged on one side, lead to a shift in the entire gantry structure, and the threaded spindles are thus subjected to unscheduled bending stress.
So while the Olympiahalle arena was being renovated, Stadtwerke München, the city of Munich’s public utility company and owners of the building, decided, together with Olympiapark GmbH, the operator, to install a monitoring system to check both the bending stress of the spindles in the building and to permanently monitor the weight of the technology suspended for an event, as well as its distribution over the gantry.
To ensure reliable and precise measurement, the experts at Dr. Linse Ingenieure designed a comparably extravagant structural solution. In the region of the lighting gantry suspension, they welded two metal holders for the strain transducers on the underside of the main girders (compression zone), at each of two points.
The variations in the load on the lighting gantry cause the supporting beam to deform, with the deformation being transferred to the transducers via the metal holders. Type SLB700A strain transducers from HBK are used here. The transducers work with strain gauge full bridges made from stainless steel and feature a very low zero offset and good temperature compensation. To increase the precision of the measurement, the transducers were fitted with an insulated housing. “This made it possible to minimize what in some cases were extreme temperature fluctuations, as well as the associated temperature gradients”, explains Dr Schmiedmayer. “We also attached temperature transducers in the housings, to perform additional temperature compensation.”
The structure is even more complex for the four spindles of the main girders. Here the engineers designed quadripartite nuts that fitted exactly onto the threaded spindles and which can be held in place by a bolted connection. Two of these nuts on each of the threaded spindles act as holders for four strain transducers. In contrast to the situation on the lighting gantries, these are not connected in parallel, they are evaluated individually. This allows any bending of the spindles that occurs with a load and which cannot be compensated by the needle bearings, to be detected.
The engineers also had to get the effects of electromagnetic interference under control. “In the first preliminary tests, we noticed that when the large spotlights right next to the measurement technology were switched on and off, there could be major interference”, remembers Dr Schmiedmayer. Shielded measuring leads then had to be used, that were also run through continuously enclosed metal pipes, to double the shielding effect.
At the same time, care was taken to ensure that none of the measuring leads were longer than 20 m. MX840A modules from the HBK QuantumX data acquisition system are used as the amplifiers. These compact amplifiers each have eight channels and are easily installed on the gantry structure, making it possible to keep measuring leads short. A total of four amplifiers transmit the measurement data with an interposed fiber-optic link to a type CX27 gateway module, acting as a central measurement node.
The CX27 QuantumX gateway module is housed in a control cabinet in the Olympiahalle lighting rostrum, together with the power supply, a UPS and the network components. From there, the measurement data is transmitted via TCP/IP to the computer center of Stadtwerke München, where there is a relevant server. The measurement node also triggers a direct display of the load monitoring. A big set of traffic lights, clearly visible inside the Olympiahalle, indicates the loading that is reached. If the traffic lights jump to amber, this means that either the planned event load, or 98% of the maximum gantry load has been reached. If the maximum load for the structure is reached, the traffic light shows red. This is a sign to the hall inspector that stage workers must stop work immediately and that some of the load must be removed from the lighting gantries. HBK catman®AP software runs on the server in the computer center, and is used to configure and perform load monitoring. The permissible loads for
can be specified for an event. The advance warning range, when the traffic light in the Olympiahalle changes from green to amber, can be configured here. The measurement frequency and thus also the traffic light control, is 1 Hz. For data archival, the average and the maximum value in a minute are stored in each case. If there is an overload situation or a system failure, the system administrator is informed by e-mail and SMS. The measured data are stored and can, at the same time, be seen from any number of places, via internet.
The resolution is so good, that I can see from the measurement data when and where I was working on the lighting gantries. It only took thermal deformation of the access gantries and associated deformations in the system to bring about system-dependent variations in the measured values, with these only affecting the immediately adjoining gantries and making up less than 1% of the entire measuring span.. The good advice that I get from HBK, and the metrological know-how of their employees, also make me feel that I am in good hands.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
