In industrial and commercial areas it is necessary to let exhaust fumes from production escape at a sufficient height. This is done by using cooling and waste gas chimneys, which partly exceed the limit of 100m.
There are several variants to choose from, depending on the construction and the chosen material. Until the beginning of the 20th century, mainly brick chimneys were used, which are limited in height for static reasons.
As developments in the field of concrete and installation techniques progress, cooling towers made of reinforced concrete are used, for example, in power plant construction and large industrial plants. These usually have a relatively small wall thickness and are usually erected using the climbing construction method.
Tubular steel towers are used in the chemical industry with acidic or basic exhaust gases. In this case, either a coating of the structural steel prevents rapid corrosion or stainless steels are used as an alternative. The individual steel pipe sections are connected to each other via ring flange connections and fastened to the foundation with anchors.
The design of the steel tube sections for chimneys is similar to that of support structures for wind turbines sehr ähnlich. Die Hauptbeanspruchung der Schornsteine stellt dabei der Wind dar. In einigen Fällen kommen noch hohe Temperaturen oder Eisansatz hinzu, welche in der Bemessung berücksichtigt werden müssen. Insbesondere müssen bei diesen schlanken und hohen Bauwerke die windinduzierten Querschwingungen untersucht werden. EIt leads to vortex induced vibrations, when on the opposite sides of a structure alternating vortices peel off. If the excitation by the wind lies in the frequency range of the structure, resonance effects and a swaying of the vibrations can occur at right angles to the wind.
Masts can be erected as steel or concrete structures. These serve as supports for different systems. They can be used for wind turbines, transmitting antennas, measuring stations or systems for the radio network (5G). In the middle of the 20th century, transmission masts were almost exclusively used as carriers for transmitting antennas.
Nowadays, hardly any classical transmitter masts are erected, since the use of existing buildings is usually sufficient for digital data radio. For this purpose, for example, available areas on the tubular towers or lattice towers of wind turbines are used. Another possibility is to use wind turbines that have reached the end of their service life. In this case, the nacelle with its hub and rotor blades is removed and the transmitter including a platform is placed on the existing support structure. In this course, the supporting structure must be examined with regard to lateral vibrations, natural frequencies and service life.
The SKI engineering company is able to accompany this conversion in an expert opinion. This includes recording the current condition of the plant and, if necessary, the existing natural frequencies using measurement technology. This serves as a basis for further investigations and evaluation of the supporting structure. The measurement data are also used to validate the calculation models on which the structural analyses are performed. Especially the susceptibility to wind induced lateral vibrations is of special importance.
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