Calculation of dynamic characteristics of a television tower

The paper considers the calculation of dynamic characteristics of a television tower exposed to wind pulsation. During the investigation, the tower outline shape was changed, as well as the material of the structure, then it was subjected to the wind load using the SCAD ++ computer complex.

Predictions on the dynamic behaviour of an aeroelastic model of a television tower in the boundary layer wind tunnel

This paper presents the process of making a set of vibration measurements on a model of a television tower in the boundary layer wind tunnel. The main objective of the study is to predict the dynamic behaviour of the full-scale structure under the turbulent wind action, specific for the Bucharest site, in Romania. Wind tunnel tests were performed on a 1:500 scale aeroelastic model, existing at the Aerodynamics and Wind Engineering Laboratory “Constantin Iamandi” from the Technical University of Civil Engineering Bucharest. As a result of the vibration measurements on the tower's model, the dynamic behaviour of the structure on the real scale could be determined by using the conditions and relationships of similitude established between the two, model and prototype (full-scale structure). The experimental analysis made in this study may be very important not only in assessing the dynamic response for a building of such importance, during the preliminary stages, but also can be very helpful for the decision makers involved in the design process to choose which is the best solution for such high and slender structures under the action of turbulent wind.

Response Control of a High-Rise Television Tower under Seismic Excitations by Friction Dampers

High-rise television towers are prone to external wind and earthquake-induced oscillations in severe environments. To avoid excessive vibration under strong earthquakes, a large television tower requires certain measures to abate its dynamic responses. Friction dampers are simple and low-cost solutions for realizing the response control of television towers. In this study, response mitigation and performance assessment are conducted on a large-scale television tower with friction dampers under strong earthquakes. A 3D finite element static model of the high-rise television tower is first established, and then a 2D lumped mass dynamic model is developed. The mechanical model for the friction dampers is presented with the axial stiffness considered. The equations of motion of the damper–tower system under seismic excitations are then determined. The control force transformation, displacement increment transformation, and numerical integration of the coupled damper–tower system’s equations of motion are defined on the basis of the two aforementioned models. Finally, the seismic responses of a high-rise television tower system constructed in China are taken as an example to investigate the validity of the proposed control approach using the friction dampers. The results demonstrate that the implementation of friction dampers with optimal parameters in a large truss tower can substantially suppress the structural seismic responses in terms of peak responses and vibrant energy.

EFFICIENT RECONSTRUCTION OF ENGINEERING BUILDINGS IN CONDITIONS OF ORGANIZATIONAL CONSTRAINTS

The article presents the results of experimental and statistical modeling and the search for effective organizationalsolutions for reconstruction of high-rise engineering structures by the example of the Ostankino television tower. Thedependences of the factors having the greatest impact on the studied parameters are found. Restrictions on possibleorganizational solutions, on effectiveness indicators are imposed. According to the analysis of diagrams containingrestrictions the most efficient organizational options for reconstruction are recommended.

High-precision quasi-continuous atmospheric greenhouse gas measurements at Trainou tower (Orléans forest, France)

Results from the Trainou tall tower measurement station installed in 2006 are presented for atmospheric measurements of CO2, CH4, N2O, SF6, CO, H2 mole fractions and radon-222 activity. Air is sampled from four sampling heights (180, 100, 50 and 5 m) of the Trainou 200 m television tower in the Orléans forest in France (47°57'53" N, 2°06'45" E, 131 m a.s.l.). The station is equipped with a custom-built CO2 analyser (CARIBOU), which is based on a commercial non-dispersive, infrared (NDIR) analyser (Licor 6252), and a coupled gas chromatography (GC) system equipped with an electron capture detector (ECD) and a flame ionization detector (FID) (HP6890N, Agilent) and a reduction gas detector (PP1, Peak Performer). Air intakes, pumping and air drying system are shared between the CARIBOU and the GC systems. The ultimately achieved short-term repeatability (1 sigma, over several days) for the GC system is 0.05 ppm for CO2, 1.4 ppb for CH4, 0.25 ppb for N2O, 0.08 ppb for SF6, 0.88 ppb for CO and 3.8 for H2. The repeatability of the CARIBOU CO2 analyser is 0.06 ppm. In addition to the in situ measurements, weekly flask sampling is performed, and flask air samples are analysed at the Laboratoire des Sciences du Climat et de l'Environnement (LSCE) central laboratory for the same species as well for stable isotopes of CO2. The comparison between in situ measurements and the flask sampling showed averaged differences of 0.08 ± 1.40 ppm for CO2, 0.7 ± 7.3 ppb for CH4, 0.6 ± 0.6 ppb for N2O, 0.01 ± 0.10 ppt for SF6, 1.5± 5.3 ppb for CO and 4.8± 6.9 ppb for H2 for the years 2008–2012. At Trainou station, the mean annual increase rates from 2007 to 2011 at the 180 m sampling height were 2.2 ppm yr−1 for CO2, 4 ppb yr−1 for CH4, 0.78 ppb yr−1 for N2O and 0.29 ppt yr−1 for SF6. For all species, the 180 m sampling level showed the smallest diurnal variation. Mean diurnal gradients between the 50 m and the 180 m sampling level reached up to 30 ppm CO2, 15 ppm CH4 or 0.5 ppb N2O during nighttime whereas the mean gradients are smaller than 0.5 ppm for CO2 and 1.5 ppb for CH4 during afternoon.

Six years of high-precision quasi-continuous atmospheric greenhouse gas measurements at Trainou Tower (Orléans Forest, France)

Results from the Trainou tall tower measurement station installed in 2006, are presented for atmospheric measurements of CO2, CH4, N2O, SF6, CO, H2 mole fractions and Radon-222 activity. Air is sampled from four sampling heights (180 m, 100 m, 50 m and 5 m) of the Trainou 200 m television tower in the Orléans forest in France (47°57'53'' N, 2°06'45'' E, 131 m a.s.l.). The station is equipped with a custom-build CO2 analyzer (CARIBOU), which is based on a commercial NDIR analyser (Licor 6252), and a coupled gas chromatographic GC system equipped with ECD and FID (HP6890N, Agilent) and a reduction gas detector (PP1, Peak Performer). Air intakes, pumping and air drying system are shared between the CARIBOU and the GC systems. After some initial problems, we achieved short-term repeatability (1 sigma, over several days) for the GC system of of 0.05 ppm for CO2, 1.4 ppb for CH4, 0.25 ppb for N2O, 0.08 ppb for SF6, 0.88 ppb for CO and 3.8 for H2. The repeatability of the CARIBOU CO2 analyser is 0.06 ppm. In addition to the in-situ measurements, weekly flask sampling is performed, and flask air samples are analysed at the LSCE central laboratory for the same species as well for stable isotopes of CO2. The comparison between in-situ measurements and the flask sampling showed averaged differences of 0.08 ± 1.4 ppm CO2, 0.69 ± 7.3 ppb CH4, 0.64 ± 0.62 ppb N2O, 0.01 ± 0.1 ppt SF6 and 1.5 ± 5.3 ppb CO for the years 2008–2012. At Trainou station, the mean annual increase rates from 2007 to 2011 at the 180 m sampling height were 2.2 ppm yr−1 for CO2, 4 ppb yr−1 for CH4, 0.78 ppb yr−1 for N2O and 0.29 ppt yr−1 for SF6 respectively. For all species the 180 m sampling level showed the smallest diurnal variation. Mean diurnal gradients between the 50 m and the 180 m sampling level reached up to 30 ppm CO2, 15 ppm CH4 or 0.5 ppb N2O during night whereas the mean gradients are smaller than 0.5 ppm for CO2 and 1.5 ppb for CH4 during afternoon.