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Nonlinear dynamic analysis of cooling towers under stochastic wind loading
2200 Comment:
We also found very severe lateral vibrations of the mast even in very symetrical situations. This is perhaps due to lateral components of the gust. This effect seems to be very important to fatigue!
Author's reply I have spent some time considering the fl.~l-spectrum, using the ESDU suggested values, which are not so large. After all, 27 m/s over the open north sea should be very neutral! Of course, the quad cancels out in the classical analysis; I found it difficult to find any significant effect for the inclined tower. I agree that lateral components have a very substantial effect; both the length scales and the aerodynamic damping differences contribute to this.
Full.Scale Measurements of Wind Force Acting on a 200m Concrete Chimney, and the Chimney°s Response. S. Sanada & H. Matsumoto C o m m e n t by J. L. Waldeck I would like to disp~Jte the fact the R M S liftcoefficientis a function of Reynolds number because ifthe same data are plotted against the turbulence parameter. In (D/L)~, it should collapse onto a well-defined relationship which is not dependent on the Reynolds number.
Author's reply I agree with you. I think I mislead you because I said high Reynold's number. What I meant to say is that RMS Cp becomes 0.07 when the velocity is high. 1 did not use the region in that figure I presented, where the Reynold's number is less than 2.0 x 10~ (20 m/s) for my conclusion, because the region the wind direction easily fluctuates, which cause a large Cp scattering. By using the data which on the high wind velocity only, I came to the conclusion, Cp~-0.6 and Cp, Ci = 0.07.
Nouli,war Dy,tamic A,mlysis of Cooliag Towers u~der Stochastic Wind Loading. G. Bartoli, C. Borri & W. Zahlten
Comment by K~i Kondo I. 2.
In the nonlinear response analysis, how do you treat the nonlinearity of the members? H o w do you think about the fatigue ofthe members?
Author's reply I.
One has to specify the meaning of the term "members". If the R/C shell elements are meant, then the four prime sources of physical nonlinearity (concrete in compression, tension cracking, yielding of reinforcement, bond) are given in the paper with references. For the geometrical nonlinearity, models ranging from small, moderate to large displacements/rotations have been implemented. In this study, small rotations have been assumed. If, however, the beams supporting the lower rim are to be discussed, they have not been modelled. Instead, membrane boundary conditions are prescribed. This is equivalent to the assumption that the beams possess sufficient strength to avoid structural failure.
2201 .
Fatigue is not included in the present model, as well as other time-dependent effects such as creep, shrinkage or corrosion. W e feel that out of these, corrosion is the most important one, fatigue playing a subordinate role.
We also found very severe lateral vibrations of the mast even in very symetrical situations. This is perhaps due to lateral components of the gust. This effect seems to be very important to fatigue!
Author's reply I have spent some time considering the fl.~l-spectrum, using the ESDU suggested values, which are not so large. After all, 27 m/s over the open north sea should be very neutral! Of course, the quad cancels out in the classical analysis; I found it difficult to find any significant effect for the inclined tower. I agree that lateral components have a very substantial effect; both the length scales and the aerodynamic damping differences contribute to this.
Full.Scale Measurements of Wind Force Acting on a 200m Concrete Chimney, and the Chimney°s Response. S. Sanada & H. Matsumoto C o m m e n t by J. L. Waldeck I would like to disp~Jte the fact the R M S liftcoefficientis a function of Reynolds number because ifthe same data are plotted against the turbulence parameter. In (D/L)~, it should collapse onto a well-defined relationship which is not dependent on the Reynolds number.
Author's reply I agree with you. I think I mislead you because I said high Reynold's number. What I meant to say is that RMS Cp becomes 0.07 when the velocity is high. 1 did not use the region in that figure I presented, where the Reynold's number is less than 2.0 x 10~ (20 m/s) for my conclusion, because the region the wind direction easily fluctuates, which cause a large Cp scattering. By using the data which on the high wind velocity only, I came to the conclusion, Cp~-0.6 and Cp, Ci = 0.07.
Nouli,war Dy,tamic A,mlysis of Cooliag Towers u~der Stochastic Wind Loading. G. Bartoli, C. Borri & W. Zahlten
Comment by K~i Kondo I. 2.
In the nonlinear response analysis, how do you treat the nonlinearity of the members? H o w do you think about the fatigue ofthe members?
Author's reply I.
One has to specify the meaning of the term "members". If the R/C shell elements are meant, then the four prime sources of physical nonlinearity (concrete in compression, tension cracking, yielding of reinforcement, bond) are given in the paper with references. For the geometrical nonlinearity, models ranging from small, moderate to large displacements/rotations have been implemented. In this study, small rotations have been assumed. If, however, the beams supporting the lower rim are to be discussed, they have not been modelled. Instead, membrane boundary conditions are prescribed. This is equivalent to the assumption that the beams possess sufficient strength to avoid structural failure.
2201 .
Fatigue is not included in the present model, as well as other time-dependent effects such as creep, shrinkage or corrosion. W e feel that out of these, corrosion is the most important one, fatigue playing a subordinate role.