Extreme Winds Software: Fortran Code for the Along-Wind Response of a Tall Building

This program supersedes the program listed in "The Buffeting of Tall Structures by Strong Winds," by E. Simiu and D. W. Lozier (NBS Building Science Series 74, Oct. 1975).

This program was authored by Dan Lozier of the NIST Mathematical and Computational Sciences Division. In 2005, Alan Heckert made a few minor updates to the code so that it would run under Fortran 77 and Fortran 90 compilers (it was originally written for Fortran 66 compilers). It consists of a main program called MAIN and eight subprograms, called INPUT, INIT, TRIPLE, F, UTILDA, XMU, STILDA, AND FISTAR.

Note: The program was further updated by Alan Heckert in 12/2007 in the following ways:

1. The original version of the program had a rigorous input format (i.e., input fields had to be entered into specific columns in a specified format). The program was modified to allow the data to be entered in free format. Note that the order of the data entered remains the same, but you are no longer required to enter the data in specific columns.

2. The program will print prompts for the input values. This should be helpful to those who are uncertain about what some of the input fields are suppossed to be.

We provide pre-built executables for the Windows 2000/XP platform and the Sun Solaris platform. You can compile this code yourself if you have a Fortran compiler available.

For the sake of discussion, let us assume that you have created the directory "C:\WINDLOAD" and that you have a sample input data file called "windload.input".

To run the program:

1. Open a command prompt window.

2. Enter
   WINDLOAD.EXE < WINDLOAD.INPUT > WINDLOAD.OUT

• windload.f source file
• windload.exe executable file for Windows 2000/XP platforms
• windload.solaris executable file for Sun Solaris platforms
• windload.input sample input file
• windload.output sample output file (generated from windload.input)

• Line 1: FORMAT (2I5)
  • RLIM = The number of modes of vibration used in the calculations (between 1 and 8)

  • IPRINT = Selects one of two options for output printing by the main program as the approximate integration progresses from FTILDA = 0 to FTILDA = some cutoff value. Option 1, obtained by setting IPRINT=1, causes running information to be printed at each sample value of FTILDA in the quadrature. Option 2, obtained by leaving IPRINT blank, suppresses this printing.

• Line 2: FORMAT (3F10.0)
  • H = Height of building in meters

  • BCON = Width of building (i.e., horizontal dimension perpendicular to wind direction) in meters

  • DCON = Depth of building (i.e., horizontal dimension parallel to wind direction) in meters.

• Line 3: FORMAT (8F10.0)
  • EN(I) = Natural frequencies of the building in modes 1, 2, ... in Hertz.

• Line 4: FORMAT (8F10.0)
  • ZETA(I) = Damping ratios in modes 1, 2, ...

• Sets of Lines 5 and 6: FORMAT (8F10.0) and (7F10.0), respectively
  A pair of lines is required for each mode of vibration used in the calculations. Line 5 includes the ordinates XMUTAB of the i-th modal shape at elevations 0, 1*H/14, 2*H/14, 3*H/14, 4*H/14, 5*H/14, 6*H/14, 7*H/14. Line 6 includes the ordinates XMUTAB of the i-th modal shape at elevations 8*H/14, 9*H/14, 10*H/14, 11*H/14, 12*H/14, 13*H/14, 14*H/14.

  If two or more vibration modes are taken into account in the calculations, the lines for the first mode must be followed by the lines for the second mode, and so forth.

• Sets of Lines 7 and 8: FORMAT (8F10.0) and (7F10.0), respectively
  Line 7 includes the weight of the building per unit height, XMASS, in Newtons/meter at elevations 0, 1*H/14, 2*H/14, 3*H/14, 4*H/14, 5*H/14, 6*H/14, 7*H/14. Line 8 includes the weight of the building per unit height, XMASS, in Newtons/meter at elevations 8*H/14, 9*H/14, 10*H/14, 11*H/14, 12*H/14, 13*H/14, 14*H/14.

• Line 9: FORMAT (I5, 5X, 7F10.0)
  • ICODE = Selects parameters corresponding to standard micromereorological conditions for various types of exposure, as fololows:
    1. Option ICODE = 1 causes selection of parameters corresponding to exposure typical of open water.

    2. Option ICODE = 2 causes selection of parameters corresponding to exposure typical of open terrain.

    3. Option ICODE = 3 causes selection of parameters corresponding to exposure typical of suburbs at considerable distances from towns, sites in rural zones sparsely built-up, with trees, hedges, etc.

    4. Option ICODE = 4 causes selection of parameters corresponding to exposure typical of towns, densely built-up suburbs, wooded terrain.

    5. Option ICODE = 5 causes selection of parameters corresponding to exposure typical of centers of large cities.

       1. Z0 = Roughness length in meters. If left blank, standard VALUE FOR EXPOSURE CORRESPONDING TO CHOSEN VALUE OF ICODE WILL BE AUTOMATICALLY SELECTED

       2. ZPSP = Zero plane displacement in meters. If left blank, standard ZPSP = 0 will be automatically selected.

       3. CZ = Exponential decay coefficient for vertical separation in expression for cross-spectra of longitudinal velocity fluctuations. If left blank, standard value CZ = 10 will be automatically selected.

       4. CY = Exponential decay coefficient for horizontal separation in expression for cross-spectra of longitudinal velocity fluctuations. If left blank, standard value CY = 16 will be automatically selected.

       5. BETACN = Ratio (RMS of longitudinal turbulent fluctuations)/(USTAR²). If left blank, standard value for exposure corresponding to chosen value of ICODE will be automatically selected.

       6. F1 = Peak similarity coordinate (see reference 3, equation 9). If left blank standard value F1 = 0.03 will be automatically selected.

       7. FS = Value of similarity coordinate beyond which similarity representation of longitudinal turbulence spectra holds. (See reference 3, equation 10). If left blank, standard value FS = 0.2 will be automatically selected.

          References pertaining to micrometeorological parameters used in this program:

          1. "Mean Wind Profiles and Change of Terrain Roughness," J. Bietry, c. Sacre, and E. Simiu, Journal of the Structural Division, ASCE, Oct. 1978, pp. 1585-1593.

          2. "On the Reliability of Gust Loading Factors," B. J. Vickery, Proceedings of Technical Meeting Concerning Wind Loads on Buildings and Structures held at the National Bureau of Standards, 1969, Building Science Series 30, National Bureau of Standards, Nov. 1970.

          3. "Wind Spectra and Dynamic Along-Wind Response," E. Simiu, Journal of the Structural Division, ASCE, Sept. 1974, pp. 1897-1910.

• Line 10: FORMAT (I5,5X,3F10.0)
  • JCODE = If the specified wind speed at 10 meters above ground in open terrain, U10, is given as a mean hourly speed in meters/sec., then set JCODE = 1. If U10 is given as a fastest-mile speed in miles/hour, then set JCODE = 2.

  • U10 = Specified wind speed at 10 m. above ground in open terrain.

  • T = Duration of storms in seconds. If left blank, standard value T = 3600 sec. will be automatically selected.

  • P = Retardation factor (see reference 1 quoted above). If left blank, standard value will be automatically selected.

• Line 11: FORMAT (3F10.0)
  • CW = Mean pressure coefficient on windward side. If left blank, value CW = 0.8 will be automatically selected.

  • CL = Absolute value of mean suction coefficient on leeward side. If left blank, value CL = 0.5 will be automatically selected.

  • RHO = Specific weight of air. If Left blank, value RHO = 12.258 newtons/meter³ will be automatically selected.

Date created: 12/1/2005
Last updated: 12/18/2007
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