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

Introduction This page describes a Fortran-77 code that calculates the along-wind response of a tall building subjected to a wind load with mean direction normal to a building face. The across-wind and the torsional response are not calculated by this program.

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.

    However, there is one issue you need to be aware of if you have used the original version of the program. The original version of the program allowed many fields to be entered as "blank" (these "blank" fields would be read as "0" which the program interpreted to mean "use the default value") . In order to allow the more flexible input format, the option of leaving fields blank no longer works. For a few of the input lines, if the blank fields are all at the end of the line, you can still leave them as blanks. However, other input lines may extend over multiple lines and leaving fields blank will not work. You can specify default values by entering a zero value for the field.

    The main point is that if you have a run file setup to run the original version of the program, it may no longer work with the new version of the program. For this reason, the original version of the program is still available.

  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/Vista platform. The source code is provided for other platforms (it should compile and run on any Unix/Linux system that has the gfortran compiler installed).

Note: The program was further updated by Alan Heckert in 10/2009 in the following ways:

  1. The input values entered by the user are automatically saved to the file "windload.echo". This makes it simpler to save and modify your interactive responses to the program in order to run the program in a batch mode (i.e., if you want to run the program with slight variations in the input parameters, you can copy "windload.echo" to a new file name, make the edits using any ASCII text editor, and then run the edited file in batch mode). You should move "windload.echo" to a new file since the next time you run the windload program it will overwrite the contents of "windload.echo".
Example under Windows 2000/XP/Vista This section describes how to run the program under the Windows 2000/XP/Vista operating system.

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
The program will then run. After it completes, the program output will be in the ASCII file WINDLOAD.OUT. This file can be viewed with any suitable editor (e.g., Notepad).

Alternatively, you can just enter

    WINDLOAD.EXE
and the program will prompt you for the appropriate input.
Download You can download the following: You can download these files to whatever directory is convenient for you. These files require no additional installation.
Description of the Input File This program has a fairly rigid input format that is described here.

  • 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.

If several sets of data are used, the above sequence of command lines can simply be repeated for each set of data. A blank line should follow the last line of data of the last set of data.
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Date created: 12/01/2005
Last updated: 03/10/2011
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