The program can be used to analyze wind dynamically utilizing a Harris wind spectrum and create a solution file containing end forces, stresses, reactions and displacements for each wind velocity to be analyzed. These results contain dynamic amplification and can be combined with the static results due to self weight, etc. Generating the dynamic results requires that aerodynamic data and the wind velocities to be analyzed be specified in the Seastate input (or SACS model file) while all other data including analysis, spectrum and plot options are designated in the Dynamic Response input file.
General Model Options
The ‘JO’ option which designates that only stresses at the joints are to be contained in the solution file should be designated in columns 27-28 on the OPTIONS line in the SACS model file. For each element, the dynamic amplification factor is based on the stress in the element and is a function of the dynamic RMS stress and the static stress. Because each member internal load will be factored by a unique dynamic amplification factor applicable only to that particular internal load, internal loads are not consistent with each other nor are they consistent with the applied loading along the member. Therefore, stresses and unity check calculations are only valid at the member ends.
Note: For extreme spectral wind analysis, the analysis option in columns 19-20 of the OPTIONS line should be left blank. The dynamic analysis option ‘DY’ should NOT be specified.
Aerodynamic and Wind Data
The ‘WIN’ Seastate option must be specified in columns 56-58 on the LDOPT line. Wind load data is specified after the LOAD line. Each load case defined should contain only wind loading with the mean wind velocity specified as the wind speed.
Note: Each wind should be specified as a separate load case. As many wind speeds and directions as desired may be specified.
The following sample input shows two wind cases with a mean velocity of 100 for the 0 degree and 90 degree directions.
Dynamic Response Options
Dynamic response options including analysis and plot options are designates in the Dynamic Response input file. Analysis Type
The analysis label ‘WIND’ must be entered in columns 7-10 on the DROPT line for spectral wind analysis. Damping Method
Note: Because fluid damping is not supported, the FDAMP line should not be used for spectral wind analysis.
Spectral Wind Data
Spectral wind data is specified on the SPCWIN line immediately following the LOAD header. Designate the extreme wind analysis option ‘EX’ in columns 8-9.
By default, 600 seconds is used as the mean wind speed averaging time used to calculate the dynamic amplification factors. This value may be overridden by entering an averaging time override in columns 39-44.
For each wind speed to be analyzed, a Harris wind spectrum is created based on the wind velocity at the reference height along with the spectrum reference length and surface roughness parameters input by the user. The program uses this generated Harris spectrum to determine model responses. Enter the reference length and surface roughness to be used for the Harris spectrum in columns 45-50 and 51-56, respectively.
By default, the program calculates the spatial correlation constant, enter ‘SK’ in columns 35-36 if a spatial correlation constant is not to be used.
The following shows the input for a spectral extreme wind analysis. Default values for wind averaging time, Harris spectrum reference length and roughness coefficient are to be used.
Output Options
By default the program creates a common solution file containing end forces, stresses, reactions and displacements for each wind load case specified in the Seastate input file.
The program also has the ability to plot a generalized force spectrum and/or a response spectrum for each wind speed. Enter ‘PL’ in columns 14-15 and 17-18 respectively to output generalized force and response spectra.
Enter the print level desired in columns 11-12 as follows:
‘MD’- Moderate print level containing one page of output for each wind analyzed
‘MX’ - Maximum print containing detailed output including spectrum for each wind analyzed. Static + Wind Combinations
The Dynamic Response has the ability to optionally combine spectral wind results with static results as part of the extreme wind analysis. When using this feature, the program creates a wind + static combination for each wind load case. If a different joint check and member check factors are specified however, two combinations are created for each wind load case.
Note: This feature requires that the static solution file exist prior to execution of the spectral wind analysis.
The wind and static combination information is input using the STCMB line. Enter the factor to be applied to the wind loads when combined with the static loads for the purpose of member and plate element check in columns 8-12. The factor to be applied to wind loads when combined with static loads for joint check is input in columns 13-17. Enter each of the static load cases to be combined with the seismic load cases and the load factor to be applied.
For example, 105% of load cases 8 and 9 contained in the static solution file are to be combined with the wind solution. For same factor wind load case factor is used for element check and joint can check.
Note: The STCMB line should follow the SDAMP, FDAMP and MODSEL lines in the input file.
Combining with Static Results Manually
The program creates a common solution file containing end forces, stresses, reactions and displacements for each wind load case specified in the Seastate input file. Because these results are obtained by combining modal results using RMS techniques, end forces, stresses, etc. have no sign associated and are taken as all positive values. Therefore, when combining spectral wind results with static results manually, the PRST and PRSC combine options must be used.