Response Spectrum Analysis to NZS 4203
An Excel spreadsheet, shown below, is available to assist in the use of Microstran Response Spectrum Analysis of structures to NZS 4203. The procedure is described briefly in notes at the top of the spreadsheet. The spreadsheet calculates scale factors that have to be entered in Microstran dialog boxes during the response spectrum analysis.
February, 2000: The spreadsheet now interpolates for values of period and ductility factor that are not equal to values tabulated in the code.
Values shown in the spreadsheet relate to this structure:
The spreadsheet is available at Free Stuff.
| MICROSTRAN RESPONSE SPECTRUM ANALYSIS - NZS4203 PART 4 | ||||
| PROCEDURE: | ||||
| 1. Do dynamic analysis without RSA box checked. | ||||
| 2. File > List/Edit File command, then choose Dynamic Log. | ||||
| 3. Find fundamental period for direction of interest. | ||||
| 4. Enter values shown in red or orange. Do not change anything else. | ||||
| 5. Do static analysis with empty load case for RSA results. | ||||
| 6. Repeat dynamic analysis with… | ||||
| a. RSA box checked. | ||||
| b. Green value entered in Response Spectrum dialog. | ||||
| c. Response spectrum curve A1, B1, or C1 selected. | ||||
| 7. Check dynamic log for 90% mass participation. | ||||
| 8. Analyse > Response Spectrum then: | ||||
| In Dynamic Load Case Scale Factors dialog… | ||||
| - transfer Reaction value to blue value below. | ||||
| 9. Repeat static analysis. | ||||
| 10. Repeat dynamic analysis with… | ||||
| a. RSA box checked. | ||||
| b. Magenta value entered in Response Spectrum dialog. | ||||
| c. Response spectrum curve A1, B1, or C1 selected. | ||||
| 11. Analyse > Response Spectrum | ||||
| 12. Create Input/Analysis report and check base shear | ||||
| for earthquake case. | ||||
| Frequency of first mode, Hz = | 2 | |||
| Fundamental trans. period of vibration, T1 = | 0.50 | sec. | ||
| Site subsoil category = | a | (Rock=a - Deep soil=c) | ||
| Total seismic weight of structure, Wt = | 5515 | kN | ||
| Structural ductility factor, u | ||||
| (Ratio: Max. displacement/Yield displacement) = | 3.00 | (1.00 to 10.00) | ||
| Structural performance factor, Sp = | 0.67 | (Always 0.67 ?) | ||
| Risk factor for structure = | 1.0 | (0.6 to 1.3) | ||
| Zone factor, Z = | 0.6 | (0.6 to 1.2) | ||
| Limit state factor, Ls = | 0.1667 | |||
| Limit state factor, Lu = | 1.0 | |||
| Equivalent Static Method: | a | b | c | |
| Serviceability limit state - | ||||
| Serviceability - Ch(T1,1) = | 0.63 | 0.77 | 1.00 | |
| Ch(T1,1)*Sp*R*Z*Ls = | 0.0422 | 0.0516 | 0.0670 | |
| Lateral force coefficient, C = | 0.0422 | |||
| Horizontal seismic shear force, V = | 233 | kN | ||
| Ultimate limit state - | ||||
| Ultimate - Ch(T1,u) = | 0.26 | 0.32 | 0.37 | |
| Ch(T1,u)*Sp*R*Z*Lu = | 0.1045 | 0.1286 | 0.1487 | |
| For site subsoil category, this = | 0.1045 | |||
| Lateral force coefficient, C = | 0.1045 | (Not less than 0.03) | ||
| Horizontal seismic shear force, V = | 576 | kN | ||
| Modal Response Spectrum Method: | ||||
| Serviceability limit state - | ||||
| Sp*R*Z*Ls = | 0.0670 | |||
| Microstran RSA scale factor = | 0.66 | |||
| Ultimate limit state - | ||||
| Sp*R*Z*Lu = | 0.4020 | |||
| Microstran RSA scale factor = | 3.94 | (Use this in first run with u=1 spectrum to obtain Vbase(1)) | ||
| Combined modal base shear, Vbase(1) = | 1136 | (Insert value from Microstran) | ||
| Design spectrum scaling factor, Sm1 = | 0.41 | |||
| Modal analysis scaling factor, Km = | 1.0 | (0.8 or 1.0) | ||
| 4.6.2.7(b) C = | 0.1045 | |||
| Design spectrum scaling factor, Sm2 = | 0.51 | |||
| Sm = | 0.51 | (Max. of Sm1, Sm2) | ||
| Sm*Sp*R*Z*Lu = | 0.2040 | |||
| Microstran RSA scale factor = | 2.00 | (Use this in final run with u=1 spectrum) |
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