Analyse Structure
Selecting this option initiates the analysis process, which comprises the following stages:
- Data check
- Included files check
- Data decomposition for analysis
- Analysis
- Results creation
Error or warning messages may result amongst which the following benefit from further explanation:
| Warning: ##% of load n may be off structure |
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| This message is issued when the total load specified by the user does not equal the load applied to the structure. This usually arises when the boundary of the load, or one or more wheels of a vehicle, falls partially outside the boundary of the grillage/line beam. 'n' is the load case reference number (see Structure Basic Load Cases). |
| Warning: Reactions differ from applied loading. Check model conditioning. |
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| For certain load cases (principally the highway loading cases) the program compares the total applied load with the total reaction force. These values should of course be equal and opposite. If there is a significant difference it is likely that the model is ill-conditioned, and all the results should be disregarded. A model is ill-conditioned if the stiffness matrix is unstable and not accurately inverted. This may occur if, for example, there are large differences in stiffness between members, or if there are large differences in length between adjacent members. |
The length of time for each stage of analysis depends on a number of factors. 'Preparing data' will take longer than normal when complex RC beams have been used, or when lane loads have been applied to a curved carriageway. 'Analysing' is dependent on the density of the mesh members and the number of load cases. Naturally the speed of the CPU and disk sub system of your computer will also affect the time taken.
The 'preparing data' phase will be shorter for second and subsequent analysis runs, and also following an influence surface calculation, provided that the structure geometry and section data have not been edited in between times.
An icon on the bottom right-hand corner of the form gives access to the Analysis Log file which records structure and load case statistics, analysis details and data input error messages. (This is not applicable for line beam analysis).
If the model is large, or has a large number of loadcases then it is possible that the default amount of virtual memory reserved for analysis is insufficient, resulting in an 'OVERFLOW' message. It can be reset in the Memory Settings form.
Hint: When 'browsing' data, use the Cancel button (or Esc key) to exit forms. Using OK will force a re-check of the structure data.