CSM Bridge Design - Superpositioning#
The SSD task 
CSM Bridge Design - Superpositioning creates result envelopes for road bridges, that can be used for the design checks.
The superpositioning is based on EN 1990, section 6.4 and 6.5.
Important
In order to use this task it is mandatory that the construction process has been calculated with the task Construction Stages.
Important
The task is only available if Eurocode (possibly plus National Annex) with the category Road Bridges has been selected as design code!
How to use the task#
Select the variable actions for the superposition.
Note
It is only necessary to select the variable actions. The permanent actions (dead load G, creep and shrinkage C, prestressing P) are considered automatically based on the results from the task Construction Stages.
Note
The National Annex for some countries prescribes the usage of formulas (6.10a), (6.10b) from EN 1990 instead of formula (6.10). You have the possibility to select your prefered combination approach with the checkbox that is available in these cases.
Created design envelopes#
Several design envelopes are created for the combinations of EN 1990 for the ulimate (ULS) and seviceability limit states (SLS).
The content of the loadcases that contain the envelopes can be seen in the loadcase title (for further information about the used shortcuts see manual of module MAXIMA, command SUPP).
Note
There are also presuperpositions created, which include only the variable actions. These will be used in the design tasks, where it is important to distinguish between forces that act on the final cross-section (i.e. the variable loads) and forces that act within a construction stage, where the cross-section may not be completed yet. For the corresponding loadcases of the individual envelopes take a look at the following table. The envelopes that contain only the variable actions are assigned to special actions (noted in the table) and can also be adressed via this action.
Combination |
Created loadcases final superposition |
Created loadcases presuperposition (only variable actions) |
|---|---|---|
rare (characteristic) |
1121-1139 |
1141-1199 (Y_1) |
nonfrequent |
1221-1239 |
1241-1299 (Y_2) |
frequent |
1321-1339 |
1341-1399 (Y_3) |
permanent |
1421-1439 |
1441-1499 (Y_4) |
non-cyclic variable loads (settlement, temperature) for fatigue design |
1821-1839 |
1841-1899 (Y_8) |
superposition with factor 1.0 |
1921-1939 |
1941-1999 (Y_9) |
ultimate limit state |
2121-2139 |
2141-2199 (Y_D) |
accidental |
2521-2539 |
2541-2599 (Y_A) |
earthquake |
2601-2699 |
2601-2699 (Y_E) |
fatigue (action FAT) |
2821-2839 |
2841-2899 (Y_F) |
for simplified fatigue design checks (using LM1) |
2921-2939 |
2941-2999 (Y_G) |
Note
Some combinations are only created if certain actions (fatigue, seismic actions) are selected.
Result Sets usually have more than 10 results, so they need more than 20 min-max loadcases. Therefore their combinations are stored in higher loadcase numbers (see following table).
Combination |
Created loadcases final superposition |
Created loadcases presuperposition (only variable actions) |
|---|---|---|
rare (characteristic) |
91001-91299 |
81001-81899 (Y_1) |
frequent |
93001-93299 (Y_3) |
83001-83899 |
permanent |
94001-94299 (Y_4) |
84001-84899 |
superposition with factor 1.0 |
99001-99299 (Y_9) |
89001-89899 |
ultimate limit state |
95001-95299 (Y_D) |
85001-85899 |
accidental |
96001-96299 (Y_A) |
86001-86899 |
earthquake |
97001-97299 (Y_E) |
87001-87899 |