In the following section it will shown how to make seismic load combinations according to Italian code DM 14/01/2008 with ARSA 2011 for a building of Service Class III.
STEP 1. Check in the job preferences that DM 14/01/2008 is the active code for load combination and seismic loads as in the image below
STEP 2. From “Analysis type” add a new modal analysis. Considering a reinforced concrete structure, a damping factor of 5% will be used. Eccentricity will be not activated in modal analisys parameters.
STEP 3. Add a new Seismic Analysis by selection the code DM 14/01/2008. The following window will appear; set the correct parameters for Cu, Vn
STEP 4. Click on the “Response spectrum parameters” button. Select a site from the “ISTAT” Database. If you click on “Coordinate grid” button a map of seismic ag will appear
STEP 5. After click on “ok” button, on the main window, select which limits states must be considered (reference table C7.1.I). In this case will be considered SLD (for resistance checks), SLO (for displacement check), SLV(for resistance check) and also SLC if necessary. See table C7.1.I
STEP 6. Click on the “Calculations of q factors” button. This utility, available as Robot Extension, helps to set different behaviour factors for different directions. Set the following parameters and click on “Save as qx” button
Then set the following parameters and click on “Save as qy” and “Save as qz” buttons.
click on ok. Q factor values will be saved and will appear in the main window
STEP 7. Set eccentricity values by clicking on “Eccentricity definition” button.
Then click on “ok” two times.
About 200 seismic load cases will be generated
STEP 8. Set correct nature for every seismic load combinations. In order to do that open the load table and activate the conditions tab.
Set all seismic SLC and SLV combination nature as “Sismiche SLU”, SLO as “Sismiche SLE”. You can use a combination of CTRL and shift in order to do that. For SLD, for this type of structure, you can leave only the combinations with eta = 2/3 and set its nature as “Accidental” limit state as below according to chapter 22.214.171.124 of Italian code. For this type of combinations for concrete structure gamma c will be considered equal to 1.
STEP 9. Activate automatic combinations with the following settings
It is important to check SIS-SLU and SIS-SLE.
Next tutorial will be available soon - Plate calculations in ARSA 2011 and Reinforcement drawing in ASD 2011 according to DM 14/01/2008