Capacity Design Method applied to Steel Structures using Robot Structural Analysis Professional

Available in the subscription center the new Italian Country Kit for Robot Structural Analysis Professional. It contains a new engine composed of six tools for seismic verifications of steel structures according to the Italian Code DM 14/01/2008 and a manual with a detailed verification of a mixed steel structure with eccentric vertical links and some concentric bracings. Chapter 7 of Italian Code, concerning Seismic verifications of Steel Structures, is very similar to the correspondent part of Eurocode 8 (Chapter six).

Summary of the main features:

- Support for Moment Resisting Frames, Concentric Bracing Frames, Eccentric Bracing frames and composite structures

- Link between seismic combinations and resistant systems allow the engineer to obtain an efficient design of steel members

- Automatic joints capacity verifications 

 - Support for Exceptional and ULS Seismic combinations with different partial safety factors

- Semi-automatic filter of bracings not in tension

- Advanced code parameters allow to disable some verifications for specific bracings (last storey generally)

- Fully automatic printout composition – two levels of details supported, general and detailed

- Eurocode 8 could be used for the generation of the seismic analysis. Time History and Spectral analysis are also supported

Next post will show the seismic verification of a steel structure using Robot Structural Analysis Professional.

Generation of simulated earthquakes compatible with prescribed Response Spectra in Robot

The procedure presented below for Italian Code DM2008 could be easily adapted for other codes likes EUROCODE 8.

STEP 1. Download and install SIMQKE from http://dicata.ing.unibs.it/gelfi/software/programmi_studenti.html

(if not installed you could install also the common package necessary to run the program)

STEP 2. Select NTC2008 as seismic code or if you have another code directly import spectrum data from the file menu

STEP 3. Set Spectrum parameters (Soil, Service class, Behaviour factor, etc..)

STEP 4. Click on SIMQKE Button

STEP 5. Press Simulated Earthquake button

STEP 6. Export the data and save the txt file. Remove the first two lines from the txt

STEP 7. In Robot add a new spectral analysis

STEP 8. Add a new spectra (Accelaration – period)

 

STEP 9. Convert Accelerogram saved in txt file to Spectrum

Season Greetings

ARSA 2011 Service Pack 5 Available

Service pack 5 available at Autodesk website:

ARSA 2011 Pro 32 bit

ARSA 2011 Pro 64 bit

ARSA 2011

Seismic Load Combinations according to Italian code DM 14/01/2008

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 7.3.7.1 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

Massimo Speziani

New book on Robot and Revit Structure available

Examples of real projects from initial stage to detailing

Analysis of aluminium, reinforced concrete and composites structures

 

 For more information www.shopping24.it

CodeName_Elipsis

Seismic conceptual design of buildings with Robot Structural Analysis

..towards real-time optimization   

A  good conceptual design of a building under seismic load must be pursue following certain criteria, as explained in Eurocode 8: simplicity, uniformity, symmetry and redundancy, torsional resistance, etc.. The above-mentioned principles allow a good response to seismic load and adequate reliability of the numerical analysis. To take into account this guidelines we developed a plug-ins for Robot, Elipsis.

A simple model in Robot Structural Analysis

The plug-ins gets the required information about the building from the model in Robot; the user can select from different models of eccentricity or insert a model from literature. It is possible to run a single analysis on a building and obtain automatically an Excel spreadsheet and export the model in Revit Structure with the results of analysis or start the optimization task and evaluate hundreds solutions.

Analysis results exported to Revit Structure

Automatic table generation in Excel

Preliminary tests on the plug-ins show how, when the building shape became complex, the fast optimization task allow the designer to make better decision in the preliminary stage of the design process and evaluate the impact of different factor on the behavior of the building.

optimization results in modeFRONTIER_ Above, optimal design Below, on the left correlation between parameters and objectives, on the right 3D Explore Graph

This is the first algorithm for structural analysis developed to take advantage of GPU computing power; towards an high optimization in the algorithm we can evalutate about 5000 design solution in three minutes on an old CoreDuo@2,2Ghz with a Nvidia QuadroFX 570. 

Massimo Speziani, Corrado Stampais