Frequently Asked Questions
Seattle May 04 FAQ : ETABS & Steel Design
1. When will the IBC 2003 code be introduced in ETABS?

All CSI programs including ETABS version 9, SAP2000 version 9 and SAFE version 8 will include the IBC 2003 code. ETABS 9 will be released later this summer.


2. In Steel Design, sometimes the beam/column is not overstressed but b/t ratio is not satisfied. How can the user be notified that there is a problem without looking in the 'Details' for every beam/column?

You can find information for all steel frame elements in the steel frame output summary. In this file, you will be able to see which elements do not meet slenderness requirements and/or have any other design warnings. You can print this text file from File>Print Tables>Steel Frame Design>output summary.


3. Where can the diaphragm accelerations be found for the Response Spectra in the output?

The diaphragm accelerations can be viewed under the Display menu>Set output table mode>displacements>press 'select load case'>select the response spectrum load case>select diaphragm accelerations from the pull down menu.


4. Can you apply a torsional load on a specific point upon a rigid or flexible diaphragm?

Currently, if you apply a torsional load on a point, it must be included in the rigid diaphragm or connected to the rest of the structure through a member. We are in the process of allowing an assembly of points to be declared as a flexible diaphragm for book keeping purposes in which case the torsional load will be distributed based upon certain rules.


5. How does ETABS handle the lateral stiffness of filled and unfilled decks?

For unfilled decks, ETABS only considers the deck material and deck shear thickness for the stiffness matrix. These values can be found under Define>Deck sections>modify/show properties. For filled decks, ETABS determines the stiffness by the values of the slab depth and the properties of the concrete. Different stiffnesses are used for the 2 deck directions i.e. along the flutes and orthogonal to the flutes becuase of different thicknesses of concrete fill.


6. Is the deck considered an isotropic material or will there be different stiffnesses in each direction?

ETABS considers the deck as an isotropic material. Isotropic behavior is usually assumed for steel and concrete, although that is not always the case. The behavior of an isotropic material is independent of the direction of loading. In addition, the shearing behavior is uncoupled from the extensional behavior and it is not affected by temperature change. (See above)

7. Is there a way to assign a global deflection limit to be set by the user at the start of the composite beam design?

Yes, In ETABS you can set global deflection limits. If you select all of your composite beam elements, then go to Design>Composite Beam Design>View/Revise Overwrites>Deflection. You will see some rows that have 'abs'. This is where you can assign as absolute global deflection for all selected members.