D8.A.7 Seismic Detailing per Section 12

Seismic detailing of steel members per portions of Section 12 of IS 800-2007 can be performed by STAAD.Pro for LSD design.

The program will check seismic detailing requirements when the design parameter SEISMIC (design detailing for earthquake load) has been specified as 1. It is also recommended that an IS 1893 seismic load definition is included in the model.

Additionally, a set of automatic load combinations is included per IS 800 (in the IS 456 / IS 800 code selection) for IS 800 Clause 12.2.3 which is intended for use with these checks. These are:

1.2×DL + 0.5×LL + 2.5×EL
1.2×DL + 0.5×LL - 2.5×EL
0.9×DL + 2.5×EL
0.9×DL - 2.5×EL

Multiple earthquake load (EL) cases will result in multiples of the different load combinations, as each combination will use only one type of earthquake load in one direction.

Note: To limit the design checks to only the pertinent seismic load combinations per Cl. 12.2.3, a LOAD LIST may be used. Otherwise, the checks for Section 12 will be done for all load cases and combinations.

Among the various seismic criteria present in the section 12 of IS800:2007 only compression and tension strength and slenderness are considered as a failure criterion. Detailed output of the seismic checks are provided only for TRACK 2 output. Other TRACK options will only report a seismic provision if it is the critical clause for member checks.

Limitations

Note: This is only available for design using the LFD method. It is not applicable to design using the ASD method.

As the design checks are performed on analytical members (rather than physical members), there are no means by which to ensure provisions of Cl. 12.5.1.2 (i.e., the "strong column, weak beam" design philosophy) are met. That is left to the engineer. Similarly, code checks which require comparison of one member's strength to another are not possible in design checks under STAAD.Pro.

Applicable Code Sections

The following portions of Section 12 have been implemented in STAAD.Pro:

12.2.1 - the R values are derived from the specified frame type. If this differs from the R values manually specified in the seismic load definition, a warning is presented in the output. If the assigned R in the local Z and local Y differs, the program will consider the minimum R.
12.2.3 - the IS 800 load combinations should be manually added or included from automatically generated load combinations
12.3 - the frame type is specified by use of the SSY and SSZ parameters
12.5.1.1
Ordinary concentrically braced frames
- 12.7.1.1 - limits the use of OCBFs in seismic zones IV and V, as well as in seismic zone III when the importance factor is greater than one
- 12.7.1.2 - the bracing type used in the model should be consistent with the SSY and SSZ parameters specified. Members used as bracing should also be specified using the IMM parameter.
- 12.7.2.1
- 12.7.2.2
- 12.7.2.4
- 12.7.2.6
Special concentrically braced frames
- 12.8.1.1
- 12.8.1.2 - the bracing type used in the model should be consistent with the SSY and SSZ parameters specified. Members used as bracing should also be specified using the IMM parameter.
- 12.8.2.1
- 12.8.2.2
- 12.8.2.3
- 12.8.2.5
- 12.8.2.7
- 12.8.4.1
12.10.1.1 - Ordinary moment frames shall not be used in seismic zones IV and V, as well as in seismic zone III when the importance factor is greater than one
Special moment frames
- 12.11.1 - checks the material grades assigned (i.e, the FYLD and FU parameter values assigned) are equal to or higher than grade E250B.
- 12.11.1.1
- 12.11.3.1