Steel structures are widely used in the construction industry as they are easily available and take less time in fabrication.
We were given an office building plan and asked to design it.
- Material used was Steel A9950
- Software used are SAP 2000
The design of steel frame in sap2000 is done. Considered frame is “pinned” which means that it resists lateral forces using a bracing system.
Only frame A-A was modeled to keep things simple and relatively accurate. Loads were first assumed according to ASCE 7-10 and then were distributed on frame A-A. Analysis was run and then using ASCE 7-10 load combinations sections were designed using sap auto list. AUTO list is a library of all the ASCE approved sections that we imported into SAAP. SAAP later uses this list to provide us preliminary design sections.
Load calculations are done for dead, live, wind and roof cases. Detailed calculation are out of scope of this text and can be provided on request.
Analysis of model:
Sketch of model :
No templates were selected at the start of the model, a grid model was prepared keeping in view of the small details of the frame so that it can be easily drawn .
Definition of sections
Following sections were assigned to corresponding members so that they can be designed separately. Steel used in all cases was A9950
Each Property was assigned to suitable autoselection list of different sections so that Sap2000 designs them according to that list.
Definition of Load Pattern
Following load patterns were defined which were applicable to our model
- Live Load
- Wind Load
- Dead Load
- Roof Load
Definition of Load Combinations:
Five different Combinations ASCE 10-07 related to our case were feeded to sap to get analysis result for the maximum possible case
Assign Pin Releases:
As our frame was not moment resisting frame moment end releases (hinges) were assigned at the joints so that moment doesn’t get transferred from one section to another
Shear Force Diagram:
Axial Force Diagram:
Bending Moment Diagram:
Design was done by sap2000 both in LRFD and ASD . During verification we found out that LRFD sections are lighter and economical.