Steel member design

image\ebx_-1773499217.gif Throughout this chapter it can be assumed that all information applies equally to all of the supported steel member design codes unless specifically stated otherwise.


This chapter describes in detail the data required to be input before a design or check can proceed. It discusses the internal methods, philosophies and assumptions that the program uses as it designs or checks members, and it explains how to initiate the actual design or checking process once the steel member design data has been input.



Before you use the steel member design module, you should read all of the assumptions described later in this chapter (see also "Steel member design/check assumptions") to verify that its performance and capabilities are adequate for your situation. It is up to you to determine whether or not the steel member design module is suitable for your requirements.



Adjustments are required when designing or checking US HSS sections due to the practice of some steel manufacturers producing HSS sections with a wall thickness at the very low end of what the specifications allow. To account for this, the US section libraries supplied with SPACE GASS 12.27 and later include adjustments to the HSS section properties (depending on the type of HSS section) and no extra adjustments are made to their properties during an AISC 360 design or check. In SPACE GASS 12.26 and earlier, the US section libraries contained non-adjusted properties for HSS sections and so to allow for this their wall thickness was multiplied by 0.93 during an AISC 360 design or check.


It is therefore important that you match the version of the US library with the same version of SPACE GASS, otherwise unsafe designs of HSS sections could result. It is also important that you don't use HSS sections from SPACE GASS 12.26 and earlier with other non-US design codes.


The steel member design module is a general purpose design and code checking program which reads the frame analysis output data, calculates the critical location and load case for each member and then selects the most suitable steel member size from a library of standard sections. Alternatively, you may specify a steel member size to be checked and the program determines whether or not the member is adequate. For a given frame, you can specify any selected number of members to be designed or checked.


The design module is also capable of passing the designed steel sizes back into the frame analysis data and re-analysing the structure. This process can be iterated until the results converge. It usually only takes two or three iterations.


During the design/check phase SPACE GASS automatically calculates the load factor for limit states codes or combined stress ratio for working stress codes at numerous stations along each member. It considers yielding of the cross section, lateral buckling, slenderness ratios, and all possible combinations of shear, tension, compression and bending for both in-plane and out-of-plane failure.


image\ebx_-1773499217.gif The steel member design module doesn’t consider torsional effects.


After all specified members have been designed or checked, a detailed report can be produced for each member showing the critical location or segment on the member, the critical load case, section properties, effective lengths, and the complete computations involved in the design. Sections of the report can be suppressed if required. A color-coded graphical representation of the design/check results can also be displayed.


The SPACE GASS steel member design module can handle most types of steel members including beams, columns, ties, struts, braces, and members subjected to combinations of axial loads, shear forces and bending moments (uniaxial or biaxial).


All references to BS5950 in this document apply to BS5950-1:2000. Although SPACE GASS still has a design module for BS5950:1990, it is now obsolete and is not referred to in this document.


The AISC-LRFD, EUROCODE 3, AS4100, NZS3404, BS5950, IS800 and HK CP2011 modules assume that second order effects have been taken into account by a second order elastic analysis. Moment magnification is not considered.


Refer to "Steel member input methods" for details on how to input steel member design data.


Refer to "Running a steel member design" for details on how to perform a steel member design.


Refer to "Steel member design results" for details and interpretation of the results of a steel member design.