AS 4100 SUPP 1-1990

This Commentary provides background material to the requirements of AS 4100, Steel structures (revisions of AS 1250-1981, SAA Steel Structures Code, and AS 1511-1984, SAA High-strength Structural Bolting Code). It gives the origin of certain requirements, departures from previous practice and explains the application of certain clauses.

The Standard sets out the minimum requirements for the limit states design, fabrication, erection, and modification of safe, serviceable and durable steel structures. There may be additional requirements not specifically covered that may also have to be considered by designers.Road bridges are covered by the AUSTROADS Bridge Design Code (currently written in limit states format), while railway bridges are covered by the Bridge Design Manual of the ANZRC (currently not written in limit state format). AUSTROADS uses the Standard as the basis of its steel bridge design provisions. Both organizations are represented on the Committee (BD/1) that drafted the Standard.Steel elements less than 3 mm in thickness are excluded for reasons of practicality and concern about corrosion, and because members from thinner material are usually cold-formed and then fall within the scope of AS 1538. In addition, the connections in elements less than 3 mm thick are better handled by the provisions of AS 1538 than by the Standard.The limit of 450 MPa for the yield stress used in design stems from a lack of research data on steel grades above this value, and the applicability of all of the member design provisions for a higher design yield stress cannot be confirmed. Australian steel standards generally contain no steel grades with a specified yield stress above 450 MPa, with the exception of one grade (XF500) in AS 1594. Additional provisions to those in the standards may be required for steels of higher yield stress.The Clause does not preclude the use of steels having a specified yield stress greater than 450 MPa provided that the yield stress used in design ( Note, however, that the use of a steel having a fy) is limited to 450 MPa. specified yield stress greater than 450 MPa is specifically excluded from plastic design by Clause 4.5.2. Hollow section members to AS 1163 are most commonly cold-formed, but have traditionally been designed using the previous editions of the Standard since they were for many years hot-formed. Tests carried out on members manufactured to AS 1163 confirm the applicability of the provisions of the Standard for such members. All other cold-formed members must be designed in accordance with AS 1538. Cold-formed hollow section members to AS 1163 with a wall thickness less than 3 mm should be designed in accordance with AS 1538, since the Clause excludes such members. Composite steel-concrete members, including concrete encased steel members, should be designed using the provisions of AS 2327-SAA Composite Construction Code. The Standard is not intended to be used for thin walled shell or plate structures since such structures are subject to failure modes not addressed in the Standard. It is, however, considered reasonable to design floor plates using the Standard. (See Introduction to Commentary on Section 5.)

First published as AS 4100 Supplement 1-1990.