Comparison of AS 3990 & AS 4100 Design Provisions for Application to Bulk Handling Machinery

Simon Edgar (Senior Structural Engineer)

Abstract: The structural steelwork design of a bulk handling machine in accordance with AS 4324.1 allows a choice between AS 4100, for use of the limit state design approach, or AS 3990 for use of the permissible stress design approach. Intuitively, it would be expected that the design of an AS 4324.1 compliant machine structure using either approach would yield similar design outcomes with similar structural reliabilities. However, numerous differences exist between the detail design provisions of these standards, which can affect the final design outcomes for the design of structural members. This paper explores where the main theoretical differences between the two standards occur for both the existing standard and the proposed revision to AS4324.1, and details the likely practical and economic implications for the overall design of a bulk handling machine.

KEYWORDS: Structural Steel Design, Bulk Handling Machinery, AS 4324.1, AS 4100, AS 3990, Reliability

1. INTRODUCTION

AS 4324.1-1995 is the Australian Standard for Mobile Equipment for Continuous Handling of Bulk Materials, Part 1: General Requirements for the Design of Steel Structures. This standard is currently being revised. The draft revision of the standard was released for public comment in October 2014.

AS 4324.1 offers a machine designer the choice between the use of the limit state design method or the permissible stress design method for structural steel design.

The limit state design approach detailed in AS 4100-1998 Steel Structures is currently the generally accepted method for the design of steel structures such as buildings. AS 4100 was originally published in 1990 and superseded the permissible stress design standard, AS 1250-1981 SAA Steel Structures Code. AS 4100 has since had several revisions and amendments, the latest of which was completed in 2012.

Despite the limit states design method (AS 4100) being the preferred method of designing structural steelwork, it was deemed “necessary to continue the working stress design method for some mechanical structures where the application standards apply” [1]. AS 3990-1993 Mechanical Equipment - Steelwork was written in 1993 for this purpose and is almost unchanged from the previous standard, AS 1250-1981. AS 3990 has not been revised since its first publication.

Intuitively, it would be expected that the design of a bulk handling machine to AS 4324.1 using either the limit states approach of AS 4100 or the permissible stress design approach of AS 3990 would yield similar design outcomes with similar structural reliabilities.

This paper compares the main design provisions of the two structural steelwork design standards permitted to be used for the design of bulk handling machinery to AS 4324.1. This comparison includes the theoretical point of view, detailing areas where ‘theoretical’ differences in design outcomes may occur. It also considers the ‘practical’ viewpoint by detailing the practical differences in overall design outcomes of actual machines based on the results of numerous case studies of existing machine designs.

The paper has been prepared using the loads defined in AS 4324.1-1995 and the changes proposed in the 2014 public comment draft of the forthcoming revision to that standard (which will be termed AS4324.1-2016 in this paper).

The differences in overall design outcomes of actual machines has also been compared between AS 4324.1-1995 and its proposed revision.

TO READ THIS ARTICLE FREE OF CHARGE, PLEASE FILL IN THE BELOW FORM AND OUR TEAM WILL E-MAIL THE FULL DOCUMENT