Steel Design Codes Research Articles

Developments in modern steel design standards

Abstract We are experiencing world-wide the later phases of a transition from deterministic allowable stress design standards to probability-based limit states design. This paper is a review of the history of modern steel design code developments. The bases for probabilistic design will be presented. Experimental and theoretical research on the behavior of steel structures, as it relates to code issues, will be discussed. Practical considerations of code development and design office acceptance will be examined. Current research on probability-based design will be reviewed. The paper will conclude with research needs and an outlook to the future of structural steel design codes. The paper will especially emphasize the experience with the limit states specifications of the American Institute of Steel Construction (buildings).

Microcomputer‐Based Optimization of Steel Structures in Professional Practice

The paper concerns the computer‐automated design of least‐weight structural steel frameworks, where members are automatically sized using commercial standard steel sections in full conformance with steel design code provisions for strength/stability and stiffness. The necessary features and functions of such a design system are first identified. Two alternative approaches to the optimal design of steel frameworks are then discussed. Finally, a microcomputer software system is applied for the least‐weight design of a steel framework comprised of a variety of member types and subject to a number of load effects. A number of alternative designs of the framework are conducted to illustrate differing optimization strategies and corresponding outcomes.

Least‐Weight Design of Steel Frameworks Accounting for P‐Δ Effects

The paper addresses the problem of efficiently sizing steel frameworks to account for nonlinear load‐displacement (P‐Δ) effects. The design objective is to produce a minimum weight structure while simultaneously ensuring acceptable levels of combined first‐order and second‐order displacements and stresses in accordance with the governing steel design code. Conventional fabrication conditions are imposed and members are sized using commercially available standard sections. The design method involves coordinated use of second‐order elastic analysis, sensitivity analysis and optimization techniques within an iterative synthesis process. For a given trial design of the structure, second‐order elastic analysis and first‐order sensitivity analysis are together employed to approximate the performance constraints on displacements and stresses as explicit linear functions of the member‐sizing variables. Optimization techniques are then applied to find an improved (lower weight) design for the structure, which satisfies all performance constraints. The formulation of the design problem is updated for the new design and the synthesis process is repeated until convergence to the least‐weight structure occurs. The synthesis process is implemented in a comprehensive computer system developed for the least‐weight design of steel frameworks. The designs of two building frames are considered from a variety of viewpoints to illustrate both the features of the design method and some underlying issues related to second‐order design.

A comparative parametric study of the AISC 1978, DIN 18–800 (1) and BS5950 steel design codes

This is a comparative study of three different steel design codes, each with a unique philosophy in their approach to the design of structural members. The three compared are the AISC 1978 design code, DIN 18–800 Part 1/4114 German design code and the BS5950 British design code. A brief description of the major aspects of the design codes is provided along with examples of how the differences affect the design of typical structures.

Computer-automated synthesis of building frameworks

The paper surveys recent work carried out at the University of Waterloo concerning the computer-automated synthesis of minimum-weight planar steel frameworks. For any number of applied loading schemes, the design of the structure may be constrained by a variety of service and (or) ultimate 'limit-states' performance criteria concerning stresses, displacements, and (or) plastic collapse loads. Fabrication conditions can be imposed to ensure member-continuity and structure-symmetry requirements. Member sizes can be taken as either continuous or discrete variables to the synthesis process, depending on whether custom or commercial-standard sections are available for the design. In the latter case, the structure may be automatically sized using the standard sections specified by a variety of different steel design codes (to date, Canadian Institute of Steel Construction (CISC) and American Institute of Steel Construction (AISC) sections have been investigated).The computer-based design method is iterative in nature and is remarkably effective and efficient. Commencing with an arbitrarily chosen initial 'trial' design, the synthesis process determines the 'minimum-weight' structure satisfying all of the imposed performance and fabrication conditions without further designer intervention. The number of iterations required to achieve the optimal design is generally small and almost totally independent of the complexity of the structure.Three different designs of a building framework are presented to illustrate the scope of the method: limit-states design using CISC sections; working-stress design using AISC sections; and design under elastic and plastic performance criteria using custom sections. Key words: steel, frameworks, standard sections, custom sections, synthesis, minimum weight, limit states, computers, automated.