Abstract
The behaviour of steel structures is affected by two nonlinearities—the geometric and material nonlinearity—and by the unavoidable presence of imperfections. To evaluate the ultimate capacity of a structure, these effects should be taken into consideration during the design process, either explicitly in the analysis or implicitly through the verification checks. In this context, Eurocode 3 provides several design approaches of different complexity and accuracy. The advantages and disadvantages of these approaches are discussed. Five different methods in conformity with the Eurocode provisions are applied for the design of four moment resisting steel frames of varying slenderness. The influence of nonlinearities and imperfections in respect to the slenderness of the structure is illustrated. The examined methods are compared in terms of the predicted ultimate capacity and their efficiency is assessed against the most accurate between them, i.e., an advanced geometrically and materially nonlinear analysis. It is shown that considerable differences arise between the methods. Nevertheless, except for the commonly used 2nd order analysis followed by cross-section verifications, the remaining methods are mostly on the safe side.
Highlights
One of the major challenges when designing a structure is to strike a balance between safety and economy
Concerning steel structures, the European Standard dedicated to their design, Eurocode 3 [1], as well as the American Standard AISC 360 [2], do not impose a single design method but provide several alternatives instead
The following five methods sorted in decreasing order regarding the complexity of the analysis theory employed but in increasing order regarding the complexity of the required verification checks are examined: 1. GMNIA: Geometrically and Materially Nonlinear Analysis with Imperfections 2
Summary
One of the major challenges when designing a structure is to strike a balance between safety and economy. Concerning steel structures, the European Standard dedicated to their design, Eurocode 3 [1], as well as the American Standard AISC 360 [2], do not impose a single design method but provide several alternatives instead. The selection of the most suitable design method for the problem at hand is an important issue, demanding guidance. The various design methods differ in the analysis theory employed and the design checks subsequently required. Each method results in a different level of safety and economy, since it approaches the behaviour of the structure with varying degree of accuracy.
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