Analysis and Design of Steel-Concrete Composite Frame Systems
The lack of clear guidance regarding the value of elastic flexural rigidity (EI) that should be used in the analysis of steel-concrete composite columns is a significant unresolved issue that hinders the design of frame systems that include these members. The common approach of utilizing the rigidity of either the steel or the concrete only tends to be overly conservative. Other approaches that combine the rigidities have not been fully validated for use in strength and stability design procedures or for the determination of lateral deflections. To address this issue, research has been conducted to develop comprehensive recommendations for the elastic flexural rigidity of composite columns. A complimentary goal has been to validate common strength design procedures, including interaction diagrams, axial compression and bending moment anchor points, and analysis procedures to determine required strengths. In this paper, an assessment of current strength design methodologies is presented along with recommendations for potential improvements. Both the AISC Direct Analysis method and the ACI elastic second-order analysis method are investigated. INTRODUCTION The wide availability of structural analysis software packages that perform accurate geometric nonlinear analyses has made second-order elastic analysis design approaches very common in practice. Such design provisions exist for steel-concrete composite members in both the AISC Specification (AISC 2010b), as the Direct Analysis method, and the ACI Code (2011), as the second-order analysis method. However, neither methodology has yet been comprehensively assessed for validity and accuracy, as has been done in the past for structural steel (Kanchanalai 1977; Surovek-Maleck and White 2004) and for reinforced concrete (Hage and MacGregor 1974). This paper presents the results of a large parametric study that has been conducted to assess the current design methodologies with a particular emphasis on the elastic flexural rigidity (EI) recommended for analysis. 2605 Structures Congress 2014 © ASCE 2014
Alternative Approaches for Elastic Analysis and Design of Steel Frames. II: Verification Studies
Two methods for elastic analysis and design of steel framing systems, an American Institute of Steel Construction (AISC) load and resistance factor design (LRFD) based notional load approach and a modified elastic approach, are outlined in Part I. These approaches capture the physical behavior of sway frames more faithfully than present AISC methods and eliminate the need to calculate column buckling loads or effective length factors. In this paper, the results from a comprehensive set of benchmark studies are summarized to establish the accuracy and validity of these two approaches for evaluation of the maximum strength of steel framing members and systems. Comparisons are made to results from rigorous distributed plasticity analyses.
A thin circular plate normally and uniformly loaded over a concentric elliptic patch
ABSTRACT This paper is concerned with the small transverse displacement of a thin circular plate elastically restrained along the circular boundary and subject to uniform normal pressure distributed over the area of an ellipse concentric with the plate. The method of complex potentials is used and the general assumptions relating to the small deflexion theory of thin plates are adopted. Explicit formulae for the bending and twisting moments and shearing forces are given at any point on the boundary and at the centre of the plate.