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Analytical modelling of stress distribution under column base plates
J. Construct. Steel Res. Vol. 46, Nos. I-3, pp. 246, paper number 136, 1998 01998 Elsevier Science Ltd. All tights resexved Printed in Great Britain 0143-974X/98 $19.00 + 0.00 PII: SOl43-974X(98)000113-2 ELSEVIER
Analytical Modelling of Stress Distribution Under Column Base Plates J. Ch. Ermopoulos and G.T. Michaltsos National Technical University of Athens, Civil Engineering Department, Laboratory of Steel Structures, 42 Patission Str. 10682 Athens, Greece Paper Number 136 Full paper on enclosed CD-ROM
This paper deals with the semi-rigid behaviour of steel column bases under static loading consisting of an axial load and a bending moment. The problem is complicated due to the existing non-linearities which introduce difficulties in the research. In particular the non-linear behaviour of the concrete foundation (i.e. the distribution of compressive stresses under the base-plate etc.) is one of the most unpredictable, and the difficulty in determination of the real stress distribution still remains important for these connections. In this study a new methodology is proposed, leading to an analytical model that describes through a mathematical expression the non-linear stress distribution under the base-plate in a simple manner. The column base is classified in three types (rigid, semi-rigid and flexible) depending on the elements that form this connection (base-plate, anchor bolts, material properties etc.). For each particular type, the corresponding necessary parameters are calculated and are introduced into the proposed analytical expressions, which cover the elastic and the elastoplastic behaviour of the connection. Using the equilibrium equations and the geometrical conditions of the model considered, the unknown maximum compressive stress, the width of the compressive area and the tension force of the anchor bolts are obtained, while in the case of plastic behaviour the plastified part of the stress distribution diagram is also determined. Thus a stress distribution which is closed to the real behaviour can be used instead of the uniformly distributed approximation. 0 1998 Elsevier Science Ltd. All rights reserved
KEYWORDS
Stress distribution, tions.
column bases, analytical modelling, base-plate, connec-
Analytical Modelling of Stress Distribution Under Column Base Plates J. Ch. Ermopoulos and G.T. Michaltsos National Technical University of Athens, Civil Engineering Department, Laboratory of Steel Structures, 42 Patission Str. 10682 Athens, Greece Paper Number 136 Full paper on enclosed CD-ROM
This paper deals with the semi-rigid behaviour of steel column bases under static loading consisting of an axial load and a bending moment. The problem is complicated due to the existing non-linearities which introduce difficulties in the research. In particular the non-linear behaviour of the concrete foundation (i.e. the distribution of compressive stresses under the base-plate etc.) is one of the most unpredictable, and the difficulty in determination of the real stress distribution still remains important for these connections. In this study a new methodology is proposed, leading to an analytical model that describes through a mathematical expression the non-linear stress distribution under the base-plate in a simple manner. The column base is classified in three types (rigid, semi-rigid and flexible) depending on the elements that form this connection (base-plate, anchor bolts, material properties etc.). For each particular type, the corresponding necessary parameters are calculated and are introduced into the proposed analytical expressions, which cover the elastic and the elastoplastic behaviour of the connection. Using the equilibrium equations and the geometrical conditions of the model considered, the unknown maximum compressive stress, the width of the compressive area and the tension force of the anchor bolts are obtained, while in the case of plastic behaviour the plastified part of the stress distribution diagram is also determined. Thus a stress distribution which is closed to the real behaviour can be used instead of the uniformly distributed approximation. 0 1998 Elsevier Science Ltd. All rights reserved
KEYWORDS
Stress distribution, tions.
column bases, analytical modelling, base-plate, connec-