Monotonic Response of Exposed Base Plates of Columns: Numerical Study and a New Design Method

Héctor Díaz,Claudio Oyarzo-Vera,Eduardo Nuñez

doi:10.3390/met10030396

Héctor Díaz, Claudio Oyarzo-Vera + Show 1 more

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https://doi.org/10.3390/met10030396

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Abstract

This paper describes a numerical study of the behavior of exposed base plates of columns under the action of axial and bending loads. The aim of this research is to evaluate numerically the failure mechanisms on stiffened and non-stiffened base plates and propose a new design method. The effects of base plate thickness, location of anchor rods, location of stiffeners and tensile strength of anchor rods were considered in the analysis. Sixteen finite elements simulations were performed considering different combinations of the above mentioned parameters. The results show a fragile response in the base plates when high resistance anchor rods are used. The anchor rods worked as fuse elements in base plates with a large thickness or many stiffeners. Additionally, the models with anchor bars located outside of the column flanges showed lower flexural strength and rotational stiffness compared to the models with anchor rods located between column flanges. The simulations showed that the base plate strength was determined by the simultaneous failure mechanisms of two or more components, different to what is stated in current design guides. Finally, the new method is suitable to design base plates with stiffened and not stiffened configurations, which unlike traditional design methods, show a good adjustment with numerical models.

Highlights

IntroductionAn exposed column base consists of several components, such as: column sections, base plate, stiffeners, anchor rods, concrete foundation and shear-lug
The base plates correspond to one of the most frequent column connections of steel structures.These connections are responsible for transferring loads from the superstructure to the foundations.the performance of these connections was deficient during recent seismic events in the USA and Japan, where significant damage and failure of these joint elements was reported [1,2].An exposed column base consists of several components, such as: column sections, base plate, stiffeners, anchor rods, concrete foundation and shear-lug
Each of these components affects the connection’s capacity to withstand axial load, shear load and bending moments. Current design methods, such as those presented in the AISC Steel Design Guide 1 [3], provide design procedures that allow for sizing of the base plate of exposed columns and their anchor rods

Summary

Introduction

An exposed column base consists of several components, such as: column sections, base plate, stiffeners, anchor rods, concrete foundation and shear-lug. Each of these components affects the connection’s capacity to withstand axial load, shear load and bending moments. Current design methods, such as those presented in the AISC Steel Design Guide 1 [3], provide design procedures that allow for sizing of the base plate of exposed columns and their anchor rods. As the current guidelines do not consider joint configurations with stiffeners, the design often specifies plates with thicknesses that is not commercially available [5]

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