7/30/2019 Numerical Evaluation of CHS K Joints

1/8

RAPHAEL S. DA SILVA et al.: NUMERICAL EVALUATION OF CHS K JOINTS 1

AbstractThe intensive worldwide use of tubular structural

elements, mainly due to its associated aesthetical and structuraladvantages, led designers to be focused on technological anddesign issues. Consequently, their design methods accuracy plays

a fundamental role when economical and safety aspects areconsidered. Additionally, recent tubular joint studies indicatefurther research needs, especially for some joint geometries. Thisis even more significant for particular failure modes where thefailure load predictions lead to unsafe or uneconomical solutions.In this paper a numerical (i.e. non-linear finite elementsimulations) based on a parametric study is presented for theanalysis of K tubular joints where both chords and braces aremade of circular hollow sections. The proposed model wasvalidated by comparison to the experiments, analytical resultssuggested at the Eurocode 3 and at the new CI DECT formulationand to the classic deformation limits present in the literature.The main variables of the study were the brace diameter to chorddiameter ratio and the thickness to chord face diameter ratio.

These parameters were chosen based on recent studies resultsthat depicted some Eurocode 3 rules discrepancies.

Index TermsSteel Structures, Tubular J oints, NumericalAnalysis, Nonlinear Analysis

I. INTRODUCTIONHE intensive worldwide use of tubular structuralelements, such as the examples depicted in Figure 1,

mainly due to its associated aesthetical and structuraladvantages, led designers to be focused on their technologicaland design issues [1], [2]. Currently there is not still in Brazil

any code specifically devoted to the tubular joint design. Thisfact induces designers to use other international tubular jointdesign codes. Additionally, recent tubular joint studiesindicate that further research is needed, especially for some

particular geometries. This is even more significant for somefailure modes where the collapse load predictions lead tounsafe or uneconomical solutions.

Manuscript received February 29, 2012.

a) Footbridge Rio de Janeiro CHS K and N joints

b) Footbridge Rio de Janeiro CHS K joints

c) Oil exploration platform [3]Fig. 1. Examples of structures using hollow sections in Brazil.

One of the first comprehensive investigation published inthis area was made by Korol and Mirza [4] focusing on a

numerical FE model with shell elements, and indicated a

Numerical Evaluation of CHS K Joints

Raphael S. da Silva1, Luciano R. O. de Lima2, Pedro C. G. da S. Vellasco2,Jos G. S. da Silva2 and Luis F. da Costa Neves3

luciano@eng.uerj.br, vellasco@eng.uerj.br, jgss@eng.uerj.br, luis@dec.uc.pt

1Post Graduate Program in Civil Engineering - UERJ - State University of Rio de Janeiro, Brazil.2Structural Engineering Department - UERJ - State University of Rio de Janeiro, Brazil.

3Civil Engineering Department from University de Coimbra, Portugal

T

7/30/2019 Numerical Evaluation of CHS K Joints

2/8

INTERNATIONAL JOURNAL OF MODELING AND SIMULATION FOR PETROLEUM INDUSTRY, VOL. 6, NO. 1, JUNE 2012 2

simultaneous increase of the joint resistance with the variable and/or with the increase of the variable . The authors alsoreferred to the need of establishing a deformation limit criteriafor those connections. Packer et al. [5] also observed that theconnection resistance increases with the increase of and/orwith the increase of, but they also developed a failure paththeory to estimate the connection plastic load capacity.

Some authors like Zhao and Hancock [6], Zhao [7], Lu andWardenier [8], Cao et al. [9], [10], Kosteski and Packer [11],[12] and Kosteski et al. [13] also observed that both theconnection resistance and the initial stiffness increase with theincrease of and/or with the increase of.

Recently Lu et al. [14], [15] (cited in Kosteski et al. [13]),with results also validated and accepted by Zhao [6],established an approximate 3%d0 deformation limit criteria.This 3%d0 limit (Nu) is nowadays widely accepted and is alsothe value adopted by the International Institute of Welding

(IIW) [20] for the maximum acceptable displacementassociated to the ultimate limit state, while a 1%d0 limit (Ns) isadopted for the serviceability limit state. If the ratio of Nu/Nsis greater than 1.5, the joint strength should be based on theserviceability limit state, and if Nu/Ns < 1.5, the ultimate limitstate controls the design. In the case of CHS joints, Nu/Ns