Welded portal frame eaves moment connection

This is a selected chapter from book Component-based finite element design of steel connections by prof. Wald et al. The chapter is focused on verification of welded portal frame eaves moment joint, mainly the component column web panel in shear.

Description

In this chapter, the component-based finite element method (CBFEM) for a welded portal frame eaves moment connection is verified on the component method (CM). An open section beam is welded to an open section column. The column is stiffened with two horizontal stiffeners opposite to beam flanges. Compressed plates, e.g. horizontal stiffeners of a column, column web panel in shear, compressed beam flange, are limited to 3rd class to avoid buckling. The rafter is loaded by shear force and bending moment.

Analytical model

Five components are examined in the study, namely the web panel in shear, the column web in transverse compression, the column web in transverse tension, the column flange in bending, and the beam flange in compression. All components are designed according to EN 1993-1-8:2005. Fillet welds are designed not to be the weakest component in the joint. The verification study of a fillet weld in a stiffened beam-to-column joint is in chapter 4.4.

Web panel in shear

The thickness of the column web is limited by slenderness to avoid stability problem; see EN 1993‑1‑8:2005, Cl 6.2.6.1(1). A class 4 column web panel in shear is studied in chapter 6.2. Two contributions to the load capacity are considered: resistance of the column panel in shear and the contribution from the frame mechanism of the column flanges and horizontal stiffeners; see EN 1993‑1‑8:2005, Cl. 6.2.6.1 (6.7 and 6.8).

Column web in transverse compression

Effect of the interaction of the shear load is considered; see EN 1993-1-8:2005, Cl. 6.2.6.2, Tab. 6.3. Influence of longitudinal stress in the column panel is considered; see EN 1993-1-8:2005, Cl. 6.2.6.2(2). The horizontal stiffeners are included in the load capacity of this component.

Column web in transverse tension

Effect of the interaction of the shear load is considered; see EN 1993-1-8:2005, Cl. 6.2.6.2, Tab. 6.3. The horizontal stiffeners are included in the load capacity of this component.

Column flange in bending

Horizontal stiffeners brace column flange; this component is not considered.

Beam flange in compression

The horizontal beam is designed to be class 3 cross-section or better to avoid buckling.

Overview of the considered examples and the material are given in the Tab. 9.1.1. Geometry of the joint with dimensions is shown in Fig. 9.1.1. The considered parameters in the study are beam cross-section, column cross-section, and thickness of the column web panel.

Tab. 9.1.1 Examples overview

Example
 Material  BeamColumnColumn stiffener 
 fyfuE\(\gamma_{M0}\)\(\gamma_{M2}\)SectionSectionbsts
 [MPa][MPa][GPa][-][-]  [mm][mm]
IPE14023536021011,25IPE140HEB2607310
IPE16023536021011,25IPE160HEB2608210
IPE18023536021011,25IPE180HEB2609110
IPE20023536021011,25IPE200HEB26010010
IPE22023536021011,25IPE220HEB26011010
IPE24023536021011,25IPE240HEB26012010
IPE27023536021011,25IPE270HEB26013510
IPE30023536021011,25IPE300HEB26015010
IPE33023536021011,25IPE330HEB26016010
IPE36023536021011,25IPE360HEB26017010
IPE40023536021011,25IPE400HEB26018010
IPE45023536021011,25IPE450HEB26019010
IPE50023536021011,25IPE500HEB26020010
Example
 Material  BeamColumnColumn stiffener 
 fyfuE\(\gamma_{M0}\)\(\gamma_{M2}\)SectionSectionbsts
 [MPa][MPa][GPa][-][-]  [mm][mm]
HEB16023536021011,25IPE330HEB16016010
HEB18023536021011,25IPE330HEB18016010
HEB20023536021011,25IPE330HEB20016010
HEB22023536021011,25IPE330HEB22016010
HEB24023536021011,25IPE330HEB24016010
HEB26023536021011,25IPE330HEB26016010
HEB28023536021011,25IPE330HEB28016010
HEB30023536021011,25IPE330HEB30016010
HEB32023536021011,25IPE330HEB32016010
HEB34023536021011,25IPE330HEB34016010
HEB36023536021011,25IPE330HEB36016010
HEB40023536021011,25IPE330HEB40016010
HEB45023536021011,25IPE330HEB45016010
HEB50023536021011,25IPE330HEB50016010
Example
 Material  BeamColumn Column stiffener 
 fyfuE\(\gamma_{M0}\)\(\gamma_{M2}\)SectionSectiontwbsts
 [MPa][MPa][GPa][-][-]  [mm][mm][mm]
tw423536021011,25IPE330HEA320416010
tw523536021011,25IPE330HEA320516010
tw623536021011,25IPE330HEA320616010
tw723536021011,25IPE330HEA320716010
tw823536021011,25IPE330HEA320816010
tw923536021011,25IPE330HEA320916010
tw1023536021011,25IPE330HEA3201016010
tw1123536021011,25IPE330HEA3201116010
tw1223536021011,25IPE330HEA3201216010
tw1323536021011,25IPE330HEA3201316010
tw1423536021011,25IPE330HEA3201416010
tw1523536021011,25IPE330HEA3201516010
tw1623536021011,25IPE330HEA3201616010

Fig. 9.1.1 Joint geometry and dimensions

Numerical model

Nonlinear elastic-plastic material status is investigated in each layer of an integration point. Assessment is based on the maximum strain given according to EN 1993-1-5:2006 by the value of 5%. 

Global behavior

Comparison of the global behavior of a portal frame moment connection, described by moment-rotation diagram, is presented. Main characteristics of the moment-rotation diagram are initial stiffness, elastic resistance, and design resistance. An open section beam IPE 330 is welded to a column HEB 260 in the example. A portal frame moment connection with horizontal stiffeners in the column is considered according to component method as a rigid joint with Sj,ini = ∞. Therefore a joint without horizontal stiffeners in the column is analyzed. The moment-rotation diagram is shown in Fig. 9.1.2, and the results are summarised in Tab. 9.1.2. The results show very good agreement in initial stiffness and joint global behavior.

Tab. 9.1.2 Rotational stiffness of a portal frame moment connection in CBFEM and CM

  CMCBFEMCM/CBFEM
Initial stiffness Sj,ini[kNm/rad]48423,758400,00,83
Elastic resistance 2/3 Mj,Rd[kNm]93,393,01,00
Design resistance Mj,Rd[kNm]140,0139,00,99

Fig. 9.1.2 Moment-rotation diagram for a joint without column stiffeners

Verification of resistance

The results calculated by CBFEM are compared with CM. The comparison is focused on the design resistance and the critical component. The study is performed for three different parameters: beam cross-section, column cross-section, and thickness of the column web panel.

An open section column HEB 260 is used in an example where the parameter is beam cross-section. The column is stiffened with two horizontal column stiffeners of thickness 10 mm opposite to the beam flanges. The width of stiffeners is corresponding to the width of beam flange. The beam IPE sections are selected from IPE 140 to IPE 500. The results are shown in Tab. 9.1.3. The influence of beam cross-section on the design resistance of a welded portal frame moment connection is shown in Fig. 9.1.3.

Tab. 9.1.3 Design resistances and critical components in CBFEM and CM

ParameterComponent method
 CBFEM
 ResistanceCritical componentResistanceCritical component
 [kN/kNm] [kN/kNm] 
IPE14024Beam flange in compression27Beam flange in compression
IPE16033Beam flange in compression34Beam flange in compression
IPE18044Beam flange in compression48Beam flange in compression
IPE20059Beam flange in compression67Beam flange in compression
IPE22077Beam flange in compression80Beam flange in compression
IPE24098Beam flange in compression103Beam flange in compression
IPE270113Beam flange in compression125Beam flange in compression
IPE300142Web panel in shear142Beam flange in compression
IPE330155Web panel in shear145Web panel in shear
IPE360168Web panel in shear167Web panel in shear
IPE400186Web panel in shear183Web panel in shear
IPE450209Web panel in shear202Web panel in shear
IPE500231Web panel in shear223Web panel in shear

Fig. 9.1.3 Sensitivity study of beam size in a portal frame moment connection

An open section beam IPE330 is used in an example where the parameter is column cross-section. The column is stiffened with two horizontal column stiffeners with a thickness of 10 mm opposite to the beam flanges. The width of stiffeners is corresponding to the width of beam flange. The combined width of stiffeners is 160 mm. The column sections are selected from HEB 160 to HEB 500. The results are shown in Tab. 9.1.4. The influence of column cross-section on the design resistance of a welded portal frame moment connection is shown in Fig. 9.1.4.

Tab. 9.1.4 Design resistances and critical components of a moment connection in CBFEM and CM

ParameterComponent method
 CBFEM
 ResistanceCritical componentResistanceCritical component
 [kN/kNm] [kN/kNm] 
HEB16073Web panel in shear70Web panel in shear
HEB18084Web panel in shear88Web panel in shear
HEB200103Web panel in shear101Web panel in shear
HEB220116Web panel in shear124Web panel in shear
HEB240139Web panel in shear139Web panel in shear
HEB260155Web panel in shear145Web panel in shear
HEB280170Web panel in shear179Beam flange in compression
HEB300198Web panel in shear196Beam flange in compression
HEB320216Web panel in shear226Beam flange in compression
HEB340226Beam flange in compression240Beam flange in compression
HEB360228Beam flange in compression245Beam flange in compression
HEB400234Beam flange in compression251Beam flange in compression
HEB450241Beam flange in compression258Beam flange in compression
HEB500248Beam flange in compression266Beam flange in compression

Fig. 9.1.4 Sensitivity study of column size in a portal frame moment connection

Third example presents a portal frame moment connection made out of an open section beam IPE 330 and column HEA 320. The parameter is the thickness of the column web. The column is stiffened with two horizontal column stiffeners with a thickness of 10 mm and width 160 mm. The column web thickness is chosen from 4 to 16 mm. The results are summarised in Tab. 9.1.5. The influence of column web thickness on the design resistance of a welded portal frame moment connection is shown in Fig. 9.1.5.

Tab. 9.1.5 Design resistances and critical components of a moment connection in CBFEM and CM

ParameterComponent methodCBFEM 
 ResistanceCritical componentResistanceResistance
 [kN/kNm] [kN/kNm][kN/kNm]
tw482Web panel in shear99Web panel in shear
tw594Web panel in shear115Web panel in shear
tw6106Web panel in shear131Web panel in shear
tw7118Web panel in shear147Web panel in shear
tw8130Web panel in shear162Web panel in shear
tw9142Web panel in shear177Web panel in shear
tw10155Web panel in shear190Beam flange in compression
tw11167Web panel in shear203Beam flange in compression
tw12179Web panel in shear216Beam flange in compression
tw13191Web panel in shear227Beam flange in compression
tw14203Web panel in shear236Beam flange in compression
tw15215Beam flange in compression240Beam flange in compression
tw16222Beam flange in compression241Beam flange in compression

Fig. 9.1.5 A sensitivity study of column web thickness

To illustrate the accuracy of the CBFEM model, the results of the parametric studies are summarized in a diagram comparing the resistances of CBFEM and component method; see Fig. 9.1.6. The results show that the difference between the two calculation methods is less than 5%, which is a generally acceptable value. The study with parameter column web thickness gives higher resistance for CBFEM model compared to component method. This difference is caused by considering welded cross-sections. The transfer of shear load is in component method considered only in web and contribution of the flanges is neglected.

Fig. 9.1.6 Verification of CBFEM to CM

Benchmark example

Inputs

Column

  • Steel S235
  • HEB260
  • Column offset over beam: 20 mm

Beam

  • Steel S235
  • IPE330

Column stiffeners

  • Thickness ts = 10 mm
  • Width 80 mm
  • Opposite to beam flanges

Weld

  • Beam flange: fillet weld throat thickness af  = 9 mm
  • Beam web: fillet weld throat thickness aw  = 5 mm
  • Butt weld around stiffeners

Outputs

  • Design resistance in shear VRd = –145 kN
  • Design resistance in bending MRd = 145 kNm
  • Critical component: Column web panel in shear

Sample files

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