Design of Steel Members & Joint to Concrete.pdf

Conceptual Design of Buildings (Course unit code 1C2)

Module C Design of Steel Members and Joints J.P. Jaspart (University of Liège)

European Erasmus Mundus Master Course

Sustainable Constructions under Natural Hazards and Catastrophic Events 520121-1-2011-1-CZ-ERA MUNDUS-EMMC

Conceptual Design of Buildings

Module C – Design of Steel Members and Joints

List of contents Simple joints Examples Hollow section joints Design of column bases Examples

 Simple joints are assumed to transfer no bending moments and should be designed accordingly.  Main typologies: end plate of partial depth; fin plate or web cleats.

- Beyond the EC3-1-8 rules, some additional requirements are provided in the publication European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events

nº 126 of ECCS: “European Recommendations for the Design of Simple Joints in Steel Structures”. These type of joints will be included in the Manual “Design of Joints in Steel and Composite Structures”, ECCS (J.P. Jaspart and K. Weynand). L21 – Simple joints and hollow section joints. Behaviour and design of column bases.

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 A simple joint is designed to resist to axial and shear forces only. As a consequence, the development of bending moment may be potentially unsafe, in particular if the joint presents a reduced ductility.  The "hinge assumption" is safe if, beyond the joint resistance checks, the two following requirements are fulfilled: - the joint possesses a sufficient rotation capacity (to not develop bending moment); - the joint possesses a sufficient ductility (to allow redistribution of forces by the several joint components).

European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events

 With the aim to permit a rotation without increasing too much the bending moment which develops into the joint, the contact between the lower beam flange and the supporting member has to be strictly avoided. L21 – Simple joints and hollow section joints. Behaviour and design of column bases.

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 The design of a simple joint involves the verification of the resistance (VEd ≤ VRd), the condition available ≥ required and some additional ductility requirements, which depend of joint configuration.

Notations – fin plate joint European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events

L21 – Simple joints and hollow section joints. Behaviour and design of column bases.

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EXAMPLE 1 Check the safety of the following simple joint submitted to a vertical shear force VEd = 100 kN (complete resolution may be find in P126 of ECCS). VEd = 100 kN



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EXAMPLE 1  Requirements for sufficient rotatation capacity

(1) hp ≤ db (2) available > required where: if

z > z  g h 

2

 hp     h e   2 

2

 available  "  "


if not:

 available 

   arcsin    

z

z  g h 

2

  hp    h e    2

2

       arctg z  g h  hp   he    2  


      6




EXAMPLE 1  Requirements for sufficient rotatation capacity

 Requirements to avoid premature weld failure

 w f yp  M 2 a tp 2 f up  M0



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EXAMPLE 1  Joint shear resistance 1. Bolts in shear 2. Fin plate in bearing 3. Gross section of the fin plate in shear 4. Net section of the fin plate in shear 5. Shear block of the fin plate 6. Fin plate in bending

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VRd  min VRdi i 1

7. Buckling of the fin plate 8. Beam web in bearing 9. Gross section of the beam web in shear European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events

10. Net section of the beam web in shear 11. Shear block of the beam web L21 – Simple joints and hollow section joints. Behaviour and design of column bases.

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EXAMPLE 1

Shear resistance of the joint: VRd = 146.18 kN (= VRd8) Failure Mode: Beam web in bearing  Requirements to allow a plastic redistribution of internal forces (ductility)

(the other is for fin plate) European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events

(If VRd = VRd3, VRd4, VRd5, VRd6, VRd9, VRd10, VRd11 then VRd1>min (VRd2, VRd8)) L21 – Simple joints and hollow section joints. Behaviour and design of column bases.

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 The Eurocode 3, part 1.8 provides actual design rules for joints between both open and hollow sections.  Design rules for hollow section joints (semi-empirical rules calibrated with experimental tests) were developed by CIDECT (International Committee for Research and Technical Support for Hollow Section Structures).  These type of joints are used essentially in trussed structures or lattice girders.



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 Failure modes a) Chord face failure

b) Chord web failure

c) Chord shear failure d) Punching shear failure e) Brace failure European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events

f) Local buckling failure L21 – Simple joints and hollow section joints. Behaviour and design of column bases.

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 Current typologies of column bases



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 Anchor bolts

 Anchor bolts may be manufactured in accordance with one of the following standards: EN 10025 (current mild steel), EN 10080 (reinforcing bars), EN ISO 898 or EN 14399 (bolts). L21 – Simple joints and hollow section joints. Behaviour and design of column bases.

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 Behaviour and active components V

 Steel components (column and base plate) – similar to beam-column joint with end-plate  Additional components associated with concrete foundation:

i) Concrete in compression + base plate in bending due to compression T-stub in compression (clause 6.2.5 - EC3-1-8 and EC2-1-1); ii) Tension resistance (clause 6.2.6.12 of EC3-1-8) and lifting of anchor bolts (EC2-1-1); iii) Shear resistance of anchor bolts (clause 6.2.2 of EC3-1-8), including concrete crushing (EC2-1-1); European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events

iv) Friction resistance between base plate and concrete foundation (clause 6.2.2 of EC3-1-8). L21 – Simple joints and hollow section joints. Behaviour and design of column bases.

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 Characterization of components associated with concrete foundation i) Concrete in compression + base plate in bending due to compression - T-stub in compression (6.2.5 - EC3-1-8 and EC2-1-1).

Uniform pressure in concrete fjd

c

f t2 y M  Rd 6

FC,Rd = fjd beff leff fjd European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events

c = t [fy / (3 fjd γM0)]0.5 fjd - Design bearing strength of concrete.

M

Ed



f

jd 2


c2

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List of contents  Characterization of components associated with concrete foundation

k



C



fc

d

fc

d

d

 

c fj

- The design bearing strength (fjd) of concrete may conservatively be taken as:

fj

Simple joints Examples Hollow section joints Design of column bases Examples

fcd - Design value of concrete compressive strength; fck - Characteristic compressive cylinder strength of concrete at 28 days.

- A more accurate value of fjd should be obtained in accordance with clause 6.7 of EC2-1-1, as specified in clause 6.2.5 (7) of EC3-1-8. European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events


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 Characterization of components associated with concrete foundation ii) Tension resistance (6.2.6.12 of EC3-1-8) and lifting of anchor bolts (EC2-1-1)

Minimum of:

Ft .Rd  B p.Rd 

0.9  fub  As

 M2

0 . 6    d m  t p  fu

 M2

 0.85 Anchor bolts with threads nonconform with EN 1090

and resistance to lifting of anchor bolts: - bond resistance (8.4 - EC2-1-1) – anchorage by hooks; - pull-out failure (9.2.3 - CEB) – headed anchors; - concrete cone failure (9.2.4 - CEB); - splitting failure (9.2.5 - CEB).



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 Characterization of components associated with concrete foundation iii) Shear resistance of anchor bolts (6.2.2 of EC3-1-8), including concrete crushing (EC2-1-1)

Fv. Rd 

0.6  f ub  A

M2

Minimum of:

F2,vb. Rd  Fb.Rd 

or

 bc  f ub  As M2

Fv. Rd 

0.6  f ub  As

M2

 0.85

 bc  0.44  0.0003 f yb

k1   b  fu  d  t

 M2

Anchor bolts with threads non-conform with EN 1090

NEd

fyb- yield strength of the anchor bolt, within 235 N/mm2 ≤ fyb ≤ 640 N/mm2.

- shear resistance with lever arm (9.3.2.2 - CEB) and crushing resistance of concrete:

Fv,Ed

v

- concrete pry-out failure (9.3.3 - CEB) - concrete edge failure (9.3.4 - CEB); European Erasmus Mundus Master Course Sustainable Constructions under Natural Hazards and Catastrophic Events


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 Characterization of components associated with concrete foundation iv) Friction resistance between base plate and concrete foundation (6.2.2 of EC3-1-8)

Cf,d

Ff,Rd = Cf,d Nc,Ed

- the coefficient of friction between base plate and grout layer (=0.20 for sandcement mortar and should be obtained by testing in accordance with Annex D of EN 1990 for other types).

Nc,Ed - the design value of the normal compressive force in the column.

 Compression resistance The design resistance Nj,Rd of a column base plate under axial compression may be determined by adding the individual design resistance FC,Rd of the 3 T-stubs (not overlapping) shown in the following figure.



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 Resistance to compression + bending moment Design tension and compression forces and the lever arms are defined as following: FT,l,Rd - design tension resistance on the left side; FT,r,Rd - design tension resistance on the right side; FC,l,Rd - design compression resistance on the left side; FC,r,Rd - design compression resistance on the right side.



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 Resistance to compression + bending moment The design moment resistant Mj,Rd (combined with Nj,Ed) should be determined in accordance with the following table (neglecting T-stub 2):

 Rotational stiffness


– stiffness coefficients are defined in Table 6.11 and evaluated in accordance with Table 6.12 of EC3-1-8. L21 – Simple joints and hollow section joints. Behaviour and design of column bases.

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EXAMPLE 2 Design the joint of a column HEB 260 (S 275) to a concrete foundation (C25/30) through a base-plate connected to the foundation by anchor bolts, under the following load combinations: a) Axial compression NEd = 800 kN; b) Axial compression NEd = 800 kN combined with a bending moment MEd = 150 kNm and a shear force VEd = 200 kN.


a)

b)


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This lecture was prepared for the Edition 1 of SUSCOS (2012/14) by RUI SIMÕES (UC) and FLOREA DINU (UPT). Adaptations brought by J.P. Jaspart (Ulg) for Edition 2 of SUSCOS

The SUSCOS powerpoints are covered by copyright and are for the exclusive use by the SUSCOS teachers in the framework of this Erasmus Mundus Master. They may be improved by the various teachers throughout the different editions.

Thank you for your attention http://steel.fsv.cvut.cz/suscos

Design of Steel Members & Joint to Concrete.pdf

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