Conceptual Design of Buildings (Course unit code 1C2)

Transcription

1 (Course unit code 1C2) Module C Design of Steel Members J.P. Jaspart (University of Liège) CZ-ERA MUNDUS-EMMC

2 Simple Simple 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 nº 126 of ECCS: European Recommendations for the Design of Simple Joints in Steel Structures. These type of will be included in the Manual Design of Joints in Steel and Composite Structures, ECCS (J.P. Jaspart and K. Weynand). L21 Simple and hollow section. Behaviour and design of column. 2

3 Simple 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). 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 and hollow section. Behaviour and design of column. 3

4 Simple The design of a simple joint involves the verification of the resistance (V Ed V Rd ), the condition available required and some additional ductility requirements, which depend of joint configuration. Notations fin plate joint L21 Simple and hollow section. Behaviour and design of column. 4

5 Simple EXAMPLE 1 Check the safety of the following simple joint submitted to a vertical shear force V Ed = 100 kn (complete resolution may be find in P126 of ECCS). V Ed = 100 kn L21 Simple and hollow section. Behaviour and design of column. 5

6 Simple EXAMPLE 1 Requirements for sufficient rotatation capacity (1) h p d b (2) available > required where: if z> z g h 2 h p 2 h e 2 available " " if not: available arcsin 2 p 2 h h p z g h h e L21 Simple and hollow section. Behaviour and design of column. h z 2 e arctg z g 2 h 6

7 Simple EXAMPLE 1 Requirements for sufficient rotatation capacity Requirements to avoid premature weld failure a w 2 f f yp up M2 M0 t p L21 Simple and hollow section. Behaviour and design of column. 7

8 Simple 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 7. Buckling of the fin plate V Rd 11 min i 1 V Rdi 8. Beam web in bearing 9. Gross section of the beam web in shear 10. Net section of the beam web in shear 11. Shear block of the beam web L21 Simple and hollow section. Behaviour and design of column. 8

9 Simple EXAMPLE 1 Shear resistance of the joint: V Rd = kn (= V Rd8 ) Failure Mode: Beam web in bearing Requirements to allow a plastic redistribution of internal forces (ductility) (the other is for fin plate) (If V Rd = V Rd3, V Rd4, V Rd5, V Rd6, V Rd9, V Rd10,V Rd11 then V Rd1 >min (V Rd2,V Rd8 )) L21 Simple and hollow section. Behaviour and design of column. 9

10 Simple The Eurocode 3, part 1.8 provides actual design rules for between both open and hollow sections. Design rules for hollow section (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 are used essentially in trussed structures or lattice girders. L21 Simple and hollow section. Behaviour and design of column. 10

11 Simple Failure modes a) Chord face failure b) Chord web failure c) Chord shear failure d) Punching shear failure e) Brace failure f) Local buckling failure L21 Simple and hollow section. Behaviour and design of column. 11

12 Simple Current typologies of column L21 Simple and hollow section. Behaviour and design of column. 12

13 Simple Anchor bolts Anchor bolts may be manufactured in accordance with one of the following standards: EN (current mild steel), EN (reinforcing bars), EN ISO 898 or EN (bolts). L21 Simple and hollow section. Behaviour and design of column. 13

14 Simple Behaviour and active components Steel components (column and base plate) similar to beam-column joint with end-plate Additional components associated with concrete foundation: V i) Concrete in compression + base plate in bending due to compression - T-stub in compression (clause EC3-1-8 and EC2-1-1); ii) Tension resistance (clause of EC3-1-8) and lifting of anchor bolts (EC2-1-1); iii) Shear resistance of anchor bolts (clause of EC3-1-8), including concrete crushing (EC2-1-1); iv) Friction resistance between base plate and concrete foundation (clause of EC3-1-8). L21 Simple and hollow section. Behaviour and design of column. 14

15 Simple Characterization of components associated with concrete foundation i) Concrete in compression + base plate in bending due to compression - T-stub in compression ( EC3-1-8 and EC2-1-1). Uniform pressure in concrete f jd F C,Rd = f jd b eff l eff c M Rd f t 2 y 6 c = t [f y / (3 f jd γ M0 )] 0.5 f jd - Design bearing strength of concrete. f c 2 jd 2 L21 Simple and hollow section. Behaviour and design of column. M Ed f jd 15

16 Simple Characterization of components associated with concrete foundation - The design bearing strength (f jd ) of concrete may conservatively be taken as: ffffckjd jdc f cd - Design value of concrete compressive strength; f ck - Characteristic compressive cylinder strength of concrete at 28 days.ccd- A more accurate value of f jd should be obtained in accordance with clause 6.7 of EC2-1-1, as specified in clause (7) of EC L21 Simple and hollow section. Behaviour and design of column. 16

17 Simple Characterization of components associated with concrete foundation ii) Tension resistance ( of EC3-1-8) and lifting of anchor bolts (EC2-1-1) Minimum of: B F p. Rd 0.9 f A ub s t. Rd M d m M 2 t p f u 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 ( CEB) headed anchors; - concrete cone failure ( CEB); - splitting failure ( CEB). L21 Simple and hollow section. Behaviour and design of column. 17

18 Simple 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) Minimum of: F F F v. Rd 2, vb. Rd b. Rd 0.6 f k 1 bc M 2 f b f M 2 u M 2 ub A s d t F 0.6 f A ub s v. Rd M 2 f yb - yield strength of the anchor bolt, within 235 N/mm 2 f yb 640 N/mm 2. - shear resistance with lever arm ( CEB) and crushing resistance of concrete: - concrete pry-out failure ( CEB) - concrete edge failure ( CEB); ub A or bc f yb 0.85 Anchor bolts with threads non-conform with EN 1090 F v,ed v N Ed L21 Simple and hollow section. Behaviour and design of column. 18

19 Simple Characterization of components associated with concrete foundation iv) Friction resistance between base plate and concrete foundation (6.2.2 of EC3-1-8) F f,rd = C f,d N c,ed C f,d - 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). N c,ed - the design value of the normal compressive force in the column. Compression resistance The design resistance N j,rd of a column base plate under axial compression may be determined by adding the individual design resistance F C,Rd of the 3 T-stubs (not overlapping) shown in the following figure. L21 Simple and hollow section. Behaviour and design of column. 19

20 Simple Resistance to compression + bending moment Design tension and compression forces and the lever arms are defined as following: F T,l,Rd - design tension resistance on the left side; F T,r,Rd - design tension resistance on the right side; F C,l,Rd - design compression resistance on the left side; F C,r,Rd - design compression resistance on the right side. L21 Simple and hollow section. Behaviour and design of column. 20

21 Simple Resistance to compression + bending moment The design moment resistant M j,rd (combined with N j,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 EC L21 Simple and hollow section. Behaviour and design of column. 21

22 Simple 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 N Ed = 800 kn; b) Axial compression N Ed = 800 kn combined with a bending moment M Ed = 150 knm and a shear force V Ed = 200 kn. a) b) L21 Simple and hollow section. Behaviour and design of column. 22

23 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.

24 Thank you for your attention