Steel Seminar overview Design of steel structures standard S16-09

1. Steel Seminar overviewDesign of steel structures standard S16-09 Presenter: michaelfowlie

2. Steel seminar • Seminar on Nov 19 • Gave an general overview of what’s new and what’s changed with new S16 • Typically new edition roughly every 5 years (9th edition), to coincide with updates of National Building Code • Don’t know when new one goes into effect? • Also discussed common problems and solutions in steel design • Put on by CSCE – by Dr. Michael Gilmor • Editor of the CSCE Handbook in Steel Construction • Worked for CSCE for over 30 years • Worked on the development of S16 for several editions

3. Purpose of Lunch & learn • Give an overview of the information he presented, including • helpful tips in Steel Design • What’s NEW and what’s CHANGED in S-16 • Turn 8 hours of presentation into 1 • Throw in my two cents • Try to answer any questions • KEN, MIKE S and MUHOMMAD also attended, so feel free to add where necessary

4. S16 -09 Topics • General Comments • Beams and Girders • Tension/Compression Members • Trusses and OWSJ • Composite Beams, Trusses and OWSJ • Plate Walls • Connections • Annex L • Annex K • Seismic Requirements • Questions

5. General Comments

6. General Comments • S16 NEW format • Format change to LIST format (from paragraph format) • May be easier to read • S16 is typically used for steel design in CAN U.N.O. • Supplementary Design Guides (ex. 11- Vibration) are also used • CAN S16 equivalent to USA AISC

7. General comments • Helpful Hints • General Principles of Economic Steel Design • Visualize flow of forces (top to BOTTOM) • Heavier can be cheaper sometimes • Can lead to better performance which won’t require additional items of reinforcement (stiffeners, plates, etc…) • Design is not an isolated act • How will it be connected? • How will it be erected? • Handbook has Check List for Drawings (pg 7-50) • a helpful tool in being comprehensive

8. General Comments • Definition– • Inspector • A qualified person who act for and on behalf of the owner or designer on all inspection and quality matters within the scope of the contract documents • Protected Zone • Areas of members in a seismic force resisting system that undergo larger inelastic strains and in which limitations apply to fabrication and attachment • Both our and shop drawings need to show ZONES

9. General Comments • BIM • Building Information Modeling (BIM) • New Wave of design • Example – RAM • CISC Code of Standard Practice now has appendix dealing with subject • ISSUES • Who owns the model? • Who can modify the model? • What does it produce in terms of drawings and their contractual requirements? • If shop drawings produced from model, are CONSULTANTS responsible for correctness? Could be BIG responsibility.

10. General Comments • Material Selection • W-shapes not made in CAN • ASTM572 grd 50 (345MPa) is approximately = 350MPA • ASTM A992 – newer spec with Fy/Fu controlled • For ductile seismic elements • Becoming basic steel grade • Don’t know how CAN will adapt to this? • ASTM500 B for HSS is NOT = to Grade Class C or H • WWF is a Canadian product. It originally was developed in CAN to compete with large sizes being produced in the States.

11. General Comments • Material Selection (cont’d) • Bolts • ASTM A325 most common bolt • A490 less common • ASTM F1852 (twist off style for A325 applications) • becoming more commonly used • Quiet and faster

12. General comments • Design Requirements • Clause 6.7 • Requirements under fire conditions (more later) • MANDITORY • Clause 6.8 • Guidance for risk of brittle fracture • INFORMATIVE • S16 refers to NBCC for • New service loads • New factored loads • Load factors, Importance, etc…

13. General comments • Design Requirements (cont’d) • Wind Loads • NBCC removed the exposure C from wind load commentary • Building in dense urban environments require exposure B min • Factored Loads • Overturning • DON’T FORGET TO THINK GLOBALLY

14. Beams and Girders

15. Beams and Girders • Key Items • Moment • Shear • Strength • Stiffness • Stability – the forgotten one

16. Beams and Girders • Changes • 13.5 – Flexural Strength • NEW – singly symmetric I and T sections are not permitted to yield under service conditions • b/t replaced with bet / t • To avoid confusion of the b/2t in compression ratios for classes, with b of flange widths • 13.6 Laterally Unsupported Members • New ω2 • Old Def : • ω2 = 1.75+1.05κ+0.3κ2 ≤ 2.5 • Can still use when moment distribution is linear

17. Beams and Girders • New • Position of load w.r.t. shear center • Unbraced beam segments loaded above the shear center between brace points, where the method of load delivery to the member provides neither lateral nor rotational restraint, the associated destabilization effects shall be taken into account • For loads applied to top flange • Mu may be determined using ω2 =1.0 and effective length • = 1.2L for pinned • = 1.4L for other cases

18. Beams and Girders • Monosymetric shapes (YAH!!!!!!) • New edition gives users methods to determine flexural resistances for • Tees • I shapes with unequal flanges • Any section with a single axis of symmetry • WHOLE BUNCH OF NEW FORMULA

19. Beams and Girders • Shear • 13.4 re-organized • No technical changes but users felt new layout better • New formulas • for calculating Vr for HSS (YAH AGAIN!)

20. Tension/Compression Members

21. Tension • Tension • 13.2 • Ultimate Tensile Expression • Old : Tr=.85øAnFu • New: Tr= øuAnFu • New Øu = .85 Ø (same difference) • 12 – Changes to Block Shear Calculations • Modifications of terms related to bolted and/or welded segments • New expression and table replaces old edition (MORE NEW FORMULAS)

22. Compression • Compression • Modified determination of λ • Adding k into expression for λ • Compression of Single angles (YAH!) • For individual members • For trusses, box trusses, planner trusses • 13.3.2 Flexural/Torsional buckling • Added note regarding angles • 13.3.5 Elastic Local Buckling • More options for Class 4 members

23. Compression • Column Bases • NEED 4 ANCHORS • When not feasible, take special precautions • Don’t know how this applies yet, but could have significant effect where Mr. Architect wants 2 in walls • Anchor Rods • Call’em Rods, not Bolts • New ASTM specs as well as G40.20/G40.21 • Changes in An expressions (.85Ag) • Bearing Concrete • Updated Øto 0.65 to match A23.3

24. Trusses & OWSJ

25. Trusses & OWSJ • Changes (quickly): • Joint eccentricities to be taken into account • Splices can occur anywhere • New loading requirements • For roof joists, 100% snow load and 40% of downward wind pressure • THIS COULD EFFECT HOW WE SPECIFY JOIST LOADS TO SUPPLIER • Additional requirements for joist supplier with deck welds, stability, testing, cambers, manufacturing tolerances, and erection tolerances

26. Composite Beams, Trusses & OWSJ Composite Columns

27. Composite • Changes (quickly): • Calculations of deflections due to shrinkage strain are changed (more math) • Partially Encased Composite Columns (new tech) • Steel column, that is filled with concrete once installed on site, giving better strength • W shape, forms from flange tips, filled in, poured as you go up on building • “suitable” technology for multi story buildings

28. Side Note • Mr. Gilmor suggested we stop calling for primer on steel, as primer indicates we are priming for the surface to be painted again, which in most cases we do not apply additional paint (in bldgs). • Mr. Gilmor suggested 70% humidity or less, primer may not even be required • Don’t know what our local conditions are, but steel can be exposed while erecting • THOUGHTS?

29. Plate Walls (STEEL OF COURSE)

30. Plate walls • Changes: • Lateral- force-resisting structural system consisting of a framework of columns, beams with relatively thin infill plates in plane of frame connecting all around to the surrounding members • Can be moment resisting and/or simply shear resisting • Advantage: Steel is more ductile than other materials, which is GOOD in seismic resistance • Relies on post buckling strength of plate • Work like a series of individual stripes alternately stressed in tension and buckling in compression

31. Plate walls • Changes (cont’d): • Advantage: can be post installed in buildings already constructed, as material is easier to get into building than other (concrete, etc…) • Clauses Changed • To comply with new seismic design requirements

32. Connections

33. Connections • Comments • Make sure you choose good pieces to connect • Forces always follow stiffest path • Rarely is a connection true pin or true fixed, but we can design them as such

34. Connections • Changes • Bolts : New ASTM for twist-offs for A490 (F2280) • Bearing on bolts ø moved up to 0.8 (from 0.67) • Bolts in bearing and shear • 13.11 (c) - modified for inclusion of long slotted holes

35. Connections • Changes • New requirements dealing with tension and block shear, bolt tearout • Bolts in tension • Fatigue sent to Clause 26.5 • Fillet Welds • Recognize that failure of base material may occur if electrode overmatched • Not a problem on typical welds • Multi-directional fillet weld strength addressed • Perpendicular welds carrying forces • New formulation for welds and bolts in combo

36. Connections • Changes • Restrained members changed • Filler in bolts changed • Long slotted holes • Plate washers no longer required on bearing-type connections in double shear • Joist surface conditions • Information regarding prep of surfaces for welds • Been welding thru paint for years, formalization of new in S16 of what’s good and what’s bad (hopefully)

37. The AnnexesAnnex L - BrittleAnnex K - fire

38. Annex L • New – Design to prevent brittle fracture • Mechanism accompanied by limited or no plastic deformation • Steel subjected to tensile stresses when the rate of applied loading is high (i.e. dynamic) • Statistically loaded structures that are subjected to low temperatures do not normally require the use of notch-tough steel • Bridge guys would be more familiar with these requirements…

39. Annex L • Depends on • Steel strength • Material thickness • Loading rate • Minimum service temperature • Material toughness • Type of structural element • Discontinuities • Residual stresses • Importance of structural element • Weld metal toughness

40. Annex K • New • Related Clause 6.7 Requirements under fire conditions • Two methods • Design by engineering analysis • Design by qualification testing (traditional approach) • (Firewalls I believe?)

41. Annex K • ANNEX K • Criteria for the design and evaluation of structural steel components, systems, and frames for fire conditions • Factors • Heat input • Thermal expansion • Degradation of mechanical properties due to elevated temperatures • Performance objectives • Design to maintain load bearing function during fire • Satisfy performance requirements specified for occupancy • Deformation criteria for structure • Forces don’t cause a horizontal or vertical fire separation

42. Annex K • Structural Design • Adequate strength and deformation capacity to withstand the structural actions developed within the prescribed limits of deformation • Fire HOT – Building members expand/heat up, cause different structural capacity/situations than prior to fire • Two methods of analysis • Simplified analysis • Advanced analysis • HOPEFULLY, there will be more than words for this type of analysis. This appears to be very difficult.

43. Seismic requirements

44. seismic • Seismic • New/adjusted items in Clause 27 • Protected zones • Buckling restrained braced frames –BRBFs • Plate Walls • Ordinary Frames

45. Questions or comments Book is available in my office to borrow