Introduction to Seismic Essentials in Groningen 7.2 Steel - - PowerPoint PPT Presentation

Introduction to Seismic Essentials in Groningen

7.2

Steel Structures

By Prof Milan Veljkovic MSc PhD – TU Delft

Design Codes for New Steel Structures

Eurocode 3 Eurocode 8

8

Eurocode 3: Design of steel structures - Part 1-8: Design

• f joints

Eurocode 3: Design of steel structures - Part 1-1: General rules and rules for buildings

EN 1998-1

Eurocode 8: Design of structures for earthquakes resistance - Part 1: General rules, seismic actions and rules for buildings

December 2015

Standard and Steel Grade Nominal thickness of the element t [mm] t ≤ 40 mm 40 mm ≤ t ≤ 80 mm fy[N/mm2] fu [N/mm2] fy[N/mm2] fu [N/mm2] EN 10210-1 S 235 H S 275 H S 355 H S 275 NH/NLH S 355 NH/NLH S 420 NH/NLH S 460 NH/NLH 235 275 355 275 355 420 460 360 430 510 390 490 540 560 215 255 355 255 335 390 430 340 410 490 370 470 520 550 EN 10219-1 S 235 H S 275 H S 355 H S 275 NH/NLH S 355 NH/NLH S 460 NH/NLH S 275 MH/MLH S 355 MH/MLH S 420 MH/MLH S 460 MH/MLH 235 275 355 275 355 460 275 355 420 460 360 430 510 370 470 550 360 470 500 530

Table 3.1

“Nominal values of yield strength fy and ultimate tensile strength fu for structural hollow sections”

Selection Table for Steel Grades

Design Codes for New Steel Structures

When there is no danger for earthquake actions, there is only need for at least low ductility, although even in those cases the preference is to have at least medium ductility.

Brittle Type Failure

Examples of Ductile Behaviour

types of beam-to- column connections hysteresis loops of beam-to- column connections

Farm Buildings, Industrial Halls and Offices

Structural Schematisation

pitch roof frame two story office building

braced direction

Pitch Roof Frame

Pitch Roof Frame

unbraced direction

Two Story Office Building

Energy-dissipative Bracing System

Storage Rackings

Possible Structural Solutions

Determine ductility class via a nonlinear push-over analysis and calculate the q-factor When the ductility is low (DCL) in the unbraced direction:

• Strenghten the frame to take the horizontal forces when necessary

When the ductility is medium (DCM) or high (DCH) in the unbraced direction:

• Strenghten the frame to improve the energy dissipation when necessary

Unbraced direction

Determine ductility class via a nonlinear push-over analysis and calculate the q-factor

Possible Structural Solutions

Determine ductility class via a nonlinear push-over analysis and calculate the q-factor When the ductility is low (DCL) in the braced direction:

• Add sufficient bracings to take the horizontal forces when necessary
• If not possible, than improve the existing bracing in terms of energy

dissipation When the ductility is medium (DCM) or high (DCH) in the braced direction:

• Improve the existing bracing in terms of energy dissipation when necessary

Braced direction

Determine ductility class via a nonlinear push-over analysis and calculate the q-factor

Concluding Remarks

Determine the actual behaviour of the existing steel structure Analyse what is necessary to adapt the structure to the effects of earthquake actions Steel is an adequate material to resist seismic actions

Thank you for your attention!

7.2

References and further reading

NPR 9998 (2015). Assessment of buildings in case of erection, construction and disapproval – Basic rules for seismic actions: induced earthquakes. Published by NEN, Delft. EN 1993 - Eurocode 3 (2005). Design of steel structures - Part 1-1: General rules and rules for buildings, Part 1-8: Design of joints and Part 1-10: Material toughness and through-thickness properties. Published by CEN/CENELEC, Brussels. EN 1998-1, Eurocode 8-part 1 (2005). Design of structures for earthquake resistance – Part 1: General rules, seismic actions and rules for buildings. Published by CEN/CENELEC, Brussels. TNO report (2015), Push-over analyse stalen 3 scharnierspant – tbv NPR 9998:2015.