Progression of Structural Design Approaches
- 1. Naveed Anwar, AIT Solutions Progression of Structural Design Approaches Design ofTall Buildings:Trends and Advancements for Structural Performance Bangkok-Thailand November 7-11, 2016 NaveedAnwar, PhD
- 2. Naveed Anwar, AIT Solutions 2 Trends and Advancements in for Structural Performance Why this Seminar andWorkshop ? And why is this topic imporant
- 3. Demand and Complexity is Increasing
- 4. Naveed Anwar, AIT Solutions Percentage of Urbanized World 4
- 5. Naveed Anwar, AIT Solutions World’s Population Urban-to-Rural Ratio 5 (www.un.org)
- 6. Naveed Anwar, AIT Solutions Visions 6 Japan, 4000m Sky MileTower, 1700 m JapanDubai City Tower, 2400 m One DubaiTower, 1008 m
- 7. Naveed Anwar, AIT Solutions The Reality 7
- 8. Naveed Anwar, AIT Solutions 8 Source: CTBU Report, 2015
- 9. Naveed Anwar, AIT Solutions 9 Source: CTBU Report, 2015
- 10. Naveed Anwar, AIT Solutions 10 Source: CTBU Report, 2015
- 11. Naveed Anwar, AIT Solutions 11 Source: CTBU Report, 2015
- 12. Naveed Anwar, AIT Solutions 12 TheTwistingTurningTowersTrend Source: CTBU Report, 2015
- 13. Naveed Anwar, AIT Solutions 13
- 14. Naveed Anwar, AIT Solutions Source: CTBU Report, 2015 Tall Buildings in Bangkok (> 200m)
- 15. Naveed Anwar, AIT Solutions 15 Source: CTBU Report, 2015
- 16. Naveed Anwar, AIT Solutions Buildings and Structures are expected to be • Safe • Secure • Serviceable • Reliable • The contents of the structures are often much more valuable than structure itself • The loss of service/operations/business is a often larger than repair costs • Protective • Friendly • Sustainable • Affordable
- 17. Naveed Anwar, AIT Solutions 17 Needs Changes in Structural Design Approaches
- 18. Naveed Anwar, AIT Solutions 18 Is my Structure safe? (What level of Richter earthquake my structure sustain? Or what tornado level can it withstand, or is it safe for explosions or How long can it withstand the fire?)
- 19. Naveed Anwar, AIT Solutions 19 How long do we have before the building will collapse in this fire? - Asks the Fire Chief from the structural engineer 1974
- 20. Naveed Anwar, AIT Solutions The Towering Inferno (1974) 20 https://www.youtube.com/watch?v=FagbC09BO2o
- 21. Naveed Anwar, AIT Solutions Evolution of our Understanding of Structures Limits on the allowable stresses to achieve in-direct FOS Explicit consideration of partial FOS. Formulation of limit state design principles. Formulation of ultimate strength. The recognition of the difference between brittle and ductile failure. The introduction of capacity based design approaches. Performance based design and more explicit linkage between demand and performance. Risk integrated based design, and a more and holistic approach towards consequence based engineering.
- 22. Naveed Anwar, AIT Solutions Design Approaches Intuitive Design Code Based Design Performance Based Design Consequences and Risk Based Design Resilience Based Design
- 23. Naveed Anwar, AIT Solutions Design Approaches Intuitive Design Code Based Design Performance Based Design Consequences and Risk Based Design Resilience Based Design
- 24. Naveed Anwar, AIT Solutions Development of Formal Buildings Codes 24 “Rebuilding of London Act” after the “Great Fire of London” in 1666 AD. In 1680 AD, “The Laws of the Indies” Spani sh Crown London Building Act of 1844. In USA, the City of Baltimore first building code in 1859. In 1904, a Handbook of the Baltimore City In 1908 , a formal building code was drafted and adopted. The Internat ional Building Code (IBC) by (ICC). European Union, the Eurocodes.
- 25. Naveed Anwar, AIT Solutions The Modern Codes – With “intent” to make buildings safe for public 25 (ACI 318 – 11) Extremely Detailed prescriptions and equations using seemingly arbitrary, rounded limits with implicit meaning (IS 456-2000)
- 26. Naveed Anwar, AIT Solutions The General Code Families 26 UBC, IBC ACI, PCI, CRSI, ASCE, AISI, AASHTO British,CP and BS Euro-codes China, USSR, Japan
- 27. Naveed Anwar, AIT Solutions Are All Buildings Codes Correct ? • If they differ, can all of them be correct ? • Did we inform the structures to follow which code when earthquake or hurricane strikes ? • Codes change every 3 or years, should we upgrade our structures every 3 or 5 years to conform ? • Codes intend for “Life Safety”, not damage limits or cost implications 27
- 28. Naveed Anwar, AIT Solutions Prescriptive Codes – A Shelter • Public: • Is my structure safe ? • Will it be damaged, how much, how long to repair • Structural Engineer: • Not sure, but I did follow the “Code” As long as engineers follow the code, they can be sheltered by its provisions 28
- 29. Naveed Anwar, AIT Solutions Shortcomings of Code Based Design for Tall Buildings • Traditional codes govern design of general, normal buildings Over 95% buildings are covered, which are less than about 50 m • Not specifically developed for tall buildings > 50 m tall • Prescriptive in nature, no explicit check on outcome • Permit a limited number of structural systems • Do not include framing systems appropriate for high-rise • Based on elastic methods of analysis • Enforce uniform detailing rules on all members • Enforce unreasonable demand distribution rules • Do not take advantage of recent computing tools
- 30. Naveed Anwar, AIT Solutions 30
- 31. Naveed Anwar, AIT Solutions The First Building Code: Code of Hammurabi (1792 BC to 1750 BC) 31 Clause 229: If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death.
- 32. Naveed Anwar, AIT Solutions Design Approaches Code Based Design Performance Based Design Consequences and Risk Based Design Resilience Based Design
- 33. Naveed Anwar, AIT Solutions Performance Based Design (PBD) • An approach in which structural design criteria are expressed in terms of achieving a set of performance objectives or levels. • Ensures structures reaches specified demands level in both service and strength design levels. • Why it was needed? • Traditional codes not suitable/adequate • Explicit verification not specified or required in most codes • Public does not care about the code, or theories or procedures, they care about “safety” and ‘performance” 33
- 34. Naveed Anwar, AIT Solutions Define Performance Levels 34 Based on FEMA 451 B
- 35. Naveed Anwar, AIT Solutions Link the Hazard to Performance Levels 35 Structural Displacement LoadingSeverity Resta urant Resta urant Resta urant Hazard Vulnerability Consequences
- 36. Naveed Anwar, AIT Solutions Is this acceptable? Even though it satisfies CBD and PBD
- 37. Naveed Anwar, AIT Solutions Design Approaches Code Based Design Performance Based Design Consequence and Risk Based Design Resilience Based Design
- 38. Naveed Anwar, AIT Solutions Beyond PBD • For public, the performance criteria still does reduce the effects of the events • Insurance companies want to have greater reliability of assessment of risk and damages 38
- 39. Naveed Anwar, AIT Solutions Questions still un-answered • What if the chance that performance level is not achieved? • What is the risk ? • What are the consequences? • What if the performance levels are not sufficient? Code based was implicit, with not confirmation of response PBD is explicit, can help to confirm the response and performance level
- 40. Naveed Anwar, AIT Solutions Why do we need to go Beyond PBD • For public and society, the performance criteria still does reduce the effects of the events, but it can reduce the risk level • The non structural damage is not acceptable in modern buildings • The disruption and loss goes much beyond the building • Insurance companies want to have greater reliability of assessment of risk and damages
- 41. Naveed Anwar, AIT Solutions Consequence Based Engineering • It is not enough to say “Cracking and non-structural damage is acceptable, as long as structure does not collapse” • A natural extension of the performance-based design approach • Structural consequences > DDD (dollars, deaths and downtime) (Porter, 2003). 41 The trigger of an event is not important, the consequences of an event are
- 42. Naveed Anwar, AIT Solutions Consequence Based Engineering • “Structural consequence and non-structural effects” determined entirely from the analysis of structural member as well as overall system behavior. • Proceeds through the analysis of expected system consequences, irrespective of the event triggering these consequences. • Requires the structural members to be designed for variable reliability levels, depending upon their contribution in causing adverse system consequences. 42
- 43. Naveed Anwar, AIT Solutions Risk Based Design Process Safety Studies (Probability and Consequence Analysis) Risk Quantification Safety Critical Element Design Accidental Load Structure Design
- 44. Naveed Anwar, AIT Solutions Special Purposes Guidelines from USA 44 Applied Technology Council (ATC) Federal Emergency Manageme nt Agency (FEMA) and National Earthquake Hazards Reduction Program (NEHRP) PEER Guidelines forTall Buildings Tall Buildings Initiatives (TBI) CTBUH Guidelines
- 45. Naveed Anwar, AIT Solutions What Next: What is still missing • Adequacy, Performance and Risk reduction of Structure alone is not enough • Structure serves a purpose in society, economy, community > Should be integrated with other aspects • A more holistic approach, beyond structural design needed 45
- 46. Naveed Anwar, AIT Solutions Design Approaches Code Based Design Performance Based Design Consequences and Risk Based Design Resilience Based Design
- 47. Naveed Anwar, AIT Solutions RESILIENCE Economic Social Organizational Technical Resourcefulness Redundancy Rapiditty Robustness Lower Consequences Faster Recovery More Reliability 4 Dimensions of Resilience 4 Properties of Resilience 3 Results of Resilience 47
- 48. Naveed Anwar, AIT Solutions Resilience Based Earthquake Design • A holistic approach which seeks to identify all hazard- induced risks (including those outside the building envelope) and mitigate them using integrated multi- disciplinary design and contingency planning to achieve swift recovery objectives in the aftermath of a major earthquake. • The key principle in resilience-based design is to limit expected damage to structural and architectural components and egress systems (elevators, stairs, and doors) 48 Economic Loses Loss of Community and Culture Loss of Quality of Life Go Beyond Life Safety
- 49. Naveed Anwar, AIT Solutions Link Performance to other Indicators 49 Restaurant Restaurant Restaurant Operational (O) Immediate Occupancy (IO) Life Safety (LS) Collapse Prevention (CP) 0 % Damage or Loss 99 % Ref: FEMA 451 B CasualtiesLowest Highest Rehab Cost to Restore after eventLowest Highest Retrofit Cost to Minimize ConsequencesHighest Lowest Downtime for RehabLowest Highest Impact on Sustainability of CommunityLowest Highets
- 50. Naveed Anwar, AIT Solutions Green Buildings Resilient Buildings 50 Main authors : Arup Supported by USRC and many others
- 51. Naveed Anwar, AIT Solutions 51 ARUP
- 52. Tools: How to design efficiently?
- 53. Naveed Anwar, AIT Solutions The Growing Computational Requirements • Dynamic Analysis • Nonlinear modelling • Nonlinear Time History Analysis • Progressive Collapse • Staged construction analysis • A new and major concern for structural safety • Structure should not collapse completely if one or two elements are “destroyed” • Backup systems, alternate load paths, additional redundancy
- 54. Naveed Anwar, AIT Solutions The Role of Computers and Software 54 • Initially, computers were used to program the procedure we had • Now, we develop procedures that are suited for computing
- 55. Naveed Anwar, AIT Solutions Design Approaches evolved to match computing revolution 55
- 56. Naveed Anwar, AIT Solutions A Swing Towards the AI • Rich Pictures • Analytical Hierarchy Process (AHP) • Artificial Neural Networks (ANN) • Genetic Algorithms (GA) • Expert Systems (ES) • Fuzzy Logic • Deep Thinking • Big Data and Data Mining 56
- 57. Naveed Anwar, AIT Solutions Mobile computing might change how we design 57
- 58. Naveed Anwar, AIT Solutions Can we make it safe, sustainable and resilient? 58
- 59. Thank you View publication statsView publication stats