Performance Based Design, Value Engineering, and Peer Review
- 1. Dr. Naveed Anwar Performance Based Design, Value Engineering and Peer Review Design of Tall Buildings: Trends and Advancements for Structural Performance Bangkok-Thailand November 7-11, 2016 Naveed Anwar, PhD
- 2. Dr. Naveed Anwar 2 Is this acceptable? (For the people who purchased apartment and lived here)
- 3. Dr. Naveed Anwar 3 Who are the stakeholders Developers (Rely on designers and contractors to make profit) Designers (Satisfying building codes and regulations and developer) Owners (Ultimate Stakeholder Pays/owns and uses) Building Officials (enforce the building codes and responsible for public safety) BuildingCodes (Provideminimumrequiremsfor publicsafet) Contractors (Carry out the construction based instructions of Designers and developers and work for a profit) Residents and Public (Uses the space)
- 4. Dr. Naveed Anwar 4 Make buildings as primary business Care about reputation, brand and continued business Main focus on profit Own/use the building for living or making living Care about livability, safety, comfort Focus on value for money Developers Buyers/Residents Willing to spend more to increase profit and reputation Willing to pay more for higher value
- 5. Dr. Naveed Anwar 5 How can we increase the value so the buyers are willing to pay more And the developer gets higher profit Public gets a better building Everyone wins!
- 6. Dr. Naveed Anwar 6 What “Value” are we considering • Structural Safety is of prime concern and has a high value • Other value may be in location, brand, finishes, design quality etc. • Additional value may be “Green” and sustainability
- 7. Dr. Naveed Anwar 7 • A safer and high performance building is more environmentally sustainable • People pay more for higher sustainability so should pay more for higher and performance
- 8. Dr. Naveed Anwar 8 • Compare Value Engineering and PBD • What the developers want • Increase profit • Reputation/ branding • Reducing cost is one way > Value Engineering • PBD - increasing safety, value, selling price and branding is another • Give example of cost /Sq m and cost of review, PBD etc • How PBD Works
- 9. Dr. Naveed Anwar 9 • Explicit confirmation of higher or expected performance level Performance Based Design • Get the best “value” for resourcesValue Engineering • Provide an independent view and confirmation Peer Review
- 10. Dr. Naveed Anwar Ensuring Explicit Safety Performance (Specially for extreme events)
- 11. Dr. Naveed Anwar 11 How does CTBUH look at Tall Buildings 11 Relatively Tall. Both for public and the professions who design and construct Proportion Slenderness, in plan and in elevations Systems and Technologies Uses something “different” than ordinary buildings
- 12. Dr. Naveed Anwar 12 How modern codes intent to ensure “Safety” • Define appropriate/estimated hazard or load levels • Prescribe limits on structural systems, members, materials • Define procedures for analysis and design • Provide rules for detailing • Provide specifications for construction and monitoring • Hope that all of this will lead to safe structures …
- 13. Dr. Naveed Anwar The Modern Codes – With “intent” to make buildings safe for public 13 (ACI 318 – 11) Extremely Detailed prescriptions and equations using seemingly arbitrary, rounded limits with implicit meaning (IS 456-2000)
- 14. Dr. Naveed Anwar The General Code Families 14 UBC, IBC ACI, PCI, CRSI, ASCE, AISI, AASHTO British, CP and BS Euro-codes China, USSR, Japan
- 15. Dr. Naveed Anwar 15 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 ?
- 16. Dr. Naveed Anwar 16 Concerns • Public Will the building be safe? • Owner Will the building collapse/ will it be damaged ? Can I use the building after a given earthquake? (blast, hurricane..) How much will repair cost? How long will it take to repair? Can I make building that will not be damaged and will not collapse • Public Officials Who is responsible if loss of life occurs Who should have all the answers?
- 17. Dr. Naveed Anwar 17 Structural Engineer’s Dilemma • Can not answer most of the these questions explicitly • Answers are always qualified • There is no warranty for the structure • There are too many unknowns • Public understanding and engineers understanding of safety is different • Has to hide behind the design codes
- 18. Dr. Naveed Anwar 18 Prescriptive Codes – A Shelter • Public: • Is my structure safe ? • Structural Engineer: • Not sure, but I did follow the “Code” As long as engineers follow the code, they can be sheltered by its provisions
- 19. Dr. Naveed Anwar 19 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
- 20. Dr. Naveed Anwar 20 Motivation for PBD • Lack of explicit performance in design codes is primary motivation for performance based design • Performance based methods require the designer to assess how a building is likely perform under earthquake shaking and other extreme events and their correct application will help to identify unsafe designs. • At the same time this approach enables arbitrary restrictions to be lifted and provides scope for the development of safer and more cost-effective structural solutions
- 21. Dr. Naveed Anwar 21 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”
- 22. Dr. Naveed Anwar 22 Performance based design can be applied to any type of loads, but is typically suitable and targeted for earthquake loads
- 23. Dr. Naveed Anwar 23 Explicit Performance Objective in PBD Performance based design investigates at least two performance objectives explicitly Service-level Assessment Negligible damage with frequent hazards (Earthquake having a return period of about 50) Collapse-level Assessment Collapse prevention under extreme hazards (the largest earthquake with a return period of 2500 years) Codes arbitrary “Design Level”
- 24. Dr. Naveed Anwar 24 Performance Level Definitions Owner Will the building be safe? Can I use the building after the hazard? How much will repair cost in case of damage? How long will it take to repair? Engineer amount of yielding, buckling, cracking, permanent deformation, acceleration, that structure, members and materials experiences Need a third party to ensure public safety and realistic Performance Guidelines Peer Review
- 25. Dr. Naveed Anwar 25 Typical Review Objectives Enhance Structural Performance • Improved serviceability, safety and reliability • Explicit check on various performance indicators Improve Cost Effectiveness • Achieve efficient use of materials, resources and time • Direct reduction cost through reduction of structural material quantities Objectives to be achieved through • Better structural system selection and its proportions • Use of advanced design methodologies and tools
- 26. Dr. Naveed Anwar 26 Typical Review Objectives Enhancement of Performance • Dynamic response parameters • Lateral load response • Vertical load response • Demand and capacity ratios • Response irregularity, discontinuity • Explicit Performance Evaluation at Service, DBE and MCE Cost Effectiveness • Capacity utilization ratio • Reinforcement ratios • Reinforcement volume ratios • Concrete strength and quantity • Rebar quantity • Constructability, time and accommodation of other constraints
- 27. Dr. Naveed Anwar 27 Performance Objectives Level of Earthquake Seismic Performance Objective Frequent/Service (SLE): 50% probability of exceedance in 30 years (43-year return period) Serviceability: Structure to remain essentially elastic with minor damage to structural and non-structural elements Design Basis Earthquake (DBE): 10% probability of exceedance in 50 years (475-year return period) Code Level: Moderate structural damage; extensive repairs may be required Maximum Considered Earthquake (MCE): 2% probability of exceedance in 50 years (2475-year return period) Collapse Prevention: Extensive structural damage; repairs are required and may not be economically feasible
- 28. Dr. Naveed Anwar 28 Site Specific Ground Motions
- 29. Dr. Naveed Anwar 29 Seismic Hazard Spectrum, SLE, DBE. MCE MCE Level Service Level
- 30. Dr. Naveed Anwar 30 Standard Structural Performance Levels Restaurant Restaurant Restaurant Operational Immediate Occupancy Life Safety Collapse Prevention 0 % Damage or Loss 99 % Ref: FEMA 451 B
- 31. Dr. Naveed Anwar 31 Judging Performance Acceptability • Acceptance criteria are indicators of whether the predicted performance is adequate for • Local (component based) Example: Drift ratio, structural component deformation • Global (overall structure-based) Example: Roof drift , base shear
- 32. Dr. Naveed Anwar 32 Performance Based Design Process Acceptance Criteria for Primary Components
- 33. Dr. Naveed Anwar 33 Performance Based Design Process Acceptance Criteria for Secondary Components
- 34. Dr. Naveed Anwar 34 Classification of Actions Element Action Type Classification Expected Behavior RC column Axial-flexure Shear Ductile Brittle Linear Linear RC shear wall Flexure Shear Ductile Brittle Nonlinear Linear RC coupling beams (Deep beam, ln/d<4.0) Shear Ductile Nonlinear RC coupling beams (slender beam, ln/d≥4.0 Flexure Shear Ductile Brittle Nonlinear Linear
- 35. Dr. Naveed Anwar 35 How to Work with PBD Architect Structural Engineer PBD Specialist PBD Peer Reviewer Site Specific Consultant Performance Based Design Client
- 36. Dr. Naveed Anwar Value Engineering Balancing Cost and Performance
- 37. Dr. Naveed Anwar 37 Cost and Performance PCC Cost Effective Design Can be done PC General Belief Easy to do ! PC Highly Innovative Design Hard to do! PC High Performance Design Can be done
- 38. Dr. Naveed Anwar 38 What is the Cost of a Project? • Cost may include – Financial Cost (loan, interest, etc) – Planning and Design Cost – Direct Construction Cost – Maintenance Cost – Incidental Cost – Liquidated Cost (lost profit etc) – Opportunistic Cost – Environmental Cost – Emotional Cost – Non-determinist Resources Cost may be: “Consumption of Particular Resources, at Particular Time” Sustainability may be: <Consumption of all resources, and their impacts through throughout the life cycle>
- 39. Dr. Naveed Anwar 39 Cost and Performance • Enhancement of Performance • Dynamic response parameters • Lateral load response • Vertical load response • Demand and capacity ratios • Response irregularity, discontinuity • Explicit Performance Evaluation at Service, DBE and MCE • Cost Effectiveness • Capacity utilization ratio • Reinforcement ratios • Reinforcement volume ratios • Concrete strength and quantity • Rebar quantity • Constructability, time and accommodation of other constraints 39
- 40. Dr. Naveed Anwar 40 Optimization • Need to define What to optimize? And what are the parameters that can be changes? • Optimizing one or two items may “un-optimize” others • Optimizing everything is a “Holy Grail” – …. and “Holy Grail” doesn't exist • Tools – Genetic Algorithms (GA) – Artificial Neural Networks (ANN) – Linear and Nonlinear programing
- 41. Dr. Naveed Anwar 41 Levels of Optimization Levels of Optimization Micro-Micro Level One part of a component, “Steel” Micro Level One Component, “Column” Local One part or aspect Global Entire Problem, Project Universal Entire System
- 42. Dr. Naveed Anwar 42 • Simple Example of a Column Stack – What and how can we optimize ? • Concrete Strength • Steel Strength • Column Size • Rebar Amount • Composite Section • Material Cost, Labor Cost, Formwork Cost, Management and operations Cost, Time ?? Local Vs Global Optimization
- 43. Dr. Naveed Anwar 43 Cost and Performance (Base Cost and Performance) (Increased Performance, Same Cost) (Base Cost and Performance) (Reduced Cost for Same Performance) P M P M
- 44. Dr. Naveed Anwar 44 Demand Capacity (DC Ratio) • Definition of D/C: It is an index that gives an overall relationship between affects of load and ability of member to resists those affects. • This is a normalized factor that means D/C ratio value of 1 indicates that the capacity (strength, deformation etc) member is just enough to fulfill the load demand. • Two types of D/C ratio Members with brittle behavior D/C is checked by Strength (Elastic) Members with ductile behavior D/C is checked by deformation (Inelastic) • Total D/C ratio of the member is combined of these two.
- 45. Dr. Naveed Anwar 45 Cost Effectiveness > Utilization Ratio • Utilization Ratio • Compare, What is Needed against What is Required • One measure • The Demand/ Capacity Ratio (D/C) Demand/ Capacity Columns No. % D/C<0.5 178 16% 0.5<D/C<0.7 534 49% 0.7<D/C<1 346 31% 1<D/C<1.5 30 3% 1.5<D/C<2.5 12 1% D/C>2.5 0 0% Total 1100 100.00% Ideal Not Cost Effective Not Safe
- 46. Dr. Naveed Anwar 46 Focus should be “Maximum Value for Resources” Cost effective, not Low Cost
- 47. Dr. Naveed Anwar Peer Review To ensure Basic Design the Performance Evaluation and Value Enginering are done right
- 48. Dr. Naveed Anwar 48 The Responsibility Building Officials Structural Designer Architect Structural Design Codes General Building Codes Legal and Justice System Public/ Users/ Occupants Client/Owner Law Makers Builder/Contractor Peer Reviewer Geotech Consultants
- 49. Dr. Naveed Anwar 49 Peer Review • What exactly is design peer review? • It is a process whereby a design project (or aspect of) is reviewed and evaluated by a person, or team, not directly involved with the project, but appropriately qualified to provide input that will either reinforce a design solution, or provide a route to an improved alternative. • Why is it so important? • Very few can claim to be all-encompassing experts. The invaluable input from broad base and independent experience at each stage of a design project will often result in technical improvements, lower costs, avoidance of sourcing issues, and improved performance.
- 50. Dr. Naveed Anwar 50 When is Peer Review needed • Structural Peer Review is required for: • Buildings included in Structural Occupancy Category IV as defined in the Building Code. • Buildings with aspect ratios of seven or greater. • Buildings greater than 500 feet (160 m) in height or more than 1,000,000 square feet (100,000 Sqm) in gross floor area. • Buildings taller than seven stories where any element supports in aggregate more than 15 percent of the building area. • Buildings designed using nonlinear time history analysis, pushover analysis or progressive loading techniques. New York Building Code, adopted by many cities Important Slender Tall or large Critical Use NLA
- 51. Dr. Naveed Anwar 51 Responsibility • Structural Engineer of Record (SER). • The structural engineer of record shall retain sole responsibility for the structural design. The activities and reports of the Reviewing Engineer shall not relieve the structural engineer of record of this responsibility. • Reviewing Engineer. • The Reviewing Engineer’s report states his or her opinion regarding the design by the engineer of record. • The standard of care to which the Reviewing Engineer shall be consistent with Structural Peer Review services performed by professional engineers licensed/approved Retains Responsibility Evaluates, and gives opinion that may or may not be accepted by Client or SER
- 52. Dr. Naveed Anwar 52 Typical Scope of Work for Review • Check structural engineering concepts • Potential behavioral or value improvement suggestions • Constructability review • Presentation of peer review findings and peer review report writing • Review and confirmation of the owner’s seismic performance objectives • Meeting(s) with the design team to review the project assumptions and the project approach • Review structural design criteria and analysis/design methodology • Review available geotechnical and site seismicity reports • Review all available relevant documents as the design progresses, including drawings, and specifications • Review of analysis results. This may require implementation of one or more parallel verification models for comparison purposes • Technical review of the design and details of the proposed structural system • Preparation of peer review report and comment list • Meeting(s) with the design team to review and reconcile the peer review comment
- 53. Dr. Naveed Anwar 53 Client PBD Value Engineering Peer Review Basic Design Public Officials Design Codes and Guidelines High performance, Higher safety higher value, cost effective Sustainable
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