1. NZ Society of Actuaries March 2017

2. The Alphabet Soup of Engineers
IEP
ULS
NBS
CSW
BIL
DSA
ESG
URM

3. What Engineers Design To
Ultimate Limit State (ULS)
- Level of load that a building has been designed to so that the building will not collapse
- Corresponds to 1 in 500 year return period shaking (10% probability of occurrence in 50 years)
Key Point – Damage is Expected at ULS
Serviceability Limit State (SLS)
- Design so that structural and non-structural component do not require repair after 1/25 year event

4. How we Design Buildings
Newton’s Second Law of Motion – the simple basis of all seismic design
Force = Mass x acceleration
We know what structures weigh.
The “acceleration” is defined by the building code.
Earthquakes cannot read design codes and may misbehave by shaking the building harder than the design acceleration.
Consequently, designers need to make buildings “tough” to withstand overstressing without collapse

5. Design Spectra
Zone Factors. Wellington always pretty High – CHCH for example was 0.22, now up to 0.3, Auckland and Dunners 0.13 In 4203, previously 1.2 vs 0.8.

6. Zone Factors
This is from the code and is effectively a map of relative seismicity across the country.
Wellington 0.4
Christchurch now 0.3
Auckland 0.13
Dunedin 0.13

7. Risk Factors

8. Design Spectra

9. Design Spectra

10. Design Spectra

11. Design Spectra

12. Capacity Design
Strong Columns
Weak Beams

13. Beam Hinging

14. Traditional Design Approach
Ductility = Damage = Repair or Demolish

18. How big was the 14th November 2016 Earthquake in Wellington?

19. How big was the 14th November 2016 Earthquake in Wellington?

20. How big was the 14th November 2016 Earthquake in Wellington?
CHCH 22nd Feb 2011

21. Types of Building Damage
Structural Damage
Large Cracks in Beams where they intersect the Columns
Column cracking at the base of the building
Large diagonal cracks in shear walls (or horizontal cracks at the base)
Large Cracks in the floor beside beams and walls.
Large is >1mm
No Damage of this type has been noted for this building.
Non-Structural Damage
Shrinkage cracking of concrete
Cracking of Gib lining
Movement at designed seismic gaps
Falling ceiling tiles
Un-restrained services
Breaking windows
Most non structural damage is related to incompatibility to movement.
Gib walls are stiff and do not recover from movement

22. Era Overview Design Code Eras Pre - 1935 No seismic design
1935 To 1965
First earthquake code, basic seismic design, one size fits all
1965 to 1975
Seismic zones introduced
1975 to 1996
Progressive refinements to seismic hazard
Ductility introduced into loadings; detailing requirements for difference materials
1995 to present
Further refinements to seismic hazard and detailing ‘Modern structures’

23. IEP – Initial Evaluation Procedure
Objective
Coarse screening to give an indication of where a building sits (hence quite conservative)
Method
Compares original design coefficient with that of equivalent new building
Modifies further to take account of ‘better’ or ‘worse’ factors
Knowledge based using readily available information (Qualitative)

24. DSA – Detailed Seismic Assessment
Objective
To establish with greater confidence the likely performance of buildings in earthquakes
In a moderate earthquake (EQ Prone Yes / No)
In a code-level earthquake
Across all levels of seismicity
Method
Calculation of the capacity of building and comparing against ULS requirement for equivalent new building (Quantitative)
Analysis based using range of methods
Increasing levels of effort

25. Rapid Building Evaluation (Post-disaster, during a state of emergency)
Objective
Rapid evaluation of buildings in an affected area
Method
Knowledge based (experience and training)
A subsequent Detailed Engineering Evaluation is recommended for all affected buildings
Output
Level 1 and Level 2 reports for buildings, and building placards

26. IEP+ DSA Objective Method
DEE – Detailed Engineering Evaluation (Post-disaster, during recovery phase)
Objective
To identify damage and its consequence for future building performance and risks that may affect ongoing use
Method
Qualitative Assessment Procedure may be used initially to determine need for further analysis
Quantitative Assessment Procedure (Detailed Seismic Assessment) will be required in cases where there is significant damage, and when the building capacity <33%NBS
Note: ‘IEP+’ means starting with a review of the plans
IEP+
DSA

27. Building Resilience - Introduction
What does Resilience mean to you?
Design to minimise losses due to seismic events/damage
Rapid post event recovery and rehabilitation
Possible to use targeted approach of smart design for recoverable structural systems
Achieving long term certainty in high seismic areas
Asset Resilience is a choice – world best practise for high seismic zones

28. Building Resilience – Why do it?
What do occupants and facility users want
Functionality?
Safety?
Certainty in recovery post natural disaster?
What does the client and stakeholders want
Value not cost
Performance
Market drivers affect delivery of resilient buildings
Cost of and Complexity of construction
Cost of Labour and materials
Buildability/knowledge of industry

29. The Principal of Resilient Design
Let it rock or let it slide - reduces the seismic forces on the building Have replaceable fuses – makes it repairable

30. Building Resilience – Normal Building Performance Against Code
Limit State Criteria – Normal Buildings
Limit State
Importance Level
Return Period (events per interval)
%NBS Analogy
Likely Post Event State
Post Event – Use Requirement
Expected Loss State
Serviceability Limit State (SLS) 2
1 in 25
~25%
Minor cracking damage but no compromise to function allowed
Fully - Operable
Minor if any
Ultimate Limit State (ULS)
1 in 500
100%
Building may be heavily damaged but must allow safe egress
Non Operable – heavily damaged – may need to be demolished
Major
Maximum Considered Event (MCE)
1 in 2,500 %
Beyond ULS, its implied the building may collapse, but intent of the code is that it remains intact up to MCE levels
Total
“Code only” based designs may not provide resilience

31. Te Puni Student Accommodation – Wellington 2007
Sliding Hinge Joints (SHJ) bolted connections
Concentric Braced Rocking Frames with Ringfedder hold down springs

32. The worlds first post tensioned timber rocking shear wall building
NMIT Building – Nelson 2010
The worlds first post tensioned
timber rocking shear wall building
Energy
Dissipaters
Post tensioning
tendons
Timber Rocking Walls

33. Hutt Hospital - Lower Hutt 2012
Base Isolation using Lead Rubber Bearings (LRB)
Bearing Movement at ULS ~+/-400mm

34. Tait Building – Christchurch 2013
Timber gravity structure with inter-span concrete floor system
Steel concentric braced rocking frames for seismic bracing
Ringfedder springs used to provide restoring

35. Elevate Apartments - Wellington 2014
Moment Resisting Frames with Sliding Hinge Joints (SHJs)
Low damage rocking K Brace frames
Ringfedder restoring springs at base of K brace frames

36. Rutherford House – Wellington 2016
Low Damage - Structural Steel Two Way Sliding Hinge Joint Frame

37. Recent Resilient Designs - Wellington
Te Puni Student Accommodation
BRANZ Head Office
Elevate Apartments
Nouvo Apartments and Townhouses - Rugby Street
Bellagio Apartments - Taranaki Street
Rutherford House
Halifax Street
Hutt Hospital ED/Theatres - Lower Hutt
HVDC Pole 3
+ many other projects throughout New Zealand