2013 EERI Annual Meeting Session: Christchurch Earthquakes Workshop

1. Rebuilding the Garden City
Impacts to the Canterbury Built
Environment
John Hare, Holmes Consulting Group,
Christchurch

2. Outline
1. Brief summary of findings
2. Overview of damage, by building type
3. Summary of outcomes
4. Discussion
5. Some lessons learnt
6. Issues for the recovery
7. Recap conclusions
2

3. Conclusions
• The Christchurch Earthquakes have provided some
valuable lessons on building performance – especially
concrete structures
– More research is required
• Our older building stock needs greater consideration
– A capacity based evaluation only identifies part of the problem
– Our buildings’ vulnerabilities need to be better understood
• Faster action is required to address these issues
– A passive approach is too slow and ineffective
3

4. Conclusions
• Proximity issues should be considered, especially
for critical facilities
• Other hazards must be considered, eg rockfall,
lateral spread
• Training is required to maximise preparedness
– Of engineering profession
– Of the general public
4

5. Damage
• Residential
• Heritage
• Commercial – Low and Medium Rise
• Commercial – High Rise
• Infrastructure
5

6. Damage
• Residential
• Heritage
• Commercial – Low and Medium Rise
• Commercial – High Rise
• Infrastructure
6

7. Shaking Damage
7

8. Shaking Damage
8

9. Shaking Damage
9

10. Shaking Damage
Rolleston Courts Cambridge Courts
10

11. Shaking Damage
11

12. Shaking Damage
12

13. Liquefaction/Lateral Spread
13

14. Liquefaction/Lateral Spread
14

15. Liquefaction/Lateral Spread
15

16. Liquefaction/Lateral Spread
16

17. Cliff tops
17

18. Cliff tops
18

19. Cliff tops
19

20. Cliff Collapse
20

21. Cliff Collapse
21

22. Rockfall
22

23. Rockfall
23

24. Rockfall
24

25. Rockfall
25

26. Damage
• Residential
• Heritage
• Commercial – Low and Medium Rise
• Commercial – High Rise
• Infrastructure
26

27. Christchurch Cathedral
27

28. Christchurch Cathedral
28

29. St Pauls Church. Madras Street
29

30. Press Company
30

31. Press Company
31

32. Knox Church
32

33. Arts Centre – College Hall
33

34. Arts Centre – Clock Tower
34

35. Arts Centre - Observatory
35

36. Arts Centre - Observatory
36

37. Basilica
37

38. Durham Street Methodist Church
38

39. Damage
• Residential
• Heritage
• Commercial – Low and Medium Rise
• Commercial – High Rise
• Infrastructure
39

40. Colombo Street
40

41. Manchester Street
41

42. Tuam Street
42

43. Colombo Street
43

44. Worcester Towers
44

45. CTV
45

46. CTV
46

47. CTV
47

48. PGC Building
48

49. PGC Building
49

50. Crowne Plaza
53

51. CDHB Carpark
57

52. CDHB Carpark
58

53. CDHB Carpark
59

54. CDHB Carpark
61

55. Anonymous!
62

56. Harcourts
63

57. 123 Victoria Street
64

58. 65

59. Damage
• Residential
• Heritage
• Commercial – Low and Medium Rise
• Commercial – High Rise
• Infrastructure
68

60. Grand Chancellor
69

61. Grand Chancellor
70

62. Grand Chancellor
71

63. Grand Chancellor
72

64. Grand Chancellor
73

65. Copthorne
74

66. Copthorne
75

67. Copthorne
78

68. Forsyth Barr
80

69. Forsyth Barr
81

70. Gallery apartments
88

71. Gallery Apartments
89

72. Damage
• Residential
• Heritage
• Commercial – Low and Medium Rise
• Commercial – High Rise
• Infrastructure
90

73. Bridges
91

74. Bridges
92

75. In-ground services
93

76. Roading
94

77. Overall
Outcomes
95

78. Immediately following the Feb 22 earthquake
• 185 people dead
– 115 in CTV building
– 18 in PGC building
– 5 through rockfall
– 2 infants at home
– 41 through falling masonry
– 4 related effects, after the quake
• 6,500 injured
• 12,000 homes evacuated immediately
96

79. Demolitions, CBD and suburbs
Partial Demolish Total
Civil Defence 66 241 307
Owner initiated 166 233 399
CER Act s.38/39
issued 198 713 911
Total 430 1,187 1,617
97

80. General Observations - Commercial
• Commercial
– Most modern buildings performed as expected,
with a few exceptions
– Most modern of modern buildings (post-1995)
performed well
– More damage to irregular and older structures
– Unstrengthened/unsecured masonry buildings
essentially destroyed
– Well strengthened masonry buildings performed
moderately well to very well
98

81. Building Performance
• Approx 8,000
commercial
buildings in Chch
• Approx 1200
currently slated
for demolition
– 900 in CBD
– 300 outer
• These numbers
likely to rise
99

82. 100

83. 101

84. 102

85. 103

86. 104

87. Why?
105

88. Context – Built environment
• Settled in mid-1800s
• Construction types
– First buildings in timber from 1840’s
– Stone and brick buildings 1850s to 1935
• 96 Stone masonry = 1/3 of all NZ stone masonry
– RC and Steel from early 1900s
– Most residential construction timber frame
• Seismic design provisions from 1935
– First specific seismic code 1965
– Capacity Design introduced 1976
– Non-specific timber and RM construction 1980s
– Full modern provisions from 1995
106

89. Context – Christchurch building profile
• Commercial Residential
Unreinforced masonry
Reinforced Masonry
Walls and Braced Unstrengthened
Frames Masonry
Strengthened
Masonry
Moment Frames
Timber frame
Holmes Consulting Group (estimate) Beattie (BRANZ)
108

90. Earthquake shaking in two events
5% Damped Spectra (North-South)
5% Damped Spectra (West-East)
1.80 1.60
1.80
Christchurch Botanic Gardens S01W Christchurch Botanic Gardens N89W
Christchurch Botanic Gardens N89W
Christchurch Hospital N01W Christchurch Hospital S89W
1.60 1.40 Christchurch Hospital S89W
Christchurch Resthaven N02E 1.60 Christchurch Resthaven S88E
Christchurch Resthaven S88E
Christchurch Cathedral College N26W
Christchurch Cathedral Cathedral College N64E
Christchurch College N64E
NZS1170 Spectra, Z=0.3, Soil Class D, IL2, ULS
1.40
NZS1170 Spectra, Z=0.22, Soil Class D, IL2, ULS 1.40 1.20 NZS1170 NZS1170Z=0.3, Soil Class SoilIL2, ULS IL2, ULS
Spectra, Spectra, Z=0.3, D, Class D,
NZS1170 NZS1170Z=0.22, Soil Class Soil Class D, IL2, ULS
Spectra, Spectra, Z=0.22, D, IL2, ULS
1.20 1.20
1.00
Acceleration (g)
Acceleration (g)
Acceleration (g)
1.00 1.00
0.80
0.80 0.80
0.60
0.60 0.60
0.40
0.40 0.40
0.20 0.20
0.20
0.00 0.00 0.00
0.00 1.00 2.00 3.00 4.00 5.00 6.00 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 5.00 5.00 6.00
Period (Seconds) Period (Seconds) (Seconds)
Period
September 4th February 22nd
109

91. Why?
• Ductility and Capacity design – design for
damage
• Ground ‘failure’
– Liquefaction
– Differential settlement
– Tilt up to 1 in 150 acceptable?
• Low cycle fatigue
– How much life is left in that steel?
– Testing showing many buildings have exceeded half
of the reinforcement strain capacity
• Repair costs
– >70% of value - gone
111

92. Why?
• Levels of insurance cover
– Chile 27%
– Mexico 21%
– California 17%
– Italy 14%
– Japan 12-17%
– Turkey 4%
– Haiti 1%
– New Zealand 80%
Source: Swiss Re
112

93. Insurance
• Overall insured losses estimated at
$30B – 3rd largest insurance event of
its kind.
• Process difficult
– Slow settlements
– Communication between clients and
insurers, insurers and reinsurers
• But what in the future?
– Higher cost of insurance
– Tighter conditions
– Less availability
113

94. General Observations - Residential
• Houses performed well structurally
– Light wood-framed construction – no collapses, generally
repairable
• Most failures due to ground performance
• 561,000 tons of silt removed
• 7,860 houses declared ‘red zone’, i.e. Government
buy-back of land, relocate
• 6,315 residential owners agreed to sell to government
so far (as at Dec 2012)
• 10,000 people estimated to have left Christchurch
• Unclear how many coming back, or when
114

95. Land Zones
115

96. Repairs
• EQC cover from $10,000-$100,000
– Fletcher EQR
– 31,010 homes repaired to end Jan 2013
– 65,000+ to go…..
• Private Insurers above $100,000
– More than 12,000 homes estimated as major repairs
or rebuild
– Most spread over 12 insurers
116

97. Infrastructure Rebuild
• Progress (Nov 2012)
– Completed 206 projects, totalling $80M
– 88 projects underway, totalling $220M
– Further projects in train for total of $1.5B
– 11 miles of fresh water pipe laid
– 30 miles of wastewater pipe laid
– 2 miles of stormwater pipe laid
– 19 acres of road pavement laid
– 745 miles (of 1006) of wastewater pipe videoed
– 415 miles (of675) of stormwater pipe videoed
• Total cost expected to exceed $5B
117

98. Preparedness
• Training of engineers
• Strengthening of Buildings - DO IT!!!!
It is too late after the earthquake
– Strengthen EPBs – 67% if possible
– Secure non-structural elements
– Re-evaluate critical weakness – more later
• Proximity effects
• Communication to the public
– What to do
– Expectations for buildings
– Self-reliance
119

99. Shoring – how to
120

100. ...and how not to
121

101. ...and how not to
122

102. Heritage Apartments
124

103. 208 Madras Street
125

104. CCC Tuam Street
126

105. Christchurch Art Gallery
• Temporary use as
emergency operations
centre
127

106. Issues affecting
recovery
128

107. Temporary Facilities
129

108. 130

109. 131

110. Residential
• Availability of land
– Valuations based on 2008
values
– New sections inflated in price
• Insurance
– Insurers still not re-entering
market with confidence
• Sale of properties
– Only to certain buyers
– Repairs still to be completed
limiting sales
• Standards for repair and
rebuild
132

111. DBH Map 2
133
133

112. Commercial
• Prior to earthquake:
– 4M sq ft of commercial office in CBD
– 2.75M sq ft needed
– Class A office space about $30/sq ft
– Class B office space about $22-25/sq ft
• Post earthquake
– Many tenants relocated out of CBD to office parks
on leases of 4 years plus
– Some businesses relocated out of city
– Current demand estimate 1.8M sq ft
– New building rentals $45/sq ft (class A)
134

113. Planning
• City plan rewrite
– Height limits?
– Urban planning
considerations
• Land ownership
– Mainly small,
closely held
ownership
– Amalgamation of
titles?
135

114. Central City Map
136

115. New Building Design
• Owners’ expectations
– Make it like a hospital in
Wellington!
– Low damage design
– Existing Use rights
– Individual owner vs
institutional developer
• Building Code updates?
137

116. Building Evaluation & Repair
• Detailed Engineering
Evaluations
– For all non-residential
structures
– Approx 2000 submitted,
1000 approved
• Temporary stability
concerns
• Strengthening design
loads
138

117. Detailed Engineering Evaluation Procedure – What is it?
• Developed by Engineering Advisory Group
(to DBH)
• Process of inspection, review and reporting
– Qualitative Procedure
– Quantitative Procedure – not always required
• Documents available at www.sesoc.org.nz
– Engineers briefed at CSG meetings
– Process is an overlay to work completed
already, not necessarily additional
139

118. Canterbury Earthquakes Royal Commission
(CERC)
• Seven volumes of report,
covering:
– Seismicity and soils
– Performance of CBD
buildings
– Low damage design
technology
– Earthquake Prone Buildings
– CTV collapse
– Roles and responsibilities
– Summary and
recommendations
140

119. NZ Wide – Earthquake Prone Buildings
• Consultation process
underway following
CERC report
• Dilemma
– %NBS?
– Or something else?
141

120. EPB Myth No 1 – Capacity Matters
• Current criteria for EPB – 33%NBS
• But what causes failure of buildings in
earthquake?
– Refer DEEs and IEPs….
142

121. Guess some scores
9%
143

122. Guess some scores
67%
144

123. NZ Wide – Codes and Standards
• Following CERC  MBIE  Updated
code
– When? Next 2-4 years?
– Submissions?
– Long process……
• SESOC
– Practice Note
– Design Of Conventional Structural Systems
Following The Canterbury Earthquakes
– Available for use now
– Uptake?
145

124. Conclusions
• The Christchurch Earthquakes have provided some valuable lessons
on building performance – especially concrete structures
– More research is required
• Our older building stock needs greater consideration
– A capacity based evaluation only identifies part of the problem
– Our buildings’ vulnerabilities need to be better understood
• Faster action is required to address these issues
– A passive approach is too slow and ineffective
• Proximity issues should be considered, especially for critical facilities
• Other hazards must be considered, eg rockfall, lateral spread
• Training is required to maximise preparedness
– Of engineering profession
– Of the general public
146