This building consisted of six two-bay RC frames in the east-west direction and three five-bay RC frames in the north-south direction. It was first constructed as a four-story structure in 1967 and in 2001, the top story of the old structure was removed a...

Prepared By: Edwin Lim
Occupancy: Commercial
Year Built: 1967
Height: 63 ft
Number of stories: 5
Stories below ground: 0
Size: 4715 gsf
Original Code:
Modification: Addition
Year Modified: 2001
Code of Modification:
Lateral Load System: MomentFrame
Other Load System:
Vertical Load System: Slabl_Beams_Columns
Other Vertical Load System:
Foundation : Piles or Piers
Other Foundation :
Country: New Zealand
State: Canterbury
City: Christchurch
Street: 374 Montreal Street
Latitude: -43.524221
Longitude: 172.630921


 

5-Story Building

Earthquake Information

 

 

Earthquake Date 40596
Moment Magnitude 6.1
Epicentral Distance 7.639
Local Intensity VIII MMI
Site Description Site class D (Kam et al, 2011)
PGA Lateral 0.531 (g)
PGA Vertical 0.5 (g)
SaT
Ground motion recording stations Christchurch Cathedral College (CCCC), Christchurch Botanic Gardens (CBGS), Christchurch Hospital (CHHC), Christchurch Resthaven (REHS)
Distance to station None
Station Latitude None
Station Longitude None
Ground Motion Summary The February, 2011 South Island, New Zealand earthquake occurred as part of the aftershock sequence of the M 7.0 September, 2010 Darfield, NZ earthquake. The February earthquake involved oblique-thrust faulting at the easternmost limit of previous aftershocks and like the main shock itself is broadly associated with regional plate boundary deformation as the Pacific and Australia plates interact in the central South island, New Zealand. This latest shock is significantly closer to the main population center of Christchurch, NZ. This is the September main shock, in the vicinity of several other moderate sized aftershocks located east of the main rupture zone of the 2010 event. There is no specific structure directly linking this event to the main fault of the 2010 main shock, although there have been numerous aftershocks along generally east-west linear trends extending east from the end of the previous rupture. The north or north-east trends to the possible fault planes and the oblique thrust faulting mechanism as seen in the focal mechanism solution may reflect an association with similarly-trending faults previously mapped in the Port Hills region, just south of Christchurch (USGS, 2012).

 

Damage Information

 

 

Performance summary

The tower structure on the west side was seismically isolated from the frame building and tilted 120 mm east due to ground failure. The building was subjected to significant lap splice damage and flexural damage in the February 2011 shake and was subjected to soft story mechanisms in the April 2011 aftershock (extracted from Kam et al, 2011).

Damage state description

Significant lap splice damage, triggering shear failure, was observed on the beam spanning the east-west direction on the first floor. Meanwhile on the second and third floor, the beams suffered from minor to moderate flexural cracks (Refer to top left figure in page 3) (Kam et al, 2011). Damage was also observed in some non-structural components, such as cabinets and ceilings.

Summary of causes of damage

The major cause of damage in this building for the February 2011 earthquake was the lack of adequate splicing in the beam. Also, the existing weak-story layout and damage condition led to a catastrophic building failure and soft-story collapse (extracted from Kam et al, 2011).

Observed Design and Construction Characteristics

 

Construction Quality

MaterialsNotesContribution to Damage
Concrete
Reinforcing steel Deformed rebar was observed in damage location

ExecutionNotesContribution to Damage
Conveyance/placement of concrete
Rebar
Field variance with design documents
OtherNotesContribution to Damage
Other Factors Construction Quality

Configuration

Plan IrregularitiesNotesContribution to Damage
Torsion
Perimeter boundary A tower structure on the west side. However, it was seismically isolated.
Diaphragm
Out-of-plane offsets in lateral resisting system The additional steel frame structure in the west side is offset from the lower concrete structure.
Non-orthogonal systems

Vertical IrregularitiesNotesContribution to Damage
Soft story The soft story effect did not govern in the February aftershock, but it did in the April aftershock
Weak story
Geometric variablility of lateral resisting system
In-plane discontinuity of lateral resisting system
Mass distribution
Setback
Change in stiffness

OtherNotesContribution to Damage
Other Factors Configuration

Lateral Load Resisting System‐General

StrengthNotesContribution to Damage
Overall lack of strength

StiffnessNotesContribution to Damage
Extreme Flexibility

Load PathNotesContribution to Damage
Collectors/Struts
Anchorage of nonstructural elements
Out-of-plane capacity of walls
Diaphragm chords
Diaphragm openings

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting System-General

Lateral Load Resisting System‐Frames

ColumnsNotesContribution to Damage
Shear strength The base columns were well confined with 9.5 diameter bar ties spaced at 100 mm on-center.
Flexural strength
Axial load ratio
Vertical load columns drift capacity
Interference of frame action by infill

BeamsNotesContribution to Damage
Strength relative to columns
Shear controlled behavior Ground floor beam at the short lap spliced region
Continuity of longitudinal reinforcing Short lap splices
Loss of vertical capacity
Interference of frame action by infill beams

JointsNotesContribution to Damage
Interior
Exterior
Corner

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting System-Frames Flexural crack in second and third floor beams

Lateral Load Resisting System‐Shear Walls

ShearNotesContribution to Damage
Diagonal tension/compression
Sliding Shear
Flexure/shear

FlexureNotesContribution to Damage
Compression zone buckling capacity
Discontinuity of wall
Boundary reinforcing fracture/buckling
Boundary Reinforcing at openings

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting System-Shear Walls

Lateral Load Resisting System‐Infills

InfillsNotesContribution to Damage
Unreinforced
Interference with frame action
Out of plane
Attachment to framing

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting Systems-Infills

Lateral Load Resisting System‐Other

FoundationsNotesContribution to Damage
Liquefaction
Pounding
Surface Rupture

OtherNotesContribution to Damage
Pile/Pier tension capacity

MiscellaneousNotesContribution to Damage
Spread footing capacity
Other Factors Lateral Load Resisting Systems-Other-Foundations Foundation failure on west tower side

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting Systems-Other-Misc

Repair and Retrofit Information

 

 

Type of Retrofit or Repair

None (demolished/abandoned)

Other Retrofit or Repair

During April 2011 aftershocks, the building collapsed with an indication of a soft-story effect at the ground floor

Performance Level

NA

Hazard Level

NA

Retrofit or Repair Code

NA

Other Retrofit or Repair Code

Lateral Analysis

NA

Other Lateral Analysis

Design Strategy

Retrofit Summary

References

 

http://db.concretecoalition.org/static/data/6-references/NZ002_Reference_3.pdf
Kam, W.Y., Pampanin, S., and Elwood, K., 2011. Seismic Performance of Reinforced Concrete Buildings in the 22 February Christchurch (Lyttelton) Earthquake,Bulletin of the New Zealand Society for Earthquake Engineering,44.


http://www.geonet.org.nz/earthquake/historic-earthquakes/top-nz/quake-14.html
GeoNet, 2011.M 6.3, Christchurch, February 22 2011. (Accessed: 12 July 2012).


http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usb0001igm/
United States Geological Survey (USGS), 2011.Magnitude 6.1 - SOUTH ISLAND OF NEW ZEALAND, (Accessed: 12 July 2012)


http://strongmotioncenter.org
Center for Earthquake Strong Motion Data (CESMD), 2011.New Zealand Earthquake of 21 February 2011, (Accessed: 10 July 2012).


Berkowitz, R., 2011. Select photos from 21 February 2011 Christchurch, New Zealand Earthquake. Earthquake Engineering Research Institute Photo Library, Oakland, CA.