This building was an 8 story RC frame - C shape core wall building. The typical square columns had dimensions of 457 mm and were reinforced with 12 D-28mm longitudinal bars and D10-230 mm stirrups (Refer to the figure in the next page for more detailed in...

Prepared By: Edwin Lim
Occupancy: Commercial
Year Built: 1973
Height: 79.75 ft
Number of stories: 8
Stories below ground: 0
Size: 3513 gsf
Original Code:
Modification: Unknown
Year Modified:
Code of Modification:
Lateral Load System: Moment Frame and Shear Wall Combination
Other Load System:
Vertical Load System: Two-way slab and beams with columns
Other Vertical Load System:
Foundation : Piles or Piers
Other Foundation :
Country: New Zealand
State: Canterbury
City: Chirstchurch
Street: 221 Gloucester street at Madras street
Latitude: -43.530891
Longitude: 172.647201


 

8-Story Building

Earthquake Information

 

 

Earthquake Date 40596
Moment Magnitude 6.1
Epicentral Distance 6.369
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). It is of interest to notice that, in general, the ground motion in the east-west direction is stronger than the north-south direction.

 

Damage Information

 

 

Performance summary

By most account, this early 1970's RC building has performed reasonably well despite the onset of the brittle mode in the columns. The redundancy provided by the dual frame-wall systems ensures the building remains standing despite the onset of brittle failure of the east-west perimeter frames. In addition, the core wall did not seem to resist a significant amount of the seismic inertial forces (extracted from Kam et al, 2011).

Damage state description

The first floor columns on the north elevation failed in shear with the upturned spandrel beam creating a short-column effect. In both northern and southern elevation frames, the beam-column joints were cracked with limited spalling. No apparent damage of the shear-corewall was observed. Only relatively minor cracks were observed within the core walls (extracted from Kam et al, 2011).

Summary of causes of damage

Damage in first floor column shear failure was caused by these reasons: 1. The upturned spandrel beam creating a captive column effect (Kam et al, 2011) 2. Indication of torsion, since the columns in the north face were subjected to severe damage. Meanwhile, the columns in the south face only suffered light shear cracks (Elwood, 2011). Shear cracks in the beam-column joint indicated that the flexibility of the joint needed to be considered in frame analysis even if the performance was not governed by this failure (Elwood, 2011).

Observed Design and Construction Characteristics

 

Construction Quality

MaterialsNotesContribution to Damage
Concrete
Reinforcing steel Smooth bar in transverse rebar

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
Diaphragm
Out-of-plane offsets in lateral resisting system
Non-orthogonal systems

Vertical IrregularitiesNotesContribution to Damage
Soft story
Weak story
Geometric variablility of lateral resisting system
In-plane discontinuity of lateral resisting system
Mass distribution
Setback
Change in stiffness Column size was reduced in increasing stories but this was insignificant to the observed damage

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
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
Continuity of longitudinal reinforcing
Loss of vertical capacity
Interference of frame action by infill beams

JointsNotesContribution to Damage
Interior
Exterior Diagonal cracks (X shape)
Corner Diagonal cracks (X shape)

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting System-Frames

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

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

Performance Level

Unknown

Hazard Level

Unknown

Retrofit or Repair Code

Unknown

Other Retrofit or Repair Code

Lateral Analysis

Unknown

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, 239178.


Elwood, K., 2011. Performance of Concrete Buildings in the 22 February 2011 Christchurch Earthquake and Implications for Canadian Code,Canadian Journal of Civil Engineering. (Under Review)???


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


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)


Kam, W.Y., 2011. Select photos from 21 February 2011 Christchurch, New Zealand Earthquake. Earthquake Engineering Research Institute Photo Library, Oakland, CA.