The Champagne Tower is a 16-story residential building in Santa Monica at the intersection of Ocean Avenue and Wiltshire Boulevard. Seismic forces are resisted by eight bays of non-ductile sway frames in the longitudinal direction and two coupled shear wa...

Prepared By: Quinn Peck
Occupancy: Residential
Year Built: 1971
Height: ft
Number of stories: 16
Stories below ground:
Size: gsf
Original Code: UBC 1962
Modification: Unknown
Year Modified:
Code of Modification:
Lateral Load System: Moment Frame and Shear Wall Combination
Other Load System:
Vertical Load System: Unknown
Other Vertical Load System:
Foundation : Unknown
Other Foundation :
Country: United States
State: California
City: Santa Monica
Street: 1221 Ocean Avenue, Santa Monica, CA 90401
Latitude: 34.0163
Longitude: -118.5001


 

Champagne Tower

Earthquake Information

 

 

Earthquake Date 1/17/1994
Moment Magnitude 6.7
Epicentral Distance 22
Local Intensity VIII MMI
Site Description
PGA Lateral None (g)
PGA Vertical None (g)
SaT
Ground motion recording stations CSMIP Station No. 24538
Distance to station 0.3
Station Latitude 34.0112
Station Longitude -118.492
Ground Motion Summary The earthquake occurred along the Pico thrust fault, a previously undiscovered Northridge blind thrust fault, and produced some of the strongest ground motions ever recorded in North America. The earthquake started at the down-dip, southeastern corner of the Pico fault plane and ruptured up northwest approximately 15 km, with no evidence of slip above 7 km below the earth's surface. The hypocenter is believed to lie at a depth of about 19 km km at a location of 34.213, -118.537. An overall maximum horizontal ground acceleration of 1.93g was recorded at Tarzana, about 11.2 km from the epicenter. While the Champagne Tower was not instrumented to record ground motion, a recording station 0.3 km away at the Santa Monica City Hall Grounds recorded a PGA of 0.93g.

 

Damage Information

 

 

Performance summary

The Champagne Tower was significantly damaged during the Northridge earthquake, with severe X-cracking in the columns of the longitudinal perimeter sway frames and the coupling beams in the transverse direction.

Damage state description

The worst damage was observed in the columns at the lower floors of the northeast face. Here the presence of monolithic parapet beam drastically shortened the clear heights of the columns, leading to severe shear failures. The contribution of the parapet beams is obvious, as the southeast face exhibited little to no damage. The coupling beams between the perimeter shear walls in the transverse direction were also significantly damaged.

Summary of causes of damage

1. The stiff parapet beams stiffened the columns on the northeast face of the building, which likely attracted more load from the more flexible interior frames. 2. The tall, monolithic parapet also significantly shortened the clear-height of the columns, leading to shear failures before they were able to develop their flexural capacity. 3. The damage to the transverse coupling beams between shear walls could have been partially caused by a torsional response resulting from the significantly stiffer northeast face. However, the internal layout of the building was unknown so the torsional behavior could have been a result of an asymmetrical layout.

Observed Design and Construction Characteristics

 

Construction Quality

MaterialsNotesContribution to Damage
Concrete
Reinforcing steel

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

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 Shear strength was inadequate where full column-heights could not be engaged.
Flexural strength Frames on southwest face seemed to behave well.
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
Corner

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting System-Frames Interference of frame action by parapets. Presence of concrete parapets significantly shortened the columns on the northeast face of the building, resulted in severe shear failures.

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 Insufficient reinforcing in coupling beams.

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

Stabilization

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

The extensive damage to lateral force-resisting system and the shortening of the columns on the northeast face of the structure prompted the installation of temporary shoring to decrease the risk of collapse in an aftershock.

Retrofit Summary

The badly fractured columns were strengthened with external ties and plates and the vertical load-carrying capacity was reinforced through supplementary steel columns.

References

 

http://db.concretecoalition.org/static/data/6-references/USA010_Reference_1.pdf
Lew, H. S., Cooper, J. D., Hacopian, S., Hays, W., Mahoney, M., 1994. January 17, 1994, Northridge Earthquake, California.National Institute of Standards and Technology (NIST) Special Publications778.


http://db.concretecoalition.org/static/data/6-references/USA001_Reference_4.pdf
Comartin, Craig, Kenneth Elwood, and Heidi Faison, 2004. "Reinforced Concrete Moment Frame Building without Seismic Details." World Housing Encyclopedia.http://www.world-housing.net/WHEReports/wh100108.pdf ( 9 July 2012).


http://db.concretecoalition.org/static/data/6-references/USA001_Reference_2.pdf
Earthquake Engineering Field Investigation Team (EEFIT), 1994. The Northridge, California Earthquake of 17 January 1994: A Field Report by EEFIT. EEFIT, Institute of Structural Engineers.


http://db.concretecoalition.org/static/data/3-additional-ground-motion/USA001_Ground_Motion_1.jpeg
United States Geological Survey (USGS), 2009.CISN ShakeMap for Northridge Earthquake,http://earthquake.usgs.gov/earthquakes/shakemap/sc/shake/Northridge/ (9 July 2012).


http://eqs.eeri.org/resource/1/easpef/v12/iS1/p49_s1
Osteraas, John, and Peter Somers, 1996. Reinforced Concrete Structures.Earthquake Spectra,11, Supplement C, Vol. 2, 5961.


http://eqs.eeri.org/resource/1/easpef/v11/iS2/p13_s1
Huang, M.J., and A. F. Shakal, 1995. Recorded ground and structure motions.Earthquake Spectra,11, Supplement C, Vol. 1,1396.


http://www.wiley.com/WileyCDA/WileyTitle/productCd-0470048433.html
Erdey, Charles K., 2007.Earthquake Engineering: Application to Design. John Wiley & Sons, Hoboken, NH.