The Barrington Medical Center was a 6-story medical office building in West Los Angeles with plan dimensions of approximately 104 feet by 131 feet. Above the second floor, a significant stepback in the northeast corner gave the building it's characterist...

Prepared By: Quinn Peck
Occupancy: HospitalHealthcare
Year Built: 1968
Height: 77 ft
Number of stories: 6
Stories below ground:
Size: gsf
Original Code:
Modification: none
Year Modified: N/A
Code of Modification: N/A
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: United States
State: California
City: Santa Monica
Street: 11665 W Olympic Blvd, Santa Monica, CA
Latitude: 34.034
Longitude: -118.448


 

Barrington Bldg.

Earthquake Information

 

 

Earthquake Date 1/17/1994
Moment Magnitude 6.7
Epicentral Distance 21
Local Intensity MMI
Site Description "The original soil report shows 'moderately firm' sands and silts to a depth of about twenty feet, with somewhat firmer sands below and no water encountered for fifty feet. The description is consistent with UBC Soil Type S2: "dense or stiff soil.' (ATC, 1996)
PGA Lateral None (g)
PGA Vertical None (g)
SaT
Ground motion recording stations USGS - NSMP Station 5284
Distance to station 0.7
Station Latitude 34.04
Station Longitude -118.445
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.

 

Damage Information

 

 

Performance summary

The building experienced severe damaged during the Northridge earthquake and was "red tagged". Officials were worried about the possibility of collapse in aftershocks, so five days later, on January 22, the building was demolished with its contents intact.

Damage state description

The Barrington Medical Center was designed to utilize both the various shear walls throughout the building and the perimeter frames to resist lateral loads, but the lack of significant damage to the shear walls suggest that the vast majority of the seismic loads were resisted by the perimeter frames. Classic shear cracks were widespread in the columns at the second, third, and fourth floors, particularly on the west, south and north sides of the building. Significant column shortening was obvious from the buckled mullions, concentrated at the second floor. The exterior shear walls survived with little or no damage, possibly indicating a rocking of the foundation.

Summary of causes of damage

1. The deep spandrel beams concentrated shear forces in the columns, and, as the earthquake shaking repeatedly switched directions, classic x-shaped shear cracks opened up in the columns. 2. As the x-cracks in the columns became increasingly severe, the area in each column capable of carrying a vertical load began to decrease precipitating concrete crushing and subsequent shortening of the columns. This shortening was apparent in the buckling of the steel mullions on the building's exterior. 3. The lack of damage to the shear walls suggest that they did not resist seismic forces as expected. It has been postulated that the shear walls rocked, inducing significant shear forces in the pier-spandrel frames, ultimately causing the observed shear failures.

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
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
Corner

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 Possible inadequate anchorage of wall resulting in wall rocking.

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 Possible rocking of shear wall footing.

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://eqs.eeri.org/resource/1/easpef/v12/iS1/p49_s1?isAuthorized=no
Osteraas, John, and Peter Somers, 1996. Reinforced Concrete Structures.Earthquake Spectra,11, Supplement C, Vol. 2, 5253.


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://db.concretecoalition.org/static/data/3-additional-ground-motion/USA003_Ground_Motion_2.jpeg
United States Geological Survey (USGS), 2009.CISN Peak Accel. (in %g) for Northridge Earthquake,http://earthquake.usgs.gov/earthquakes/shakemap/sc/shake/Northridge/#Peak_Ground_Acceleration (9 July 2012).


http://eqs.eeri.org/resource/1/easpef/v11/iS2/p1_s1
Hauksson, Egill, 1996. Seismology.Earthquake Spectra,11, Supplement C, Vol. 2, 1-12.


Comartin, Craig, 1999. Personal photo collection.


https://www.atcouncil.org/Rehabilitation-of-Engineered-Buildings/Seismic-Evaluation-and-Retrofit-of-Concrete-Buildings/flypage.tpl.html?keyword=atc-40
Applied Technology Council (ATC), 1996.Seismic Evaluation and Retrofit of Concrete Buildings, Vol. 2,Report No. ATC-40, Redwood City, CA.