The majority of the structural system is concrete walls. The south face of the building has a steel moment frame encased in concrete. In the transverse (E-W) direction, there are four interior concrete shear walls on one side of the building which are...

Prepared By: Sarah Bettinger
Occupancy: Commercial
Year Built: 1955
Height:
Number of stories: 12
Stories below ground: 1
Size:
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: One-way slab and beams with columns
Other Vertical Load System: one-way cip floor with steel framing
Foundation : Spread Footings
Other Foundation :
Country: United States
State: California
City: Northridge
Street: 6505 Wilshire Blvd
Latitude: 34.06435
Longitude: -118.4437002


 

Jewish Federation Council Building

Earthquake Information

 

 

Earthquake Date 34351
Moment Magnitude 6.7
Epicentral Distance 4
Local Intensity
Site Description
PGA Lateral 0.458 (g)
PGA Vertical None (g)
SaT
Ground motion recording stations LABSN Station 00003, 17645 Saticoy St., Northridge, CA
Distance to station 2.5
Station Latitude 34.2
Station Longitude -118.517
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

There was widespread moderate damage, but the building was not a collapse hazard.

Damage state description

Numerous hairline cracks and concrete spalling. There was cracking in a deep spandrel beam. There was evidence of horizontal shear/ sliding cracks at the stairwells. The concrete around the steel columns cracked. There was minor overstress in the walls.

Summary of causes of damage

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 Minor irregularity of shear walls; long wall on one side of the building with smaller walls on the opposite side.
Perimeter boundary
Diaphragm High number of perforations in walls
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 High number of perforations in walls.

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 Cracking in concrete around steel column

Lateral Load Resisting System‐Shear Walls

ShearNotesContribution to Damage
Diagonal tension/compression Series of minor diagonal shear cracks
Sliding Shear Horizontal shear/ sliding cracks at stairwell.
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 Liquefaction zone in the area; piles for 3-story building. Might have been a concern. Likely did not contribute to damage, if present.
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

Improved Performance

Other Retrofit or Repair

Performance Level

Life safety

Hazard Level

Unknown

Retrofit or Repair Code

Other

Other Retrofit or Repair Code

1994 UBC

Lateral Analysis

Unknown

Other Lateral Analysis

Design Strategy

The objective of the retrofit was life-safety with full upgrade (more than restoration to original condition). The entire building was brought up to the current code (UBC 94).

Retrofit Summary

Cracks were repaired, and damaged walls were epoxied. Shotcrete was used to supplement existing walls. In the transverse direction, four interior concrete shear walls were added, each 8 inches thick. In the longitudinal direction, a concrete shear wall on the north side and a steel moment frame on the south side were added. Concrete moment frames were added to walls

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.jpg
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.jpg
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.


Nabih Youssef Associates. Interview, professional expertise, photos, drawings. August 17, 2012.