The JFK Senior High School Administration Building A was a 3-story concrete frame and concrete masonry wall building built in 1971 as part of a 15 building high school campus. The Administration Building has a typical plan dimensions of approximately 153 ...

Prepared By: Quinn Peck
Occupancy: Education
Year Built: 1971
Height: ft
Number of stories: 3
Stories below ground:
Size: 64000 gsf
Original Code: 1967 UBC
Modification: none
Year Modified: N/A
Code of Modification: N/A
Lateral Load System: Shear Wallrete
Other Load System: w/ concrete-block masonry shear walls
Vertical Load System: One-way slab and beams with columns
Other Vertical Load System:
Foundation : Piles or Piers
Other Foundation :
Country: United States
State: California
City: Granada Hills
Street: 11254 Gothic Avenue, Granada Hills, CA 91344
Latitude: 34.2744
Longitude: -118.4885


 

JFK HS Admin.

Earthquake Information

 

 

Earthquake Date 1/17/1994
Moment Magnitude 6.7
Epicentral Distance 8
Local Intensity VIII MMI
Site Description The building sat on loose sands and silts between 5 and 15 feet thick.
PGA Lateral None (g)
PGA Vertical None (g)
SaT
Ground motion recording stations LADWP Rinaldi
Distance to station 1.2
Station Latitude 34.281
Station Longitude -118.479
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 JFK Senior High School Administration Building A was not instrumented to record gorund motion, a LADWP recording station 1.2 km away recorded a PGA of 0.84g.

 

Damage Information

 

 

Performance summary

The building experienced severe structural damage during the Northridge earthquake and was immediately "red tagged". Damage to the exterior shear walls was widespread and the concrete slab on grade exhibited wide cracks emanating from the columns in the west wall toward the building's interior.

Damage state description

The first floor exterior walls exhibited diagonal or X-pattern cracking and the second and third floor walls exhibited harline cracks. The east face of the first floor had severely damaged shear walls with wide diagonal cracks, extensive failure of the masonry walls, including damage at the bottom corners of the walls, and consistent cracking and failure of columns. The west face of the first floor exhibited severe failure of the narrow concrete shear walls between precast concrete channels and significant spalling of masonry walls. Walls on the north and south faces also exhibited diagonal cracking, but to a lesser extent than the east and west walls. The concrete slab on grade near the main entrance of the building exhibited wide cracking emanating from the columns in the west wall toward the interior of the building and appeared to have lifted up slightly in some locations. It is possible that the extensive failure of drypack joints between masonry walls and concrete beams above resulted in a progressive transfer of loads to different elements. It is generally believed that if the earthquake had continued much longer, the progressive failure in the lateral force resisting system would have resulted in a collapse.

Summary of causes of damage

1. A lack of physical elements to transfer shear forces between concrete columns and masonry infill resulted in a failure of the drypack joint at the concrete masonry block shear walls which may have lead to overstressing of nonseismic concrete columns resulting in cracking and subsequent shear failure. 2. The failure of the exterior walls in the north-south direction forced the interior shear walls to carry significantly larger seismic forces than they were designed for, leading to damage at each wall, including diagonal cracking near the ends and spalling dear the base of the jamb reinforcing steel. 3.The exterior walls on the west face of the building exhibited typical shear failures, suggesting that they were not properly detailed for ductile behavior.

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

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 The concrete slab on grade near the main entrance of the building exhibited wide cracking emanating from the columns in the west wall toward the interior of the building and appeared to have lifted up slightly in some locations.

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

Repair and Retrofit Information

 

Type of Retrofit or Repair

Unknown

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://www.seismic.ca.gov/pub.html
Seismic Safety Commission (SSC), 1994. JFK Senior High School, Administration Building.Northridge Building Case Studies Project. Kawasaki, Isao, Brandow & Johnston Associates for the California Seismic Safety Commission. Second Draft, September 26.


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/v11/iS2/p13_s1
Huang, M.J., and A. F. Shakal, 1995. Recorded ground and structure motions.Earthquake Spectra,11, S13S96.


http://db.concretecoalition.org/static/data/6-references/USA002_Ground_Motion_4.jpeg
Hartzell, S., P. Liu, and C. Mendoza, 1996. The 1994 Northridge, California, earthquake: Investigation of rupture velocity, risetime, and high-frequency radiation,Journal of Geophysical Research,101, 2009120108.


http://db.concretecoalition.org/static/data/4-illustration-of-damage/USA002_Damage_1.jpg
EERI, 1994. Earthquake Engineering Research Institute Photo Library, Oakland, CA.