The Saint Monica Catholic Church is a concrete frame building with multi-wythe thickness of unreinforced, non-gravity-load-bearing masonry infill. The plan of the building is generally one long nave in the longitudinal direction, with a semi-circular apse...

Prepared By: Sarah Bettinger
Occupancy: Religious
Year Built: 1925
Height:
Number of stories:
Stories below ground: unknown
Size:
Original Code:
Modification: none
Year Modified: N/A
Code of Modification: N/A
Lateral Load System: Frames with Masonry Infill
Other Load System:
Vertical Load System: Slabl_Beams_Columns
Other Vertical Load System:
Foundation : Spread Footings
Other Foundation : Shallow footings
Country: United States
State: California
City: Santa Monica
Street: 725 California Avenue, Santa Monica, CA
Latitude: 34.0231
Longitude: -118.4971


 

Saint Monica Church

Earthquake Information

 

 

Earthquake Date 34351
Moment Magnitude 6.7
Epicentral Distance 21
Local Intensity
Site Description
PGA Lateral 0.93 (g)
PGA Vertical None (g)
SaT
Ground motion recording stations CGS-CSMIP Station 24538 : Santa Monica- City Hall Grounds. This station location is listed as alluvium.
Distance to station 1.5
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.

 

Damage Information

 

 

Performance summary

The building was significantly damaged.

Damage state description

Most visible damage was to the non-gravity bearing unreinforced masonry infill. The gable over the altar (north) end of the church suffered an out-of-plane collapse of the masonry infill, and there were large (6"-7") cracks in the exterior concrete blocks observed at various locations around the building. The tower in the front (south) of the building was substantially damaged and cracked. There was out of plane collapse of the masonry infill in the apse behind the altar.

Summary of causes of damage

1. Out of plane collapse of unreinforced masonry infill wall at apse and gable. 2. Diagonal cracking and widespread large (6"-7") cracking along the walls and tower 3. Detachment of the lower roof diaphragm from the high walls of the central nave, and subsequent pounding between those two areas.

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 Insufficient diaphragm connectivity between higher nave walls and lower nave roof resulted in pounding
Out-of-plane offsets in lateral resisting system Structural plans required to assess 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 Large diagonal cracks were observed in multiple locations
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 Weak diaphragm connection between upper nave walls and lower nave roofs caused 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

Stabilization

Performance Level

Life safety

Hazard Level

Unknown

Retrofit or Repair Code

Unknown

Other Retrofit or Repair Code

Lateral Analysis

Unknown

Other Lateral Analysis

Design Strategy

The strategy was for stabilization of the existing building and life safety.

Retrofit Summary

1. A solid concrete shear wall was added along the entire length and height of the semi-circular apse behind the altar. 2. A concrete frame and associated new spread footings were added at the end of the apse. 3. A wythe of masonry was removed at the low walls in the longitudinal direction and replaced by shear walls. 4. A concrete frame and concrete shear walls were added to the tower. 5. Reduction of masonry falling hazard.

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.