This large complex is a category 2 building, which refers to a building constructed after the 1954 earthquake, under French building regulations. This building complex comprised three large buildings that were separated by thermal expansion joints (10-20 ...

Prepared By: Edwin Lim
Occupancy: Mixed Use
Year Built: 1962
Height:
Number of stories: 2
Stories below ground: 0
Size: 22500 gsf
Original Code: AS 55 Recomendation
Modification: Unknown
Year Modified:
Code of Modification:
Lateral Load System: Frames with Masonry Infill
Other Load System:
Vertical Load System: Waffle or pan-joist with columns
Other Vertical Load System: (In most of the buildings)
Foundation : Spread Footings
Other Foundation :
Country: Algeria
State:
City: El-Asnam/Chlef
Street:
Latitude: 36.166632
Longitude: 1.332326


 

Cite An Nasr Market

Earthquake Information

 

 

Earthquake Date 29/5/04
Moment Magnitude 7.3
Epicentral Distance 4.035
Local Intensity IX MMI
Site Description El-Asnam is located in a broad alluvial valley flanked to the north and south by ranges of hills that rise to a height of approximately 1000 m. No major slope failures were observed in the city of El-Asnam. (Source: Bertero & Shat, et al, 1983)
PGA Lateral 0.4 (g)
PGA Vertical 0.5 (g)
SaT
Ground motion recording stations There was an earthquake ground motion recorded by IZIIS Center at Skopye (Macedonia) for this earthquake. After this earthquake event, some ground motion recorders were installed at the field to measure the aftershocks. From this record, it is interesting to note that the vertical acceleration was larger than the horizontal acceleration. (Source: Bertero & Shah, et al, 1983)
Distance to station
Station Latitude None
Station Longitude None
Ground Motion Summary The main shock was produced by displacement on a northeast trending thrust fault that dips to the northwest; this fault has subsequently been named the Oued Fodda fault after the closest principal city aligning its surface trace. Numerous secondary fissures and normal faults occur on the upthrown block of the main thrust within a zone that extends to 2 km from the main trace. Surface faulting also occurred along Beni Rached fault, a normal fault that may also be a secondary fault. Surface faulting occurred along the Oued Fodda fault, which is located south and east of El-Asnam; the closest distance of surface trace to El-Asnam is about 7 km. The surface faulting occurred along a zone that extends at least 30 km. Secondary normal faulting and ground cracking suggests that the primary thrust fault rupture may extend an additional 2 km to the southwest and 4 km further eastward to El-Abadia, suggesting an overall rupture length of 35 km. In most places, the primary fault is a low angle thrust that dips 10 to 20 degree northwest. Locally, the dip of the primary fault steepens to form a reverse fault that dips as steeply as 55 degree. Because there is no record for this main event, there was much debate regarding the earthquake's duration. According to some, the strong motion of the main shock lasted over 15 seconds, while the total duration lasted about 35 to 40 seconds. (Source: Bertero & Shah,et al, 1983)

 

Damage Information

 

 

Performance summary

During the El-Asnam earthquake, the two buildings (no.14, top left figure of page 3) collapsed within a few seconds. The remaining section is shown by the "i" letter on page 3. Although it was standing, this remaining unit was subjected to severe damage and it was in need of demolition. (Source: Bertero & Shah, et al, 1983)

Damage state description

The primary structural damage in this building was found to result from plastic hinges, which formed in the columns due to the significant displacement of a heavy second story. On the second floor, the heavy roof structure was supported by weak columns. In addition, the masonry wall was ineffective in resisting the earthquake loads. Because of a lack of proper reinforcement and weak concrete, the columns could not receive these forces that developed at the roof once the walls began to fail (Bertero & Shah, et al, 1983). Collapse of the second story led to the collapse of the first story, which might have initialized from the interior columns. These columns were forced to receive a major part of the lateral shear at the first story because they were captive by the infilled partitions and because of the presence of beams supporting the mezzanine. Similar to the columns in the second story, these short columns could not receive the forces because they lacked proper reinforcement. The failure of the first story interior columns led to a cave-in of the waffle slab and failure of the external columns (Bertero & Shah, et al, 1983).

Summary of causes of damage

Main reasons for failure in this building complex: 1. Poor seismic-resistant layout, particularly in height, which caused too sudden a change in stiffness and strength between the first and second stories, and between exterior and interior columns of the first story 2. Long cantilever 3. Heavy roof and floor systems 4. Heavy parapets on the roof, heavy unreinforced walls and partitions improperly anchored to the structure 5. Poor design and detailing of structural members 6. Poor quality and placement of concrete, particularly in columns (Source: Bertero & Shah, et al, 1983)

Observed Design and Construction Characteristics

 

Construction Quality

MaterialsNotesContribution to Damage
Concrete The concrete strength was probably lower than the specified 210 kg/cm2 or 3000 psi
Reinforcing steel

ExecutionNotesContribution to Damage
Conveyance/placement of concrete Significant concrete honey comb was observed in several columns
Rebar Lack of ductile detailing
Field variance with design documents
OtherNotesContribution to Damage
Other Factors Construction Quality

Configuration

Plan IrregularitiesNotesContribution to Damage
Torsion Due to structural configuration and unbalanced additional mass
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 There were more columns in the first story than the second story.
Mass distribution Due to heavy roof and mezzanine area
Setback
Change in stiffness Sudden significant change in column stiffness between the first and second story

OtherNotesContribution to Damage
Other Factors Configuration Changes in stiffness and strength between exterior and interior columns, and long cantilever

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 Interior columns in the first story
Vertical load columns drift capacity
Interference of frame action by infill Captive column in first story

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 Non structural deformation compatibility
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

None (demolished/abandoned)

Other Retrofit or Repair

Performance Level

NA

Hazard Level

NA

Retrofit or Repair Code

NA

Other Retrofit or Repair Code

Lateral Analysis

NA

Other Lateral Analysis

Design Strategy

Retrofit Summary

References

 

https://www.eeri.org/products-page/reconnaissance-reports/el-asnam-algeria-earthquake-of-october-10-1980-2/
Bertero, V.,Shah, H.,et al. 1980. El - Asnam, Algeria Earthquake of October 10, 1980 - A Reconnaissance and Engineering Report. NRC & EERI.


http://earthquake.usgs.gov/earthquakes/eqarchives/significant/sig_1980.php
United States Geological Survey (USGS), 2012.Significant Earthquakes of the world 1980, (accessed: 10 August 2012).


http://nisee.berkeley.edu/elibrary/search?in=null&ss=El+Asnam+earthquake&start=1
Colored images are courtesy of the National Information Service for Earthquake Engineering, EERC, University of California, Berkeley