"Lift-slab buildings had one or more cast-in-place concrete cores and precast-concrete columns supporting the slabs. Apparently, all slabs were cast on the ground level and lifted up to their appropriate positions as the casting of the core progressed. Th...

Prepared By: Sarah Bettinger
Occupancy: Residential
Year Built: 1970
Height:
Number of stories: 16
Stories below ground: unknown
Size:
Original Code: SNiP 62? Part 2, Chapter 1 of Standards and Regulations for Construction (1984)?
Modification: none
Year Modified:
Code of Modification:
Lateral Load System: Precast Concrete
Other Load System: Lateral loads resisted by the concrete core
Vertical Load System: Slabl_Beams_Columns
Other Vertical Load System: Precast columns provided support for vertical loads only.
Foundation : Other
Other Foundation : Columns supported on spread footings and core on mat foundation.
Country: Armenia
State: N/A
City: Leninakan (now Gyumri)
Street:
Latitude: 40.796138
Longitude: 43.847755


 

PC Lift-Slab Building

Earthquake Information

 

 

Earthquake Date 32484
Moment Magnitude 6.9
Epicentral Distance 40
Local Intensity IX Other
Site Description Leninakan is located in a broad valley of poorly consolidated material. Aftershock recordings indicate significantly increased ground motion at Leninakan at longer periods than at other sites in the vicinity.
PGA Lateral 0.4 (g)
PGA Vertical None (g)
SaT
Ground motion recording stations Four (of eight) of the strong-motion instruments in Leninakan at the time of the quake produced usable data, as well as a strong-motion accelerograph in Ghoukasain (27km N. of Leninakan), a network of instruments in Yerevan (80km S. of the epicenter), and data from instruments at the nuclear power plant in Medzamor (80km S. of the epicenter).
Distance to station None
Station Latitude None
Station Longitude None
Ground Motion Summary The USGS (United States Geologic Survey) indicates that the focal depth of the quake was 10km, and that the quake occurred at the boundary of the Arabian and Eurasian plates.

 

Damage Information

 

 

Performance summary

There were two lift-slab buildings in Leninakan at the time of the earthquake. The 10-story building collapsed completely, and the 16-story building sustained severe structural damage.

Damage state description

"The 16-story building sustained severe structural and nonstructural damage, but was still standing. Main structural damage was crushing of the entire core at the first floor level. The crushing was most extensive at the front entrance of the building. The vertical bars buckled in the circumferential plane of the core, indicating a torsional movement of the core or twist in the floors about the circular core as there were no dowels at the joints. The torsional movement was confirmed by the displacement of the exterior precast panels in the circumferential direction along the height of the building. Inspection of the core's interior along the entire height of the building also revealed that diagonal cracks formed in the core wall. "Vertical reinforcing bars in the core were lap-spliced with fillet welds. It appears that the splices performed well during the earthquake. Because of the meager quantity of lateral reinforcing, many horizontal bars fractured and consequently were not effective in resisting shear. "With large lateral and torsional movements, the interior partitions were severely damaged. These partitions consisted of 3" thick precast-concrete blocks installed as masonry. In many cases, the partitions were broken into many pieces, which certainly posed a threat to life and safety" (Wyllie, 1989).

Summary of causes of damage

1. Because of the meager quantity of lateral reinforcing in the core, many horizontal bars fractured and consequently were not effective in resisting shear. 2. Slabs were only grouted to the core, rather than being dowelled. 3. Highly stressed concrete walls did not have carefully prepared construction joints and adequate horizontal reinforcing and ties. 4. Large lateral and torsional movements contributed to the destruction of partition walls.

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 Torsional movement was confirmed (Wyllie, 1989).
Perimeter boundary Both buildings were symmetrical around shear cores, but had nontraditional floorplans (Wyllie, 1989).
Diaphragm
Out-of-plane offsets in lateral resisting system
Non-orthogonal systems All lateral forces were resisted by circular stair/elevator cores (Wyllie, 1989).

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 Bars fractured and were unable to adequately resist shear (Wyllie, 1989).

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 75mm thick PC concrete block masonry partitions shattered (Wyllie, 1989).
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 No evidence of liquefaction in Leninakan (Yegian and Ghahraman, 1992).
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

 

http://eqs.eeri.org/resource/1/easpef/v5/iS1
Wyllie, L. A. and Filson J. R., August 1989. Performance of Engineered Structures. Earthquake Spectra, Special Supplement, Armenia Earthquak


http://www.eeri.org/products-page/other-learning-from-earthquakes/eeri-annotated-slide-collection-cd-rom-2/
Earthquake Engineering Research Institute (EERI).Annotated Slide Collection.1997.


Yelgian, M. K. and Ghahraman, V. G. October 1992. "The Armenia Earthquake of December 1988." Northeastern University, Boston, Massachusetts.


http://earthquake.usgs.gov/earthquakes/world/events/1988_12_07_ev.php
United States Geological Survey (USGS), 2012.Notes about the Armenia Earthquake, 7 December 1988 (Accessed: 24 July 2012).