These buildings, named Soviet Series 111 (also 110 and 112?), are typical PC concrete frame structures designed by a central Soviet agency in Moscow and adapted for local use by Armenian engineers. In Leninakan, the buildings were 9-story apartment comple...

Prepared By: Sarah Bettinger
Occupancy: Residential
Year Built: 1970
Height:
Number of stories: 9
Stories below ground: unknown
Size:
Original Code: SNiP 62? Part 2, Chapter 1 of Standards and Regulations for Construction (1984)? SNiP II-A 12.62
Modification: none
Year Modified:
Code of Modification:
Lateral Load System: Moment Frame and Shear Wall Combination
Other Load System: Moment resisting frames in one direction and shear walls in the other.
Vertical Load System: Bearing Walls
Other Vertical Load System:
Foundation : Other
Other Foundation :
Country: Armenia
State: N/A
City: Leninakan (now Gyumri)
Street:
Latitude: 40.796138
Longitude: 43.847755


 

PC Frame 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. The location of the epicenter is 40.996N +/- 2.9km, 44.197E +/- 1.8km.

 

Damage Information

 

 

Performance summary

Of the 133 of this type of building in Leninakan, 72 collapsed and 55 were heavily damaged and had to be demolished. They often collapsed in compact piles, making search and rescue of survivors difficult, and adding to the high death toll of the earthquake.

Damage state description

Columns suffered bar buckling and failure, leading to building collapse. The spandrel beams above and between the openings in the shear walls were lightly reinforced and sustained substantial damage. Extensive shear cracking was observed in the beams at the end of the steel angle embedded in the column. The floor panels collapsed.

Summary of causes of damage

1. Column splice details called for the 4 or 6 bars of the column to be aligned and butt welded with full penetration welds, but they were often misaligned with short pieces of steel side welded to the bars in each precast section, causing an eccentricity between the longitudinal column reinforcing. Additionally, weak concrete was used in the splice region. 2. The hollow core floor slab was grouted between units, but had no interconnections to adjacent planks. The weakness of the floor diaphragms prevented forces from being redistributed once a failure occurred in the building. 3. The designs called for insufficient shear walls, which were often perforated with stacked door openings. 4. Codes used did not require ductile detailing. 5. Beams were not strong enough in shear to develop the reverse plastic hinge capacity of the beam at its ends. 6. Weak link in the shear walls was the spandrel or coupling beams between the stacked doorways, which were lightly reinforced.

Observed Design and Construction Characteristics

 

Construction Quality

MaterialsNotesContribution to Damage
Concrete
Reinforcing steel

ExecutionNotesContribution to Damage
Conveyance/placement of concrete Poor strength concrete at column splice weld
Rebar
Field variance with design documents Column splice weld not to construction documents
OtherNotesContribution to Damage
Other Factors Construction Quality

Configuration

Plan IrregularitiesNotesContribution to Damage
Torsion
Perimeter boundary
Diaphragm Nominal or very weak floor 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 Eccentricity at column splices

StiffnessNotesContribution to Damage
Extreme Flexibility

Load PathNotesContribution to Damage
Collectors/Struts
Anchorage of nonstructural elements "Nonstructural elements also sustained considerable damage in these buildings. Interior partitions were of thin masonry or concrete elements and were often shattered and lying on the floor. Exterior cladding was connected with welded clips and, in some cases, appeared to have connections that allowed some movement. In some cases, exterior, nonstructural panels fell off buildings and many were no longer aligned with the frame, indicating connection distress or failure. In general, nonstructural elements were heavily damaged in buildings of this type and remained standing" (Wyllie, 1989).
Out-of-plane capacity of walls
Diaphragm chords
Diaphragm openings In two of the three typical floor plans, there are door openings in the shear walls, which affect the strength of those walls.

OtherNotesContribution to Damage
Other Factors Lateral Load Resisting System-General "Stair risers were precast and sat on a short bearing. A small weld-clip was provided for attachment. Many of these stair segments collapsed in the earthquake when the building movements were sufficient to allow the frames to move and pull the stairs off its bearing" (Wyllie, 1989).

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 "One photo shows an interior beam-column joint in an upper story where cracks and shear failures were consistently seen in the beams in two buildings inspected. The joints themselves appear intact, but significant shear cracking in the beams suggest high stresses and indicate that beam shear was the weak link o the moment-resisting frame system" (Wyllie, 1989).
Continuity of longitudinal reinforcing
Loss of vertical capacity
Interference of frame action by infill beams

JointsNotesContribution to Damage
Interior "Debris from collapsed buildings in several cases suggested joint failure, although the distress could have resulted from the collapse process or from demolition for rescue efforts" (Wyllie, 1989).
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 "Solid shear walls worked their connections, spalling some cover at the weld connections to the columns and cracking the horizontal joints at the floors" (Wyllie, 1989).
Flexure/shear

FlexureNotesContribution to Damage
Compression zone buckling capacity
Discontinuity of wall
Boundary reinforcing fracture/buckling
Boundary Reinforcing at openings Photo shows a lintel or spandrel over the doorway in a shear wall in a building with the square floor plan. Note the weld connection o the column on the left. The lintel is well shattered with shear cracks. In other photos, lintels and one pier are very heavily damaged (Wyllie, 1989).

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 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

See below for analysis

Performance Level

Life safety

Hazard Level

NA

Retrofit or Repair Code

Other

Other Retrofit or Repair Code

UBC88

Lateral Analysis

NA

Other Lateral Analysis

Design Strategy

A dynamic analysis was performed in ETABS on both the Series 111-11 and 111-07 buildings to determine the periods and mode shapes, The period corresponding to the first mode shape in each direction was used to determine the equivalent static earthquake load, and the results compared to five codes of practice: SNiP62, UBC64, UBC77, UBC85, and UBC88. From this, two sets of analyses were made; First, the SNiP62 loads were applied to both structures in both directions and the capacity/demand ratios were determined, and second, additional shear walls were added and the UBC88 loads applied to both buildings to determine what type of strengthening would be required to bring the buildings up to UBC88 code compliance. A plan was developed to strengthen the 111-11 buildings, which included the addition of four shear walls in the longitudinal direction and two shear walls in the transverse direction. These additional shear walls were to be dispersed as much as possible to make up for the lack of diaphragm action in the original design. The transverse shear walls were to be installed between the layers of precast cladding on the outside of the building. The longitudinal shear walls were to be cast-in-place, and would have had one or two openings in each (Wyllie, unpublished data).

Retrofit Summary

To the best of our information, no retrofit was performed.

References

 

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.


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 Earthquake Reconnaissance Report, 70-92.


http://www.iitk.ac.in/nicee/wcee/article/10_vol1_63.pdf
Wyllie, L. A. (1992) "Analysis of the collapsed Armenian precast concrete frame buildings." Earthquake Engineering, Tenth World Conference. Balkema, Rotterdam.


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, http://earthquake.usgs.gov/earthquakes/world/events/1988_12_07_ev.php (24 July 2012).


Wyllie, L. Unpublished report on the analysis and strengthening requirements of the Soviet Series 111 buildings.