More than 15,000 people are dead, 23,000 injured, and 500,000 homeless after a devastating earthquake struck Turkey on August 17. Measured at 7.4 on the Richter Scale at the U.S. Geological Service in Golden, Colorado, the temblor was centered in northwest Turkey between Izmit and Bursa, about 55 miles east of Istanbul. This is the most powerful earthquake ever to hit Turkey.
Photo by Mark Aschheim
More than 15,000 people are dead, 23,000 injured, and 500,000 homeless after a devastating earthquake struck Turkey on August 17. Measured at 7.4 on the Richter Scale at the U.S. Geological Service in Golden, Colorado, the temblor was centered in northwest Turkey between Izmit and Bursa, about 55 miles east of Istanbul. This is the most powerful earthquake ever to hit Turkey. Slide Presentation by Mark Aschheim is available at http://mae.cee.uiuc.edu/Research/TurkeyEarthquake/index.htm. (Download Presentation source)
Kocaeli Earthquake of 17 August 1999 Effects on Buildings
The 1999 Kocaeli earthquake caused severe damage or collapse of buildings in 7 provinces over a 250 km distance from Istanbul to Bolu. Severe damage or collapse occurred to as many as 70% or more of the buildings in portions of the cities of Adapazari, Golcuk, Izmit, Topcular, and Kular. Nearly all the fatalities and injuries of the earthquake can be attributed to building collapse. As of 6 September 1999, the Government Crisis Center reported 20,957 buildings were heavily damaged or collapsed, with 15,135 people confirmed dead. Turkey's National Security Council estimated 200,000 people were made homeless. Other reports suggest 120,000 buildings were damaged beyond repair and 600,000 people were made homeless. Building losses are reported to amount to about $5 billion US dollars.
Sources of damage were manifold. Buildings experienced ground shaking, and in some regions were subjected to ground settlement, liquefaction, or subsidence and inundation of sea water (Fig B1). Numerous buildings were located on top of the fault trace, and experienced lateral offsets of up to 4 m or vertical offsets of up to 2 m due to fault rupture, though collapse did not necessarily result. Some buildings reportedly were "washed" into the Marmara Sea by waves resulting from ground subsidence.
Reinforced Concrete Frames with Hollow Clay Tile Infill
Almost all urban residential buildings were reinforced concrete frames with hollow clay tile infill walls, typically 3 to 7 stories in height. As in the 1992 Erzincan earthquake, those frames having 4 or more stories were much more likely to be damaged or collapse. Even so, the range of damage varied greatly among neighboring buildings that resembled one another, with some collapsing and others having moderate or little apparent damage.
Column cross sections typically have large aspect ratios (e.g. 25 by 60 cm), with hollow clay tile infill placed directly against the narrow sides of the column. This allows the columns to be located within the partition wall, and results in the columns having irregular locations and orientations since they are positioned within the partition walls. Smooth bars are typically used for longitudinal and transverse reinforcing. Transverse hoops having short 90-degree hooks are typically spaced at 20 to 25 cm along the clear height of the column; cross ties were not evident. Column splices usually are located just above the floors, consisting of a straight extension from below, with a hooked bar from above terminating at the floor slab.
Flexural hinging at the ends of the columns often led to buckling of longitudinal reinforcement and apparent shear failures at the hinges under weak axis bending. Strong-axis demands typically resulted in shear failures in the mid-heights of the columns. Few columns showed indications of large demands in both directions. Soft (or weak) story mechanisms were common. In some cases, column axial forces resulting from overturning moments appeared to contribute to column failures. Loss of joint integrity was infrequent but appeared to contribute significantly to collapse in at least several cases.
Other types of construction also suffered damage or collapse, but their relative paucity results in anecdotes rather than generalizations. Some damage to reinforced concrete shear walls in high-rise apartment buildings was reported. Shear failures were observed in reinforced concrete columns at the Petkim and Ford plants. A precast concrete warehouse under construction collapsed, presumably because the roof diaphragm had not been installed, leaving the framing without lateral restraint. A flexible roof diaphragm in another precast building led to excessive roof deflections and out-of-plane failure of the infill. Buckled steel braces were observed in other buildings including those at the PacMaya plant. Bolts at the connections between steel columns and roof trusses sheared at a recently designed automobile manufacturing plant. Older construction, typically 1 to 2 stories in height and often consisting of adobe or clay brick masonry bearing wall construction usually performed well, though severe damage was observed on occasion.
Building Codes and Practices
The Great Erzincan Earthquake of 1939 led to the development of the first seismic codes in Turkey, beginning with temporary regulations in 1940 and the first code in 1942. Numerous revisions have been made, with the most recent codes issued in 1975 and 1997. The 1975 code is a modern code that includes ductile detailing requirements of that era, such as the use of 135-degree hooks in column hoops and cross ties, the use of denser transverse reinforcing in the vicinity of beam column joints (and within the joints) and strong column weak beam design concepts. Most of the damaged region lies in the highest seismic zone in Turkey. However, codification of earthquake-resistive details and design philosophies apparently had little influence on construction practices, since ductile details were observed rarely if at all.
Subsidence led to inundation of some buildings in Golcuk.
Material from this article was contributed to EERI by Mark Aschheim, a member of the EERI team
Kocaeli Earthquake of 17 August 1999 Effects on Buildings
The 1999 Kocaeli earthquake caused severe damage or collapse of buildings in 7 provinces over a 250 km distance from Istanbul to Bolu. Severe damage or collapse occurred to as many as 70% or more of the buildings in portions of the cities of Adapazari, Golcuk, Izmit, Topcular, and Kular. Nearly all the fatalities and injuries of the earthquake can be attributed to building collapse. As of 6 September 1999, the Government Crisis Center reported 20,957 buildings were heavily damaged or collapsed, with 15,135 people confirmed dead. Turkey's National Security Council estimated 200,000 people were made homeless. Other reports suggest 120,000 buildings were damaged beyond repair and 600,000 people were made homeless. Building losses are reported to amount to about $5 billion US dollars.
Sources of damage were manifold. Buildings experienced ground shaking, and in some regions were subjected to ground settlement, liquefaction, or subsidence and inundation of sea water (Fig B1). Numerous buildings were located on top of the fault trace, and experienced lateral offsets of up to 4 m or vertical offsets of up to 2 m due to fault rupture, though collapse did not necessarily result. Some buildings reportedly were "washed" into the Marmara Sea by waves resulting from ground subsidence.
Reinforced Concrete Frames with Hollow Clay Tile Infill
Almost all urban residential buildings were reinforced concrete frames with hollow clay tile infill walls, typically 3 to 7 stories in height. As in the 1992 Erzincan earthquake, those frames having 4 or more stories were much more likely to be damaged or collapse. Even so, the range of damage varied greatly among neighboring buildings that resembled one another, with some collapsing and others having moderate or little apparent damage.
Column cross sections typically have large aspect ratios (e.g. 25 by 60 cm), with hollow clay tile infill placed directly against the narrow sides of the column. This allows the columns to be located within the partition wall, and results in the columns having irregular locations and orientations since they are positioned within the partition walls. Smooth bars are typically used for longitudinal and transverse reinforcing. Transverse hoops having short 90-degree hooks are typically spaced at 20 to 25 cm along the clear height of the column; cross ties were not evident. Column splices usually are located just above the floors, consisting of a straight extension from below, with a hooked bar from above terminating at the floor slab.
Flexural hinging at the ends of the columns often led to buckling of longitudinal reinforcement and apparent shear failures at the hinges under weak axis bending. Strong-axis demands typically resulted in shear failures in the mid-heights of the columns. Few columns showed indications of large demands in both directions. Soft (or weak) story mechanisms were common. In some cases, column axial forces resulting from overturning moments appeared to contribute to column failures. Loss of joint integrity was infrequent but appeared to contribute significantly to collapse in at least several cases.
Other types of construction also suffered damage or collapse, but their relative paucity results in anecdotes rather than generalizations. Some damage to reinforced concrete shear walls in high-rise apartment buildings was reported. Shear failures were observed in reinforced concrete columns at the Petkim and Ford plants. A precast concrete warehouse under construction collapsed, presumably because the roof diaphragm had not been installed, leaving the framing without lateral restraint. A flexible roof diaphragm in another precast building led to excessive roof deflections and out-of-plane failure of the infill. Buckled steel braces were observed in other buildings including those at the PacMaya plant. Bolts at the connections between steel columns and roof trusses sheared at a recently designed automobile manufacturing plant. Older construction, typically 1 to 2 stories in height and often consisting of adobe or clay brick masonry bearing wall construction usually performed well, though severe damage was observed on occasion.
Building Codes and Practices
The Great Erzincan Earthquake of 1939 led to the development of the first seismic codes in Turkey, beginning with temporary regulations in 1940 and the first code in 1942. Numerous revisions have been made, with the most recent codes issued in 1975 and 1997. The 1975 code is a modern code that includes ductile detailing requirements of that era, such as the use of 135-degree hooks in column hoops and cross ties, the use of denser transverse reinforcing in the vicinity of beam column joints (and within the joints) and strong column weak beam design concepts. Most of the damaged region lies in the highest seismic zone in Turkey. However, codification of earthquake-resistive details and design philosophies apparently had little influence on construction practices, since ductile details were observed rarely if at all.
Subsidence led to inundation of some buildings in Golcuk.
Material from this article was contributed to EERI by Mark Aschheim, a member of the EERI team
