Overview of Highway Damage: Kocaeli, Turkey Earthquake, August 17, 1999
by John B. Mander, Associate Professor, Department of Civil, Structural and Environmental Engineering, University at Buffalo
Considering the magnitude of the fault rupture movements and the significant ground shaking, both in terms of accelerations and velocities, the engineered structures on the highway system fared quiet well. Damage to bridges was restricted to an area south-south east of Adapazari. In this area, two main highways run west-east (Istanbul to Ankara), parallel to the fault. The E80, also known as the TEM (Trans European Motorway), is a four-lane divided toll road, and the E100 (the old main highway) is a two lane road. Several overpasses crossing the E80 sustained minor damage in the form of pier tilting (arising from ground movement), cover concrete spalling of the decks at movement joints, and approach fill settlement. Such damage did not impair the use of the roads over the motorway.
One overpass crossing the E80 did collapse. This was not surprising as the fault rupture passed directly beneath the bridge. The fault movement exceeded the available seat width causing the span to fall to the ground. In so doing, it dragged the remaining three spans off their seats as shown in Figure 1. One of the spans collapsed onto a passing bus killing 10 people.
Problems were also encountered with four highway bridges crossing the Sakarya River. Most notable was the bridge carrying the west-bound lanes of the E80 motorway. This 10 span bridge is shown in figure 2. It consists of simply supported prestressed concrete box girders seated on laminated elastomeric bearing pads. A shear key is provided at the end of each box to inhibit transverse movement; the elastomeric bearings are evidently for accommodating longitudinal thermal movements. The large impulsive fault-normal ground shaking coupled with high vertical accelerations caused several spans to fail the shear keys and unseat from their bearings. This is shown in figure 3. The bridge has been closed to traffic awaiting repairs. The eastbound sister bridge sustained less damage to the shear keys and only partial walk-out of the bearing pads; complete unseating did not occur and the bridge has remained fully operational.
Figure 2. Looking south at the west-bound E80 bridge over the Sakarya River.
Figure 3. The east (left) and west (right) bound bridges over the Sakarya River. Note shifting of the spans and the unseating of the bearings in the west-bound bridge. The bearings on the east-bound bridge have partially "walked out", but not unseated.
The extent of damage to the engineered fills on the E80 motorway extended some 10 km to the west and east of the Adapazari area. Settlements ranging from 100 mm to 500 mm were observed. This was evident at most single span bridge and culvert locations on that road, resulting in classic bump-onto-the-bridge problems. One example is shown in figure 4. Repair of this damage was swift. Initial repairs, made in the first few days following the earthquake, consisted of placing asphalt ramps and maintaining a 50 km/h speed restriction. Within 10 days, more long-term repairs were made. Re-profiling and re-paving large stretches of the road surface enabled the speed restrictions to be removed and the motorway returned to its normal 120 km/h operating speed.
Figure 4. A typical view of the bump-onto-the bridge on the E80 motorway. Up to 500mm embankment settlements were common over a 20km stretch of road. Notice the guard rail in the photograph as further evidence of the embankment settlement.
Note: Professor Mander was also part of the Earthquake Engineering Research Institute's (EERI) reconnaissance team. Additional information is posted on EERI's web site at http://www.eeri.org.