Damage of Bridges Resulting from Surface Rupture of Faults in the ...

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EDU+VDS MOVABLE EDU EDU MOVABLE EDU Fig.12 Supporting Condition of Typical 10-Span Continuous Deck (EDU: Energy Dissipating Unit, VDS: Viscous Damper Stopper, Movable: Sliding Pot Bearings) ends tilted on the embankments. The fault crossed the north abutment. 3. DUZCE, TURKEY, EARTHQUAKE (1) Duzce Earthquake A part of the Istanbul-Ankara Motorway at Bolu suffered extensive damage in the Duzce Earthquake (refer to Fig. 1). Viaduct No. 1 (Bolu Viaduct) suffered extensive damage in the Duzce Earthquake 1), 3), 7) . Fig. 11 shows the ground acceleration recorded at Bolu and Duzce in the Duzce Earthquake 4) . The Bolu Viaduct was close to the stations. The peak acceleration of the two lateral components was 0.76 g and 0.82 g at Bolu. Long period pulses were included in the record. Response acceleration of 0.05 damping ratio was 2.3 g in the L-component. (2) Bolu Viaduct The Bolu Viaduct consisted of a westbound deck and an eastbound deck as shown in Photo 9. It was 59 span and 58 span in the west bound and east bound, respectively. Averaged span length was 40m. Total deck length was 2313m and 2273m long in the west bound and east bound, respectively. Superstructure consisted of 7 prestressed concrete U-beam placed in transverse direction, and they were connected together by a reinforced concrete deck. Although the U-beams were simply supported, the concrete deck was continuous in the 10 spans. Hence the Viaduct behaved as 10 span continuous bridges. They were supported by reinforced concrete piers with height from 10m to 49m. Most piers were taller than 40m. The piers were supported by pile foundations. A pile foundation was of 12 1.8m diameter piles and a 3m thick 18.7m x 16m footing. Pile depth varied from 15m to 40m depending on soil condition. When the Duzce Earthquake occurred, the Viaduct was almost completed, i.e., foundations, piers, and decks were completed, and only pavement was not ready. A unique supporting system was adopted in the Bolu Viaduct1 4) . As shown in Fig. 12, in a standard 10 span continuous 10x40m=400m long deck, the deck was supported by means of pot bearings that allowed multi-directional sliding. An energy dissipating unit (EDU in Fig. 12) was provided at 10 piers, except one of the two deck ends. They achieved energy dissipation for multidirectional movement of the deck in an earthquake. Except at one of the two deck ends and the mid-pier, a viscous damper stopper (VDS in Fig. 12) was provided. It was connected to the energy dissipating unit in series. The viscous damper stoppers allowed free movement of the deck in longitudinal direction due to creep, shrinkage and thermal effects. Under seismic loading, the viscous damper stopper is locked, so that the energy dissipating units dissipated the energy. ALGA S.p.A mechanical hysteretic dampers consisting of 8 C-shaped mild steel damping elements were used as the energy dissipating unit. At one of the deck ends, the energy dissipating unit was provided, while the other deck moved freely in longitudinal direction. In transverse direction, the energy dissipating device was provided at both deck ends. A set of cable restrainers was provided at the deck ends to prevent excessive relative displacement between the decks. The site was located at the complex transition area between the Duzce fault and the North Anatoria fault. From the preliminary design stage of the Bolu Viaduct, it was known that the site is 178
Photo 9 Bolu Viaduct Photo 10 Girder Offset from the Pier Photo 11 Shear Failure of Deck resulting from the Offset of Girder from the Pier Photo 12 Damaged Energy Dissipating Unit and Viscous Damper Stopper Photo 13 Energy Dissipating Elements that suffered Damage resulting from Excessive Movement of the Deck seismically active and a fault offset was anticipated 3) . The Viaduct was designed assuming the maximum ground acceleration of 0.4g in accordance with the 1983 AASHTO Specifications 8) with some modifications. Main difference from the AASHTO Guide Specifications was the response modification factor R; Although AASHTO specified a value of R=3 for single columns, R=1 was used in design of Bolu Viaduct to ensure elastic response in the piers 3) . (3) Damage of Bolu Viaduct In 1999, the Bolu Viaduct experienced the Kocaeli Earthquake as well as the Duzce Earthquake. Although the epicenter of the Kocaeli Earthquake was about 100km away from the Bolu Photo 14 Cable Restrainers Viaduct, it was not far from the east end of the fault rupture. The energy dissipating unit had elastic displacements in the order of 44-80mm 3) . The epicenter of Duzce Earthquake was about 6km south of Duzce, and the Bolu Viaduct was close to Duzce. The fault crossed the Bolu Viaduct at Pier 45 and Pier 47 at an angle of approximately 20-30 degrees with the bridge axis. The right lateral offset was approximately 2-2.5m 3) . Most decks moved in longitudinal and transversal directions. At several piers, the girders offset from the pedestal, and were hung only by the concrete decks as shown in Photo 10. Consequently, the concrete deck suffered extensive shear failure as shown in Photo 11. Some decks were about to fall down. Based on the site inspection, it seemed that 179
Page 1 and 2: Seismic Fault-induced Failures, 171
Page 3 and 4: Photo 1 4.3m Offset of a Concrete F
Page 5 and 6: Fig.7 Section of Piers, Arifiye Ove
Page 7: Acceleration (g) Acceleration (g) A
Page 11 and 12: Root 1 Expressway Root 13 Root 3 Fe
Page 13 and 14: 2 Acceleration (g) 1.5 1 0.5 NS EW
Page 15 and 16: D13 D12 D11 D10 S N About 25m D1 P1
Page 17 and 18: North Side South Side Root 3 N60E
Page 19 and 20: 4) Bogazici University Kandilli Obs

Damage of Bridges Resulting from Surface Rupture of Faults in the ...

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