The seismic performance of the Bolu Viaduct in the Duzce, Turkey, earthquake of November 1999 was studied via a non-linear, time-history analysis of a multi-degree of freedom model. The viaduct had a seismic isolation system consisting of yielding-steel energy dissipation units and sliding pot bearings. The Duzce earthquake caused a surface rupture across the viaduct, which resulted in excessive superstructure movement and widespread failure of the seismic isolation system. The effect of the rupture was modeled by a static, differential ground displacement in the fault-parallel direction across the rupture. The ground motions used in the analysis contain common near-fault features including a directivity pulse in the fault-normal direction and a fling step in the fault-parallel direction. The analysis used a finite element package capable of modeling the mechanical behavior of the seismic isolation system and focused on the structural response of a 10-span module of the viaduct. This analysis showed that the displacement of the superstructure relative to the piers exceeded the capacity of the bearings at an early stage of the earthquake, causing damage to the bearings as well as to the energy dissipation units. The analysis also indicated that shear keys, both longitudinal and transverse, played a critical role in preventing collapse of the deck spans. Published in 2004 by John Wiley Sons, Ltd.

This paper summarizes the results of a comparative study on seismic design of highway bridges jointly undertaken by the US. Federal Highway Administration and Japan's Public Works Research Institute. The seismic design specifications for highway bridges of the two countries are reviewed and compared with respect to their design philosophies and procedures. Some major design parameters including design seismic forces, response modification factors and minimum support lengths are addressed in detail. The differences between the two specifications are illustrated via a design example of a reinforced concrete column for simple, two-span bridges common in both countries. Three different scale models of the column are designed in accordance with the seismic design specifications of the United States and Japan, and tested on a shake table for their comparative seismic performance. The results of the shake table tests are discussed separately in a companion paper.

The North Anatolian Fault (NAF), which runs east west across northern Turkey with an approximate length of 1100 km again ruptured on August 17, 1999, resulting in a 7.4 magnitude earthquake. The epicenter of the earthquake was near the town of Golcuk, a province of Kocaeli, which is about 80 km east of Istanbul. This Kocaeli Earthquake resulted in more than 15,000 deaths and caused extensive destruction to residential and commercial buildings and industrial facilities in many cities. The NAF has been studied jointly by both Turkish and U.S. scientists for many years. In particular, U.S. scientists have been interested in the NAF because there is a strong similarity between the creep rate and energy release of both the North Anatolian and the San Andreas fault in California. Both faults have generated large magnitude earthquakes within the last 100 years. Since the devastating 1939 Erzincan Earthquake with its epicenter almost 1000 km east of Istanbul, earthquakes with a magnitude larger than 6.5 have occurred frequently along the NAF with their epicenters moving progressively westward towards Istanbul. This has long caused much concern in Turkey and the recent Kocaeli earthquake with its magnitude of 7.4 and its close proximity to Istanbul has elevated these concerns. The scientists at the Istanbul Technical University have suggested that a large magnitude earthquake much closer to Istanbul can be expected in the near future. Soon after the Kocaeli Earthquake, a Federal Highway Administration (FHWA) team of scientists and engineers were dispatched to Turkey at the invitation of the Turkish General Directorate (KGM) to inspect structures on the Trans European Motorway (TEM) and to evaluate their condition. In addition to scientists and engineers from the FHWA, the team included members from the California Department of Transportation and Imbsen and Associates, Inc. This team spent 3 weeks in Turkey, working very closely with their Turkish counterparts. This paper provides an overview of the team's observations and findings on the structures along the TEM and the lessons learned. In general, the bridges on the TEM performed acceptably. There was only one bridge collapse that affected the TEM directly, and minor to moderate damage to others along the TEM.

Seismic performance of reinforced concrete bridge column under repeated earthquake ground motions is investigated through shake-table experimentation on a scale model. The specimen is subjected to a series of simulated ground motions at different levels of shaking intensity. The deformation and damage evolution of the test column is addressed in terms of selected mechanical quantities including the effective stiffness, hysteretic energy dissipation, residual displacement, and dominant vibration frequency. The test column, designed according to the AASHTO seismic design specifications, survived successive ground motions by virtue of its outstanding energy-absorption and ductility capacity. Analysis of the experimental data indicates that structural degradation of the column closely correlates with its decreasing effective stiffness and increasing hysteretic energy dissipation. The residual displacement measured at the column top after each shaking event increases with the growth of damage in the column. A frequency-domain analysis of the vibration response of the column during successive ground motions indicates that increase in the structural degradation of the column results in a decrease in the dominant vibration frequency of the column.