The characteristics of 1994 Northridge motions with respect to permanent slope deformations are consistent with much larger world-wide database of excitations. The paper describes the application of a recently developed procedure to compute abutment fill settlements caused by earthquakes to predict fill settlements. The study used 58 excitations from 1994 Northbridge earthquake recorded in the free field with acceleration higher than .1g to investigate the influence of vertical acceleration on permanent abutment fill settlements. It was found that the influence of vertical accelerations is insignificant. The comparison between predicted and observed abutment fill settlements aft4r the 1994 Northbridge earthquake using data from 18 bridge sites near the epicentral area has been reported. The study indicates that the existing computational model yields conservative estimates and it may be used as a first approximation for evaluating abutment fill settlements in moderate to large earthquakes.

As low cycle fatigue failure in the longitudinal reinforcement is unavoidable, it necessitates the concept of using replaceable plastic hinges in which specially-detailed reinforcing fuse-bars are installed. Three one-third scale model pier specimens were constructed. The first renewable-hinge column was tested and repaired five times. The second pre-cast column was also constructed using the fuse-bar connections and subsequently repaired ten times. For comparative purposes, a conventionally reinforced column was constructed and tested. It was found that each of the repaired columns performed as well as the undamaged virgin columns. This new approach to construction enables rapid restoration to full service following a damaging earthquake.

In order to provide experimental background for current seismic design of bridge footings, a 0.4:1 scale circular-column footing model was tested. The model was designed and constructed based on a footing of an actual prototype bridge which was built following current bridge design standards. The model pier was tested in a vertical cantilever condition with cyclic horizontal displacements and constant axial load applied to the top of the column. The pier was supported on rubber pads simulating the compressive flexibility of pile foundation, with high tensile strength bars simulating the compressive flexibility of pile foundation, with high horizontal displacement, the pier developed a satisfactory hysteretic response with a full plastic hinge formed at the bottom of the column. However, test results and theoretical analyses revealed potential problems in current bridge footing design, in particular, the lack of the column/footing joint shear design as well as non-conservative flexural and shear designs which are based on full effectiveness of the entire footing width.

A program of field a laboratory tests to study the seismic response of reinforced-concrete double-deck bridge structures has been conduced at the University of California Berkeley. The research was prompted by the poor performance of these structures during the 1989 Loma Prieta Earthquake. The program had three phases of testing. The first phase was conducted in-situ immediately after the earthquake on a section of the Cypress Street Viaduct that had not collapsed. This test showed the need for confinement in the critical beam column joint region as well as the need for a ductile lateral-load-resisting system. The second phase of testing was the proof test of a comprehensive retrofit concept for a bent of the Alemany Freeway. The test showed that a ductile system, combined with a conservatively designed beam-column connection, provides adequate structural performance under unidirectional and bidirectional lateral loading. The third phase of testing focused on the current design criteria for beam-column connections in ductile double-deck bridge structures. In this phase of testing, two one-third scale models of beam-column connections in ductile frames designed according to current criteria were tested in the laboratory. Results from this test series showed that proper detailing, without excessive amount of reinforcement, increases the load-resisting capacity of beam-column connections and relocates the yield mechanism from the joint to the column. The goal of this paper is to provide the reader with a comprehensive overview of the work.

The January 17, 1995 Hyogoken-Nanbu earthquake severely damaged highway bridges throughout the Kobe area. Most of the damaged bridges were of older construction (20 to 30 years old), but some modern bridges were also damaged. This appear reports on the seismic response of three representative bridges with reinforced concrete (RC) substructures. Two of these bridges had RC superstructures, and one had a steel superstructure. Reasons for the damage are discussed, and lessons which may be applicable to RC bridge design in the United States are outlined.