Earthquake resistant structures

About: Earthquake resistant structures is a research topic. Over the lifetime, 1126 publications have been published within this topic receiving 27467 citations.

Structural analysis and retrofitting of existing highway bridges subjected to strong motion seismic loading

Abstract: The objective of this project was to determine cost effective means for modifying existing intermediate size bridges so as to better withstand the damaging effects of intense earthquake ground motions. Research studies were performed to identify and define, through structural analysis, practical techniques and criteria for retrofitting the bridges selected during the program. The need for retrofitting is based on the philosophy that damage should be limited so that collapse does not occur and traffic can be restored after minimum repairs. Seven different bridge structures were selected throughout the United States in high risk seismic regions. Seismic loads were determined for each bridge based on the soil conditions and seismicity at its site. A simplified analysis procedure was defined during the project and validated by selective comparisons with nonlinear response analyses. Each bridge was analyzed for horizontal seismic loads. Failures and potential weaknesses are indicated for several of the structures and retrofit measures are recommended. All known retrofit concepts which are of potential value in reducing seismic bridge damage are described and illustrated. Based on this study, many bridges located in high seismic risk zones may be subjected to severe damage and potential failure during the life of the structure.

Seismic design of bridges

Abstract: This bulletin consists of 2 parts. The first part reviews recent New Zealand research on the ductile design of reinforced concrete bridge piers. The inelastic dynamic analysis of bridge structures, including the effect of soil-structure interaction, to establish the ductility demand of typical reinforced concrete bridge piers when responding to severe earthquakes was studied. Reinforced concrete bridge piers were analytically and experimentally investigated in order to establish the available ductility capacity and hysteretic energy dissipation. A study of the quantity of spiral reinforcement required to confine the concrete and to prevent buckling of longitudinal bars was an important part of the study. The second part of this bulletin presents recent developments in an alternative to the current seismic resistant design approach for bridges and other structures based usually on flexural yielding of members designed to deform in a ductile manner. The alternative method is based on two elements: firstly, the structure is supported on flexible mountings to isolate it from the predominant earthquake ground motion frequencies, and secondly, extra damping is provided to keep deflections within acceptable limits. Details of devices to provide extra damping are described. Results of dynamic analysis studies to investigate the sensitivity of seismic response to principal parameters for bridges incorporating energy dissipators are described and design charts to determine forces and displacement for various earthquake excitations are presented.

Effects of liquefaction-induced large ground displacement on earthquake resistance of foundations during the hyogoken-nanbu earthquake

Abstract: This paper introduces performances of foundations under a condition of liquefaction-induced ground displacement and investigates the effects of the ground displacements on the earthquake resistance of the foundations. It also introduces some examples of undamaged foundations even when the surrounding ground largely moved horizontally. The 1995 Hyogoken-nanbu earthquake caused significant soil liquefaction in an extensive area of reclaimed land in Kobe and its neighboring cities. The soil liquefaction also induced large ground displacements in the horizontal direction, which resulted in serious damage to buried lifeline facilities and foundations of bridges and buildings. The authors have investigated the liquefaction during the earthquake and the damage it caused to various kinds of civil engineering structures. They also measured the liquefaction-induced ground displacements in reclaimed lands along the waterfront of Hanshin area by an aerial survey using both pre- and post-earthquake photographs and by referring to the results from field surveys. Typical examples of damage related liquefaction-induced ground displacements are presented. In addition, the authors discuss the performances of foundations in the area of the liquefaction and large ground displacements, by referring to the foundation types, and seek effective countermeasures to ground liquefaction.