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 Optimization of Viscous Dampers Using Genetic Algorithms for Improving Seismic Performance of Existing Buildings

Abstract: This paper presents a new technique for optimizing the design of viscous dampers when they are used to improve the seismic performance of existing buildings. The technique uses a genetic algorithm optimization routine that is applicable to the highly complex and nonlinear relationship between damper properties, building response and cost. The paper describes the use of nonlinear static analyses in a manner that significantly reduces the amount of analysis required to determine building response. This makes the genetic algorithm highly efficient and reduces the time required to obtain an optimized solution. The method is illustrated with two buildings – a four-story reinforced concrete moment frame building and a nine-story steel moment frame building. Analyses of the buildings shows that the method produces excellent results, even after relatively few iterations. Typical values of optimization parameters that give good convergence are recommended. The paper also suggests criteria that can be used to determine when a near optimum design has been achieved.

Damage Analyses of Imperial County Services Building

Abstract: The failure of the Imperial County Services Building in El Centro, California, during the Imperial Valley Earthquake on October 15, 1979 is examined. The event was exceptional insofar as a modern reinforced concrete building, designed to comply with a recent code, extensively instrumentated and previously subjected to dynamic testing, was severely damaged. Available records of measured dynamic characteristics and traces of the motions induced by the earthquake in both the adjacent ground and the structure, enable critical analyses to be made of the failure modes. Building configuration and composition are summarized, together with the strong motion records obtained during the earthquake. A three-dimensional mathematical model of the building is developed and the results of computer analyses are presented. Elastic analyses are used as a basis of justifying the model and both elastic and non-linear three-dimensional time history analyses are described. Good correlation between analytical results and field observations is established. In particular the combined effect of biaxial moment and axial load in causing ground floor column failure is demonstrated.

Earthquake Research Needs for Nuclear Power Plants

Abstract: The high degree of safety required for nuclear power plants has given prominence to the problems of earthquake-resistant design. Extreme conservatism can lead to overly large factors of safety. Certain aspects of the earthquake design problem are discussed, such as, ground acceleration, response of structures, influence of damping, frequency content of ground motion, failure characteristics, and effect of foundation. Recommendations are made for research that would lead to more economic design.

Seismic retrofit of bridge columns by steel jacketing

Abstract: Inadequate flexural strength and ductility of shear strength of concrete bridge columns has resulted in collapse or severe damage of a number of California bridges in recent moderate earthquakes. In general these bridges were designed prior to the new seismic design methods which were implemented in the mid-seventies. Bridges constructed in accordance with the new design methods have performed well in recent earthquakes. However, the large number of older bridges that are in service, particularly freeway overpasses designed and constructed in the 1950's to 1970's, are now recognized to have substandard design details and are presenting a cause for major concern. This paper reports the results of a theoretical and experimental program investigating retrofit techniques for circular columns by encasing the critical regions with a steel jacket. The jacket is bonded to the column using grout. Results from six large-scale column tests show that the casing acts efficiently as confinement reinforcement enabling displacement ductility factor of greater than 6 to be achieved. The casing also inhibits bond failures at the laps of longitudinal reinforcement in the critical regions of the column by restraining the dilation and spalling of the cover concrete which degenerates into bond failure. Comparisons of "as-built" and retrofitted columns are presented, and experimental strengths and ductilities are compared with analytical predictions.