Damage-based design earthquake loads for SDOF inelastic structures

Journal of Structural Engineering (ASCE) 01/2011; 137:456-467.

ABSTRACT This paper develops a new framework for modeling design earthquake loads for inelastic structures. Limited information on strong ground motions is assumed to be only available at the given site. The design earthquake acceleration is expressed as a Fourier series, with unknown amplitude and phase angle, modulated by an envelope function. The design earthquake is estimated by solving an inverse dynamic problem, using nonlinear programming techniques, such that the structure performance is minimized. At the same time, the design earthquake is constrained to the available information on past recorded ground motions. New measures of the structure performance that are based on energy concepts and damage indices are introduced in this paper. Specifically, the structural performance is quantified in terms of Park and Ang damage indices. Damage indices imply that the structure is damaged by a combination of repeated stress reversals and high stress excursions. Furthermore, the use of damage indices provides a measure on the structure damage level and thus a decision on necessary repair is possible. The material stress-strain relationship is modeled as either bilinear or elastic-plastic. The formulation is demonstrated by deriving the design earthquake loads for inelastic frame structures at a firm soil site. The damage spectra for the site are also established, which provide upper bounds of damage under possible future earthquakes.

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    ABSTRACT: This paper deals with damage assessment of adjacent colliding buildings under strong ground motion. In previous studies, the structure input-response pair is used to examine pounding effects on adjacent buildings under seismic loads. In this paper, pounding of adjacent buildings is assessed using input energy, dissipated energy and damage indices. Damage indices (DI) are computed by comparing the structure’s responses demanded by earthquakes and the associated structural capacities. Damage indices provide quantitative estimates of structural damage level, and thus, a decision on necessary repair can be taken. Adjacent buildings with fixed-base and isolated-base are considered. The nonlinear viscoelastic model is used for capturing the induced pounding forces. Influences of the separation distance between buildings, buildings properties, such as, base-condition (fixed or isolated), and yield strength on damage of adjacent buildings are investigated. The set of input ground motions includes short-, moderate- and long-duration accelerograms measured at near-fault and far-fault regions with different soil types. Earthquake records with different characteristics are considered to study damage of adjacent buildings under seismic loads. Numerical illustrations on damage of fixed-base and isolated-base adjacent buildings with elastic–plastic force–deformation relation are provided.
    Engineering Structures 03/2014; 61:153–165. · 1.77 Impact Factor
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    Advances in Geotechnical Earthquake Engineering - Soil Liquefaction and Seismic Safety of Dams and Monuments, 02/2012; , ISBN: 978-953-51-0025-6
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    ABSTRACT: Inelastic analysis procedures are more dependable means for predicting the actual seismic response compared with elastic analysis methods. Encouragement to use the former procedures is still limited and designers tend to favour elastic analysis procedures. The permissible reduction in response parameters obtained from elastic analysis unlike those from inelastic analysis procedures discourages the effective use of the latter analysis methods in design. This paper proposes a simple and theoretically-based approach that utilises inelastic structural response in design. To describe the approach, the correlation of seismic demands obtained from ineleastic and elastic analysis procedures carried out using a wide range of reinforced concrete buildings of different characteristics, ranging from 8 to 60 storeys, is investigated. Verified fibre element models and diverse input ground motions are employed in the inelastic simulations. The presented approach enables designers to arrive at a realistic and cost-effective design without compromising safety.
    Structures & Buildings 06/2013; 166(6):282-297. · 0.61 Impact Factor


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May 31, 2014