Seismic drift and ductility demands and their dependence on ground motions

Krawinkler, Helmut; Medina, Ricardo A.; Alavi, Babak

doi:10.1016/s0141-0296(02)00174-8

Cited by 147 publications

(70 citation statements)

References 2 publications

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“…A total of 20 ground motions, denoted as large-magnitude-small-distance (LMSR), were considered in this investigation, including strong motions recorded during the Loma Prieta (1989), Northridge (1994), and San Fernando (1971), California, earthquakes [17]. The mean pseudo-velocity (V ) response spectrum for the ground motion ensemble is shown in Figure 2, where three spectral regions are identiÿed: acceleration-sensitive region (T n ¡0:6sec), velocitysensitive region (0:66T n 63 sec), and displacement-sensitive region (T n ¿3 sec).…”

Section: Earthquake Excitation and Spectral Regionsmentioning

confidence: 99%

Asymmetric one‐storey elastic systems with non‐linear viscous and viscoelastic dampers: Earthquake response

Lin

Chopra

2003

Earthq Engng Struct Dyn

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SUMMARYInvestigated are earthquake responses of one-way symmetric-plan, one-storey systems with non-linear uid viscous dampers (FVDs) attached in series to a linear brace (i.e. Chevron or inverted V-shape braces). Thus, the non-linear damper is viscous when the brace is considered rigid or viscoelastic (VE) when the brace is exible. The energy dissipation capacity of a non-linear FVD is characterized by an amplitude-dependent damping ratio for an energy-equivalent linear FVD, which is determined assuming the damper undergoes harmonic motion. Although this formulation is shown to be advantageous for single-degree-of-freedom (SDF) systems, it is di cult to extend its application to multi-degree-offreedom (MDF) systems for two reasons: (1) the assumption that dampers undergo harmonic motion in parameterizing the non-linear damper is not valid for its earthquake-induced motion of an MDF system; and (2) ensuring simultaneous convergence of all unknown amplitudes of dampers is di cult in an iterative solution of the non-linear system. To date, these limitations have precluded the parametric study of the dynamics of MDF systems with non-linear viscous or VE dampers. However, they are overcome in this investigation using concepts of modal analysis because the system is weakly non-linear due to supplemental damping. It is found that structural response is only weakly a ected by damper non-linearity and is increased by a small amount due to bracing exibility. Thus, the e ectiveness of supplemental damping in reducing structural responses and its dependence on the planwise distribution of non-linear VE dampers were found to be similar to that of linear FVDs documented elsewhere. As expected, non-linear viscous and VE dampers achieve essentially the same reduction in response but with much smaller damper force compared to linear dampers. Finally, the ÿndings in this investigation indicate that the earthquake response of the asymmetric systems with non-linear viscous or VE dampers can be estimated with su cient accuracy for design applications by analysing the same asymmetric systems with all non-linear dampers replaced by energy-equivalent linear viscous dampers.

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Section: Earthquake Excitation and Spectral Regionsmentioning

confidence: 99%

Asymmetric one‐storey elastic systems with non‐linear viscous and viscoelastic dampers: Earthquake response

Lin

Chopra

2003

Earthq Engng Struct Dyn

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“…Krawinkler et al (Krawinkler et al 2003) studied the dependence of drift and ductility demands on ground motions and the relationships of the parameters to ground motion intensity measures. A set of 80 ordinary (not near-fault) ground motions from the PEER NGA database were compiled and divided into four bins according to magnitude and distance from the fault.…”

Section: Representative Crustal Earthquake Setmentioning

confidence: 99%

Bridge Seismic Retrofit Measures Considering Subduction Zone Earthquakes

Dusicka¹,

Bazaez²,

Knoles³

2015

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Research was conducted to investigate the effect of subduction zone earthquakes on structural damage. The study suggests that large magnitude ground motions of long duration have the potential of significantly increasing the number of inelastic excursions and consequently incur more extensive structural damage as compared to ground motions with similar elastic spectral demands but of shorter duration. This increase in demand plays a crucial role in the Pacific Northwest where a mega subduction zone earthquake is impending. Typical reinforced concrete bridge bents constructed in the 1950 to mid-1970 in the State of Oregon were designed and built with minimum seismic considerations. This resulted in inadequate detailing within plastic hinge zones, leaving numerous RC bents highly susceptible to damage following an earthquake. In this study, the cyclic performance of an asbuilt RC square column and a reinforced concrete bridge bent retrofitted using buckling restrained braces (BRBs) was experimentally evaluated using quasi-static cyclic loading protocols aiming to reflect subduction zone earthquake demands up to displacement ductility. The buckling restrained braces were designed as replaceable elements in order to take the earthquake-induced energy and dissipate it through nonlinear hysteretic behavior. Two BRB designs were considered in the study in an effort to assess the influence of BRB stiffness on the overall structural performance. The results of these large-scale experiments successfully demonstrated the effectiveness of utilizing buckling restrained braces for achieving high displacement ductility of the retrofitted structure, while also controlling the damage of the existing vulnerable reinforced concrete bent up to the design performance levels. The potential of improving the overall seismic behavior and the design performance levels with BRBs offers structural design professionals a viable method for performance driven retrofit of reinforced concrete bents. 17. Key Words Subduction zone earthquakes, reinforced concrete bridge bents, plastic hinge zone, performance levels, bridge seismic retrofit, quasi-static loading protocol, buckling restrained braces.18. Distribution Statement: Copies available from NTIS, and online at

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“…It should be pointed out that the conclusion reached by Takizawa and Jennings in regard to the influence of ground motion duration in a structural collapse contradicts, as indicated later on, the findings reported by Ibarra and Krawinkler in their 2004 study. It is also opposite to the observations from other investigators ͑e.g., Hall et al 1995;Krawinkler et al 2003͒ that near-field ground motions, which can be characterized as short-duration, pulselike motions, are capable of causing severe distress in long-period structures.…”

Section: Single-degree-of-freedom Modelsmentioning

confidence: 99%

Methods to Assess the Seismic Collapse Capacity of Building Structures: State of the Art

Villaverde

2007

J. Struct. Eng.

165

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Abstract:The collapses of building structures during recent earthquakes have raised many questions regarding the adequacy of current seismic provisions to prevent a partial or total collapse. They have also brought up questions as to how to determine the collapse safety margin of structures, what is the inherent collapse safety margin in code-designed structures, and how to strengthen structures to effectively augment such margin. The purpose of this paper is to present a comprehensive review of the analytical methods that are currently available to assess the capacity of building structures to resist an earthquake collapse, point out the limitations of these methods, describe past experimental work in which specimens are tested to collapse, and identify what is required for an accurate evaluation of the seismic collapse capacity of a structure and the safety margin against such a collapse. It is contended that further research is needed before the collapse capacities of structures and their safety margin against collapse may be evaluated with confidence.

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Seismic drift and ductility demands and their dependence on ground motions

Cited by 147 publications

References 2 publications

Asymmetric one‐storey elastic systems with non‐linear viscous and viscoelastic dampers: Earthquake response

Asymmetric one‐storey elastic systems with non‐linear viscous and viscoelastic dampers: Earthquake response

Bridge Seismic Retrofit Measures Considering Subduction Zone Earthquakes

Methods to Assess the Seismic Collapse Capacity of Building Structures: State of the Art

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