A measure of the capacity of earthquake ground motions to damage structures (original) (raw)
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Earthquake Magnitude, Ground Motion and Structural Safety
Seismic events are most uncertain events that we have to consider for the safety of structures, ultimately the safety of people and loss of probable damage. Shaking during the earthquake is a terrible moment that strikes the people for a long time of post disaster era as traumatic effect. Prediction of the earthquake is not yet a successful story among the scientific community but early warning to the people of far distant is in practice since 90s. Earthquake early warning system works when the epicenter is more or less about 30 km, in case of centralized system where dense network of seismometers are set in the field near by the epicenter. Mechanism of early warning system based on the difference of speed of two body waves those propagate from the focus or hypocenter. P-wave is the primary wave to travel faster than the secondary S-wave which is more destructive. In early warning system, P wave will be detected by the seismometers near by the epicenter and then processed to disseminate the information. Time available to act before the major shaking depends on the epicentral distance and processing time of the system. 2015 Nepal Earthquake Mw7.8 which struck on 25 th April and following major aftershock on 12 th May claimed nearly 9,000 lives where more than 600,000 structures salvaged within few seconds. Several heritage structures got grounded in Kathmandu valley, Gorkha, and Nuwakot. Liquefaction in few areas inside Kathmandu valley and other location showed the potential disaster. The long period dominated ground motion of the Gorkha earthquake was a major relief to the short natural period structures of lower height that limits the casualties and losses in a lower level (Parajuli & Kiyono, 2015) (Sharma, Subedi, Parajuli, & Pokharel, 2017). Most of the structures those perished during the earthquakes are non-engineered buildings whereas some of the engineered buildings also had suffered from heavy damage. Despite the several damages in numbers of structures, casualties are lower in comparison with other large earthquake events. Kobe earthquake in 1995 in Japan destroyed about 150,000 buildings and claimed around 6434 lives. Haiti earthquake 2010 that commonly taken as an reference even during the reconstruction process claimed more than 220,000 lives but the numbers of structures collapsed were just around 280,000. Event time and culture of local community has the major role to have such scenario in Nepal, where ratio of number of structures collapsed to casualties is much higher than other countries.
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2001
In this study, various ground shaking, response and damage parameters are examined for post-earthquake applications. Peak ground motion values, elastic response spectra, spectrum intensity, drift spectrum, inelastic spectra, and hysteretic energy spectrum are examined. Two improved damage spectra are also examined. The improved damage spectra will be zero if the response remains elastic, and will be unity when the displacement capacity under monotonic deformation is reached. Furthermore, the proposed damage spectra can be reduced to the special cases of normalized hysteretic energy and displacement ductility spectra. The proposed damage spectra are promising for various seismic vulnerability studies and post-earthquake applications. In this study the above parameters are examined. Additionally, improved damage spectra are introduced and examined in details. The damage spectra are based on normalized response quantities of a series of inelastic single-degree-of-freedom (SDOF) systems...
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Comprehensive studies have been carried out to investigate the correlation between structural damage indexes (SDIs) and a number of widely used ground motion intensity (GMI) parameters. To this, Nonlinear time–history analyses of steel and concrete frames are performed under a set of many ground motion records. The frames reflect the features of typical lowto medium-rise structures. The records used in nonlinear time history analyses have intensities to represent a wide range of seismic forces that impose various degrees of elastic as well as inelastic response of the frames. The SDIs were compared with the GMI parameters and correlations between them were investigated through coefficients of correlation and determination. The results revealed that spectrum intensity parameters, having the strongest correlation, are superior to other parameters such as peak ground velocity, peak ground acceleration, and spectral acceleration. It was concluded that both peak ground acceleration/peak ...
THE INFLUENCE OF EARTHQUAKE DURATION AND SUCCESSIVE GROUND MOTIONS IN THE STRUCTURAL RESPONSE
10th Int. Symposium on Structure Engineering, Changsha, China, 19-21 October, 1881-1886, 2008
This study analyses the behaviour of an unreinforced masonry wall under ground motions with different duration and intensities. The influence of successive ground motions with different intensities is also taken into account. This work present four different cases that compare: i) records with the same intensity and different duration, ii) records with the same duration and different intensities, iii) a single long-duration ground motion against a sequence of ground motions with equivalent duration, and iv) the effect of a single ground motion against the same ground motion that followed by several aftershocks. The preliminary results of the numerical model are presented. The results reveal the importance of the earthquake duration in the structural response under the action of single records; and the accumulation of the damage, when the structure is affected by a sequence of ground motions.
Effects of Near-fault Strong Ground Motions on Probabilistic Structural Seismic-induced Damages
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Seismic fragility curves measure induced levels of structural damage against strong ground motions of earthquakes, probabilistically. These curves play an important role in seismic performance assessment, seismic risk analysis and making rational decisions regarding seismic risk management of structures. It has been demonstrated that the calculated fragility curves of structures are changed while the structures are excited by near-field strong ground motions in comparison with far-field ones. The objective of this paper is to evaluate the extents of modification for various performance levels and variety of structural heights. To achieve this goal, Incremental Dynamic Analysis (IDA) method is applied to calculate seismic fragility curves. To investigate the effects of earthquake characteristics, two categories of strong ground motions are assumed through IDA method, i.e. near and far-field sets. To study the extent of modification for various heights of structures, 4 – 6 and 10 stor...
Talenta Conference Series: Energy and Engineering (EE)
Seismic input energy is transmitted into building consists of the kinetic energy, elastic strain energy, damping energy, and hysteretic energy. The amount of the input energy induced by earthquake transmitted into a building depends on earthquake characteristics and building dynamic properties. In this context, the hysteretic energy directly associated with damage to structural members through a parameter which known as the damage index were introduced. For this purposes, influence of earthquake characteristic on energy spectra for SDOF system were described and presented. In addition, influence of structural dynamic properties are also described and discussed. Next, to assess the damage potential to a building under seismic excitation, four story steel moment resisting frame were investigated under three selected ground motion records matching to the response spectra design the new Indonesian code. Furthermore, nonlinear dynamic time history analysis were performed using ABAQUS to ...