Earthquake Disaster Control - Damping and Structural Behavior (original) (raw)
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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.
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.
A measure of the capacity of earthquake ground motions to damage structures
Earthquake Engineering & Structural Dynamics, 1994
Even though a number of parameters have been proposed in the literature for measuring the capacity of earthquake ground motions to damage structures, most of them are not consistent with building damage observed during earthquakes. In this study, a parameter for measuring seismic damage capacity is proposed. It uses the energy dissipated by a structure in inelastic deformations and a structural overall drift, and it is evaluated for three typical ground motions recorded in severe earthquakes. By using this parameter, consistent results with building damage observed in these earthquakes are obtained, which indicate the importance of displacement control for minimizing seismic damage.
IJERT-Earthquake Response Of Structures Under Different Soil Conditions B.Neelima
International Journal of Engineering Research and Technology (IJERT), 2014
https://www.ijert.org/earthquake-response-of-structures-under-different-soil-conditions https://www.ijert.org/research/earthquake-response-of-structures-under-different-soil-conditions-IJERTV1IS7348.pdf Earthquake is a spasm of ground shaking caused by sudden release of energy in the earth"s lithosphere. It is an endogenous natural hazard which occurs sudden and destruction takes place within a short period of time. History and geological evidences show that the rate of occurrence of earthquakes has become a frequently recurring phenomenon all over the world. Bitter experiences left by past earthquakes, especially in urban regions; reveal the importance of terrain evaluation and influence of soil-structure interaction on response of structures during earthquakes. In the present study, a part of Vijayawada city, located on eastern side of the state Andhra Pradesh, India, covered by many high rise buildings supported on different type of soils, is chosen as study area. A conventional three storied building when rests on different soils is chosen for the study. Earthquake analysis is carried out using mode superposition method as given in IS 1893-2002 [5] and the response parameters like; frequencies, time periods, base shears and displacements are obtained when the structure rests on different soils or rocks. The influence of soil-structure interaction is compared with the results obtained when the structure is assumed to be fixed at the base. In the present study, it is observed that the fundamental natural frequencies increase and base shears decrease with the increase of soil stiffness and this change is found more in soft soils. In general, it is seen that the displacements increase with the decrease of soil stiffness, which is mainly attributed due to rocking effect of the soil. Hence soil-structure interaction cannot be ignored while designing important structures like nuclear power plants, liquid storage structures, dams etc., against expected earthquake forces.
EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS
How to select a limited number of ground motion records (GMRs) is an important challenge for the nonlinear analysis of structures. Since epsilon (ε Sa ) is an indicator of spectral shape, which has a significant correlation with the non-linear response of a structure, the selection of GMRs based on the hazard-related target ε Sa is a reasonable approach. In this paper, an alternative indicator of spectral shape is proposed, which results in a more reliable prediction of the non-linear response for the structures with the natural period of 0.25 to 3.0 s. This new parameter, named eta ( ), is a linear combination of ε Sa and the peak ground velocity epsilon (ε PGV ). It is shown that , as a non-linear response predictor, is remarkably more efficient than the well-known and convenient parameter ε Sa . The influence of -filtration in the collapse analysis of an eight-story reinforced concrete structure with special moment-resisting frames was studied. Statistical analysis of the results confirmed that the difference between ε-filtration and -filtration can be very significant at some hazard levels. In the case of this structure, the resulting annual frequency of collapse was found to be lower in the case of -based record selection, in comparison with the ε-based record-selection approach.
Mechanism of Earthquake and Damages of Structures
The mechanism of earthquake consists of generation of seismic waves due to the rupture of the rock in the Earth and their propagation within the earth crest due to the movement of the Earth. The rupture surface is called a fault plane. There are three kinds of faults, namely, strike slip, dip slip and oblique slip. The severity of earthquake depends on the slip. The seismic waves comprises of P wave, S waves, R or Rayleigh waves and L or Love waves. The P and S waves constitute the body waves and the R and L waves constitute surface waves. The surface waves are dangerous and causes extensive damages on the Earth surface. Normally structures are founded on the Earth. So due to the motion of the Earth the ground vibrates and this sets in motion the structures. Many structures consisting of masonry, concrete, road and railway were damaged in the past earthquakes globally. The paper presents the mechanism of earthquake and the damages it can cause to structures of varied types by reviewing the available literature.
Dynamic Response Characteristics of Buildings Subjected to Pulse-Like Ground Motions
2014
We have investigated the fundamental but very important response characteristics of buildings against the pulse-like ground motions which are predicted in the near-fault region of inland shallow earthquake. Especially, the soil structure interaction effects (SSI effects), contribution of each vibration mode, propagation of pulse-like wave in a building, and effects of viscous and hysteresis dampers are discussed in detail. In conclusion, the natural periods normalized by the pulse period Tp are very important characteristic values to evaluate the maximum response and building damage as well as the peak ground velocity or peak ground displacement. INTRODUCTION It is expected that destructive pulse-like ground motions are predicted to occur in the near-fault region of massive inland shallow earthquake and many tall buildings may suffer severe damage including collapse. However, uncertainty in estimating ground motion characteristics cannot be avoided. For example, Figure 1 shows the e...
Earthquake Response Of Structures Under Different Soil Conditions
2012
Earthquake is a spasm of ground shaking caused by sudden release of energy in the earth"s lithosphere. It is an endogenous natural hazard which occurs sudden and destruction takes place within a short period of time. History and geological evidences show that the rate of occurrence of earthquakes has become a frequently recurring phenomenon all over the world. Bitter experiences left by past earthquakes, especially in urban regions; reveal the importance of terrain evaluation and influence of soil-structure interaction on response of structures during earthquakes. In the present study, a part of Vijayawada city, located on eastern side of the state Andhra Pradesh, India, covered by many high rise buildings supported on different type of soils, is chosen as study area. A conventional three storied building when rests on different soils is chosen for the study. Earthquake analysis is carried out using mode superposition method as given in IS 1893-2002 [5] and the response parameters like; frequencies, time periods, base shears and displacements are obtained when the structure rests on different soils or rocks. The influence of soil-structure interaction is compared with the results obtained when the structure is assumed to be fixed at the base. In the present study, it is observed that the fundamental natural frequencies increase and base shears decrease with the increase of soil stiffness and this change is found more in soft soils. In general, it is seen that the displacements increase with the decrease of soil stiffness, which is mainly attributed due to rocking effect of the soil. Hence soil-structure interaction cannot be ignored while designing important structures like nuclear power plants, liquid storage structures, dams etc., against expected earthquake forces. 2. Soil-Structure Interaction Usually, when earthquake occurs, seismic waves travel through different rock and soil media and
Chinese Science Bulletin, 2004
Influences on the ground motion simulations by soil amplification effects and multiple seismic wave interferences in the heterogeneous medium are investigated. Detailed velocity structure obtained from the microtremor array survey is adopted in the ground motion simulation. Analyses for amplification ratios of core samples of ten drill holes with 40 m deep in the sedimentary layers show that the soil amplification ratio influences nonlinearly the seismic ground motion. Based on the above analysis results, the ground motion in the heavily damaged zone in the Japanese Kobe earthquake of 1995 is simulated in a digital SH seismic wave model by using the pseudospectral method with the staggered grid RFFT differentiation (SGRFFTD). The simulated results suggest that the heterogeneous velocity structure results in a complicated distribution of the maximum amplitudes of acceleration waveforms with multiple peaks at the surface. Spatial distribution of the maximum amplitudes coincides well with that of collapse ratios of buildings in Kobe. The dual peaks of the collapse ratios away from the earthquake fault coincide well with the double peak amplitudes of simulated seismic acceleration waves also. The cause for the first peak amplitude of the ground motion is attributable to the interference of the secondary surface wave from the bedrock propagating horizontally along the surface sedimentary layer and the body wave from the basin bottom according to analyses of wave snapshots propagating in inhomogeneous structure of the Osaka group layers. The second peak amplitude of the ground motion may be attributive to the interference of the secondary surface wave from the tunneling waves in the shallow sediments and the body wave. It is important for the study on complicated distributions of earthquake damages to investigate influences on the ground motion by soil amplification effects and multiple seismic wave interferences due to the structure. Explorations of the structure to the bedrock are necessary for the urban mitigation disaster. Seismic wave simulations are valid for aseismatic study.
A Parametric Study: Effect of Soil and Material Characteristics on Seismic Behavior of Structures
In this parametric study, effect of soil and material characteristics on seismic behavior of structures is investigated. The soil parameters such as shear strength, unit weight; geometrical parameters of the structure such as foundation depth and height of building; and material properties such as weight of concrete were selected as input parameters. A real accelerogram of 1989 El-Centro Earthquake recorded by the USGS in Imperial Valley is used for this study. It is contained in the standard Strong Motion CD-ROM (SMC) format, which can be recognized and interpreted by FEM software used. The soil-structure interaction model subjected to above-mentioned earthquake was analyzed for 729 cases. Effect of input parameters on relative displacements occurring in the structure was then investigated and the interaction between the input and output parameters is presented in graphical form. Findings showed that all input parameters have significant effects on relative displacements occurring in the structure.