Development of fragility curves by incorporating new spectral shape indicators and a weighted damage index:case study of steel braced frames in the city of Mashhad,Iran

In this study, strong ground motion record （SGMR） selection based on Eta （~/） as a spectral shape indicator has been investigated as applied to steel braced flame structures. A probabilistic seismic hazard disaggregation analysis for the definition of the target Epsilon （ε） and the target Eta （η） values at different hazard levels is presented, taking into account appropriately selected SGMR＇s. Fragility curves are developed for different limit states corresponding to three representative models of typical steel braced frames having significant irregularities in plan, by means of a weighted damage index. The results show that spectral shape indicators have an important effect on the predicted median structural capacities, and also that the parameter r/is a more robust predictor of damage than searching for records with appropriate c values.

The Modification on the Discreteness of Park-Ang Damage Index Based on Bayesian Methodology

The discreteness is a common deficiency which impedes damage indices' practical application. It is caused by the arbitrary linear combination and some missing necessary variables. In order to deal with this problem,the correction term was added to the widely cited Park-Ang damage index. The unknown parameters in the correction term were obtained by the maximum likelihood estimation of these parameters' posterior distributions updated through Bayesian methodology. And the specimens for Bayesian updating were selected from PEER column database and Kawashima Earthquake Engineering Laboratory. Through model simplification process,a simplified modification was adopted,which has improved its goodness of fit to the experimental data. It has been found that the concrete core area and cross sectional area ratio,the longitudinal reinforcement ratio and the damage concentration factor are the critical variables affecting the error of the original damage index.

Experimental study on the degree and damage-control mechanisms of fuzzy-ball-induced damage in single and multi-layer commingled tight reservoirs

Fuzzy-ball working fluids(FBWFs)have been successfully applied in different development phases of tight reservoirs.Field reports revealed that FBWFs satisfactorily met all the operational and reservoir damage control requirements during their application.However,the damage-control mechanisms and degree of formation damage caused by fuzzy-ball fluids have not been investigated in lab-scale studies so far.In this study,the degree of fuzzy-ball-induced damage in single-and double-layer reservoirs was evaluated through core flooding experiments that were based on permeability and flow rate indexes.Additionally,its damage mechanisms were observed via scanning electron microscope and energy-dispersive spectroscopy tests.The results show that:(1)For single-layer reservoirs,the FBWF induced weak damage on coals and medium-to-weak damage on sandstones,and the difference of the damage in permeability or flow rate index on coals and sandstones is below 1%.Moreover,the minimum permeability recovery rate was above 66%.(2)For double-layer commingled reservoirs,the flow rate index revealed weak damage and the overall damage in double-layer was lower than the single-layer reservoirs.(3)There is no significant alteration in the microscopic structure of fuzzy-ball saturated cores with no evidence of fines migration.The dissolution of lead and sulfur occurred in coal samples,while tellurium in sandstone,aluminum,and magnesium in carbonate.However,the precipitation of aluminum,magnesium,and sodium occurred in sandstone but no precipitates found in coal and carbonate.The temporal plugging and dispersion characteristics of the FBWFs enable the generation of reservoir protection layers that will minimize formation damage due to solid and fluid invasion.

Energy-based damage assessment of continuous-span reinforced concrete highway bridges

This paper conducts a comparative study on seismic damage to reinforced concrete(RC)bridges,using three damage models:Park and Ang,Hindi and Sexsmith,and input energy-based damage(IEBD)indices,and presents a global cumulative damage model based on the IEBD index to establish a practical damage assessment of an overall bridge system.A series of RC bridges are studied under seismic loadings,and to compare the efficiency and reliability of the damage indices,damage curves of RC piers are developed,and damage levels of piers are calculated at design basis earthquake(DBE)and maximum considered earthquake(MCE)levels.The global cumulative damage index is calculated for bridge models regarding damage values of components.The results indicate that the IEBD index shows a gradual progression of damage and provides reasonable values for different damage levels of piers compared to two other damage indices.Moreover,the global cumulative damage index shows the impact of induced damage to a certain component regarding the damage level of the overall bridge system.Moreover,this new approach is a relatively simple and practical tool for seismic damage assessment of RC bridge systems,which can be implemented in finite element models,particularly in the absence of experimental data.

Remote Sensing Based Rapid Assessment of Flood Crop Damage Using Novel Disaster Vegetation Damage Index(DVDI)

Accurate crop-specific damage assessment immediately after flood events is crucial for grain pricing,food policy,and agricultural trade.The main goal of this research is to estimate the crop-specific damage that occurs immediately after flood events by using a newly developed Disaster Vegetation Damage Index(DVDI).By incorporating the DVDI along with information on crop types and flood inundation extents,this research assessed crop damage for three case-study events:Iowa Severe Storms and Flooding(DR 4386),Nebraska Severe Storms and Flooding(DR 4387),and Texas Severe Storms and Flooding(DR 4272).Crop damage is assessed on a qualitative scale and reported at the county level for the selected flood cases in Iowa,Nebraska,and Texas.More than half of flooded corn has experienced no damage,whereas 60%of affected soybean has a higher degree of loss in most of the selected counties in Iowa.Similarly,a total of 350 ha of soybean has moderate to severe damage whereas corn has a negligible impact in Cuming,which is the most affected county in Nebraska.A total of 454 ha of corn are severely damaged in Anderson County,Texas.More than 200 ha of alfalfa have moderate to severe damage in Navarro County,Texas.The results of damage assessment are validated through the NDVI profile and yield loss in percentage.A linear relation is found between DVDI values and crop yield loss.An R2 value of 0.54 indicates the potentiality of DVDI for rapid crop damage estimation.The results also indicate the association between DVDI class and crop yield loss.

Damage index estimation by analysis of meteorological disasters on film plastic greenhouses

This study focuses on the analysis of the effect of meteorological disasters on film plastic greenhouses by typhoons,heavy snow,strong wind,and heavy rain.The data of meteorological disasters from 1998 to 2015 were analyzed on provincial basis to calculate the damage rate depending on the weather cause.The cumulative damage area is 20279 hm2.The damage rates of typhoons,heavy snow,strong wind,and heavy rain are 46.4%,47.4%,2.5%,and 3.8%,respectively.The damage index of the greenhouse,which is the ratio of the greenhouse area to the cumulative damage area,was proposed to estimate the disaster risk for 17 administrative districts.The damage index data and the cumulative damage areas were divided using the Jenks’Natural Breaks method.The average damage index is 0.66,and the damage indices are high in the metropolitan cities.

Oxygen Radical Generation as an Index of Neurotoxic Damage

Biochemical, anatomical, and physiological characteristics of the brain make it especially vulnerable to insult. Specifically, some of these characteristics such as myelin and a high energy requirement provide for the introduction of free radical-induced insult. Recently, the biochemistry of free radicals has received considerable attention. It also has become increasingly suggestive that many drug and chemical-induced toxicities may be evoked via free radicals and oxidative stress. Major points addressed in this work are the regulation of neural-free radical generation by antioxidants and protective enzymes, xenobiotic-induced disruption of cerebral redox status, and specific examples of neurotoxic agent-induced alterations in free radicals as measured by the fluorescent probe dichlorofluorescein. This article considers that free radical mechanisms may contribute significantly to the properties of several diverse neurotoxic agents and proposes that free radicals may be common phenomena of neurotoxicity.

Simulating of marble subjected to uni-axial loading using index-parabola damage model

The limitations of several existing classical rock damage models were critically appraised. Thereafter, a description of a new model to estimate the response of rock was provided. The results of an investigation lead to the development and confirmation of a new index parabola damage model. The new model is divided into two parts, fictitious damage and real damage and bordered by the critical damage point. In fictitious damage, the damage variable follows the index distribution, while in the real damage a parabolic distribution is used. Thus, the so called index parabola damage model is derived. The proposed damage model is applied to simulate the damage procedure of marble under uni axial loading. The results of the tests show that the proposed model is in excellent agreement with experimental data, in particular the nonlinear characteristic of rock deformation is adequately represented. [

Numerical investigation of the effects of soil-structure and granular material-structure interaction on the seismic response of a flat-bottom reinforced concrete silo

In this work,a numerical study of the effects of soil-structure interaction(SSI)and granular material-structure interaction(GSI)on the nonlinear response and seismic capacity of flat-bottomed storage silos is conducted.A series of incremental dynamic analyses(IDA)are performed on a case of large reinforced concrete silo using 10 seismic recordings.The IDA results are given by two average IDA capacity curves,which are represented,as well as the seismic capacity of the studied structure,with and without a consideration of the SSI while accounting for the effect of GSI.These curves are used to quantify and evaluate the damage of the studied silo by utilizing two damage indices,one based on dissipated energy and the other on displacement and dissipated energy.The cumulative energy dissipation curves obtained by the average IDA capacity curves with and without SSI are presented as a function of the base shear,and these curves allow one to obtain the two critical points and the different limit states of the structure.It is observed that the SSI and GSI significantly influence the seismic response and capacity of the studied structure,particularly at higher levels of PGA.Moreover,the effect of the SSI reduces the damage index of the studied structure by 4%.

Guided Wave Based Damage Detection Method for Aircraft Composite Structures under Varying Temperatures

Guided waves based damage detection methods using base signals offer the advantages of simplicity of signal generation and reception,sensitivity to damage,and large area coverage;however,applications of the technology are limited by the sensitivity to environmental temperature variations.In this paper,a Spearman Damage Index-based damage diagnosis method for structural health condition monitoring under varying temperatures is presented.First,a PZT sensor-based Guided wave propagation model is proposed and employed to analyze the temperature effect.The result of the analysis shows the wave speed of the Guided wave signal has higher temperature sensitivity than the signal fluctuation features.Then,a Spearman rank correlation coefficient-based damage index is presented to identify damage of the structure under varying temperatures.Finally,a damage detection test on a composite plate is conducted to verify the effectiveness of the Spearman Damage Index-based damage diagnosis method.Experimental results show that the proposed damage diagnosis method is capable of detecting the existence of the damage and identify its location under varying temperatures.

Post-earthquake building damage assessment in Yushu using airborne SAR imagery

The synthetic aperture radar （SAR） plays an important role in earthquake emergency response because of its all-time and all-weather imaging capabilities. On April 14, 2010, an Ms7.1 earthquake occurred in Yushu county, Qinghai province of China, causing a lot of buildings collapsed. In this paper, the building damage in Yushu city due to the earthquake was assessed quantitatively using high-resolution X-band airborne SAR image. The features of the buildings with different damage levels （collapsed, partial collapsed, non-collapsed） in the SAR image were analyzed first. Based on these building features, we interpreted the individual building damage in Yushu city block by block and got the numbers of the collapsed, partial collapsed and non-collapsed buildings separately for each block, referring to pre-earthquake QuickBird image when necessary. Let the damage index of individual collapsed, partial collapsed, non-collapsed building be 1, 0.5, 0 respectively, the remote sensing damage index of each block was then calculated through remote sensing damage index equation. Finally, the preliminary quantitative relationship between the remote sensing damage index interpreted from the SAR image and that interpreted from the optical image was built up. It can be concluded that a desirable damage assessment result can be derived from high-resolution airborne SAR imagery.

Stiffness degradation-based damage model for RC members and structures using fiber-beam elements

To meet the demand for an accurate and highly efficient damage model with a distinct physical meaning for performance-based earthquake engineering applications, a stiffness degradation-based damage model for reinforced concrete （RC） members and structures was developed using fiber beam-column elements. In this model, damage indices for concrete and steel fibers were defined by the degradation of the initial reloading modulus and the low-cycle fatigue law. Then, section, member, story and structure damage was evaluated by the degradation of the sectional bending stiffness, rod-end bending stiffness, story lateral stiffness and structure lateral stiffness, respectively. The damage model was realized in Matlab by reading in the outputs of OpenSees. The application of the damage model to RC columns and a RC frame indicates that the damage model is capable of accurately predicting the magnitude, position, and evolutionary process of damage, and estimating stow damage more precisely than inter-story drift. Additionally, the damage model establishes a close connection between damage indices at various levels without introducing weighting coefficients or force-displacement relationships. The development of the model has perfected the damage assessment function of OpenSees, laying a solid foundation for damage estimation at various levels of a large-scale structure subjected to seismic loading.

Damage detection of 3D structures using nearest neighbor search method

An innovative damage identification method using the nearest neighbor search method to assess 3D structures is presented.The frequency response function was employed as the input parameters to detect the severity and place of damage in 3D spaces since it includes the most dynamic characteristics of the structures.Two-dimensional principal component analysis was utilized to reduce the size of the frequency response function data.The nearest neighbor search method was employed to detect the severity and location of damage in different damage scenarios.The accuracy of the approach was verified using measured data from an experimental test;moreover,two asymmetric 3D numerical examples were considered as the numerical study.The superiority of the method was demonstrated through comparison with the results of damage identification by using artificial neural network.Different levels of white Gaussian noise were used for polluting the frequency response function data to investigate the robustness of the methods against noise-polluted data.The results indicate that both methods can efficiently detect the damage properties including its severity and location with high accuracy in the absence of noise,but the nearest neighbor search method is more robust against noisy data than the artificial neural network.

Cumulative damage effects of mainshock-aftershock sequences on RC-frame structures

Frequent aftershocks often follow a strong mainshock.They can significantly increase cumulative damage to a structure.A model of a five-story reinforced concrete frame structure was designed and a nonlinear mathematical model of the structure was developed to investigate the damage states resulting from different mainshock-aftershock sequences.Mainshock-aftershock sequences consisting of one of three recorded mainshocks combined with one of five recorded aftershocks were created for input to the mathematical model.Inelastic energy dissipation and the Park-Ang damage index were used as measures of cumulative damage to the structure.The results demonstrate that consideration of only the single mainshock ground motion in seismic building design can result in the design and construction of unsafe buildings.Total cumulative damage to a structure is caused by the combination of damage states resulting from the mainshock and the aftershock(s).

Seismic fragility assessment of existing sub-standard low strength reinforced concrete structures

An analytical seismic fragility assessment framework is presented for the existing low strength reinforced concrete structures more common in the building stock of the developing countries.For realistic modelling of such substandard structures,low strength concrete stress-strain and bond-slip capacity models are included in calibrating material models.Key capacity parameters are generated stochastically to produce building population and cyclic pushover analysis is carried out to capture inelastic behaviour.Secant period values are evaluated corresponding to each displacement step on the capacity curves and used as seismic demand.A modified capacity demand diagram method is adopted for the degrading structures,which is further used to evaluate peak ground acceleration from back analysis considering each point on the capacity curve as performance point.For developing fragility curves,the mean values of peak ground acceleration are evaluated corresponding to each performance point on the series of capacity curves.A suitable probability distribution function is adopted for the secant period scatter at different mean peak ground acceleration values and probability of exceedance of limit states is evaluated.A suitable regression function is used for developing fragility curves and regression coefficients are proposed for different confidence levels.Fragility curves are presented for a low rise pre-seismic code reinforced concrete structure typical of developing countries.

Ground motion duration effect on responses of hydraulic shallow-buried tunnel under SV-waves excitations

Although intensive research of the influence of ground motion duration on structural cumulative damage has been carried out, the influence of dynamic responses in underground tunnels remains a heated debate. This study attempts to highlight the importance of the ground motion duration effect on hydraulic tunnels subjected to deep-focus earthquakes. In the study, a set of 18 recorded accelerograms with a wide-range of durations were employed. A spectrally equivalent method serves to distinguish the effect of duration from other ground motion features, and then the seismic input model was simulated using SV-wave excitation based on a viscous-spring boundary, which was verified by the time-domain waves analysis method. The nonlinear analysis results demonstrate that the risk of collapse of the hydraulic tunnel is higher under long-duration ground motion than that of short-duration ground motion of the same seismic intensity. In a low intensity earthquake, the ground motion duration has little effect on the damage energy consumption of a hydraulic tunnel lining, but in a high intensity earthquake, dissipation of the damage energy and damage index of concrete shows a nonlinear growth trend accompanied by the increase of ground motion duration, which has a great influence on the deformation and stress of hydraulic tunnels, and correlation analysis shows that the correlation coefficient is greater than 0.8. Therefore, the duration of ground motion should be taken into consideration except for its intensity and frequency content in the design of hydraulic tunnel, and evaluation of seismic risk.

New characteristics of intensity assessment of Sichuan Lushan “4.20” M_s7.0 earthquake

The post-earthquake rapid accurate assessment of macro influence of seismic ground motion is of significance for earthquake emergency relief,post-earthquake reconstruction and scientific research. The seismic intensity distribution map released by the Lushan earthquake field team of the China Earthquake Administration(CEA) five days after the strong earthquake(M7.0) occurred in Lushan County of Sichuan Ya’an City at 8:02 on April 20,2013 provides a scientific basis for emergency relief,economic loss assessment and post-earthquake reconstruction. In this paper,the means for blind estimation of macroscopic intensity,field estimation of macro intensity,and review of intensity,as well as corresponding problems are discussed in detail,and the intensity distribution characteristics of the Lushan '4.20' M7.0 earthquake and its influential factors are analyzed,providing a reference for future seismic intensity assessments.

Incremental dynamic analysis of concrete gravity dams including base and lift joints

The growth in computer processing power has made it possible to use time-consuming analysis methods such as incremental dynamic analysis（IDA） with higher accuracy in less time.In an IDA study,a series of earthquake records are applied to a structure at successively increasing intensity levels,which causes the structure to shift from the elastic state into the inelastic state and finally into collapse.In this way,the limit-states and capacity of a structure can be determined.In the present research,the IDA of a concrete gravity dam considering a nonlinear concrete behavior,and sliding planes within the dam body and at the dam-foundation interface,is performed.The influence of the friction angle and lift joint slope on the response parameters are investigated and the various limit-states of the dam are recognized.It is observed that by introducing a lift joint,the tensile damage can be avoided for the dam structure.The lift joint sliding is essentially independent of the base joint friction angle and the upper ligament over the inclined lift joint slides into the upstream direction in strong earthquakes.

Fragility of disconnect switch subjected to random earthquake ground motions

A fragility calculation scheme is estabtished in this paper for porcelain-type equipments subjected to random earthquake ground motions. All steps of the method are illustrated by the seismic damage analysis of GW4-110 disconnect switch. The model of the equipment is built applying the finite element method with flexible joints, and the seismic response of the equipment is analyzed using elastic time history method. On the base, according to the strength damage index and Monte-Carlo Method, the seismic damage ratios are counted and the seismic fragility curves are presented. Then the seismic damage of GW4-110 disconnect switch can be predicted.

Screening of 19 genotypes of Eucalyptus spp.against gall wasp(Leptocybe invasa) in North-western India

The present study was carried out at Punjab Agricultural University,Ludhiana,India.Nineteen clones of Eucalyptus spp.were evaluated for tolerance to gall wasp.The total number of galls per plant were recorded at 1 month after planting（MAP） and the number of galls per branch were recorded at 4 and 7 MAP.Gall wasp incidence（number of galls） was recorded on a whole plant basis during the seedling stage and the number of galls were recorded from the upper,middle and lower crown places at 4 and 7 MAP.Categorization was done on the basis of relative gall-wasp damage by keeping in view the total number of galls per plant and branch（leaves and petiole）.No clone was found free from gall damage.Clones C-526,P-23 and P-103 were the least attacked by the gall wasp.Incidence as indicated by number of galls caused by Leptocybe invasa on eucalypts was higher in March than in December.