Seismic fragility analysis of clay-pile-pier systems considering the optimization of ground motion intensity measures

The performance of clay-pile-pier system under earthquake shaking was comprehensively examined via three-dimensional finite element analyses,in which the complex stress-strain relationships of a clay and piled pier system were depicted by a hyperbolic-hysteretic and an equivalent elastoplastic model,respectively.One hundred twenty ground motions with varying peak accelerations were considered,along with the variations in bridge superstructure mass and pile flexural rigidity.Comprehensive comparison studies suggested that peak pile-cap acceleration and peak pile-cap velocity are the optimal ground motion intensity measures for seismic responses of the pier and the pile,respectively.Furthermore,based on two optimal ground motion intensity measures and using curvature ductility to quantify different damage states,seismic fragility analyses were performed.The pier generally had no evident damage except when the bridge girder mass was equal to 960 t,which seemed to be comparatively insensitive to the varying pile flexural rigidity.In comparison,the pile was found to be more vulnerable to seismic damage and its failure probabilities tended to clearly reduce with the increment of pile flexural rigidity,while the influence of the bridge girder mass was relatively minor.

Effect of non-enzymatic glycation on collagen nanoscale mechanisms in diabetic and age-related bone fragility

Age and diabetes have long been known to induce an oxidative reaction between glucose and collagen,leading to the accumulation of advanced glycation end-products(AGEs)cross-links in collagenous tissues.More recently,AGEs content has been related to loss of bone quality,independent of bone mass,and increased fracture risk with aging and diabetes.Loss of bone quality is mostly attributed to changes in material properties,structural organization,or cellular remodeling.Though all these factors play a role in bone fragility disease,some common recurring patterns can be found between diabetic and age-related bone fragility.The main pattern we will discuss in this viewpoint is the increase of fibrillar collagen stiffness and loss of collagen-induced plasticity with AGE accumulation.This study focused on recent related experimental studies and discusses the correlation between fluorescent AGEs content at the molecular and fibrillar scales,collagen deformation mechanisms at the nanoscale,and resistance to bone fracture at the macroscale.

Time-varying seismic fragility analysis of durability damage of high-tensile reinforcement ECC bridge pier

The deterioration of the performance of offshore bridges is particularly prominent due to the complex natural environment,including the coupling effects of earthquake and seawater erosion.In particular,bridge piers are the main energy-consuming and load-bearing components,so that excellent seismic capacity of bridge piers is the key to avoiding bridge damage.Although earthquake resistant behavior of ordinary reinforced concrete bridge piers(ordinary pier)can be improved by increasing the section size and reinforcement ratio of piers,the improvement of the earthquake resistant behavior is limited.To further improve the earthquake resistant behavior of bridge piers,high-tensile reinforcement engineered cementitious composite(ECC)bridge piers are utilized and time-varying seismic fragility analysis are conducted in this study.The refined model of a bridge pier is built by OpenSees.First,the influence of ECC replacement height on pier curvature is analyzed to determine the reasonable ECC height.Then,the time-varying fragility analysis of high-tensile reinforcement ECC piers(ECC composite piers)with durability damage are evaluated considering the time-varying law of materials.Four damage states,slight damage,moderate damage,extensive damage and complete collapse,are utilized in the study.These fragility curves indicate the durability damage can debase the earthquake resistant behavior of piers continually,the exceedance probability of the same state of destruction increases with the increase of peak ground acceleration(PGA)and service time of pier.The results also indicate that the corrosion level of chloride ion to pier is small during the early service period,and the bridge pier vulnerable curve is similar to that of the new bridge pier.As the level of chlorine ion corrosion deepens,transcendental probability is increased.Compared with the ordinary pier,the exceedance probability in each limit state of ECC composite piers is significantly reduced.The proposed ECC composite pies leads to better realistic time-varying earthquake resistant behavior.

Comparison of seismic fragility analysis methods for arch dams

This study focuses on the seismic fragility analysis of arch dams.The multiple stripe analysis(MSA),cloud analysis(CLA),and incremental dynamic analysis(IDA)methods are compared.A comprehensive dam-reservoir-foundation rock system,which considers the opening of contraction joints,the nonlinearity of dam concrete and foundation rock,the radiation damping effect of semi-unbounded foundation,and the compressibility of reservoir water,is used as a numerical example.225,80,and 15 earthquake records are selected for MSA,CLA,and IDA,respectively.The results show that MSA provides satisfactory fragility analysis,while both CLA and IDA have assumptions that may lead to deviations.Therefore,MSA is the most reliable method among the three methods and is recommended for the fragility analysis of arch dams.It is also shown that the choice of demand level affects the reliability of fragility curves and the effect of the material uncertainty on the fragility of the dam is not significant.

Experimental Study and Fragility Analysis of Effective-Length Factors in Column Buckling

The design of columns relies heavily on the basis of Leonhard Euler’s Theory of Elastic Buckling.However,to increase the accuracy in determining the maximum critical load a column can withstand before buckling,a constant was introduced.This dimensionless coefficient is K,also known as the effective-length factor.This constant is often found in building design codes and varies in value depending on the type of column support that is applied.This paper presents experimental and analytical studies on the determination of the effective-length factor in the buckling stability of columns with partially-fixed support conditions.To this end,the accurate K value of the columns tested by the Instron Testing Machine(ITM)at California State University,Northridge’s(CSUN’s)Mechanics Laboratory is determined.The ITM is used in studying the buckling of columns where the supports are neither pinned nor fixed,and the material cross-section rather rests upon the machine while loading is applied axially.Several column specimens were tested and the experimental data were analyzed in order to estimation of the accurate effective-length factor.The calculations from the tested results as well as the conducted probabilistic analysis shed light on how a fragility curve may aid in predicting the effective-length value of future tests.

液体的fragility及其与玻璃固体力学性能的关联

Angell在20世纪80年代提出的液体fragility概念,为认识玻璃态本质打开了一扇新的窗口,是联系玻璃形成液体和固体的纽带.目前,玻璃转变的主流理论(如模态耦合理论、势能形貌等)围绕fragility展开的研究已经成为玻璃科学领域的一个热点;fragility与玻璃固体基本力学性能之间的关联研究为力学工作者开辟了一片新的研究领域.本文将就玻璃态转变相关基本现象、表征玻璃态转变动力学行为的代表性理论、液体fragility与玻璃固体力学性能关联研究现状进行分析评述,并就本领域今后值得关注的问题进行展望.

State fragility and the coronavirus disease 2019(COVID-19)pandemic:an ecologic analysis of data from 146 countries

Background:Global spread and impact of the coronavirus disease 2019(COVID-19)pandemic are determined to a large extent,by resistance to the pandemic and public response of all countries in the world;while a country's resistance and response are in turn determined by its political and socio economic conditions.To inform future disease prevention and control,we analyzed global data to exam the relationship between state vulnerabilities and COVID-19 incidences and deaths.Methods:Vulnerability was measured using the Fragile States Index(FSI).FSI is created by the Fund for Peace to assess levels of fragility for individual countries.Total FSI score and scores for 12 specific indicators were used as the predictor variables.Outcome variables were national cumulative COVID-19 cases and deaths up to September 16,2020,derived from the World Health Organization.Cumulative incidence rates were computed using 2019 National population derived from the World Bank,and case fatality rates were computed as the ratio of deaths/COVID-19 cases.Countries with incomplete data were excluded,yielding a final sample of 146 countries.Multivariate regression was used to examine the association between the predictor and the outcome measures.Results:There were dramatic cross-country variations in both FSI and COVID-19 epidemiological measurements.FSI total scores were negatively associated with both COVID-19 cumulative incidence rates(β=-0.0135,P<0.001)and case fatality rates(β=-0.0147,P<0.05).Of the 12 FSI indicators,three negatively associated with COVID-19 incidences were E1(Economic Decline and Poverty),E3(Human Flight and Brain Drain),and S2(Refugees and Internally Displaced Persons);two positively associated were P1(State Legitimacy)and X1(External Intervention).With regard to association with case fatality rates,C1(Security Apparatus)was positive,and P3(Human Rights and Rule of Law)and X1 was negative.Conclusion:With FSI measures by the Fund of Peace,overall,more fragile countries are less likely to be affected by the COVID-19 pandemic,and even if affected,death rates were lower.However,poor in state legitimacy and lack of external intervention are risk for COVID-19 infection and lack of security apparatus is risky for COVID-19 death.Implications of the study findings are discussed and additional studies are needed to examine the mechanisms underpinning these relationships.

Seismic fragility analysis of highway bridges considering multi-dimensional performance limit state

Fragility analysis for highway bridges has become increasingly important in the risk assessment of highway transportation networks exposed to seismic hazards. This study introduces a methodology to calculate fragility that considers multi-dimensional performance limit state parameters and makes a first attempt to develop fragility curves for a multi-span continuous (MSC) concrete girder bridge considering two performance limit state parameters: column ductility and transverse deformation in the abutments. The main purpose of this paper is to show that the performance limit states, which are compared with the seismic response parameters in the calculation of fragility, should be properly modeled as randomly interdependent variables instead of deterministic quantities. The sensitivity of fragility curves is also investigated when the dependency between the limit states is different. The results indicate that the proposed method can be used to describe the vulnerable behavior of bridges which are sensitive to multiple response parameters and that the fragility information generated by this method will be more reliable and likely to be implemented into transportation network loss estimation.

Major osteoporotic fragility fractures: Risk factor updates and societal impact

Osteoporosis is a silent disease without any evidence of disease until a fracture occurs. Approximately 200 million people in the world are affected by osteoporosis and 8.9 million fractures occur each year worldwide. Fractures of the hip are a major public health burden, by means of both social cost and health condition of the elderly because these fractures are one of the main causes of morbidity, impairment, decreased quality of life and mortality in women and men. The aim of this review is to analyze the most important factors related to the enormous impact of osteoporotic fractures on population. Among the most common risk factors, low body mass index; history of fragility fracture, environmental risk, early menopause, smoking, lack of vitamin D, endocrine disorders(for example insulin-dependent diabetes mellitus), use of glucocorticoids, excessive alcohol intake, immobility and others represented the main clinical risk factors associated with augmented risk of fragility fracture. The increasing trend of osteoporosis is accompanied by an underutilization of the available preventive strategies and only a small number of patients at high fracture risk are recognized and successively referred for therapy. This report provides analytic evidences to assess the best practices in osteoporosis management and indications for the adoption of a correct healthcare strategy to significantly reduce the osteoporosis burden. Early diagnosis is the key to resize the impact of osteoporosis on healthcare system. In this context, attention must be focused on the identification of high fracture risk among osteoporotic patients. It is necessary to increase national awareness campaigns across countries in order to reduce the osteoporotic fractures incidence.

Fragility curves of concrete bridges retrofitted by column jacketing

The Northridge earthquake inflicted various levels of damage upon a large number of Caltrans' bridges not retrofitted by column jacketing. In this respect, this study represents results of fragility curve development for two (2) sample bridges typical in southern California, strengthened for seismic retrofit by means of steel jacketing of bridge columns. Monte Carlo simulation is performed to study nonlinear dynamic responses of the bridges before and after column retrofit. Fragility curves in this study are represented by Iognormal distribution functions with two parameters and developed as a function of PGA. The sixty (60) ground acceleration time histories for the Los Angeles area developed for the Federal Emergency Management Agcncy (FEMA) SAC (SEAOC-ATC-CUREe) steel project are used for the dynamic analysis of the bridges.The improvement in the fiagility with steel jacketing is quantified by comparing fragility curves of the bridge before and after column retrofit. In this first attempt to formulate the problem of fragility enhancement, the quantification is made by comparing the median values of the fragility curves before and after the retrofit. Under the hypothesis that this quantification also applies to empirical fragility curves developed on the basis of Northridge earthquake damage, the enhanced version of the empirical curves is developed for the ensuing analysis to determine the enhancement of transportation network performance due to the retrofit.

Seismic fragility of flexible pipeline connections in a base isolated medical building

Flexible pipelines are often used to connect hard pipes from a foundation to a superstructure to accommodate large deformation in the base isolation layer during an earthquake. Although Chinese seismic design guidelines suggest several confi gurations, they are diff erent from the designs that have been proven in practice, e.g., Japanese styles, and extensive experimental investigation into their seismic performance is required. Three types of seals, rubber-, metal- and asbestinebased, were tested quasi-statically with infi lled pressurized water at 2.5 MPa. The asbestine-based seal leaked at a smaller deformation than the other two types of seals. Based on the test results, three damage states were defi ned and the deformation capacity was estimated. To evaluate their performance, a three-dimensional model of a base-isolated medical building was developed using OpenSees, with the fl exible pipelines simulated by a mechanical model calibrated from the experimental data. A probabilistic seismic demand model and the fragility function of the fl exible pipelines were then developed to evaluate the seismic performance.

Time-variant fragility analysis of the bridge system considering time-varying dependence among typical component seismic demands

This paper presents a copula technique to develop time-variant seismic fragility curves for corroded bridges at the system level and considers the realistic time-varying dependence among component seismic demands. Based on material deterioration mechanisms and incremental dynamic analysis, the time-evolving seismic demands of components were obtained in the form of marginal probability distributions. The time-varying dependences among bridge components were then captured with the best fitting copula function, which was selected from the commonly used copula classes by the empirical distribution based analysis method. The system time-variant fragility curves at different damage states were developed and the effects of time-varying dependences among components on the bridge system fragility were investigated. The results indicate the time-varying dependence among components significantly affects the time-variant fragility of the bridge system. The copula technique captures the nonlinear dependence among component seismic demands accurately and easily by separating the marginal distributions and the dependence among them.

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.

Study on ecological fragility of wetlands in Sanjiang Plain

As the largest inland freshwater wetlands in China. Sanjiang Plain plays an important role in environmental protection from local scale to global scale. However, due to the fragility of the wetland ecosystems and the environmental disturbances on them caused by natural disasters and human activities, loss and degeneration of wetlands in this area are considerable. Characteristics and reasons of wetlands’ ecological fragility in Sanjiang Plain are analyzed and then the evaluation method and index system on ecological fragility of wetlands in Sanjiang Plain are presented. The result of the evaluation shows that the wetlands’ ecological fragility in Sanjiang Plain is serious. The value of this method and index system is also discussed in the paper.

Earthquake Fragility Assessment of the Underground Tunnel Using an Efficient SSI Analysis Approach

This paper represents a simplified seismic fragility analysis approach of the underground tunnel structure in consideration of the soil-structure interaction (SSI) effect. SSI effect founds to be essential in the estimation of dynamic analysis of underground structures like tunnels and thus needs to be considered. The ground response acceleration method for buried structures (GRAMBS) known to be a very efficient quasi-static method that can consider SSI effect is used in the proposed approach to evaluate seismic structural responses without sacrificing much accuracy. Seismic fragility curves are then developed by applying the maximum likelihood estimates (MLE) to responses of a large set of artificial ground motion time histories generated for multiple different levels of earthquake intensity. It is also assumed in this paper that the seismic fragility curve can be represented by a two-parameter lognormal distribution function with median and log-standard deviation that need to be defined using MLE.

Machine Learning-Based Seismic Fragility Analysis of Large-Scale Steel Buckling Restrained Brace Frames

Steel frames equipped with buckling restrained braces(BRBs)have been increasingly applied in earthquake-prone areas given their excellent capacity for resisting lateral forces.Therefore,special attention has been paid to the seismic risk assessment(SRA)of such structures,e.g.,seismic fragility analysis.Conventional approaches,e.g.,nonlinear finite element simulation(NFES),are computationally inefficient for SRA analysis particularly for large-scale steel BRB frame structures.In this study,amachine learning(ML)-based seismic fragility analysis framework is established to effectively assess the risk to structures under seismic loading conditions.An optimal artificial neural network model can be trained using calculated damage and intensity measures,a technique which will be used to compute the fragility curves of a steel BRB frame instead of employing NFES.Numerical results show that a highly efficient instantaneous failure probability assessment can be made with the proposed framework for realistic large-scale building structures.

Biomedical studies on lipid peroxidation and erythrocyte fragility during the process of aging

Objective:To investigate oxidative stress,hemoglobin percentage and erythrocyte osmotic fragility in various aging groups.Methods:A total of 200 healthy volunteers of hoth genders between age group 20-65 years were selected by random method.Determination of hemoglobin percentage was done employing modified cyanide method of Dacie and Lewis.The erythrocyte lysis was observed in hypotonic solution of buffered saline at varying concentrations and optical density was measured at 540 nm.The extent of lipid peroxidation in form of malondialdehyde was measured by thiobarbituric acid method.Results:The study found a significant decrease in hemoglobin percentage,increase in erythrocyte osmotic fragility and increased lipid peroxidation in form of malondialdehyde with increasing age.Conclusions:Supplementation of antioxidants may prevent the oxidative injury in elderly group of subjects.

Seismic fragility reduction of an unreinforced masonry school building through retrofit using ferrocement overlay

The Himalayan region is one of the major seismic areas in the world.However,similar to many other seismically active locations,there are substantial numbers of unreinforced masonry(URM)buildings;the majority of which have not been designed for seismic loads.Past seismic events have shown that such buildings are highly vulnerable to earthquakes.Retrofitting of these URM buildings is an important concern in earthquake mitigation programs.Most government school buildings in rural areas of northern India are constructed of unreinforced masonry.These school buildings are socially important structures and serve as a crucial resource for rehabilitation during any disaster.The effectiveness of ferrocement(FC)to create a URM-FC composite is described in this study by estimating the performance and fragility of a URM school building before and after a retrofit.Analytical models,based on the equivalent frame method,are developed and used for nonlinear static analysis to estimate the enhancement in capacity.The capacity enhancement due to retrofitting is presented in terms of the maximum PGA sustained and damage probabilities at the expected level of earthquake hazard.

Unusual presentation of congenital radioulnar synostosis with osteoporosis,fragility fracture and nonunion:A case report and review of literature

BACKGROUND Congenital radioulnar synostosis(CRUS)is a rare deformity of the upper extremity.It is characterized by loss of rotation of the involved forearm and functional limitations in daily activities.No studies on CRUS with osteoporosis have been reported to date,and osteoporosis is usually recognized as an important dimension of genetic disorder in children.We discuss the possible relationship among this disorder,osteoporosis and fracture nonunion,investigate the strict surgical indications and recommended treatments.CASE SUMMARY A 14-year-old male patient with bilateral CRUS with osteoporosis,fragility fracture and nonunion of fractures in ulna and radius presented our institution for further treatment,complaining of limitation in rotation.The bone mineral density of the hip and lumbar spine was 0.687 g/cm2 and 0.705 g/cm2,respectively,and the Z-score for both was-2.1,which revealed osteoporosis and a high risk of fracture.Tow serum bone turnover markers indicated an imbalance of bone metabolism.Reoperation for ulna fracture with autogenous bone grafting and a postoperative physiotherapy program were adopted rather than the separation of pathological synostosis.Radiological examination,observational posture assessment and limb function scale were evaluated before and 1 year after surgery.At 1 year,the fracture nonunion had almost recovered,forearm movement function on the fracture side was restored,and function on the healthy side was significantly improved compared with that before rehabilitation.CONCLUSION Surgical indications for CRUS vary from person to person.Surgery should not be the first choice of treatment,and physiotherapy is not inferior to surgical treatment.

Lycopene Ameliorates Diabetic-Induced Changes in Erythrocyte Osmotic Fragility and Lipid Peroxidation in Wistar Rats

Introduction: Diabetes mellitus has remained one of the serious health problems in the world;and oxidative stress has been reported to be a root cause for the progression and development of diabetes mellitus and its associated complications. Aim: This study investigated the possible ameliorative effects of lycopene on diabetic-induced changes in erythrocyte osmotic fragility and lipid peroxidation in Wistar rats. Methodology: The animals were made diabetic by single intraperitoneal injection of streptozotocin at 60 mg/kg b w. Diabetes was confirmed by the presence of high fasting blood glucose level ≥ 200 after 72 hours. Thereafter, diabetic rats were randomly assigned into six groups (1, 2, 3, 4, 5 and 6) comprising five animals each. Group 1 (Diabetic control) and group 2 (Normal control) rats received 0.5 ml of olive oil, groups 3, 4, 5 rats received 10, 20, 40 mg/kg bw of lycopene respectively, while those in group 6 received 2 mg/kg bw of glibenclamide orally once daily for a period of four weeks. At the end of the treatment, all animals were sacrificed;blood samples collected for determination of erythrocyte osmotic fragility (EOF) and lipid peroxidation (LPO). Results: The results obtained showed that there was a significantly (P Conclusion: From the available findings, it can be concluded that administration of lycopene to diabetic rats attenuated diabetic-induced changes in EOF and LPO and these observed effects may be attributed to anti-oxidative property of lycopene.