Towards multiple hazard resilient bridges:a methodology for modeling frequent and infrequent time-varying loads Part I,Comprehensive reliability and partial failure probabilities

The current AASHTO load and resistance factor design （LRFD） guidelines are formulated based on bridge reliability, which interprets traditional design safety factors into more rigorously deduced factors based on the theory of probability. This is a major advancement in bridge design specifications. However, LRFD is only calibrated for dead and live loads. In cases when extreme loads are significant, they need to be individually assessed. Combining regular loads with extreme loads has been a major challenge, mainly because the extreme loads are time variables and cannot be directly combined with time invariant loads to formulate the probability of structural failure. To overcome these difficulties, this paper suggests a methodology of comprehensive reliability, by introducing the concept of partial failure probability to separate the loads so that each individual load combination under a certain condition can be approximated as time invariant. Based on these conditions, the extreme loads （also referred to as multiple hazard or MH loads） can be broken down into single effects. In Part II of this paper, a further breakdown of these conditional occurrence probabilities into pure conditions is discussed by using a live truck and earthquake loads on a bridge as an example. There are three major steps in establishing load factors from MH load distributions： （1） formulate the failure probabilities; （2） normalize various load distributions; and （3） establish design limit state equations. This paper describes the formulation of the failure probabilities of single and combined loads.

Towards multiple hazard resilient bridges:a methodology for modeling frequent and infrequent time-varying loads Part Ⅱ,Examples for live and earthquake load effects

The current AASHTO load and resistance factor design （LRFD） guidelines are formulated based on bridge reliability, which interprets traditional design safety factors into more rigorously deduced factors based on the theory of probability. This is a major advancement in bridge design specifications. However, LRFD is only calibrated for dead and live loads. In cases when extreme loads are significant, they need to be individually assessed. Combining regular loads with extreme loads has been a major challenge, mainly because the extreme loads are time variable and cannot be directly combined with time invariant loads to formulate the probability of structural failure.To overcome these difficulties, this paper suggests a methodology of comprehensive reliability, by introducing the concept of partial failure probability to separate the loads so that each individual load combination under a certain condition can be approximated a,; time invariant. Based on these conditions, the extreme loads （also referred to as multiple hazard or MH loads） can be broken down into single effects. In this paper, a further breakdown of these conditional occurrence probabilities into pure conditions is discussed by using a live truck and earthquake loads on a bridge as an example.

Integrating flood and earthquake resilience:a framework for assessing urban community resilience against multiple hazards

Floods and earthquakes are the most common natural disasters,causing significant damage and casualties in urban communities.Although academic research has focused on assessing cities'ability to withstand these natural disasters,there is a lack of established frameworks for evaluating resilience against multiple hazards.This research integrates the earthquake and flood resilience indicators to create a comprehensive resilience assess-ment framework.This study integrated seismic and flood resilience indicators and categorized them into 27 clusters.It also used the DEMATEL(Decision-Making Trial and Evaluation Laboratory)method to determine the significance of clusters and prioritize them.This research identified 13 cause clusters and 14 effect clusters of indicators for seismic and flood resilience.The‘response capacity'cluster has the most impact on seismic and flood resilience,while the‘transportation and accessibility'cluster is the most affected cluster.This article presents a framework for evaluating flood and seismic resilience and makes suggestions for future research.

Mapping and ranking global mortality,affected population and GDP loss risks for multiple climatic hazards

Coping with extreme climate events and its related climatic disasters caused by climate change has become a global issue and drew wide attention from scientists, policy-makers and public. This paper calculated the expected annual multiple climatic hazards intensity index based on the results of nine climatic hazards including tropical cyclone, flood, landslide, storm surge, sand-dust storm, drought, heat wave, cold wave and wildfire. Then a vulnerability model involving the coping capacity indicator with mortality rate, affected population rate and GDP loss rate, was developed to estimate the expected annual affected population, mortality and GDP loss risks. The results showed that： countries with the highest risks are also the countries with large population or GDP. To substantially reduce the global total climatic hazards risks, these countries should reduce the exposure and improving the governance of integrated climatic risk; Without considering the total exposure, countries with the high mortality rate, affected population rate or GDP loss rate, which also have higher or lower coping capacity, such as the Philippines, Bangladesh and Vietnam, are the hotspots of the planning and strategy making for the climatic disaster risk reduction and should focus on promoting the coping capacity.

The Proportional Hazards Model for Multiple Type Recurrent Gap Times

Recurrent events data and gap times between recurrent events are frequently encountered in many clinical and observational studies,and often more than one type of recurrent events is of interest.In this paper,we consider a proportional hazards model for multiple type recurrent gap times data to assess the effect of covaxiates on the censored event processes of interest.An estimating equation approach is used to obtain the estimators of regression coefficients and baseline cumulative hazard functions.We examine asymptotic properties of the proposed estimators.Finite sample properties of these estimators are demonstrated by simulations.

The active rotary inertia driver system for flutter vibration control of bridges and various promising applications

Active control technology has been investigated and applied in numerous building structures and infrastructures since 1972 when it was firstly introduced into the civil engineering field by Professor JTP Yao.Now,half a century has passed,a variety of control systems have been invented and implemented by researchers and engineers from all over the world.The recent years have witnessed remarkable research attempts and progress devoted to the development in this area based on modern control theory.However,there are still some unknown areas which are worthy of being explored in depth.One of such examples is the application of tuned mass dampers(TMD)to the flutter vibration control of long span bridges.Although applications of TMDs to bridges have been sighted in practice,their genuine effectiveness remains a serious question.The issues relating to how the coupled effect of TMD’s linear force being restricted by the rotational velocity of bridge’s deck during wind excitations which may eventually leads to flutter vibrations,remains unanswered.Such unusual phenomena and limitations were initially discovered and reported by the author sixteen years ago when investigating the barge ship crane hook’s swing motion control.In recent years,the author has invented the active rotary inertia driver(ARID)system which now has been granted patents in China,the US,Europe(including the UK,France,and Germany),Russia,Brazil,India,South Africa,Canada,Australia,Japan and Korean,etc.The ARID is an active control system which could exert direct control torque or moment to the target structures with rotational motions or vibrations natures,including and not limited to buildings,bridges or offshore platforms subjected to winds,earthquakes,and waves excitations.Furthermore,the ARID control system and its methodology can also be applicable to various mechanical systems including but not limited to cranes,vehicles,trains,ships,aircrafts,space crafts,satellites,and robotics.In this paper,the theory,modelling,comprehensive parametric analysis and case study of the ARID system for flutter vibration control of bridges will be discussed,as well as its promising applications in other various occasions.