Post-Earthquake Functionality Recovery Process Simulation And Resilience Assessment For Urban Residential Communities

Bearing the urban residential function,residential communities provide services and facilities for the daily life of a large number of residents.Its post-earthquake dysfunction can cause production interruption and human resources wasting,resulting in hindering the recovery of social stability and economic development.However,the existing seismic design which concentrate more on protecting life puts less attentions on maintaining functionality of communities than it should,thus it is limited in mitigation effect and the indirect economic loss reduction in destructive earthquakes.Currently,the ability of urban residential communities to resist seismic damage is still insufficient in China.Their earthquake loss risk has been a central issue that restricts the sustainable development of some domestic cities,holding back the promotion of new-type urbanization in China.From this consideration,it is significantly important for earthquake disaster mitigation in urban residential communities and sustainable development of cities to deeply investigate the post-earthquake function recovery of urban residential communities and clarify its mechanism and key factors,as well as to improve their resilience and reduce their seismic loss risk via approaches such as sufficient preparation and quick recovery.Focusing on post-earthquake recovery process analysis and resilience assessment,this paper proposes functionality indicators applying for residential buildings and urban residential communities,and establishes the corresponding simulation method in accordance with the functional dependence of various infrastructures.Furthermore,resilience metrics that can assess resilience threshold are defined with the community recovery function and its dynamic model established on the simulation results.On these effects,the influences of various factors on community resilience are investigated with parametric analysis,and an optimization analysis towards the key factor is carried out to achieve an efficient and economical resilience improvement plan.Some research has been conducted and conclusions are as follows:(1)A functionality indicator for residential buildings is established on the demandsupply relationship between buildings and residents.In accordance with resident living needs,building performance levels,seismic damages of basic components,and events in resident daily life are integrated into a functionality indicator for residential buildings using Maslow’s hierarchy of needs.This indicator can illustrate the details of post-earthquake recovery of residential buildings from multiple dimensions.The seismic response analysis and functionality quantification of a high-rise residential building is performed in virtue of the highperformance matrix solvers.The results indicate that the changes of probability of operation of basic components could affect the probability of’ the achievement of relevant events which influenced the probability distribution of functional states of the building,thus altering the postearthquake recovery process of building functionality.Similar effects are also found with the residents’ settlement willingness alternation,which indicates a same importance of the improvement of residing willingness and the enhancement of building seismic performance in the functionality recovery of residential buildings.(2)An analytic method for post-earthquake community recovery is established on the functional and structural characteristics of urban residential communities.In order to describe the post-earthquake recovery of a community accurately,a community model including a variety of lifeline networks,supporting buildings,residential buildings,as well as their functional relationships is established.Furthermore,based on residential satisfaction models,the post-earthquake resident outmigration of a community is investigated and used to quantify community functionality.With these effects,a community recovery simulation method integrating temporal parameters of repair works is proposed and used in investigating the impacts of repair sequences and times consumed of different infrastructures on community recovery.The results show that the repair progress of residential buildings has the most significant impact on community recovery.In the initial stage of recovery,supporting buildings can also stabilize population to a certain extent.Utility networks are less influential than the buildings since they are generally repaired quickly.(3)Maximum recovery efficiency metric and resilience threshold metric are established on the dynamics model of community recovery process.To measure community resilience effectively,a community recovery function and its dynamic system are established by an over-damped single degree of freedom system model in accordance with the basic recovery mechanism of the community.The maximum recovery efficiency metric is defined with the the manifold asymptote shown on the phase plane of the dynamic model.This metric is able to clearly reflect the rapidity of community recovery in some situations where existing metrics are ineffective.Considering further of non-engincering factors,a limit cycle appearing on the phase plane is identified and used to define the resilience threshold metric which can measure the maximum seismic damage that a community can withstand on adopting resilience strategy.This metric illustrates the limitation and conditionality of community resilience,and indicates the viewpoint that communities cannot always effectively reduce earthquake loss risk by using resilience strategy.(4)A multidimensional assessment frame is used to analyze the effects of various engineering and non-engineering factors on community seismic resilience.To clarify the most influential factor of community recovery,a parametric analysis about the resilience of urban residential community is carried out based on a multidimensional assessment frame which consists of multiple functionality indicators and resilience metrics.The results show that strengthening the seismic performance of buildings could significantly reduce the cumulative functional loss and recovery period of community,and increase its resilience threshold as well.The topological redundancy and internetwork cascading effects of utility networks are limited to influence community recovery,but the changes in topological redundancy could influence the basic levels of robustness and efficiency.On the other hand,disaster relief measures can improve community seismic resilience by providing residents with temporary substitutive service.Besides,a reasonable repair sequence of infrastructures can also accelerate the postearthquake recovery of a community.(5)The resilience optimization of large-scale urban residential communities is performed based on the double-level model composed of primary community and subcommunities.In order to optimize the resilience of large-scale urban residential communities,a simplified community resilience optimization model is proposed to investigate the effects of strengthening building seismic performance via reinforcement measures on improving community resilience.The reinforcement measures can improve the resilience significantly,but its effect decreases as the intensity of the earthquakes increases.Thus,non-engineering measures such as temporary resettlement are advised to ensure the rapid recovery of community in facing with strong earthquakes.After comparison,it is found that the optimal solution may change when different resilience metrics are adopted as optimization goals.Accordingly,the occurrence frequency of a particular building in different optimal solutions can be used to describe its importance to community resilience.Besides,since the increase of the type of reinforcement measures can improve the effectiveness of optimization,diversified reinforcement measures are advised to search more economical and effective resilience improvement scheme.