Research On The Assessment Of Design Led Safety Risks In Lifecycle Of Subway Projects

Subway,which is a convenient,economic,green and efficient public transportation method,is playing significant role in the development of transportation system in major cities.The development of subway has been considered as a significant approach to cure city disease by optimizing city layout,reducing environment pollution,releasing traffic jam etc.However,subway is an extremely complex giant system,consisting of huge amount of subsystems,these subsystems are tightly interconnected.The complexity of subway system has bring great challenges to the safe construction and operation of subway projects.To reduce lifecycle safety risks of subway projects,existing researches mainly focus on the construction and operation period.Unfortunately,traditional safety management method,which is separated by different stages,ignores the interactions of different stages,especially the influence of design phase on other stages.As a result,this research conducted safety risks assessment of subway projects from the perspective of lifecycle,explored the implementation of Design for Safety(DFS)in subway projects and its benefits of reducing lifecycle safety risks.By theoretical analysis and empirical study,methods of identifying and assessing lifecycle safety risks embedded in design work were proposed,which would help the adoption of DFS in the future.The following is the main work done in this research.(1)By referring to the literature and accident cases within lifecycle of subway projects,the status quo,research limitation,and research trends were identified.In addition,this research defined and enriched the concept of DFS.The literature review also helps to clarify the research framework and roadmap.Based on theoretical analysis,and with the help of “subway design code”(GB50157-2013),subway physical system network(SPSN)is built,and the model is analyzed using network analysis.Results illustrated the mechanism of DFS that design phase plays significant roles in lifecycle of subway projects.53.4% of accidents occurred in lifecycle of subway projects have are led by not addressing safety in design phase.36.1% of construction accidents were related to the concept of DFS while 69.9% of operation accidents were related to concept of DFS.(2)By studying safety requirements and design process,this research deconstructed subway design plan and find the components that constitute the design work.Meanwhile,explicit and implicit safety knowledge,i.e.,safety regulation,codes,safety records,were analyzed to explore measures of applying DFS.Using theory of ontology,this research realized systematic presentation of DFS knowledge base.In addition,with the help of database software,this research also realized main function of DFS knowledge base,i.e.,search,analysis,storage,and query of DFS knowledge.(3)The framework of intelligent identification of safety risks integrated with BIM and DFS knowledge base was developed.Through the further development of Revit software,the information within lifecycle of subway projects were integrated into BIM model during subway design phase.By matching the exported information from BIM with DFS knowledge base,it would help to realize the automatic identification of safety risks accompanied with DFS measures.(4)The design led lifecycle safety risks assessment model was developed base on fuzzy cognitive map(FCM)method.This research briefly introduced the development of FCM,its mathematical model,reasoning mechanism,how to build the FCM model.The advantage of apply FCM in assessing design led lifecycle safety risks in subway projects is also concluded,i.e.,intuition,stackable,expansible,easily feedback.Based on the mechanism of DFS,this research build the assess model of design led safety risks within lifecycle of subway projects using aggregated FCM model.The way to calculate the value of nodes and their relationships were also introduced.To improve the objectivity and stability,Nonelinear Hebbian Learning(NHL)were introduced to modify the assess model.(5)This research selected the design of subway launching plan in Nanjing to conduct the empirical study,which helps to validate the theory and method proposed in this research.the analysis of design work echoes the mechanism of DFS.Taking advantage of BIM and DFS knowledge,two major safety risks were identified.The first one is the lack of torque force provided by the launching frame,the other is the possibility of being struck by falling objects during the work of lifting machine.Based on the proposed FCM assessment model,experts of this field were invited to evaluate safety risks of the subway launching design work.The scores given by these experts were calculated using fuzzy set theory,and the results were further modified using NHL method.The modified results show that the arrangement of workers,construction methods,construction machine,and temporary safety measures have great influence on lifecycle safety risks in subway projects,while the construction material,permeant equipment,on-site environment have less impact on lifecycle safety risks in this case study.At the end of this research,principles were given to help the implementation of DFS.